Tatsuya Kume

Present status and first results of the final focus beam line at the KEK Accelerator Test Facility

ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U. S. scientists. The present status and first results are described.

Progress on the cryogenic system for the KAGRA cryogenic interferometric gravitational wave telescope

KAGRA is a project to construct a cryogenic interferometric gravitational wave detector in Japan. Its mirrors and the lower parts of the suspension systems will be cooled to 20 K in order to reduce thermal noise, one of the fundamental noise sources. One of the key features of KAGRAʼs cooling system is that it will keep the mirrors cooled without introducing vibration. This paper describes the current status of the design, manufacture and testing of the KAGRA cooling system.

Development of surface gradient integrated profiler - Precise coordinate determination of normal vector measured points by self-calibration method and new data analysis from normal vector to surface profile -

A new ultra-precision profiler has been developed to measure items such as asymmetric and aspheric profiles. In the current study, the normal vectors at each point on the surface are determined by a reflected light beam that returns along exactly the same path as the incident beam. The surface gradients at each point are calculated from the normal vector, and the surface profile is obtained by integrating the gradient. At a previous meeting, we reported that normal vector measured points with submicron accuracy can be determined by a self-calibration method. In this paper, the self-calibration method has been tested and shown to have the capability for surface profile measurement accuracy of nanometer order, using a concave mirror with a radius curvature of 2000 mm. The precise surface profile obtained from a measured normal vector has been studied as a new data analysis method that applies Fourier series expansion with the least-square method. Future development will include the following: the elimination of error propagation due to data analysis from normal vector to surface profile, unique determination of profile from normal vector, and enabling random measuring position of normal vector on the mirror.

Surface gradient integrated profiler for X-ray and EUV optics

Abstract A new ultraprecise profiler has been developed to measure, for example, asymmetric and aspheric profiles. The principle of our measuring method is that the normal vector at each point on the surface is determined by making the incident light beam on the mirror surface and the reflected beam at that point of coincident. The gradient at each point is calculated from the normal vector, and the surface profile is then obtained by integrating the gradients. The measuring instrument was designed in accordance with the above principle. In the design, four ultraprecise goniometers were applied to adjust the light axis for normal vector measurement. The angle-positioning resolution and accuracy of each goniometer are, respectively, 0.018 and 0.2 μrad. Thus, in the measuring instrument, the most important factor is the accuracy of the normal vectors measured by the goniometers. Therefore, the rotating angle-positioning errors were measured and calibrated. An elliptical profile mirror for nanometer hard-X-ray focusing was measured, and compared with the measured profile using a stitching interferometer. The absolute measurement accuracy of approximately 5 nm (peak-to-valley) was achieved. Then the measurements of 1000-mm-long flat, spherical and parabolic mirrors were demonstrated. The surface profiles of the mirrors were obtained by integrating the interpolated gradient.

A new designed ultra-high precision profiler

A new ultra-precision profiler was developed to measure X-ray and EUV optics such as asymmetric and aspheric profiles. In the present study, the normal vectors at each point on the surface are determined by a reflected light beam that follows exactly the same path as the incident beam. The surface gradients at each point are calculated from the normal vector and the surface profile is obtained by integrating the gradient. The measuring instrument was designed according to the above principles. In the design, four goniometers and three-axis movers were applied to adjust the light axis to search for the normal vector at each point on the surface. The angle-positioning resolution and accuracy of each goniometer are respectively 1.8 x 10-8 radian and 2 x 10-7 radian. A SiC flat mirror 25.4 mm in diameter and an elliptical profile mirror for nanometer hard X-ray focusing were measured using the present instrument and compared to the measured profile using a Zygo Mark IVxp phase-measuring interferometer.

Expected performance of shintake monitor (IP beam size monitor at ATF2)

Precision beam size monitor, so called Shintake monitor, based on laser interferometer is developed. The installation to the interaction point of ATF2 is on going. The beam size resolution is estimated based on the practical test and it is expected to satisfy the requirement of ATF2. The detail of Shintake monitor at ATF2 and the process of the performance expectation are presented in this article.

Surface gradient integrated profiler for x-ray and EUV optics: 3D mapping of 1m-long flat mirror and off-axis parabolic mirror

A new ultra-precision profiler has been developed in order to measure such as asymmetric and aspheric profiles. In the present study, the normal vectors at each points on the surface are determined by the reflected light beam goes back exactly on the same path as the incident beam. The surface gradients at each point are calculated from the normal vector and the surface profile is obtained by integrating the gradient. The measuring instrument was designed according to the above principle of the measuring method. In the design, four ultra-precision goniometers were applied to the adjustment of the light axis for the normal vector measurement. The angle positioning resolution and accuracy of each goniometer are respectively 0.018 μrad and 0.2 μrad. In the measuring instrument, the most important item is the measuring accuracy of the normal vectors by the goniometers. Therefore, the rotating angle positioning errors were measured and calibrated. Then the measurement of a concave mirror with 300 mm radius and 460mm, 1m long plane mirrors were measured. Then, The 3D surface profile of the mirror such 1m-long flat mirror, a concave mirror with 2000 mm radius and off-axis parabolic mirror are obtained by integrating the interpolated gradient.

High-speed surface slope measuring profiler for aspheric shapes

A new high-speed slope measuring instrument is currently under development for small-aperture aspheric lenses and mirrors. In the present study, normal vectors at each point on the lens surface were determined using the reflected light beam that follows the same path as the incident beam. The capability of the developed instrument to achieve submicroradian surface slope metrology of a small-radius aspheric lens was verified. The paper also describes in detail the design principle, aspheric lens measuring method, initial alignment and calibration procedure, shape determination procedure developed from the measured slope metrology, and the high-speed slope measuring technique.

High-precision profile measurement of a small radius lens by surface gradient integrated profiler

A new concept profiler has been developed to measure items such as asymmetric and aspheric profiles with a small radius curvature lens and mirrors. In this study, the normal vectors at each point on the surface are determined by a reflected light beam that returns along exactly the same path as the incident beam. In order to measure a small radius curvature, a compact measuring instrument was redesigned according to the above principle of the measuring method employed. The instrument is 1200 mm (W) × 1000 mm (H) × 1500 mm (V). The measurement of normal vectors of a spherical lens, which has a small f number such as a 25 mm radius curvature, has been demonstrated with a measuring accuracy for the normal vector of 0.1 μrad. The surface gradient at each point is calculated from the normal vector, and the surface profile is obtained by integrating the gradient. When integrating the gradient, measured position accuracy should be in the order of 10 nm. They were obtained by self-calibration techniques that have already developed by the authors. In this paper, we discuss methods of calculating absolute radius curvature and deviation from the ideal surface profile.

Gamma detector for the Shintake monitor (IP beam size monitor at ATF2)

A calorimetric detector for inverse-compton photons from the Shintake monitor at the ATF2 test beam facility at KEK is developed. The Shintake monitor is the precision beam size monitor based on laser interferometer, which is planned to be used at a commissioning of the ILC beam delivery system. The detector has original structure to separate the compton signal from Bremsstrahlung background using the difference in shower development. The beam test of the detector was performed at ATF in the 2007’s winter using a laser wire and a wire scanner. It was confirmed to be able to see the difference in the shower development and to separate compton photons from Bremsstrahlung photons. The beamtest plan of Shintake monitor at ATF2 on 2008’s winter is also described.