Kenichi Yanagida

Design of a new type of planar undulator for generating variably polarized radiation

Abstract A small prototype model of a new undulator is under construction for generating variably polarized radiation. This undulator consists of two pairs of planar permanent magnet arrays above and below the electron orbit plane in a storage ring. This device has no magnetic structures in the horizontal orbit plane in order to avoid the conflict with the aperture of the electron orbit. The on-axis magnetic field generated by shifting the relative position of pairs of magnet arrays in this device induces helical and sinusoidal electron orbit motions. It leads to the generation of circularly and linearly polarized undulator radiation. This new undulator will be installed in the JAERI storage ring (JSR) in order to examine the performance for generating variable polarization.

First observation of undulator radiation from APPLE-1

Abstract Various polarized radiation was observed in the visible region generated by the new type undulator APPLE-1 (Advanced Planar Polarized Light Emitted - 1). The undulator was installed in the low energy electron storage ring JSR and we have succeeded in observing linearly polarized radiation in both planes and circularly polarized radiation with the aid of a Wollaston prism. During the process of shifting the arrays and changing the undulator gap, no noticeable change of radiation axis was observed.

Stabilization of the rf system at the SPring-8 linac

Abstract Beam energy variation of the SPring-8 linac was 1% or more at the start of beam commissioning. Depending on fluctuation, beam transmission efficiency from the linac to the booster synchrotron was significantly affected, and beam intensity in the booster synchrotron changed 20–30%. This caused delay of optimization of the various parameters in the booster synchrotron. More problematic, the beam intensities stored in each rf (radio frequency) bucket of the storage ring at SPring-8 were all different from each other. The users utilizing synchrotron radiation requested that the beam intensity in each rf bucket be as uniform as possible. It was thus a pressing necessity to stabilize the beam energy in the linac. Investigation of the cause has clarified that the various apparatuses installed in the linac periodically changed depending on circumstances and utilities such as the air conditioner, cooling water and electric power. After various improvements, beam energy stability in the linac of

Overview of the SPring-8 linac future plan

We carry out incidence operation in proportion to the commissioning to the storage ring at present, after SPring-8 linac started beam commissioning from August, 1996, and after it confirmed the beam performance early. In the future, the improvement in beam performance and equipment performance is tried, while we advise the improvement of the beam monitor. We develop the new applied research with it. We consider the application using various beams as part of the effective utilization of SPring-8 linac. In this paper, we introduce the plan of the free electron laser with the aim of the lasing at 4nm wavelength as one of the inside. And, we also introduce simulation result of the RF photocathode electron gun for it.

Bunch compression and beam transport for SPring-8 linac SASE

For SASE, a bunch compression and a beam transport system which follow the layout of the present SPring-8 linac are designed. This is the first order evaluation trying to preserve the emittances at an RF photocathode gun. There are two bunch compressors in the injector section. There are one energy compressor, 90° bending system and two bunch compressors in the final compression section. The RF gun generates electron beam which has the normalized transverse emittances of 1.5πmm⋅mrad, and the longitudinal emittance of 0.16πps⋅MeV. The final emittances before a undulator become 3.5πmm⋅mrad for x direction and 0.38πps⋅MeV respectively.

Beam tracking simulation for an rf gun apparatus in the SPring-8

A photo cathode rf gun has been studied in the SPring-8 Linac to obtain a lower emittance beam. In order to perform a comparison with the beam characteristics, a beam tracking simulation code for an rf gun test apparatus has also been developed. In this code, the electric and magnetic forces between all particles are calculated. Accordingly, a lot of time is required, but a high accuracy can be expected in the calculations in comparison with other codes like PIC. In this paper, we describe the above rf gun test apparatus in the SPring-8, the simulation code, and present some calculation results such as the emittance of the emitted beam compared with MAFIA’s data.