Hiroyuki Takaki

Design and Cold Model Test of 500 MHz Damped Cavity for ASP Storage Ring RF System

TOSHIBA is manufacturing the storage ring RF system for the Australian Synchrotron Project(ASP). Two pairs of the 500MHz Higher Order Mode(HOM) damped cavities will be applied for this system. The cavity is a modified KEK-PF type with silicon-carbide(SiC) microwave absorber and has three rod-shaped HOM couplers for damping the longitudinal HOM impedance less than 20kΩ/GHz to comply with ASP Performance Specification. The shunt impedance has been improved more than 5% in comparison with the original design by reducing the beam bore diameter without degrading HOM damping capability. The design of the cavity and the test results of an aluminum (Al) cold model are described.

A lattice for the future project of VUV and soft X-ray high brilliant light source

We present a lattice for a third generation VUV and soft X-ray light source, which is a future project of the Institute for Solid State Physics (ISSP) of the University of Tokyo and is being designed in close collaboration with the Photon Factory of KEK. The storage ring has an energy of 2 GeV, a circumference of about 400 m, an emittance of less than 5 nm rad, four 13 m long straight sections and twelve 7 m semi-long straight sections. We first present the lattice design of the ring, the chromaticity correction and the dynamic aperture, and then present a new lattice which is now under study to improve the performance.

The effects of the insertion devices at the Super SOR light source

The Super SOR ring is a third generation light source constructed at Kashiwa Campus of the University of Tokyo. In this paper, we present the formalization of the circularly polarizing undulator and beam optics correction.

Status of R&D efforts toward the ERL-based future light source in Japan

The energy recovery linac is a very promising synchrotron light source in future. We are contemplating to realize a ERL_based next generation light source in Japan, under a collaboration between KEK, JAEA, ISSP, and other SR institutes. To this end, we started R&D efforts on its key technologies, including a low-emittance photocathode gun and superconducting cavities. We also plan to assemble these technologies into a small test ERL, and to demonstrate their operations. We report our R&D status.

The lattice of the 1.0 GeV VSX storage ring

The University of Tokyo has been promoting a future project to construct a third-generation VUV and soft X-ray light source (VSX). The VSX ring has an energy of 1.0 GeV, an emittance of about 0.7 nm/spl middot/rad, a circumference of about 230 m and two 30 m long straight sections for insertion devices. The most significant characteristic of the VSX ring is that its emittance is below a diffraction limit for the photon energy of 100 eV. It can provide the VUV and soft X-ray light with a maximum brilliance above 10/sup 20/[photons/sec/mm/sup 2//mrad/sup 2//0.1% b.w.] using an undulator installed in a 30 m long straight section.

Measurement of the orbit parameters at SOR-RING

In the 1992 summer shutdown, beam position monitors (BPMs) have been installed in SOR-RING as one of the R&Ds for the future plan of a VUV high-brilliant source. They have been also aimed at measuring the closed orbit of the ring and correcting it by beam steerings that have been also installed at the same time as the BPMs. With these systems, we measured the closed orbit distortion (C.O.D.) at the first time since the ring had been constructed. Horizontal and vertical C.O.D.s were then corrected within 1 mm by exciting the steerings and changing the RF frequency. We also measured the other orbit parameters such as betatron and dispersion functions, chromaticity and RF-cavity parameters. Moreover, it was proved in a recent machine study that SOR-RING is capable of accelerating the electrons up to 450 MeV or more from the present energy of 380 MeV.<<ETX>>

Simulation study of resistive-wall beam breakup for ERLS

Resistive-wall beam breakup (RWBBU) due to the long-range transverse wake is studied with a developed simulation program. The simulation program is useful and essential for fully understanding the RWBBU behaviour in ERLs. The simulations demonstrate that the position displacement or orbit distortion due to the RW wake is proportional to the square root of time and the wake strength in the early stage of the RWBBU and they are consistent with the RWBBU equations. In case of the planned test ERL in Japan, the maximum position displacements increase up to 3% and 1% of the initial position offset with all the quadrupole magnets off and on at 77 mus. A small-gap insertion device(ID) duct increases the orbit distortion in downstream of the ID section, though a focusing effect due to the ID field may reduce it.

Development of Copper Coated Chamber for Third Generation Light Sources

We describe the development of the copper coated chamber, which is suitable for the 3rd generation light sources. This chamber aims to reduce the resistive-wall impedance[1]. However, this coating might affect the ultra-high vacuum condition worse. In order to check the validity of this chamber for the ultra-high vacuum condition, we have produced the copper coated chamber and built the test bench. The measured outgassing from the inner surface of the newly developed copper coated chamber is sufficiently small to utilize in ultra-high vacuum condition.

An Electron‐Beam Profile Monitor Using Fresnel Zone Plates

We have developed a beam profile monitor using two Fresnel zone plates (FZPs) at the KEK‐ATF (Accelerator Test Facility) damping ring to measure small electron‐beam sizes for low‐emittance synchrotron radiation sources. The monitor has a structure of an X‐ray microscope, where two FZPs constitute an X‐ray imaging optics. In the monitor system, the synchrotron radiation from the electron beam at the bending magnet is monochromatized to 3.235‐keV X‐rays by a crystal monochromator and the transverse electron‐beam image is twenty‐times magnified by the two FZPs and detected on an X‐ray CCD camera. This monitor has the following advantages: (1) high spatial resolution, (2) non‐destructive measurement, (3) real‐time monitoring and (4) direct electron‐beam imaging. With the beam profile monitor, we have succeeded in obtaining a clear electron‐beam image and measuring the extremely small beam size less than 10 μm. The measured magnification of the imaging optics was in good agreement with the design value.

Lattice Design of Super SOR

The University of Tokyo has been promoting a future project to construct a third‐generation VUV and Soft X‐ray light source (Super SOR). The Super SOR ring has energy of 1.8 GeV (max. 20 GeV), an emittance of about 8 nm•rad, a circumference of about 280 m. It consists of fourteen Chasman‐Green type cells and has two 17 m long straight sections and twelve 6 m long ones. It can provide the VUV and Soft X‐ray light with maximum brilliance above 1019 [photons/sec/mm2/mrad2/0.1% b.w.].