Shen-Yaw Perng

The SRI Beam Size Monitor Developed at NSRRC

A beam size monitor based on the synchrotron radiation interferometer (SRI) was installed in the NSRRC TLS. This monitor consists of a simple diagnostic beamline with a water-cooled beryllium mirror inside and a detecting optical system for both vertical and horizontal beam size measurement. The beam sizes measured are 47 micron and 160 micron respectively and are more close to the theoretical values than the synchrotron image monitor. Comparing with other monitors, at least 1 micron beam size variation is detectable. To minimize the thermal effect, the mirror is located far away from the source point and closed to the detecting optical system. The thermal distortion of the mirror is quite small measured by a portable long trace profiler (LTP) and agrees with the simulating analysis. The detailed monitor system design and testing results are presented in this paper.

New focusing mirror system for synchrotron radiation infrared beamlines

A new Kirkpatrick-Baez-type focusing mirror system for use in synchrotron radiation IR beamlines is designed and fabricated. This mirror system, which contains two fifth-order-polynomial-corrected cylindrical mirrors, can collect and focus the long arc shape IR source from the bending magnet into a nearly perfect point image. To fabricate these two uncommon mirrors, 17-4 PH type stainless steel substrates are chosen and mechanically bent from planar to the desired fifth-order-polynomial-corrected cylindrical shapes with central radii of 3.74 and 5.43 m. The root mean square (rms) roughness and the slope error of these two mirrors are measured to be 0.3 nm and less than 6.3 µrad, respectively. The method for calculating the polynomial coefficients of both mirrors as well as the mirror fabrication process, mechanical design, and the method for adjusting the mirror shape using a long trace profiler are presented.

Integration Design and Installation of Girder Systems in the Injection Section of Taiwan Photon Source

The electron beam is injected from the end of the transport line into the injection section of the storage ring in Taiwan Photon Source (TPS). A girder system for the injection section has been designed to support AC/DC septum magnets, four kicker magnets (K1–K4), and vacuum chambers. The girder system includes three girders, a Rapson-slide mechanism, and stages for the septum/kicker magnets. To improve the reliability and the stability of the injected electron beam, the girder systems are designed and installed in the injection section of TPS, as described in this chapter. The positioning accuracy of installing three girders and the stages for septum/kicker magnet are, respectively, within 0.3 and 0.05 mm.

Design and Experiment of the Auto-alignment Control System for TPS Storage Ring Girder

The auto-alignment system is designed for aligning the magnet girder system with little manpower and time as well as improving the accuracy of girder system in the whole storage ring simultaneously. The system consists of absolute length gauges between two consecutive girders, laser position-sensitive devices (PSD) between two straight-section girders, and a precision inclination sensor on each girder. The more precise angle and length between two girders obtained from these sensors module, the more precise position that can then be located. A magnet girder system with six cam movers on three pedestals is designed to provide precise adjustments of six axes and align girders automatically driven by six electric motors. This chapter consists of the construction of system, auto-alignment process, and experimental results. In the auto-alignment process, a laser tracker is employed to acquire the data as the feedback one in auto-alignment process to locate the position of girders and to simulate the status of the whole TPS storage ring. Further verification of the proposed technique of auto-alignment based on the results of several experiments in this chapter is merited.

The Position and Correction System of Laser PSD

A laser PSD positioning system is included in the TPS girder auto-alignment system that is designed for aligning and positioning the straight-segment girders of TPS storage ring. The laser PSD positioning system consists of lasers, PSD, and lenses. This chapter describes the process of assembly, installation, adjustment, and the measurement result of the laser PSD system. Installing the laser PSD system consists of several steps. The first step is to assemble lenses and PSD in mechanism, lens PSD module. The tilt angles of lens on the lens PSD module are fine tuned and the PSD position value is adjusted to zero. The positioning fixture is designed and contains six touch sensors (absolute length gauges) for detecting the position of the lens PSD module. The lens PSD module is installed and adjusted on a girder absolute position precisely by the positioning fixture. So each module is adjusted to with equal distance to the vertical and horizontal reference plane of girder. The laser is adjusted according to the position of the PSD. Finally, use the absolute length gauges to correct the PSD. According to the aforementioned process of assembly and all parameters of PSD module, the girder can be aligned and positioned within 20 um precision scale.

Use of deep reactive ion etching in the fabrication of high-efficiency high-resolution crystal x-ray analyzers

Spherically bent silicon crystal x-ray analyzers have been employed in high-resolution inelastic x-ray scattering experiments to increase the counting efficiency due to the small cross-section of the inelastic scattering processes of interest. [1] In these bent analyzers, strain causes a distribution of lattice spacing, limiting the achievable energy resolution. Hence, the silicon wafers were diced using precision diamond saws into an array of ~1x1 mm2 blocks, and then acid etched to remove the saw damage, leaving blocks ~0.6x0.6 mm2 glued to a spherical concave substrate. With this method, meV energy resolution has been demonstrated with a bending radius of 6.5 m. [2] We seek to optimize the dicing process using the technique of deep reactive ion etching (DRIE) to develop highly efficient crystal analyzers. Ideally, each individual block subtends an angle that matches the acceptance (Darwin width) of the silicon reflection. This requires block sizes of about 500 μm2. DRIE offers the flexibility of selecting the block size, with finely controlled groove widths (i.e., minimal loss of material), and hence the possibility of controlling the energy width. We have made a prototype analyzer using DRIE with block size of 470 μm2, groove widths of 30 μm, and about 500 μm deep. The wafer was then bent and glued to a glass substrate with 2-meter radius. Tests showed encouraging results, with the DRIE analyzer performing at the 100 meV level. Details of the process and further refinements will be discussed.

Measurement of Beam Size with a SR Interferometer in TPS

Taiwan Photon Source (TPS) has operated since 2015. An optical diagnostic beamline is constructed in section 40 of TPS for the diagnosis of the properties of the electron beam. One instrument at this beamline is a synchrotron radiation interferometer (SRI), which is operated to monitor the beam size. In this paper, we present the beamline structure and recent results of measurement with the SR interferometer. INTRODUCTION Taiwan Photon Source (TPS) was commissioned in 2015. The electron beam stored in the storage ring of circumference 518 m has current 500 mA and energy 3 GeV. The beam is at present operated at 150 mA for user applications. To monitor the beam status, two facilities are adopted for the transverse beam size – an X-ray pinhole camera and a synchrotron radiation interferometer (SRI) [1]. That interferometer, presented by Dr. T. Mitsuhasi in KEK, is widely applied to monitor synchrotron light sources; it is based on visible optics and can resolve a beam size 3-4 m [2,3,4]. The monitor gives both a static and a dynamic observation of the beam size. The basic principle of a SR interferometer (SRI) is to measure the profile of a small beam through the spatial coherency of light, and is known as the Van Citter-Zernike theorem. The distribution of intensity of the object is given by the Fourier transform of the complex degree of first-order spatial coherence. The beam size is given by

Development of an X‐ray Pinhole Monitor at NSRRC

An X‐ray pinhole monitor is designed to measure the size, emittance and energy spread of the electron beam at NSRRC. The profile of the electron beam in a synchrotron radiation source is commonly assessed with a pinhole monitor of a cheap and simple design. To increase the resolution of the measurement, one method is to use the X‐ray regime. The beam passes through a pinhole and the low‐energy photons are eliminated with a filter. The beam profile is imaged with a fluorescent screen. The pinhole dimension is optimized on minimizing the diffraction blurring and maximizing the geometric resolution. The X‐ray pinhole monitor is simulated with a SRW program. We designed an X‐ray pinhole monitor to have three sets of pinhole array, six sets of filters and three sets to screens to increase the information acquired about the characteristics of the X‐ray pinhole monitor. The simulation and design are presented here.

Development of Aspherical Active Gratings at NSRRC

An active grating based on a novel optical concept with bendable polynomial surface profile to reduce the coma and defocus aberrations had been designed and proved by the prototype testing. Due to the low glass transition temperature of the glue and the difference of thermal expansion coefficient between the 17‐4 steel bender and silicon, the prototype distorted from flat polished condition when thermally de‐blocked the polishing pitch. To improve the thermal deformation of the active grating in the polishing process, a new invar bender and high curing temperature glue were adapted to glue a silicon substrate on the bender. After some tests and manufacturer polishing, it showed acceptable conditions. In this paper we will present the design and preliminary tests of the invar active grating. Meanwhile, the design and analysis of a new 17‐4 PH steel bender to be electro‐less nickel plating and mechanical ruling for a new beamline will also be discussed.

Two high-order polynomial bendable mirrors in the TLS infrared beamline

This study presents a Kirkpatrick-Baez mirror system which includes two high-order polynomial bendable mirrors in a Taiwan Light Source (TLS) infrared beamline to create and adjust more accurately collimating images on a focusing point. The source of infrared rays is synchrotron radiation from a TLS bending magnet, so the surface of a vertical focusing mirror (VFM) is designed on an elliptical shape. The Runge-Kutta numerical method is used to compute the optimal high-order polynomial shape of the horizontal focusing mirror (HFM), to focus the horizontal arc source on the point image. The HFM and VFM using 17-4 PH stainless steel substrate without an electroless nickel plate are mechanically bent from planar to the desired fifth-order polynomial shapes with central radii of 3.74 m and 5.43 m by the application of equal couples, respectively. The mirror fabrication process, mechanical design, and the method of adjusting the mirror shape using the Long Trace Profiler measurement system are described. Finally, the roughness of mirrors is 3 angstrom RMS. After the mirrors have been bent, the slope error over 2/3 of clear aperture length (170 mm) was reduced to less than 6.3 (mu) rad RMS.