Mirror Holder Research Articles

Design and vibration test of first mirror mount assembly for ITER divertor VUV spectrometer

The divertor vacuum ultraviolet (VUV) spectrometer is a diagnostic system in the ITER tokamak, monitoring impurity content and behavior in the divertor region. The first mirror of the spectrometer, made of silicon carbide (SiC), is exposed to harsh environmental conditions, including high temperatures and significant inertial loads from electromagnetic disruption events. To ensure its reliable performance, we have designed and tested a robust mirror holder assembly. This paper introduces a novel design of the first mirror holder assembly for the ITER divertor VUV spectrometer and presents the results from comprehensive vibration tests conducted on a full-scale mock-up. The design features a double-holder structure with spring plate assemblies to accommodate thermal expansion and resist vibrational loads. The mock-up underwent a series of resonance search, sine dwell, and random vibration tests, replicating the expected loads during vertical displacement events in ITER. The mirror holder assembly and the dummy mirror successfully withstood the vibration tests without damage, validating the design for the ITER environment. The results demonstrate the robustness and reliability of the mirror holder assembly, ensuring the accurate and reliable operation of the divertor VUV spectrometer in ITER.

A Pointwise-Optimal Ensemble of Surrogate Models

AbstractThe ensemble of surrogate models is commonly used to replace computationally expensive simulations due to their superior prediction accuracy and robustness compared to individual models. This paper proposes a new pointwise ensemble of surrogate models, namely, a pointwise-optimal ensemble of surrogate models (POEMs). To address the limitations of the cross-validation (CV) error in evaluating the performance of regression surrogate models, this paper introduces the compensated cross-validation error, which is more reliable in selecting better individual surrogate models and improving the accuracy of surrogate model ensembles. To overcome the limitations of CV error in calculating pointwise weight factors, this paper designs and solves an optimization problem at training points to obtain corresponding pointwise weight factors. Additionally, this paper proposes two weight calculation methods to be applied in the interpolation and extrapolation regions, respectively, to reduce the instability of ensembles caused by extrapolation. Thirty test functions are employed to investigate the appropriate hyperparameters of POEM and the Friedman test is used to verify the rationality of the α value. The thirty test functions are also used to examine the performance of POEM and compare it with state-of-the-art ensemble surrogate models. Furthermore, POEM is applied to a large-aperture mirror holder optimization case to verify its superiority. The results demonstrate that POEM presents better accuracy and robustness than individual surrogates and other compared ensembles of surrogate models.

Automated Laser-Fiber Coupling Module for Optical-Resolution Photoacoustic Microscopy.

Photoacoustic imaging has emerged as a promising biomedical imaging technique that enables visualization of the optical absorption characteristics of biological tissues in vivo. Among the different photoacoustic imaging system configurations, optical-resolution photoacoustic microscopy stands out by providing high spatial resolution using a tightly focused laser beam, which is typically transmitted through optical fibers. Achieving high-quality images depends significantly on optical fluence, which is directly proportional to the signal-to-noise ratio. Hence, optimizing the laser-fiber coupling is critical. Conventional coupling systems require manual adjustment of the optical path to direct the laser beam into the fiber, which is a repetitive and time-consuming process. In this study, we propose an automated laser-fiber coupling module that optimizes laser delivery and minimizes the need for manual intervention. By incorporating a motor-mounted mirror holder and proportional derivative control, we successfully achieved efficient and robust laser delivery. The performance of the proposed system was evaluated using a leaf-skeleton phantom in vitro and a human finger in vivo, resulting in high-quality photoacoustic images. This innovation has the potential to significantly enhance the quality and efficiency of optical-resolution photoacoustic microscopy.

3D fabrication and characterization of polymer-imprinted optics for function-integrated, lightweight optomechanical systems

Nowadays, customized optomechanics for complex optical setups are increasingly manufactured additively using the polymer-based process of fused filament fabrication. In this article, a kinematic polymer mirror holder is demonstrated, in which the mirror is imprinted and thus fixed against misalignment. Furthermore, the necessary spring system and ball joint are manufactured in a single printing process. This mirror holder can then be embedded into an also printed cage system. Mirror mounts made of different polymers are examined and compared with each other. The mechanical stress induced into the imprinted optic is determined. Regarding the 3D-printed spring system, the angular alignment range as well as the load limits are defined. The reproducibility of the mirror's angular position and the long-term stability together with the influence of thermal cycling is determined. The results will be compared with a conventional, subtractive manufactured metallic optomechanic.

Catadioptric Optical System Design of 15-Magnitude Star Sensor with Large Entrance Pupil Diameter.

The optical system is one of the core components for star sensors, whose imaging quality directly influences the performance of star sensors for star detection, thereby determining the attitude control accuracy of spacecrafts. Here, we report a new type of optical system with a catadioptric structure and a large entrance pupil diameter for a 15-magnitude star sensor. It consists of an improved Cassegrain system (R-C system), an aperture correction spherical lens group and a field of view correction spherical lens group. By embedding the secondary mirror of the R-C system into the output surface of the negative spherical lens of the aperture correction spherical lens group, the blocking of incident light is eliminated from the secondary mirror holder. After the structure optimization, the catadioptric optical system (COS) had a spectral range of 450 nm–950 nm, an entrance pupil diameter of 250 mm, a half-diagonal field of view of 1.4° and a focal length of 390 mm. By using theoretical calculations and experimental measurements, it was verified that the COS, with the ability to correct astigmatism, lateral color and distortion, can fulfill the detection of 15-magnitude dark stars.

A mirror with a scale- AR scalo mirror

The dental mouth mirror is one of the most common diagnostic instrument used in dentistry. This tool is small, cylindrical in shape, consisting of a metal/plastic bar as a handle and a metal/plastic plate as a mirror holder. The head of a dental mouth mirror is usually round and the most commonly used sizes are number 4 and number 5. The ruler used in dentistry is present either in the form of stainless steel bar or plastic rings. The ruler is used to measure the intraoral lesions, spaces between teeth in mouth or stone model, length of the tooth or implant in X-Ray, measure the length of files, paper tips and gutta-percha, etc. Therefore, AR Scalo Mirror is a combination of two dental instruments (mouth mirror and scale) which are put together as one so that it saves the time and effort as well as makes the diagnostic procedure less technique sensitive.

Study on an effective one-dimensional ion-beam figuring method.

Ion-beam figuring (IBF) is a precise surface finishing technique used for the production of ultra-precision optical surfaces. In this study, we propose an effective one-dimensional IBF (1D-IBF) method approaching sub-nanometer root mean square (RMS) convergence for flat and spherical mirrors. Our process contains three key aspects. First, to minimize the misalignment of the coordinate systems between the metrology and the IBF hardware, a mirror holder is used to integrate both the sample mirror and the beam removal function (BRF) mirror. In this way, the coordinate relationship can be calculated using the measured BRF center. Second, we propose a novel constrained linear least-squares (CLLS) dwell time calculation algorithm combined with a coarse-to-fine scheme to ensure that the resultant nonnegative dwell time closely and smoothly duplicates the required removal amount. Third, considering the possible errors induced by the translation stage, we propose a dwell time slicing strategy to divide the dwell time into smaller time slices. Experiments using our approaches are performed on flat and spherical mirrors as demonstrations. Measurement results from the nano-accuracy surface profiler (NSP) show that the residual profile errors are reduced to sub-nanometer RMS for both types of mirrors while the surface roughness is not affected by the figuring process, demonstrating the effectiveness of the proposed 1D-IBF method for 1D high-precision optics fabrication.

Microfocusing at the PG1 beamline at FLASH.

The Kirkpatrick-Baez (KB) refocusing mirror system installed at the PG1 branch of the plane-grating monochromator beamline at the soft X-ray/XUV free-electron laser in Hamburg (FLASH) is designed to provide tight aberration-free focusing down to 4 µm × 6 µm full width at half-maximum (FWHM) on the sample. Such a focal spot size is mandatory to achieve ultimate resolution and to guarantee best performance of the vacuum-ultraviolet (VUV) off-axis parabolic double-monochromator Raman spectrometer permanently installed at the PG1 beamline as an experimental end-station. The vertical beam size on the sample of the Raman spectrometer, which operates without entrance slit, defines and limits the energy resolution of the instrument which has an unprecedented design value of 2 meV for photon energies below 70 eV and about 15 meV for higher energies up to 200 eV. In order to reach the designed focal spot size of 4 µm FWHM (vertically) and to hold the highest spectrometer resolution, special fully motorized in-vacuum manipulators for the KB mirror holders have been developed and the optics have been aligned employing wavefront-sensing techniques as well as ablative imprints analysis. Aberrations like astigmatism were minimized. In this article the design and layout of the KB mirror manipulators, the alignment procedure as well as microfocus optimization results are presented.

基于灵敏度分析方法的光学镜架动力学模型修正

基于灵敏度分析方法的光学镜架动力学模型修正

Alignment Principles for ITER In-Vessel Diagnostic Mirrors

Optical mirrors inside the ITER torus vacuum are required by many of the ITER port-based diagnostic systems. As an example, the core charge exchange recombination spectroscopy (core CXRS) concept is based on a mirror labyrinth of seven consecutive in-vessel (exposed to the torus vacuum) mirrors. For this system, alignment of up to three mirrors during assembly might be needed. Because of the unique and demanding environment in the ITER diagnostic port plugs, particularly in the first meter from the plasma, existing designs of adjustable mirror holders cannot be used without modification. The wish to allow the realignment of the mirrors during maintenance of the diagnostic systems, if possible by remote handling only, adds to the complexity. This paper discusses mirror alignment principles in the light of the requirements by ITER diagnostics. The core CXRS system is used as example throughout this paper. Loads and requirements for in-vessel diagnostic mirrors are looked into. Three basic groups of alignment principles are assessed for applicability in close proximity to the ITER plasma. The strength and weaknesses of the different alignment principles are discussed, and a conclusion about their general applicability in ITER is given.

First measurements of the multichannel far-infrared polarimeter on RFX-mod

A multichannel far-infrared (FIR) polarimeter has been recently installed and improved in RFX-mod to measure the Faraday rotation angle along vertical chords on a poloidal plasma section. Polarimetric data, associated with measurements of the electron density, permit the reconstruction of the poloidal magnetic field profile, Bθ. The entire diagnostic is described and its main sections outlined. Emphasis is placed on the work performed on the polarimeter to reduce the fluctuations affecting the old diagnostic signals and to increase the S/N ratio. In the recent installation of the polarimeter the optical line was more carefully designed and the mirror holders have been made in insulating material to avoid any interaction with the variable magnetic fields. Moreover all the optics have been fixed on an inertial granite platform. Examples of the first Faraday angle measurements performed on five chords are presented and discussed. The measured Faraday rotation angles are compared to a theoretically calculated value, based on the μ&p model, showing a good agreement between experimental and predicted data in the central region of the plasma. The comparison between experimental and predicted data is reported and discussed in the present work.

1Pb-41 Improvements of Controllability in Ultrasonic Linear Motors Using Longitudinal-Bending Multilayered Transducer with Independent Electrodes and Their Applications to Mirror Holders(Poster Session)

1Pb-41 Improvements of Controllability in Ultrasonic Linear Motors Using Longitudinal-Bending Multilayered Transducer with Independent Electrodes and Their Applications to Mirror Holders(Poster Session)

Selected Design Solutions for the Integration of the CXRS Diagnostic in to ITER Upper Port Plug No. 3

Diagnostic plug for the ITER core charge exchange recombination spectroscopy (core CXRS) is located in the upper port 3. It transfers the light emitted by interaction of plasma ions with the diagnostic neutral beam (DNB). Conceptual design study of the core CXRS port plug has indicated several challenging technical problems: (1) likely too short lifetime of the first mirror, (2) quite contradictory requirements to the first mirror holder, (3) harsh environmental conditions for the “shutter”, that is a movable element protecting the first mirror, (4) a task to combine a sufficient structural integrity and nuclear shielding capability of the plug with a wide enough optical path, (5) excessive electromagnetic loads caused by the halo current and applied at the plug as a whole. This paper describes possible design solutions for the listed technical problems.

Window Preparation for Sinus Lift Procedures: A Simplified Technique

A simplified technique for preparation of the window and elevation of the sinus membrane using conventional instruments is described for the practitioner to prepare the Schneiderian membrane without perforations in an easy and time efficient method. The clinician uses a combination of a mallet and a mirror holder to break the buccal aspect of the maxillary sinus border after a small osteotomy has been made. This is a complication-free procedure.

Development of Impurity Influx Monitor (Divertor) for ITER

The optical design of Impurity Influx Monitor (divertor) was carried out for new ITER design and ray-tracing analysis shows that the spatial resolution of ITER requirement (50 mm) will be achieved by these optical systems designed here. The mechanical design of front end optics also carried out based on the optical design and results of port integration. In the upper port, front end optics can be installed inside the pipe of inner diameter of φ300 mm. In the equatorial port, all the optical component are placed to avoid the interaction with other diagnostic equipments. Heat analysis was carried out for the optimization the cooling method of mirrors, mirror holders and mounting modules to reduce the temperature rise caused by the nuclear heating. It indicates that mirrors can be cooled by the thermal conduction using mirror holders made of a copper alloy and making many cooling channels on the mounting module. Finally, the effect of the thermal deformation to the optical properties is estimated by using the optical design code.

Automatic Adjustments of a Michelson Interferometer Using Genetic Algorithms.

This paper describes automatic adjustment of a michelson interferometer using genetic algorithms. The michelson interferometer consists of optical components (such as mirrors, lens, and prisms) that must be physically positioned with micron-meter precision to obtain optimal performance. Therefore, it is very difficult to use an interferometer outside for environmental measurement such as air pollution, because outside use causes mis-alignment of optical components.In order to overcome this problem, we propose automatic adjustment method using genetic algorithms that realize the optimal and quick alignment of optical components of interferometer. We also develop new compact mirror holder that allows portable and on-site use of interferometer. We confirmed the advantage of this system by the comparison with conventional adjustment algorithms. The proposed interferometer including the new compact mirror holders has been successfully adjusted by genetic algorithm in three minutes. The quick adjustment time indicates the possibility that the system can be used for on-site measurement.

Design of a 6 DOF HFM manipulator using an external spherical joint

A new type of 5 Degrees of Freedom (DOF) modular mirror manipulator with independent adjustability had been developed at the Pohang Accelerator Laboratory. The design of the mirror manipulator was extended to a 6 DOF mirror manipulator by adding yaw adjustability. It also became applicable to mirrors that are set up laterally by replacing its mirror holder with a new L-shaped mirror holder. The moment necessary for yaw adjustment was calculated and the independent adjustability of yaw rotation was examined.

Current status of the undulator beamline BL-2C at Photon Factory

The undulator beamline BL-2C was constructed for measurements of soft X-ray spectroscopy. It is equipped with a varied line-space plane grating monochromator. High energy-resolution, high photon-flux and tiny spot-size have contributed to research on electronic structure of gaseous samples, solid samples and surfaces. In order to carry out further sophisticated measurement, we have improved the beamline at the following three points. First, optical elements were re-aligned again with great care for higher energy-resolution. To demonstrate the energy-resolution, we measured absorption spectrum of oxygen 1 s σ→ π* excitation and evaluated E/Δ E to be more than 10,000. Secondly, mirror holders were altered to reduce the effect of heat load. The remodeling and the replacement of the optical-element holders resulted in energy-drift becoming negligible. Thirdly, the carbon-contaminated optical elements were cleaned by ozone-cleaning method. The photon flux at the carbon absorption-edge is recovered by the cleaning.

An advanced UV optical cavity for the European FEL project

A European collaboration 1 Partially funded by EC Contract FMGE-CT98-0102 1 is constructing a short wavelength FEL for the ELETTRA storage ring. The optical cavity has been designed and constructed at Daresbury Laboratory for delivery to Sincrotrone Trieste in Autumn 1999, following commissioning tests over the Summer. Initial FEL operation will be at 350 nm but subsequently down to 200 nm or less and mirrors will be 40 mm diameter. The 32 m optical cavity is controllable to 0.01 μrad in mirror pitch and yaw using digital piezo translators. A novel feature is the simultaneous presence of three remotely interchangeable mirrors to extend the tuning range and also to interchange damaged mirrors immediately. In addition, a transfer arm and load-lock arrangement will permit a mirror to be withdrawn from the chamber and replaced without disruption to the UHV system. The FEL is designed to operate at high power (1–10 W) and multi-watt spontaneous emission is also present: power loading has been investigated by FEA analysis and has necessitated specification of a water cooling system on the mirror holders, a considerable challenge made more difficult by the mirror translation complexity. Full design details, construction description and test results will be presented in the paper.

Design of an optical cavity in the NIJI-IV for high output power

A new optical cavity system which efficiently takes out intense intracavity power of a storage ring free electron laser (SRFEL) in the visible and ultraviolet (UV) regions are planed. If a cavity mirror is started to rotate at the peak of an SRFEL macro-pulse to rapidly lead an SRFEL micro-pulse to the high transmission area, we can dump a part of the intracavity power sufficiently. A high-speed piezotranslator and a special mirror holder will realize this system, what is called cavity dump. The piezotranslator would make the optical cavity mirror rotate with the angular velocity of 2.52 × 10 −6rad per one round-trip. In the case of NIJI-IV FELs, the output power of the micro-pulse would be estimated at about 7600 times around 488 nm and about 2700 times around 352 nm as strong as that in the normal operation.