Yasumitsu Tsutsui

Superconducting storage ring NIJI‐III

NIJI‐III is a compact, superconducting storage ring dedicated for use in several commercial applications, especially x‐ray lithography. Assembly of the ring has been completed and NIJI‐III has been operating since August 1990. A beam current of above 450 mA was attained at an injection energy of 280 MeV. Currents of more than 200 mA can be accumulated at the final energy of 600 MeV.

NIJI-III Compact Superconducting Electron Storage Ring

The NIJI-III is a compact superconducting electron storage ring for industrial applications. Features of the ring include four strongly curved large-bore superconducting bending magnets utilizing quadrupole coils with a circular cross section surrounded by an air core and a cold bore. The circumference of the ring is 15.54 m with a critical wavelength of 13 A. Development of the NIJI-III is near completion. This report examines the design and performance of the NIJI-III.

Ion effects in a compact electron storage ring

Abstract Ion-trapping and dc clearing effects on a stored beam in the beam energy range of 90–210 MeV were studied with a compact electron storage ring. The applied voltage and the number of electrodes used to clear trapped ions are discussed and compared with experimental data. It was demonstrated that the ion effects were noticeably reduced by the beam size growth and the decrease of gas desorption by synchrotron radiation with a decrease in beam energy. It was also found that the ion trapping became harmless with ion management near 150 MeV where the Touschek lifetime in this ring was shortest. This indicates that high beam current storage is possible using low-energy injection.

High beam current storage at low energy for compact synchrotron radiation rings (invited)

A study of high beam current storage at a low energy is being conducted on the compact electron storage ring NIJI‐1. In general, it is said that the stored beam lifetime is rapidly shortened as the beam energy decreases, and the high beam current storage is difficult to obtain. However, a stored beam current above a 350 mA was obtained at an injection energy of 100 MeV, and the lifetime of the stored beam is considerably long. For example, e‐folding lifetime is about 2 h at 100 MeV. In this paper, we estimate the beam current decay rate due to the residual gas scattering, the ion trapping effect, and the Touschek effect, and make clear these contributions to the beam lifetime. It was clear that the Touschek lifetime is lengthened according to the bunch size growth, which is roughly explained by the longitudinal coupled bunch instability.

Effects of Increasing Injection Repetition Rate of Low-Energy Injection into a Compact Storage Ring

The relation between the injection repetition rate and beam accumulation in an electron storage ring were studied through experiments and beam tracking calculations. The rate is an important parameter which limits beam current storage. It was believed that the stored beam current could not be increased even if the injection repetition rate was increased over the inverse of the radiation damping time of the betatron oscillations. This is an important consideration for low-energy injection. The experiment was performed at 90 MeV using an NIJI-I compact electron storage ring, and a beam current accumulation rate was obtained above the limit determined by the radiation damping time. It was found that beam current accumulation depended on the kick angle of the kicker magnet.

X-ray-written optical waveguides in germanosilicate glasses

We irradiated 3% GeO/sub 2/-97% SiO/sub 2/ glasses with 1-5 keV X-rays from a synchrotron radiation source. The samples were prepared by vapor-phase axial deposition and polished to a 0.2-mm thickness. We show the induced UV-VUV absorption in the sample after irradiation. The spectrum was obtained by subtracting the spectrum of the sample before irradiation from that after irradiation.

Operational performance of the NIJI-III superconducting storage ring

The operational performance of the NIJI-III superconducting storage ring has been studied with particular attention focused on the vacuum performance of the cold-bore chamber. Photon-stimulated gas desorption in the cold-bore chamber was examined after commissioning the storage ring. It was confirmed that the photon-stimulated gas desorption due to diffuse reflection of synchrotron radiation at the absorber was not dominant in the gas desorption when the electron beam was accumulated in the storage ring.

EXCHANGE REACTIONS ON SOLID SURFACE INDUCED BY VUV UNDULATOR RADIATION

Abstract Quasi-monochromatic undulator radiation was applied to surface modification of poly-tetrafluoroethylene (PTFE), which is one of the most chemically stable polymeric materials. Solid-liquid interface was excited and fluorine atoms on the surface were replaced by oxygen-containing functional groups and hydrogen under VUV undulator light irradiation. The contact angle to water and XPS spectra were measured after the irrradiation. Experimental results show a water layer on PTFE surface promotes the exchange reaction near the absorption edge(165–180nm).

An Energy Compression System for High-Efficiency Injection in a Compact Storage Ring

An energy compression system was installed in the beam transport system of the NIJI-II compact storage ring in order to improve the momentum spread of the linac and increase injection efficiency. The system consisted of three separate magnets and a short accelerating section. The measured spectrum width was improved to a satisfactory level with this system.

Influence of Synchrobetatron Resonance on Low-Energy Injection Beam with a Compact Storage Ring

The effects of synchrobetatron resonance on a low-energy beam were studied using a compact storage ring. The beam profile and lifetime were measured on and off the resonance line. Although the first and second resonances were dangerous, the beam lifetime became long on the third and fourth resonances due to the vertical beam size enlargement. Through DC ion clearing, it was also found that the betatron tune shift and spread, which are caused by trapped ions, were reduced with a decrease in beam energy, contrary to expectations. These results indicate that the operating point for injection is not particularly limited in narrow regions. Moreover, the possibility of high current beam storage at low energy is suggested by making full use of the third and fourth resonances.