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@ -1670,13 +1670,12 @@ CLOSED: [2025-04-17 Thu 16:48]
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**** Accelerating electrons to produce intense X-ray
Synchrotron radiation facilities function as particle accelerator light sources, where electrons are accelerated to near the speed of light.
Synchrotron radiation facilities, are particle accelerators where electrons are accelerated to near the speed of light.
As these electrons traverse magnetic fields, typically generated by insertion devices or bending magnets, they produce exceptionally bright light known as synchrotron light.
This intense electromagnetic radiation, particularly in the X-ray spectrum, is subsequently utilized for the detailed study of matter.
Approximately 70 synchrotron light sources are operational worldwide, with prominent facilities illustrated in Figure ref:fig:introduction_synchrotrons.
The global distribution underscores the significant utility of synchrotron light for the scientific community.
Approximately 70 synchrotron light sources are operational worldwide, some of which are indicated in Figure ref:fig:introduction_synchrotrons.
This global distribution of such facilities underscores the significant utility of synchrotron light for the scientific community.
#+name: fig:introduction_synchrotrons
#+caption: Major synchrotron radiation facilities in the world. 3rd generation Synchrotrons are shown in blue. Planned upgrades to 4th generation are shown in green, and 4th generation Synchrotrons in operation are shown in red.
@ -1685,12 +1684,12 @@ The global distribution underscores the significant utility of synchrotron light
These facilities fundamentally comprise two main parts: the accelerator complex, where electron acceleration and light generation occur, and the beamlines, where the intense X-ray beams are conditioned and directed for experimental use.
**** The European Synchrotron Radiation Facility
The European Synchrotron Radiation Facility (ESRF), shown in Figure ref:fig:introduction_esrf_picture, is a joint research institution supported by 19 member countries.
Since commencing user operations in 1994, the ESRF was recognized as the world's first third-generation synchrotron source.
Its accelerator complex, schematically depicted in Figure ref:fig:introduction_esrf_schematic, includes a linear accelerator, a booster synchrotron for accelerating electrons close to light speed, and an 844-meter circumference storage ring where electrons are maintained for light production.
Radiating from the storage ring are over 40 beamlines, each equipped with specialized instrumentation catering to a diverse range of scientific disciplines, including structural biology and materials science under various conditions.
The ESRF commenced user operations in 1994 as the world's first third-generation synchrotron.
Its accelerator complex, schematically depicted in Figure ref:fig:introduction_esrf_schematic, includes a linear accelerator where electrons are initially generated and accelerated, a booster synchrotron to further accelerate the electrons, and an 844-meter circumference storage ring where electrons are maintained in a stable orbit.
Synchrotron light are emitted in more than 40 beamlines surrounding the storage ring, each having specialized experimental stations.
These beamlines host diverse instrumentation that enables a wide spectrum of scientific investigations, including structural biology, materials science, and study of matter under extreme conditions.
#+name: fig:instroduction_esrf
#+caption: Schematic (\subref{fig:introduction_esrf_schematic}) and picture (\subref{fig:introduction_esrf_picture}) of the European Synchrotron Radiation Facility, situated in Grenoble, France
@ -1710,13 +1709,12 @@ Radiating from the storage ring are over 40 beamlines, each equipped with specia
#+end_subfigure
#+end_figure
**** 3rd and 4th Generation Light Sources
In August 2020, following an extensive 20-month upgrade period, the ESRF inaugurated its Extremely Brilliant Source (EBS), establishing it as the world's premier fourth-generation synchrotron [[cite:&raimondi21_commis_hybrid_multib_achrom_lattic]].
This advancement was predicated on a novel storage ring concept engineered to significantly enhance the brilliance and coherence of the emitted X-ray beams.
Brilliance, a key figure of merit for synchrotron sources, experienced an approximate 100-fold increase with the implementation of EBS, as shown in the historical evolution depicted in Figure ref:fig:introduction_moore_law_brillance.
While this enhanced beam quality presents unprecedented scientific opportunities, it concurrently introduces considerable engineering challenges, particularly concerning sample positioning.
# TODO - Say that regarding what is interesting for us: sample positioning
This upgrade implemented a novel storage ring concept that substantially increases the brilliance and coherence of the X-ray beams.
Brilliance, a measure of the photon flux, is a key figure of merit for synchrotron facilities.
It experienced an approximate 100-fold increase with the implementation of EBS, as shown in the historical evolution depicted in Figure ref:fig:introduction_moore_law_brillance.
While this enhanced beam quality presents unprecedented scientific opportunities, it concurrently introduces considerable engineering challenges, particularly regarding experimental instrumentation and sample positioning systems.
#+name: fig:introduction_moore_law_brillance
#+caption: Evolution of the peak brilliance (expressed in $\text{photons}/s/mm^2/mrad^2/0.1\%BW$) of synchrotron radiation facilities. Note the vertical logarithmic scale.
@ -1727,18 +1725,13 @@ While this enhanced beam quality presents unprecedented scientific opportunities
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**** Beamline Layout
# TODO - Make a short introduction to the beamline goal
The term "beamline layout" encompasses the sequence of optical components situated between the X-ray source (an insertion device in this context) and the sample.
Initially, a "white" beam, characterized by high power (often exceeding several kilowatts) and a broad energy spectrum, is generated by the source.
This "white" beam is generally unsuitable for direct sample irradiation and is therefore processed through a series of optical elements housed within shielded enclosures known as Optical Hutches (OH), illustrated for ID31 in Figure ref:fig:introduction_id31_oh.
These elements, including absorbers, mirrors, slits, and monochromators, are employed to filter, shape, and select the desired energy range of the X-ray beam.
Following the optical hutches, the conditioned beam enters the Experimental Hutch (Figure ref:fig:introduction_id31_cad), where, for experiments pertinent to this work, focusing optics are utilized.
The sample is mounted on a positioning stage, referred to as the "end-station," which facilitates precise alignment relative to the X-ray beam.
Detectors are used to capture the X-rays transmitted through or scattered by the sample.
Throughout this thesis, the standard ESRF coordinate system is adopted, wherein the X-axis aligns with the beam direction, Y is transverse horizontal, and Z is vertical upwards against gravity.
Each beamline begins with a "white" beam generated by the insertion device.
This beam carries substantial power, typically exceeding kilowatts, and is generally unsuitable for direct application to samples.
Instead, the beam passes through a series of optical elements—including absorbers, mirrors, slits, and monochromators—that filter and shape the X-rays to the desired specifications.
These components are housed in multiple Optical Hutches, as depicted in Figure ref:fig:introduction_id31_oh.
#+name: fig:introduction_id31_oh
#+caption: Schematic of the two ID31 optical hutches: OH1 (\subref{fig:introduction_id31_oh1}) and OH2 (\subref{fig:introduction_id31_oh2}). Distance from the source (the insertion device) is indicated in meters.
@ -1760,15 +1753,15 @@ Throughout this thesis, the standard ESRF coordinate system is adopted, wherein
#+end_subfigure
#+end_figure
**** Positioning End Station: The Micro-Station
Following the optical hutches, the conditioned beam enters the Experimental Hutch (Figure ref:fig:introduction_id31_cad), where, for experiments pertinent to this work, focusing optics are utilized.
The sample is mounted on a positioning stage, referred to as the "end-station", that enables precise alignment relative to the X-ray beam.
Detectors are used to capture the X-rays transmitted through or scattered by the sample.
Throughout this thesis, the standard ESRF coordinate system is adopted, wherein the X-axis aligns with the beam direction, Y is transverse horizontal, and Z is vertical upwards against gravity.
The specific end-station employed on the ID31 beamline is designated the "micro-station".
As depicted in Figure ref:fig:introduction_micro_station_dof, it comprises a stack of positioning stages: a translation stage (blue), a tilt stage (red), a spindle for continuous rotation (yellow), and a micro-hexapod (purple).
The sample itself (cyan), potentially housed within complex sample environments (e.g., for high pressure or varying temperatures) and weighing up to 50kg, is mounted on top of this assembly.
Each stage serves distinct positioning functions; for example, the micro-hexapod enables fine static adjustments, while the Ty translation and Rz rotation stages are utilized for specific scan types.
The design objectives prioritized maximum stiffness and minimal positioning errors across its operational stroke.
The main components within the experimental hutch—focusing optics, sample stage, sample, and detector—are affixed to a common granite base for enhanced stability, as shown in Figure ref:fig:introduction_id31_cad.
As depicted in Figure ref:fig:introduction_micro_station_dof, it comprises a stack of positioning stages: a translation stage (in blue), a tilt stage (in red), a spindle for continuous rotation (in yellow), and a micro-hexapod (in purple).
The sample itself (cyan), potentially housed within complex sample environments (e.g., for high pressure or extreme temperatures), is mounted on top of this assembly.
Each stage serves distinct positioning functions; for example, the micro-hexapod enables fine static adjustments, while the $T_y$ translation and $R_z$ rotation stages are utilized for specific scanning applications.
#+name: fig:introduction_micro_station
#+caption: CAD view of the ID31 Experimal Hutch (\subref{fig:introduction_id31_cad}). There are typically four main elements: the focusing optics in yellow, the sample stage in green, the sample itself in purple and the detector in blue. All these elements are fixed to the same granite. CAD view of the The micro-station with the associated degrees of freedom (\subref{fig:introduction_micro_station_dof}).
@ -1788,21 +1781,18 @@ The main components within the experimental hutch—focusing optics, sample stag
#+end_subfigure
#+end_figure
**** Example of Scientific experiments performed on ID31
The high mobility afforded by the multi-stage configuration of the micro-station enables diverse imaging techniques.
The "stacked-stages" configuration of the micro-station provides high mobility, enabling diverse scientific experiments and imaging techniques.
Two illustrative examples are provided.
Firstly, tomography experiments are conducted as illustrated schematically in Figure ref:fig:introduction_tomography_schematic.
In this technique, the sample is placed in the X-ray beam path, and its orientation is controlled via a rotation stage.
Projection images are acquired by the detector at numerous discrete angular positions.
Provided the point of interest within the sample remains accurately centered on the beam throughout the rotation, a three-dimensional reconstruction, such as the one presented in Figure ref:fig:introduction_tomography_results, can be generated [[cite:&schoeppler17_shapin_highl_regul_glass_archit]].
Tomography experiments, schematically represented in Figure ref:fig:introduction_tomography_schematic, involve placing a sample in the X-ray beam path while controlling its vertical rotation angle using a dedicated stage.
Detector images are captured at numerous rotation angles, allowing the reconstruction of three-dimensional sample structure (Figure ref:fig:introduction_tomography_results) [[cite:&schoeppler17_shapin_highl_regul_glass_archit]].
This reconstruction depends critically on maintaining the sample's point of interest within the beam throughout the rotation process.
Secondly, mapping or scanning experiments are performed, often involving focused X-ray beams, as depicted in Figure ref:fig:introduction_scanning_schematic.
The sample is translated, typically in the plane perpendicular to the beam (Y and Z directions), while data is collected at each position.
Mapping or scanning experiments, depicted in Figure ref:fig:introduction_scanning_schematic, typically utilize focusing optics to have a small beam size at the sample's location.
The sample is then translated perpendicular to the beam (along Y and Z axes), while data is collected at each position.
An example [[cite:&sanchez-cano17_synch_x_ray_fluor_nanop]] of a resulting two-dimensional map, acquired with 20nm step increments, is shown in Figure ref:fig:introduction_scanning_results.
The fidelity and resolution of such images are intrinsically linked to the focused beam size and the precision with which the sample position relative to the beam can be maintained.
Positional instabilities, such as vibrations and thermal drifts, inevitably lead to blurring and distortion in the acquired data.
The fidelity and resolution of such images are intrinsically linked to the focused beam size and the positioning precision of the sample relative to the focused beam.
Positional instabilities, such as vibrations and thermal drifts, inevitably lead to blurring and distortion in the obtained image.
Other advanced imaging modalities practiced on ID31 include reflectivity, diffraction tomography, and small/wide-angle X-ray scattering (SAXS/WAXS).
#+name: fig:introduction_tomography
@ -1845,7 +1835,6 @@ Other advanced imaging modalities practiced on ID31 include reflectivity, diffra
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**** A push towards brighter and smaller beams
Continuous advancements in both synchrotron source technology and X-ray optics have led to the availability of smaller, more intense, and more stable X-ray beams.
The ESRF-EBS upgrade, for instance, resulted in a significantly reduced source size, particularly in the horizontal dimension, coupled with increased brilliance, as illustrated in Figure ref:fig:introduction_beam_3rd_4th_gen.
@ -1878,12 +1867,10 @@ Presently, focused beam dimensions in the range of 10 to 20 nm (Full Width at Ha
#+attr_latex: :scale 0.9
[[file:figs/introduction_moore_law_focus.png]]
**** New Dynamical Positioning Needs
The increased brilliance and flux density associated with modern synchrotron sources exacerbate the issue of radiation damage, particularly for sensitive samples and at high-energy beamlines like ID31.
The increased brilliance introduces challenges related to radiation damage, particularly at high-energy beamlines like ID31.
Consequently, prolonged exposure of a single sample area to the focused beam must be avoided.
Traditionally, experiments were conducted in a "step-scan" mode, illustrated in Figure ref:fig:introduction_scan_step.
In this mode, the sample is moved to the desired position, the detector acquisition is initiated, and a beam shutter is opened for a brief, controlled duration to limit dose before closing; this cycle is repeated for each measurement point.
In this mode, the sample is moved to the desired position, the detector acquisition is initiated, and a beam shutter is opened for a brief, controlled duration to limit radiation damage before closing; this cycle is repeated for each measurement point.
While effective for mitigating radiation damage, this sequential process can be time-consuming, especially for high-resolution maps requiring numerous points.
#+name: fig:introduction_scan_mode
@ -1906,31 +1893,29 @@ While effective for mitigating radiation damage, this sequential process can be
An alternative, more efficient approach is the "fly-scan" or "continuous-scan" methodology [[cite:&xu23_high_nsls_ii]], depicted in Figure ref:fig:introduction_scan_fly.
Here, the sample is moved continuously while the detector is triggered to acquire data "on the fly" at predefined positions or time intervals.
This technique significantly accelerates data acquisition, enabling better utilization of valuable beamtime and potentially finer spatial sampling [[cite:&huang15_fly_scan_ptych]].
This technique significantly accelerates data acquisition, enabling better utilization of valuable beamtime while potentially enabling finer spatial resolution [[cite:&huang15_fly_scan_ptych]].
Furthermore, recent developments in detector technology have yielded sensors with improved spatial resolution, lower noise characteristics, and substantially higher frame rates [[cite:&hatsui15_x_ray_imagin_detec_synch_xfel_sourc]].
Whereas typical integration times for scanning or tomography experiments were previously in the range of 0.1 to 1 second, modern detectors permit integration times on the order of milliseconds, corresponding to frame rates of 100 Hz or higher.
Recent developments in detector technology have yielded sensors with improved spatial resolution, lower noise characteristics, and substantially higher frame rates [[cite:&hatsui15_x_ray_imagin_detec_synch_xfel_sourc]].
Historically, detector integration times for scanning and tomography experiments were in the range of 0.1 to 1 second.
This extended integration effectively filtered high-frequency vibrations in beam or sample position, resulting in apparently stable but larger beam.
With higher X-ray flux and reduced detector noise, integration times can now be shortened to approximately 1 millisecond, with frame rates exceeding 100 Hz.
This reduction in integration time has two major implications for positioning requirements.
Firstly, for a given spatial sampling ("pixel size"), faster integration necessitates proportionally higher scanning velocities.
Secondly, the shorter integration times make the measurements more susceptible to high-frequency vibrations.
Previously, longer integration effectively averaged out rapid positional fluctuations, resulting in an apparently larger but stable effective X-ray beam.
With millisecond-scale integration, however, vibrations up to the kilohertz range can significantly degrade data quality.
Therefore, not only must the sample position be stable against long-term drifts, but it must also be actively controlled to minimize vibrations, especially during dynamic fly-scan acquisitions.
** Existing Nano Positioning End-Stations
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**** Introduction :ignore:
To contextualize the system developed within this thesis, a brief overview of existing strategies and technologies for high-accuracy, high-dynamics end-stations is provided.
The aim is to identify the specific characteristics that distinguish the proposed system from current state-of-the-art implementations.
**** End-Station with Stacked Stages
Positioning systems can be broadly categorized based on their kinematic architecture, typically serial or parallel, as exemplified by the 3-Degree-of-Freedom (DoF) platforms in Figure ref:fig:introduction_kinematics.
Stacked stages, representing serial kinematics (Figure ref:fig:introduction_serial_kinematics), offer decoupled control for each DoF and generally provide larger ranges of motion.
However, positioning errors (e.g., guiding inaccuracies, thermal expansion) accumulate through the stack, compromising overall accuracy.
Serial kinematics (Figure ref:fig:introduction_serial_kinematics) utilizes stacked stages where each degree of freedom is controlled by a dedicated actuator.
This configuration offers great mobility, but positioning errors (e.g., guiding inaccuracies, thermal expansion) accumulate through the stack, compromising overall accuracy.
Similarly, the overall dynamic performance (stiffness, resonant frequencies) is limited by the softest component in the stack, often resulting in poor dynamic behavior when many stages are combined.
#+name: fig:introduction_kinematics
@ -1940,23 +1925,22 @@ Similarly, the overall dynamic performance (stiffness, resonant frequencies) is
#+attr_latex: :caption \subcaption{\label{fig:introduction_serial_kinematics} Serial Kinematics}
#+attr_latex: :options {0.49\textwidth}
#+begin_subfigure
#+attr_latex: :scale 1
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[[file:figs/introduction_serial_kinematics.png]]
#+end_subfigure
#+attr_latex: :caption \subcaption{\label{fig:introduction_parallel_kinematics} Parallel Kinematics}
#+attr_latex: :options {0.49\textwidth}
#+begin_subfigure
#+attr_latex: :scale 1
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[[file:figs/introduction_parallel_kinematics.png]]
#+end_subfigure
#+end_figure
Conversely, parallel kinematic architectures (Figure ref:fig:introduction_parallel_kinematics) involve the coordinated motion of multiple actuators to achieve the desired end-effector pose.
While theoretically capable of similar DoFs, practical implementations are often restricted to smaller workspaces.
The primary advantage lies in significantly higher structural stiffness and consequently superior dynamic performance.
Conversely, parallel kinematic architectures (Figure ref:fig:introduction_parallel_kinematics) involve the coordinated motion of multiple actuators to achieve the desired end-effector motion.
While theoretically offering the same controlled degrees of freedom as stacked stages, parallel systems generally provide limited stroke but significantly enhanced stiffness and superior dynamic performance.
Due to the requirement for extensive mobility in many synchrotron experiments, most end-stations are constructed using stacked stages.
Achieving acceptable stability and accuracy in such systems relies heavily on the inherent precision of individual components and environmental control.
Most end stations, particularly those requiring extensive mobility, employ stacked stages.
Their positioning performance consequently depends entirely on the accuracy of individual components.
Strategies include employing a limited number of high-performance stages, such as air-bearing spindles [[cite:&riekel10_progr_micro_nano_diffr_at]], and maintaining extremely stable thermal environments within the experimental hutch, often requiring extended stabilization times [[cite:&leake19_nanod_beaml_id01]].
Examples of such end-stations, including those at beamlines ID16B [[cite:&martinez-criado16_id16b]] and ID11 [[cite:&wright20_new_oppor_at_mater_scien]], are shown in Figure ref:fig:introduction_passive_stations.
However, when a large number of DoFs are required, the cumulative errors and limited dynamic stiffness of stacked configurations can make experiments with nano-focused beams extremely challenging or infeasible.
@ -1965,62 +1949,56 @@ However, when a large number of DoFs are required, the cumulative errors and lim
#+caption: Example of two nano end-stations without online metrology: (\subref{fig:introduction_endstation_id16b}) [[cite:&martinez-criado16_id16b]] and (\subref{fig:introduction_endstation_id11}) [[cite:&wright20_new_oppor_at_mater_scien]]
#+attr_latex: :options [htbp]
#+begin_figure
#+attr_latex: :caption \subcaption{\label{fig:introduction_endstation_id16b}ID16b}
#+attr_latex: :caption \subcaption{\label{fig:introduction_endstation_id16b}ID16b end-station}
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#+begin_subfigure
#+attr_latex: :scale 1
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[[file:figs/introduction_endstation_id16b.png]]
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#+attr_latex: :caption \subcaption{\label{fig:introduction_endstation_id11}ID11}
#+attr_latex: :caption \subcaption{\label{fig:introduction_endstation_id11}ID11 end-station}
#+attr_latex: :options {0.49\textwidth}
#+begin_subfigure
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[[file:figs/introduction_endstation_id11.png]]
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**** Online Metrology
The concept of employing external metrology systems to measure and potentially correct for positioning errors is well-established.
The concept of using an external metrology to measure and potentially correct for positioning errors is increasing used for nano-positioning end-stations.
Ideally, the relative position between the sample's point of interest and the X-ray beam focus would be measured directly.
In practice, direct measurement is often impossible; instead, the sample position is typically measured relative to a reference frame associated with the focusing optics or defining apertures, providing an indirect measurement.
In practice, direct measurement is often impossible; instead, the sample position is typically measured relative to a reference frame associated with the focusing optics, providing an indirect measurement.
This metrology data can be utilized in several ways: for post-processing correction of acquired data; for calibration routines to compensate for repeatable, systematic errors; or, most relevantly here, for real-time feedback control.
For applications demanding precise position control, such as maintaining a nanoparticle within a nano-beam during tomography, real-time feedback is essential.
This measured position can be utilized in several ways: for post-processing correction of acquired data; for calibration routines to compensate for repeatable errors; or, most relevantly here, for real-time feedback control.
Various sensor technologies have been employed, with capacitive sensors [[cite:&schroer17_ptynam;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&schropp20_ptynam]] and, increasingly, fiber-based interferometers [[cite:&nazaretski15_pushin_limit;&stankevic17_inter_charac_rotat_stages_x_ray_nanot;&holler17_omny_pin_versat_sampl_holder;&holler18_omny_tomog_nano_cryo_stage;&engblom18_nanop_resul;&schropp20_ptynam;&nazaretski22_new_kirkp_baez_based_scann;&kelly22_delta_robot_long_travel_nano;&xu23_high_nsls_ii;&geraldes23_sapot_carnaub_sirius_lnls]] being prominent choices.
Two examples illustrating the integration of online metrology are presented in Figure ref:fig:introduction_metrology_stations.
The system at NSLS X8C utilized capacitive sensors for rotation stage calibration and image alignment during tomography post-processing [[cite:&wang12_autom_marker_full_field_hard]].
The PtiNAMi microscope at DESY P06 employs interferometers directed at a spherical target below the sample for position monitoring during tomography, with plans for future feedback loop implementation [[cite:&schropp20_ptynam]].
The system at NSLS X8C (Figure ref:fig:introduction_stages_wang) utilized capacitive sensors for rotation stage calibration and image alignment during tomography post-processing [[cite:&wang12_autom_marker_full_field_hard]].
The PtiNAMi microscope at DESY P06 (Figure ref:fig:introduction_stages_schroer) employs interferometers directed at a spherical target below the sample for position monitoring during tomography, with plans for future feedback loop implementation [[cite:&schropp20_ptynam]].
#+name: fig:introduction_metrology_stations
#+caption: Two examples of end-station with integrated online metrology. (\subref{fig:introduction_stages_wang}) [[cite:&wang12_autom_marker_full_field_hard]] and (\subref{fig:introduction_stages_schroer}) [[cite:&schroer17_ptynam]]
#+attr_latex: :options [htbp]
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#+attr_latex: :caption \subcaption{\label{fig:introduction_stages_wang} Wang}
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[[file:figs/introduction_stages_wang.png]]
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#+attr_latex: :caption \subcaption{\label{fig:introduction_stages_schroer} Schroer}
#+attr_latex: :options {0.49\textwidth}
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[[file:figs/introduction_stages_schroer.png]]
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**** Active Control of Positioning Errors
For applications requiring active compensation of measured errors, particularly with nano-beams, feedback control loops are implemented.
Actuation is typically achieved using piezoelectric actuators [[cite:&nazaretski15_pushin_limit;&holler17_omny_pin_versat_sampl_holder;&holler18_omny_tomog_nano_cryo_stage;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&nazaretski22_new_kirkp_baez_based_scann]], 3-phase linear motors [[cite:&stankevic17_inter_charac_rotat_stages_x_ray_nanot;&engblom18_nanop_resul]], or voice coil actuators [[cite:&kelly22_delta_robot_long_travel_nano;&geraldes23_sapot_carnaub_sirius_lnls]].
In published studies, feedback bandwidth specifications are often omitted.
Historically, the feedback bandwidth reported for such systems has often been relatively low (around 1 Hz), primarily targeting the compensation of slow thermal drifts.
While often omitted, feedback bandwidth for such stages are relatively low (around 1 Hz), primarily targeting the compensation of slow thermal drifts.
More recently, higher bandwidths (up to 100 Hz) have been demonstrated, particularly with the use of voice coil actuators [[cite:&kelly22_delta_robot_long_travel_nano;&geraldes23_sapot_carnaub_sirius_lnls]].
Figure ref:fig:introduction_active_stations showcases two end-stations incorporating online metrology and active feedback.
The ID16A system at ESRF (Figure ref:fig:introduction_stages_villar) uses capacitive sensors and a piezoelectric hexapod to compensate for rotation stage errors and perform accurate scans [[cite:&villar18_nanop_esrf_id16a_nano_imagin_beaml]].
Figure ref:fig:introduction_active_stations showcases two end-stations incorporating online metrology and active feedback control.
The ID16A system at ESRF (Figure ref:fig:introduction_stages_villar) uses capacitive sensors and a piezoelectric hexapod to compensate for rotation stage errors and to perform accurate scans [[cite:&villar18_nanop_esrf_id16a_nano_imagin_beaml]].
Another example, shown in Figure ref:fig:introduction_stages_nazaretski, employs interferometers and piezoelectric stages to compensate for thermal drifts [[cite:&nazaretski15_pushin_limit;&nazaretski17_desig_perfor_x_ray_scann]].
A more comprehensive review of actively controlled end-stations is provided in Section [...].
@ -2028,50 +2006,45 @@ A more comprehensive review of actively controlled end-stations is provided in S
#+caption: Example of two end-stations with real-time position feedback based on an online metrology. (\subref{fig:introduction_stages_villar}) [[cite:&villar18_nanop_esrf_id16a_nano_imagin_beaml]]. (\subref{fig:introduction_stages_nazaretski}) [[cite:&nazaretski17_desig_perfor_x_ray_scann;&nazaretski15_pushin_limit]]
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#+begin_figure
#+attr_latex: :caption \subcaption{\label{fig:introduction_stages_villar} ID16a. =KB= is the focusing optics, =S= the sample, =C= the capacitive sensors and =LM= is the light microscope}
#+attr_latex: :options {0.49\textwidth}
#+attr_latex: :caption \subcaption{\label{fig:introduction_stages_villar} ID16a. KB is the focusing optics, S the sample, C the capacitive sensors and LM is the light microscope}
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#+begin_subfigure
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[[file:figs/introduction_stages_villar.jpg]]
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#+attr_latex: :caption \subcaption{\label{fig:introduction_stages_nazaretski} 1 and 2 are stage to position the focusing optics. 3 is the sample location, 4 the sample stage and 5 the interferometers}
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[[file:figs/introduction_stages_nazaretski.png]]
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#+end_figure
For tomography experiments, correcting spindle guiding errors is critical.
Correction stages are typically placed either below the spindle [[cite:&stankevic17_inter_charac_rotat_stages_x_ray_nanot;&holler17_omny_pin_versat_sampl_holder;&holler18_omny_tomog_nano_cryo_stage;&villar18_nanop_esrf_id16a_nano_imagin_beaml;&engblom18_nanop_resul;&nazaretski22_new_kirkp_baez_based_scann;&xu23_high_nsls_ii]] or above it [[cite:&wang12_autom_marker_full_field_hard;&schroer17_ptynam;&schropp20_ptynam;&geraldes23_sapot_carnaub_sirius_lnls]].
In most reported cases, only translational (XYZ) corrections are applied.
In most reported cases, only translation errors are actively corrected.
Payload capacities for these high-precision systems are usually limited, typically handling calibrated samples on the micron scale, although capacities up to 500g have been reported [[cite:&nazaretski22_new_kirkp_baez_based_scann;&kelly22_delta_robot_long_travel_nano]].
The system developed in this thesis aims for payload capabilities approximately 100 times heavier (up to 50 kg) than previous stations.
**** Long Stroke - Short Stroke architecture
The system developed in this thesis aims for payload capabilities approximately 100 times heavier (up to 50 kg) than previous stations with similar positioning requirements.
End-stations integrating online metrology for active nano-positioning often exhibit limited operational ranges, typically constrained to a few degrees of freedom with strokes around $100\,\mu m$.
Recently, voice coil actuators were used to increase the stroke up to $3\,\text{mm}$ [[cite:&kelly22_delta_robot_long_travel_nano;&geraldes23_sapot_carnaub_sirius_lnls]]
An alternative strategy involves a "long stroke-short stroke" architecture, illustrated conceptually in Figure ref:fig:introduction_two_stage_schematic.
In this configuration, a high-accuracy, high-bandwidth short-stroke stage is mounted on top of a less precise long-stroke stage.
The short-stroke stage actively compensates for errors based on metrology feedback, while the long-stroke stage provides the coarse, large-range motion.
This approach allows combining extended travel with high precision and good dynamic response, but is often implemented for only one or a few DoFs, as seen in Figures ref:fig:introduction_two_stage_control_example and ref:fig:introduction_two_stage_control_h_bridge.
#+name: fig:introduction_two_stage_schematic
#+caption: Typical Long Stroke - Short Stroke architecture. The long stroke stage is ...
[[file:figs/introduction_two_stage_schematic.png]]
The short-stroke stage actively compensates for errors based on metrology feedback, while the long-stroke stage performs the larger movements.
This approach allows combining extended travel with high precision and good dynamical response, but is often implemented for only one or a few DoFs, as seen in Figures ref:fig:introduction_two_stage_schematic and ref:fig:introduction_two_stage_control_h_bridge.
#+name: fig:introduction_two_stage_example
#+caption: (\subref{fig:introduction_two_stage_control_example}) [[cite:&shinno11_newly_devel_long_range_posit]], (\subref{fig:introduction_two_stage_control_h_bridge}) [[cite:&schmidt20_desig_high_perfor_mechat_third_revis_edition]]
#+caption: (\subref{fig:introduction_two_stage_schematic}), (\subref{fig:introduction_two_stage_control_h_bridge}) [[cite:&schmidt20_desig_high_perfor_mechat_third_revis_edition]] $y_1$, $y_2$ and $x$ are 3-phase linear motors. Short stroke actuators are voice coils.
#+attr_latex: :options [htbp]
#+begin_figure
#+attr_latex: :caption \subcaption{\label{fig:introduction_two_stage_control_example} Two stage control with classical stage and voice coil}
#+attr_latex: :options {0.59\textwidth}
#+attr_latex: :caption \subcaption{\label{fig:introduction_two_stage_schematic} Typical Long Stroke - Short Stroke control architecture}
#+attr_latex: :options {0.64\textwidth}
#+begin_subfigure
#+attr_latex: :width 0.95\linewidth
[[file:figs/introduction_two_stage_control_example.png]]
[[file:figs/introduction_two_stage_schematic.png]]
#+end_subfigure
#+attr_latex: :caption \subcaption{\label{fig:introduction_two_stage_control_h_bridge} H-bridge. $y_1$, $y_2$ and $x$ are 3-phase linear motors. Short stroke actuators are voice coils.}
#+attr_latex: :options {0.39\textwidth}
#+attr_latex: :caption \subcaption{\label{fig:introduction_two_stage_control_h_bridge} H-bridge}
#+attr_latex: :options {0.32\textwidth}
#+begin_subfigure
#+attr_latex: :width 0.95\linewidth
[[file:figs/introduction_two_stage_control_h_bridge.png]]

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% Created 2025-04-17 Thu 19:01
% Created 2025-04-17 Thu 21:14
% Intended LaTeX compiler: pdflatex
\documentclass[a4paper, 10pt, DIV=12, parskip=full, bibliography=totoc]{scrreprt}
@ -25,13 +25,11 @@
\clearpage
\chapter{Context of this thesis}
\section*{Synchrotron Radiation Facilities}
\subsubsection*{Accelerating electrons to produce intense X-ray}
Synchrotron radiation facilities function as particle accelerator light sources, where electrons are accelerated to near the speed of light.
Synchrotron radiation facilities, are particle accelerators where electrons are accelerated to near the speed of light.
As these electrons traverse magnetic fields, typically generated by insertion devices or bending magnets, they produce exceptionally bright light known as synchrotron light.
This intense electromagnetic radiation, particularly in the X-ray spectrum, is subsequently utilized for the detailed study of matter.
Approximately 70 synchrotron light sources are operational worldwide, with prominent facilities illustrated in Figure \ref{fig:introduction_synchrotrons}.
The global distribution underscores the significant utility of synchrotron light for the scientific community.
Approximately 70 synchrotron light sources are operational worldwide, some of which are indicated in Figure \ref{fig:introduction_synchrotrons}.
This global distribution of such facilities underscores the significant utility of synchrotron light for the scientific community.
\begin{figure}[htbp]
\centering
@ -40,12 +38,13 @@ The global distribution underscores the significant utility of synchrotron light
\end{figure}
These facilities fundamentally comprise two main parts: the accelerator complex, where electron acceleration and light generation occur, and the beamlines, where the intense X-ray beams are conditioned and directed for experimental use.
\subsubsection*{The European Synchrotron Radiation Facility}
The European Synchrotron Radiation Facility (ESRF), shown in Figure \ref{fig:introduction_esrf_picture}, is a joint research institution supported by 19 member countries.
Since commencing user operations in 1994, the ESRF was recognized as the world's first third-generation synchrotron source.
Its accelerator complex, schematically depicted in Figure \ref{fig:introduction_esrf_schematic}, includes a linear accelerator, a booster synchrotron for accelerating electrons close to light speed, and an 844-meter circumference storage ring where electrons are maintained for light production.
Radiating from the storage ring are over 40 beamlines, each equipped with specialized instrumentation catering to a diverse range of scientific disciplines, including structural biology and materials science under various conditions.
The ESRF commenced user operations in 1994 as the world's first third-generation synchrotron.
Its accelerator complex, schematically depicted in Figure \ref{fig:introduction_esrf_schematic}, includes a linear accelerator where electrons are initially generated and accelerated, a booster synchrotron to further accelerate the electrons, and an 844-meter circumference storage ring where electrons are maintained in a stable orbit.
Synchrotron light are emitted in more than 40 beamlines surrounding the storage ring, each having specialized experimental stations.
These beamlines host diverse instrumentation that enables a wide spectrum of scientific investigations, including structural biology, materials science, and study of matter under extreme conditions.
\begin{figure}[htbp]
\begin{subfigure}{0.49\textwidth}
@ -62,28 +61,25 @@ Radiating from the storage ring are over 40 beamlines, each equipped with specia
\end{subfigure}
\caption{\label{fig:instroduction_esrf}Schematic (\subref{fig:introduction_esrf_schematic}) and picture (\subref{fig:introduction_esrf_picture}) of the European Synchrotron Radiation Facility, situated in Grenoble, France}
\end{figure}
\subsubsection*{3rd and 4th Generation Light Sources}
In August 2020, following an extensive 20-month upgrade period, the ESRF inaugurated its Extremely Brilliant Source (EBS), establishing it as the world's premier fourth-generation synchrotron \cite{raimondi21_commis_hybrid_multib_achrom_lattic}.
This advancement was predicated on a novel storage ring concept engineered to significantly enhance the brilliance and coherence of the emitted X-ray beams.
Brilliance, a key figure of merit for synchrotron sources, experienced an approximate 100-fold increase with the implementation of EBS, as shown in the historical evolution depicted in Figure \ref{fig:introduction_moore_law_brillance}.
While this enhanced beam quality presents unprecedented scientific opportunities, it concurrently introduces considerable engineering challenges, particularly concerning sample positioning.
This upgrade implemented a novel storage ring concept that substantially increases the brilliance and coherence of the X-ray beams.
Brilliance, a measure of the photon flux, is a key figure of merit for synchrotron facilities.
It experienced an approximate 100-fold increase with the implementation of EBS, as shown in the historical evolution depicted in Figure \ref{fig:introduction_moore_law_brillance}.
While this enhanced beam quality presents unprecedented scientific opportunities, it concurrently introduces considerable engineering challenges, particularly regarding experimental instrumentation and sample positioning systems.
\begin{figure}[htbp]
\centering
\includegraphics[scale=1,scale=0.9]{figs/introduction_moore_law_brillance.png}
\caption{\label{fig:introduction_moore_law_brillance}Evolution of the peak brilliance (expressed in \(\text{photons}/s/mm^2/mrad^2/0.1\%BW\)) of synchrotron radiation facilities. Note the vertical logarithmic scale.}
\end{figure}
\section*{The ID31 ESRF Beamline}
\subsubsection*{Beamline Layout}
Each beamline begins with a ``white'' beam generated by the insertion device.
This beam carries substantial power, typically exceeding kilowatts, and is generally unsuitable for direct application to samples.
The term ``beamline layout'' encompasses the sequence of optical components situated between the X-ray source (an insertion device in this context) and the sample.
Initially, a ``white'' beam, characterized by high power (often exceeding several kilowatts) and a broad energy spectrum, is generated by the source.
This ``white'' beam is generally unsuitable for direct sample irradiation and is therefore processed through a series of optical elements housed within shielded enclosures known as Optical Hutches (OH), illustrated for ID31 in Figure \ref{fig:introduction_id31_oh}.
These elements, including absorbers, mirrors, slits, and monochromators, are employed to filter, shape, and select the desired energy range of the X-ray beam.
Following the optical hutches, the conditioned beam enters the Experimental Hutch (Figure \ref{fig:introduction_id31_cad}), where, for experiments pertinent to this work, focusing optics are utilized.
The sample is mounted on a positioning stage, referred to as the ``end-station,'' which facilitates precise alignment relative to the X-ray beam.
Detectors are used to capture the X-rays transmitted through or scattered by the sample.
Throughout this thesis, the standard ESRF coordinate system is adopted, wherein the X-axis aligns with the beam direction, Y is transverse horizontal, and Z is vertical upwards against gravity.
Instead, the beam passes through a series of optical elements—including absorbers, mirrors, slits, and monochromators—that filter and shape the X-rays to the desired specifications.
These components are housed in multiple Optical Hutches, as depicted in Figure \ref{fig:introduction_id31_oh}.
\begin{figure}[htbp]
\begin{subfigure}{\textwidth}
@ -102,14 +98,16 @@ Throughout this thesis, the standard ESRF coordinate system is adopted, wherein
\end{subfigure}
\caption{\label{fig:introduction_id31_oh}Schematic of the two ID31 optical hutches: OH1 (\subref{fig:introduction_id31_oh1}) and OH2 (\subref{fig:introduction_id31_oh2}). Distance from the source (the insertion device) is indicated in meters.}
\end{figure}
\subsubsection*{Positioning End Station: The Micro-Station}
Following the optical hutches, the conditioned beam enters the Experimental Hutch (Figure \ref{fig:introduction_id31_cad}), where, for experiments pertinent to this work, focusing optics are utilized.
The sample is mounted on a positioning stage, referred to as the ``end-station'', that enables precise alignment relative to the X-ray beam.
Detectors are used to capture the X-rays transmitted through or scattered by the sample.
Throughout this thesis, the standard ESRF coordinate system is adopted, wherein the X-axis aligns with the beam direction, Y is transverse horizontal, and Z is vertical upwards against gravity.
The specific end-station employed on the ID31 beamline is designated the ``micro-station''.
As depicted in Figure \ref{fig:introduction_micro_station_dof}, it comprises a stack of positioning stages: a translation stage (blue), a tilt stage (red), a spindle for continuous rotation (yellow), and a micro-hexapod (purple).
The sample itself (cyan), potentially housed within complex sample environments (e.g., for high pressure or varying temperatures) and weighing up to 50kg, is mounted on top of this assembly.
Each stage serves distinct positioning functions; for example, the micro-hexapod enables fine static adjustments, while the Ty translation and Rz rotation stages are utilized for specific scan types.
The design objectives prioritized maximum stiffness and minimal positioning errors across its operational stroke.
The main components within the experimental hutch—focusing optics, sample stage, sample, and detector—are affixed to a common granite base for enhanced stability, as shown in Figure \ref{fig:introduction_id31_cad}.
As depicted in Figure \ref{fig:introduction_micro_station_dof}, it comprises a stack of positioning stages: a translation stage (in blue), a tilt stage (in red), a spindle for continuous rotation (in yellow), and a micro-hexapod (in purple).
The sample itself (cyan), potentially housed within complex sample environments (e.g., for high pressure or extreme temperatures), is mounted on top of this assembly.
Each stage serves distinct positioning functions; for example, the micro-hexapod enables fine static adjustments, while the \(T_y\) translation and \(R_z\) rotation stages are utilized for specific scanning applications.
\begin{figure}[htbp]
\begin{subfigure}{0.52\textwidth}
@ -126,21 +124,19 @@ The main components within the experimental hutch—focusing optics, sample stag
\end{subfigure}
\caption{\label{fig:introduction_micro_station}CAD view of the ID31 Experimal Hutch (\subref{fig:introduction_id31_cad}). There are typically four main elements: the focusing optics in yellow, the sample stage in green, the sample itself in purple and the detector in blue. All these elements are fixed to the same granite. CAD view of the The micro-station with the associated degrees of freedom (\subref{fig:introduction_micro_station_dof}).}
\end{figure}
\subsubsection*{Example of Scientific experiments performed on ID31}
The high mobility afforded by the multi-stage configuration of the micro-station enables diverse imaging techniques.
The ``stacked-stages'' configuration of the micro-station provides high mobility, enabling diverse scientific experiments and imaging techniques.
Two illustrative examples are provided.
Firstly, tomography experiments are conducted as illustrated schematically in Figure \ref{fig:introduction_tomography_schematic}.
In this technique, the sample is placed in the X-ray beam path, and its orientation is controlled via a rotation stage.
Projection images are acquired by the detector at numerous discrete angular positions.
Provided the point of interest within the sample remains accurately centered on the beam throughout the rotation, a three-dimensional reconstruction, such as the one presented in Figure \ref{fig:introduction_tomography_results}, can be generated \cite{schoeppler17_shapin_highl_regul_glass_archit}.
Tomography experiments, schematically represented in Figure \ref{fig:introduction_tomography_schematic}, involve placing a sample in the X-ray beam path while controlling its vertical rotation angle using a dedicated stage.
Detector images are captured at numerous rotation angles, allowing the reconstruction of three-dimensional sample structure (Figure \ref{fig:introduction_tomography_results}) \cite{schoeppler17_shapin_highl_regul_glass_archit}.
This reconstruction depends critically on maintaining the sample's point of interest within the beam throughout the rotation process.
Secondly, mapping or scanning experiments are performed, often involving focused X-ray beams, as depicted in Figure \ref{fig:introduction_scanning_schematic}.
The sample is translated, typically in the plane perpendicular to the beam (Y and Z directions), while data is collected at each position.
Mapping or scanning experiments, depicted in Figure \ref{fig:introduction_scanning_schematic}, typically utilize focusing optics to have a small beam size at the sample's location.
The sample is then translated perpendicular to the beam (along Y and Z axes), while data is collected at each position.
An example \cite{sanchez-cano17_synch_x_ray_fluor_nanop} of a resulting two-dimensional map, acquired with 20nm step increments, is shown in Figure \ref{fig:introduction_scanning_results}.
The fidelity and resolution of such images are intrinsically linked to the focused beam size and the precision with which the sample position relative to the beam can be maintained.
Positional instabilities, such as vibrations and thermal drifts, inevitably lead to blurring and distortion in the acquired data.
The fidelity and resolution of such images are intrinsically linked to the focused beam size and the positioning precision of the sample relative to the focused beam.
Positional instabilities, such as vibrations and thermal drifts, inevitably lead to blurring and distortion in the obtained image.
Other advanced imaging modalities practiced on ID31 include reflectivity, diffraction tomography, and small/wide-angle X-ray scattering (SAXS/WAXS).
\begin{figure}[htbp]
@ -175,8 +171,6 @@ Other advanced imaging modalities practiced on ID31 include reflectivity, diffra
\caption{\label{fig:introduction_scanning}Exemple of a scanning experiment. The sample is scanned in the Y-Z plane (\subref{fig:introduction_scanning_schematic}). Example of one 2D image obtained after scanning with a step size of 20nm (\subref{fig:introduction_scanning_results}).}
\end{figure}
\section*{Need of Accurate Positioning End-Stations with High Dynamics}
\subsubsection*{A push towards brighter and smaller beams}
Continuous advancements in both synchrotron source technology and X-ray optics have led to the availability of smaller, more intense, and more stable X-ray beams.
The ESRF-EBS upgrade, for instance, resulted in a significantly reduced source size, particularly in the horizontal dimension, coupled with increased brilliance, as illustrated in Figure \ref{fig:introduction_beam_3rd_4th_gen}.
@ -206,12 +200,11 @@ Presently, focused beam dimensions in the range of 10 to 20 nm (Full Width at Ha
\includegraphics[scale=1,scale=0.9]{figs/introduction_moore_law_focus.png}
\caption{\label{fig:introduction_moore_law_focus}Evolution of the measured spot size for different hard x-ray focusing elements. CRL, KB, FZP, MLL. Adapated from~\cite{barrett24_x_optic_accel_based_light_sourc}}
\end{figure}
\subsubsection*{New Dynamical Positioning Needs}
The increased brilliance and flux density associated with modern synchrotron sources exacerbate the issue of radiation damage, particularly for sensitive samples and at high-energy beamlines like ID31.
The increased brilliance introduces challenges related to radiation damage, particularly at high-energy beamlines like ID31.
Consequently, prolonged exposure of a single sample area to the focused beam must be avoided.
Traditionally, experiments were conducted in a ``step-scan'' mode, illustrated in Figure \ref{fig:introduction_scan_step}.
In this mode, the sample is moved to the desired position, the detector acquisition is initiated, and a beam shutter is opened for a brief, controlled duration to limit dose before closing; this cycle is repeated for each measurement point.
In this mode, the sample is moved to the desired position, the detector acquisition is initiated, and a beam shutter is opened for a brief, controlled duration to limit radiation damage before closing; this cycle is repeated for each measurement point.
While effective for mitigating radiation damage, this sequential process can be time-consuming, especially for high-resolution maps requiring numerous points.
\begin{figure}[htbp]
@ -232,48 +225,47 @@ While effective for mitigating radiation damage, this sequential process can be
An alternative, more efficient approach is the ``fly-scan'' or ``continuous-scan'' methodology \cite{xu23_high_nsls_ii}, depicted in Figure \ref{fig:introduction_scan_fly}.
Here, the sample is moved continuously while the detector is triggered to acquire data ``on the fly'' at predefined positions or time intervals.
This technique significantly accelerates data acquisition, enabling better utilization of valuable beamtime and potentially finer spatial sampling \cite{huang15_fly_scan_ptych}.
This technique significantly accelerates data acquisition, enabling better utilization of valuable beamtime while potentially enabling finer spatial resolution \cite{huang15_fly_scan_ptych}.
Furthermore, recent developments in detector technology have yielded sensors with improved spatial resolution, lower noise characteristics, and substantially higher frame rates \cite{hatsui15_x_ray_imagin_detec_synch_xfel_sourc}.
Whereas typical integration times for scanning or tomography experiments were previously in the range of 0.1 to 1 second, modern detectors permit integration times on the order of milliseconds, corresponding to frame rates of 100 Hz or higher.
Recent developments in detector technology have yielded sensors with improved spatial resolution, lower noise characteristics, and substantially higher frame rates \cite{hatsui15_x_ray_imagin_detec_synch_xfel_sourc}.
Historically, detector integration times for scanning and tomography experiments were in the range of 0.1 to 1 second.
This extended integration effectively filtered high-frequency vibrations in beam or sample position, resulting in apparently stable but larger beam.
With higher X-ray flux and reduced detector noise, integration times can now be shortened to approximately 1 millisecond, with frame rates exceeding 100 Hz.
This reduction in integration time has two major implications for positioning requirements.
Firstly, for a given spatial sampling (``pixel size''), faster integration necessitates proportionally higher scanning velocities.
Secondly, the shorter integration times make the measurements more susceptible to high-frequency vibrations.
Previously, longer integration effectively averaged out rapid positional fluctuations, resulting in an apparently larger but stable effective X-ray beam.
With millisecond-scale integration, however, vibrations up to the kilohertz range can significantly degrade data quality.
Therefore, not only must the sample position be stable against long-term drifts, but it must also be actively controlled to minimize vibrations, especially during dynamic fly-scan acquisitions.
\section*{Existing Nano Positioning End-Stations}
To contextualize the system developed within this thesis, a brief overview of existing strategies and technologies for high-accuracy, high-dynamics end-stations is provided.
The aim is to identify the specific characteristics that distinguish the proposed system from current state-of-the-art implementations.
\subsubsection*{End-Station with Stacked Stages}
Positioning systems can be broadly categorized based on their kinematic architecture, typically serial or parallel, as exemplified by the 3-Degree-of-Freedom (DoF) platforms in Figure \ref{fig:introduction_kinematics}.
Stacked stages, representing serial kinematics (Figure \ref{fig:introduction_serial_kinematics}), offer decoupled control for each DoF and generally provide larger ranges of motion.
However, positioning errors (e.g., guiding inaccuracies, thermal expansion) accumulate through the stack, compromising overall accuracy.
Serial kinematics (Figure \ref{fig:introduction_serial_kinematics}) utilizes stacked stages where each degree of freedom is controlled by a dedicated actuator.
This configuration offers great mobility, but positioning errors (e.g., guiding inaccuracies, thermal expansion) accumulate through the stack, compromising overall accuracy.
Similarly, the overall dynamic performance (stiffness, resonant frequencies) is limited by the softest component in the stack, often resulting in poor dynamic behavior when many stages are combined.
\begin{figure}[htbp]
\begin{subfigure}{0.49\textwidth}
\begin{center}
\includegraphics[scale=1,scale=1]{figs/introduction_serial_kinematics.png}
\includegraphics[scale=1,scale=0.9]{figs/introduction_serial_kinematics.png}
\end{center}
\subcaption{\label{fig:introduction_serial_kinematics} Serial Kinematics}
\end{subfigure}
\begin{subfigure}{0.49\textwidth}
\begin{center}
\includegraphics[scale=1,scale=1]{figs/introduction_parallel_kinematics.png}
\includegraphics[scale=1,scale=0.9]{figs/introduction_parallel_kinematics.png}
\end{center}
\subcaption{\label{fig:introduction_parallel_kinematics} Parallel Kinematics}
\end{subfigure}
\caption{\label{fig:introduction_kinematics}Two positioning platforms with \(D_x/D_y/R_z\) degrees of freedom. One is using serial kinematics (\subref{fig:introduction_serial_kinematics}), while the other uses parallel kinematics (\subref{fig:introduction_parallel_kinematics})}
\end{figure}
Conversely, parallel kinematic architectures (Figure \ref{fig:introduction_parallel_kinematics}) involve the coordinated motion of multiple actuators to achieve the desired end-effector pose.
While theoretically capable of similar DoFs, practical implementations are often restricted to smaller workspaces.
The primary advantage lies in significantly higher structural stiffness and consequently superior dynamic performance.
Conversely, parallel kinematic architectures (Figure \ref{fig:introduction_parallel_kinematics}) involve the coordinated motion of multiple actuators to achieve the desired end-effector motion.
While theoretically offering the same controlled degrees of freedom as stacked stages, parallel systems generally provide limited stroke but significantly enhanced stiffness and superior dynamic performance.
Due to the requirement for extensive mobility in many synchrotron experiments, most end-stations are constructed using stacked stages.
Achieving acceptable stability and accuracy in such systems relies heavily on the inherent precision of individual components and environmental control.
Most end stations, particularly those requiring extensive mobility, employ stacked stages.
Their positioning performance consequently depends entirely on the accuracy of individual components.
Strategies include employing a limited number of high-performance stages, such as air-bearing spindles \cite{riekel10_progr_micro_nano_diffr_at}, and maintaining extremely stable thermal environments within the experimental hutch, often requiring extended stabilization times \cite{leake19_nanod_beaml_id01}.
Examples of such end-stations, including those at beamlines ID16B \cite{martinez-criado16_id16b} and ID11 \cite{wright20_new_oppor_at_mater_scien}, are shown in Figure \ref{fig:introduction_passive_stations}.
However, when a large number of DoFs are required, the cumulative errors and limited dynamic stiffness of stacked configurations can make experiments with nano-focused beams extremely challenging or infeasible.
@ -281,70 +273,66 @@ However, when a large number of DoFs are required, the cumulative errors and lim
\begin{figure}[htbp]
\begin{subfigure}{0.49\textwidth}
\begin{center}
\includegraphics[scale=1,scale=1]{figs/introduction_endstation_id16b.png}
\includegraphics[scale=1,scale=0.9]{figs/introduction_endstation_id16b.png}
\end{center}
\subcaption{\label{fig:introduction_endstation_id16b}ID16b}
\subcaption{\label{fig:introduction_endstation_id16b}ID16b end-station}
\end{subfigure}
\begin{subfigure}{0.49\textwidth}
\begin{center}
\includegraphics[scale=1,scale=1]{figs/introduction_endstation_id11.png}
\includegraphics[scale=1,scale=0.9]{figs/introduction_endstation_id11.png}
\end{center}
\subcaption{\label{fig:introduction_endstation_id11}ID11}
\subcaption{\label{fig:introduction_endstation_id11}ID11 end-station}
\end{subfigure}
\caption{\label{fig:introduction_passive_stations}Example of two nano end-stations without online metrology: (\subref{fig:introduction_endstation_id16b}) \cite{martinez-criado16_id16b} and (\subref{fig:introduction_endstation_id11}) \cite{wright20_new_oppor_at_mater_scien}}
\end{figure}
\subsubsection*{Online Metrology}
The concept of employing external metrology systems to measure and potentially correct for positioning errors is well-established.
The concept of using an external metrology to measure and potentially correct for positioning errors is increasing used for nano-positioning end-stations.
Ideally, the relative position between the sample's point of interest and the X-ray beam focus would be measured directly.
In practice, direct measurement is often impossible; instead, the sample position is typically measured relative to a reference frame associated with the focusing optics or defining apertures, providing an indirect measurement.
In practice, direct measurement is often impossible; instead, the sample position is typically measured relative to a reference frame associated with the focusing optics, providing an indirect measurement.
This metrology data can be utilized in several ways: for post-processing correction of acquired data; for calibration routines to compensate for repeatable, systematic errors; or, most relevantly here, for real-time feedback control.
For applications demanding precise position control, such as maintaining a nanoparticle within a nano-beam during tomography, real-time feedback is essential.
This measured position can be utilized in several ways: for post-processing correction of acquired data; for calibration routines to compensate for repeatable errors; or, most relevantly here, for real-time feedback control.
Various sensor technologies have been employed, with capacitive sensors \cite{schroer17_ptynam,villar18_nanop_esrf_id16a_nano_imagin_beaml,schropp20_ptynam} and, increasingly, fiber-based interferometers \cite{nazaretski15_pushin_limit,stankevic17_inter_charac_rotat_stages_x_ray_nanot,holler17_omny_pin_versat_sampl_holder,holler18_omny_tomog_nano_cryo_stage,engblom18_nanop_resul,schropp20_ptynam,nazaretski22_new_kirkp_baez_based_scann,kelly22_delta_robot_long_travel_nano,xu23_high_nsls_ii,geraldes23_sapot_carnaub_sirius_lnls} being prominent choices.
Two examples illustrating the integration of online metrology are presented in Figure \ref{fig:introduction_metrology_stations}.
The system at NSLS X8C utilized capacitive sensors for rotation stage calibration and image alignment during tomography post-processing \cite{wang12_autom_marker_full_field_hard}.
The PtiNAMi microscope at DESY P06 employs interferometers directed at a spherical target below the sample for position monitoring during tomography, with plans for future feedback loop implementation \cite{schropp20_ptynam}.
The system at NSLS X8C (Figure \ref{fig:introduction_stages_wang}) utilized capacitive sensors for rotation stage calibration and image alignment during tomography post-processing \cite{wang12_autom_marker_full_field_hard}.
The PtiNAMi microscope at DESY P06 (Figure \ref{fig:introduction_stages_schroer}) employs interferometers directed at a spherical target below the sample for position monitoring during tomography, with plans for future feedback loop implementation \cite{schropp20_ptynam}.
\begin{figure}[htbp]
\begin{subfigure}{0.49\textwidth}
\begin{subfigure}{0.48\textwidth}
\begin{center}
\includegraphics[scale=1,scale=1]{figs/introduction_stages_wang.png}
\includegraphics[scale=1,scale=0.9]{figs/introduction_stages_wang.png}
\end{center}
\subcaption{\label{fig:introduction_stages_wang} Wang}
\end{subfigure}
\begin{subfigure}{0.49\textwidth}
\begin{subfigure}{0.48\textwidth}
\begin{center}
\includegraphics[scale=1,scale=1]{figs/introduction_stages_schroer.png}
\includegraphics[scale=1,scale=0.9]{figs/introduction_stages_schroer.png}
\end{center}
\subcaption{\label{fig:introduction_stages_schroer} Schroer}
\end{subfigure}
\caption{\label{fig:introduction_metrology_stations}Two examples of end-station with integrated online metrology. (\subref{fig:introduction_stages_wang}) \cite{wang12_autom_marker_full_field_hard} and (\subref{fig:introduction_stages_schroer}) \cite{schroer17_ptynam}}
\end{figure}
\subsubsection*{Active Control of Positioning Errors}
For applications requiring active compensation of measured errors, particularly with nano-beams, feedback control loops are implemented.
Actuation is typically achieved using piezoelectric actuators \cite{nazaretski15_pushin_limit,holler17_omny_pin_versat_sampl_holder,holler18_omny_tomog_nano_cryo_stage,villar18_nanop_esrf_id16a_nano_imagin_beaml,nazaretski22_new_kirkp_baez_based_scann}, 3-phase linear motors \cite{stankevic17_inter_charac_rotat_stages_x_ray_nanot,engblom18_nanop_resul}, or voice coil actuators \cite{kelly22_delta_robot_long_travel_nano,geraldes23_sapot_carnaub_sirius_lnls}.
In published studies, feedback bandwidth specifications are often omitted.
Historically, the feedback bandwidth reported for such systems has often been relatively low (around 1 Hz), primarily targeting the compensation of slow thermal drifts.
While often omitted, feedback bandwidth for such stages are relatively low (around 1 Hz), primarily targeting the compensation of slow thermal drifts.
More recently, higher bandwidths (up to 100 Hz) have been demonstrated, particularly with the use of voice coil actuators \cite{kelly22_delta_robot_long_travel_nano,geraldes23_sapot_carnaub_sirius_lnls}.
Figure \ref{fig:introduction_active_stations} showcases two end-stations incorporating online metrology and active feedback.
The ID16A system at ESRF (Figure \ref{fig:introduction_stages_villar}) uses capacitive sensors and a piezoelectric hexapod to compensate for rotation stage errors and perform accurate scans \cite{villar18_nanop_esrf_id16a_nano_imagin_beaml}.
Figure \ref{fig:introduction_active_stations} showcases two end-stations incorporating online metrology and active feedback control.
The ID16A system at ESRF (Figure \ref{fig:introduction_stages_villar}) uses capacitive sensors and a piezoelectric hexapod to compensate for rotation stage errors and to perform accurate scans \cite{villar18_nanop_esrf_id16a_nano_imagin_beaml}.
Another example, shown in Figure \ref{fig:introduction_stages_nazaretski}, employs interferometers and piezoelectric stages to compensate for thermal drifts \cite{nazaretski15_pushin_limit,nazaretski17_desig_perfor_x_ray_scann}.
A more comprehensive review of actively controlled end-stations is provided in Section [\ldots{}].
\begin{figure}[htbp]
\begin{subfigure}{0.49\textwidth}
\begin{subfigure}{0.48\textwidth}
\begin{center}
\includegraphics[scale=1,width=0.95\linewidth]{figs/introduction_stages_villar.jpg}
\end{center}
\subcaption{\label{fig:introduction_stages_villar} ID16a. =KB= is the focusing optics, =S= the sample, =C= the capacitive sensors and =LM= is the light microscope}
\subcaption{\label{fig:introduction_stages_villar} ID16a. KB is the focusing optics, S the sample, C the capacitive sensors and LM is the light microscope}
\end{subfigure}
\begin{subfigure}{0.49\textwidth}
\begin{subfigure}{0.48\textwidth}
\begin{center}
\includegraphics[scale=1,scale=1]{figs/introduction_stages_nazaretski.png}
\includegraphics[scale=1,scale=0.9]{figs/introduction_stages_nazaretski.png}
\end{center}
\subcaption{\label{fig:introduction_stages_nazaretski} 1 and 2 are stage to position the focusing optics. 3 is the sample location, 4 the sample stage and 5 the interferometers}
\end{subfigure}
@ -353,37 +341,31 @@ A more comprehensive review of actively controlled end-stations is provided in S
For tomography experiments, correcting spindle guiding errors is critical.
Correction stages are typically placed either below the spindle \cite{stankevic17_inter_charac_rotat_stages_x_ray_nanot,holler17_omny_pin_versat_sampl_holder,holler18_omny_tomog_nano_cryo_stage,villar18_nanop_esrf_id16a_nano_imagin_beaml,engblom18_nanop_resul,nazaretski22_new_kirkp_baez_based_scann,xu23_high_nsls_ii} or above it \cite{wang12_autom_marker_full_field_hard,schroer17_ptynam,schropp20_ptynam,geraldes23_sapot_carnaub_sirius_lnls}.
In most reported cases, only translational (XYZ) corrections are applied.
In most reported cases, only translation errors are actively corrected.
Payload capacities for these high-precision systems are usually limited, typically handling calibrated samples on the micron scale, although capacities up to 500g have been reported \cite{nazaretski22_new_kirkp_baez_based_scann,kelly22_delta_robot_long_travel_nano}.
The system developed in this thesis aims for payload capabilities approximately 100 times heavier (up to 50 kg) than previous stations.
\subsubsection*{Long Stroke - Short Stroke architecture}
The system developed in this thesis aims for payload capabilities approximately 100 times heavier (up to 50 kg) than previous stations with similar positioning requirements.
End-stations integrating online metrology for active nano-positioning often exhibit limited operational ranges, typically constrained to a few degrees of freedom with strokes around \(100\,\mu m\).
Recently, voice coil actuators were used to increase the stroke up to \(3\,\text{mm}\) \cite{kelly22_delta_robot_long_travel_nano,geraldes23_sapot_carnaub_sirius_lnls}
An alternative strategy involves a ``long stroke-short stroke'' architecture, illustrated conceptually in Figure \ref{fig:introduction_two_stage_schematic}.
In this configuration, a high-accuracy, high-bandwidth short-stroke stage is mounted on top of a less precise long-stroke stage.
The short-stroke stage actively compensates for errors based on metrology feedback, while the long-stroke stage provides the coarse, large-range motion.
This approach allows combining extended travel with high precision and good dynamic response, but is often implemented for only one or a few DoFs, as seen in Figures \ref{fig:introduction_two_stage_control_example} and \ref{fig:introduction_two_stage_control_h_bridge}.
The short-stroke stage actively compensates for errors based on metrology feedback, while the long-stroke stage performs the larger movements.
This approach allows combining extended travel with high precision and good dynamical response, but is often implemented for only one or a few DoFs, as seen in Figures \ref{fig:introduction_two_stage_schematic} and \ref{fig:introduction_two_stage_control_h_bridge}.
\begin{figure}[htbp]
\centering
\includegraphics[scale=1]{figs/introduction_two_stage_schematic.png}
\caption{\label{fig:introduction_two_stage_schematic}Typical Long Stroke - Short Stroke architecture. The long stroke stage is \ldots{}}
\end{figure}
\begin{figure}[htbp]
\begin{subfigure}{0.59\textwidth}
\begin{subfigure}{0.64\textwidth}
\begin{center}
\includegraphics[scale=1,width=0.95\linewidth]{figs/introduction_two_stage_control_example.png}
\includegraphics[scale=1,width=0.95\linewidth]{figs/introduction_two_stage_schematic.png}
\end{center}
\subcaption{\label{fig:introduction_two_stage_control_example} Two stage control with classical stage and voice coil}
\subcaption{\label{fig:introduction_two_stage_schematic} Typical Long Stroke - Short Stroke control architecture}
\end{subfigure}
\begin{subfigure}{0.39\textwidth}
\begin{subfigure}{0.32\textwidth}
\begin{center}
\includegraphics[scale=1,width=0.95\linewidth]{figs/introduction_two_stage_control_h_bridge.png}
\end{center}
\subcaption{\label{fig:introduction_two_stage_control_h_bridge} H-bridge. $y_1$, $y_2$ and $x$ are 3-phase linear motors. Short stroke actuators are voice coils.}
\subcaption{\label{fig:introduction_two_stage_control_h_bridge} H-bridge}
\end{subfigure}
\caption{\label{fig:introduction_two_stage_example}(\subref{fig:introduction_two_stage_control_example}) \cite{shinno11_newly_devel_long_range_posit}, (\subref{fig:introduction_two_stage_control_h_bridge}) \cite{schmidt20_desig_high_perfor_mechat_third_revis_edition}}
\caption{\label{fig:introduction_two_stage_example}(\subref{fig:introduction_two_stage_schematic}), (\subref{fig:introduction_two_stage_control_h_bridge}) \cite{schmidt20_desig_high_perfor_mechat_third_revis_edition} \(y_1\), \(y_2\) and \(x\) are 3-phase linear motors. Short stroke actuators are voice coils.}
\end{figure}
\chapter{Challenge definition}
The advent of fourth-generation light sources, coupled with advancements in focusing optics and detector technology, imposes stringent new requirements on sample positioning systems.
@ -447,13 +429,13 @@ A central challenge addressed in this thesis is the optimal mechatronic design o
\begin{center}
\includegraphics[scale=1,width=0.95\linewidth]{figs/introduction_stewart_du14.png}
\end{center}
\subcaption{\label{fig:introduction_stewart_du14}PZT based, for positioning purposes}
\subcaption{\label{fig:introduction_stewart_du14}Piezo based, for positioning purposes}
\end{subfigure}
\begin{subfigure}{0.49\textwidth}
\begin{center}
\includegraphics[scale=1,width=0.95\linewidth]{figs/introduction_stewart_hauge04.png}
\end{center}
\subcaption{\label{fig:introduction_stewart_hauge04}Voice coil based, Cubic architecture, for vibration isolation}
\subcaption{\label{fig:introduction_stewart_hauge04}Voice coil based, for vibration isolation}
\end{subfigure}
\caption{\label{fig:introduction_stewart_platform_piezo}Example of Stewart platforms. (\subref{fig:introduction_stewart_du14}) \cite{du14_piezo_actuat_high_precis_flexib} and (\subref{fig:introduction_stewart_hauge04}) \cite{hauge04_sensor_contr_space_based_six}}
\end{figure}