In Taiwan photon source facilities, soft x-ray beamlines are equipped with self-developed active high-precision mirrors or gratings. It is crucial to establish more advanced optical surface metrology instruments to satisfy the demands of optical production, installation, and testing in synchrotron optics. A long trace profiler (LTP) is an instrument used to measure the optical surface’s slope. This assists in monitoring the installation processes of optical instruments to ensure that the final optical components satisfy the required specifications in terms of quality. In this study, we propose a new air-bearing slide design to achieve nanometer-level precision for the LTP. This new design replaces ceramic and granite structures and addresses rail deformation and surface imperfections. This LTP features a specially designed bendable linear slide comprising four airbrushes, two shafts, and eight end mounts. The motion stage, supported and guided by four airbrushes against two parallel steel shafts, carries the optical head. End mounts are installed on the tilting stage at both ends, using flexure guides with manually adjusted screws and fine-tuning piezo. The rail system can be bent to a third-order polynomial rail profile to compensate for the effect of gravity when moving the optical head, enabling the achievement of the desired rail pitch variation within a distance of 400 mm with 2.5 μrad (RMS). To further enhance the precision, dynamic correction methods can be employed by utilizing PZT actuators and bender mechanisms. These mechanisms enabled rail pitch variation as low as 0.2 μrad (RMS).We introduce a new design for an air-bearing slide and its corresponding performance. This slide design is employed in LTP measurements. The outcomes of our study demonstrate a correlation between the observed results and the rail pitch profile.
This study is to design glass windows for soft X-ray mirror cleaning by UV light. The soft X-ray mirror will operate in the synchrotron radiation light source for several months, and the mirror surface will be covered with a carbon layer. Soft X-ray mirror cleaning uses UV light on the mirror surface and adds a little oxygen to the vacuum chamber. The carbon will be cleaned by UV light and oxygen. Thus, mirror cleaning is needed to design narrow and long windows to let the UV light arrive at the mirror. In the mirror mount in the original design, the bolt joint force causes the mirror to break. Therefore, this study cut the mount's four corners to absorb the bolt joint deformation, not to transfer to the window. A 2 mm diameter tin wire seals the window mount and successfully compensating the bolt joint forces caused the vacuum chamber and window mount deformation. The simulation result shows that this design can make success decline by 28% maximum deformation. The window mounting test is also sealing the achieve 5.5 E-11 mbar l/s.
To achieve an ultrahigh-resolution for soft X-ray beamlines, the slope error of a highly precise grating is required on the level of 0.1 μrad root-mean-square (RMS) under thermal loading. To realize the goal, a specially designed 25-actuator optical surface bender for the gratings and mirrors is developed and operated at Taiwan Photon Source (TPS) [1]. In this paper, the construction and operation of the in situ LTP measuring system is described[2]. This LTP consists of a switchable optical reflection system that let the LTP can switch to measure horizontal or vertical mounting mirrors/gratings in the beamline. The other is a low optical distortion and bakeable to 120 ˚C glass viewport which is used for the ultra-high vacuum[3,4] interface for the beamlines optics and LTP. The surface slope error being reduced down to 0.1 and 0.15 μrad (RMS) by the 25-actuator bender without/with the glass viewport as verified by the in situ LTP measurements in the beamline.
The small radius x-ray mirror in the interferometer stitching measurement is needed high angle resolution rotation stage to get reliable angle information. The rotation stage rotary range requirement is not wide, because of the X-ray mirror radius generally large than 200M, and the mirror length small than 1.2M. The angle resolution is needed high resolution, therefore, in interferometer stitching measurement, the interferogram is easily affected by the rotation angle difference. Thus, this study is to design a small angle traveling range (rotation angle maximum ± 1.5 degrees), high angle resolution (10 nrad.), and high loading capacity (loading maximum 75 Kg) rotation stage, the rotation mechanism is applied pivot bearing to get high-resolution rotation angle. The rotation stage design is finished, this article discusses system assembly and test.
Long trace profiler (LTP) is used to measure the large radius mirror surface profile. The in-situ LTP can be used to measure the X-ray mirror of an adaptive mirror bending system inside the vacuum chamber. In this study, the in-situ LTP measure head is outside of vacuum chamber. Therefore, the vacuum chamber and window glass thermal effect can introduce errors into the measurement results. This study calculated temperature distribution and deformation using the finite element method (FEM) software and calculate incident ray through the window glass. The incident ray through window glass with thermal gradient could increase optical path difference (OPD). The calculation resulted in an evaluation of in-situ LTP measurement error by thermal deformation.
To achieve an ultrahigh resolution for soft X-ray beamlines at Taiwan Photon Source (TPS), the slope error of a highly precise grating is required on level of 0.1 μrad (rms) under thermal loading with various curvatures. On the beamline, some optics are usually operating under high power density from undulator magnet, the thermal load will introduce a thermal bump on the optics profile and degrade the beamline performance, such as energy resolution and beam size.
To realize the high resolution goal, a specially designed bender with 25 actuators for the grating is designed and a In situ long trace profiler (LTP) with precision of 0.1 μrad (rms) has been developed to measure the mirror profile in soft X-ray beamlines.
This article introduces the design and construction of in situ LTP. It can provide a feedback guideance for the adjustment of actuators of bender mechanism to achieve the optium profile. A suitable adjustment procedure from the input of in-situ LTP , performance of bender and energy spectrums are presented.
There are several benders as the active mirrors and active gratings in operation in TPS 41A resonant inelastic X-ray scattering (RIXS) and TPS 45A angle-resolved photoemission spectroscopy (ARPES) beamlines. In the meantime, three in situ LTPs have been developed to monitor the grating profile under the thermal load in the beamlines. They are providing a feedback to measure the surface figure and to find the optimal surface profile. They would increase our efficiency to reach the energy resolving power of 35,000 and 28,000 in the RIXS and ARPES beamlines, respectively.
The goal of an in situ Long Trace Profiler (LTP) is to adjust the mirror to 0.1 μrad Root Mean Square (RMS) under thermal load. Here we introduce the measurement configuration for in situ LTP. To avoid lens aberration, the moving optical head keeps the optical paths constant, and the reference beam is used to the correct of the unavoidable air bearing errors. The window glass in this test has a rather high optical quality, with a flatness of 1/150 (RMS) over 120 × 20 mm. The optical quality of the window was specified to be ± 1 μrad slope distortion in an aperture length of 100 mm. The window glass deformation for the air pressure was calculated by the Finite Element Method (FEM) software (ANSYS). The window glass deformation results can be fitting by the Zernike polynomial, and then bring it into the sequential optical ray tracing software (ZEMAX), and evaluating the window glass effect on the LTP measurement results. By this approach, we found that this has a constant error. Thus, the window glass air pressure error can be effectively removed from the measurement result to reveal the real mirror profile. Using the in situ LTP measuring result and the data iteration process, the bendable mirror can control the optical surface locate profile and thereby minimize the thermal distort effect. The slope error will be reduced to 0.1 μrad at the thermal load.
The project “High loading precision rotation stage design for synchrotron radiation mirror measurement” aims to provide an ultra-high-precision heavy-duty rotation stage and X-ray mirror interference optical measurements. Since the shape of an X-ray lens is very different from that of the general visible optical lens, the measurement system is very different from the general visible light optical measurement system. This paper describes a high-load precision rotating platform for obtaining stitching interferometer measurements for a synchrotron radiation mirror. The synchrotron radiation mirror is usually rectangular, and the length is greater than the interferometer measurement size. Therefore, for the mirror measurement, the stitching method is usually used to obtain synchrotron radiation mirror measurements. The interference measurements are obtained at different positions. In order to obtain the measurements, the center line of the interferometer must be perpendicular to the tangent of the mirror surface, so that appropriate interference fringes can be obtained. As the mirror radius becomes smaller, the interferometer rotation angle sensitivity increases. Development of the stitching interferometer high-load precision rotating platform design target requires an angle rotation resolution <10 nrad, considering the weight of the general interferometer plus the reference lens, related accessories, and safety factors is about 50 kg so that the rotating platform design load is 70 kg.
A long trace profiler in NSRRC is used to develop a bendable mirror, for the mirror-mounting mechanism and to inspect the mirrors of TPS beamlines. We upgraded the air bearing, the motor and gear, the penta-mirror, the CCD and the software. ELCOMATT 3000 is our calibration reference. To maintain constant the measurement of the optical path, we adopted a scheme for a moving optical head that decreases the various optical paths through a focusing lens to avoid lens homogeneity. The measurement environment (temperature, vibration, air turbulence) is effectively controlled. In measuring a curved mirror (radius 9.7 m), the repeatability is below 0.1 μrad. This paper describes the upgraded performance and engineering details.
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