Hirokazu Fujita

Electron storage ring, KSR for light source with synchrotron radiation

A small electron storage ring (KSR) in a race track shape with the triple bend doubly achromatic lattice and a circumference of 25.7 m is now under construction. Its maximum energy and radius of curvature in the bending section is 300 MeV and 0.835 m, respectively. The critical wavelength of the radiation from the dipoles is 17 nm. In order to enable future installation of a insertion device for much shorter wavelength, two long straight sections, 5.62 m in length are provided. The magnet system consisting of dipole, quadrupole and sextupole magnets are already aligned with precision of a few tenth mm.

A 100 MeV injector for the electron storage ring at Kyoto University

An electron linear accelerator has been constructed at Kyoto University, which is an injector for the 300 MeV storage ring. The output beam energy from the injector is 100 MeV and the designed beam current is 100 mA at the pulse width of 1 /spl mu/sec. The component test is underway. The electron beam of 300 mA is extracted from the electron gun and the peak RF power of 20 MW is successfully fed to the accelerating structures at the pulse width of 2 /spl mu/sec.

KSR as a pulse stretcher

A pulse stretcher mode of the electron storage ring, KSR, is presented. Such a scheme as includes the extraction system in the same straight section as the injection line is adopted in order to enable coexistence of the stretcher mode with the insertion device. This scheme also has a merit that it can use the same beam dump as the output beam from the electron linac.

Slow extraction of electron beam with combination of the third order resonance and RFKO

The stretcher mode of KSR has been experimentally tested. Up to now, a beam spill longer than 8 seconds has been attained by reducing RF knockout power. Improvement of extraction efficiency will be realized by ramping of betatron tune and formation of closed-orbit-distortion without the effect of non-linear sextupole magnets to make an aperture minimum at the first septum for extraction.

First beam circulation test of an electron storage/stretcher ring, KSR

In Kyoto University, we are constructing a compact electron storage/stretcher ring (KSR). The circumference is 25.7 m and the maximum beam energy is 300 MeV. The electron beam is injected from a 100 MeV linac through the doubly achromatic transport line. The beam test of the injection line was finished and the beam size and the dispersion were measured. The results are consistent with the design calculation. The beam current is 100 mA and the energy spread is +/-0.5% (FWHM). KSR uses the 1-turn injection scheme. The bump orbit is created by the perturbation magnet for the injection. The test of the bump magnet was carried out.

Longitudinal beam emittance monitor for 433 MHz proton linac

We have developed a longitudinal emittance monitor for a 7 MeV proton beam provided by the 433 MHz linac at the Institute for Chemical Research, Kyoto University. In the present system, the beam first hits a thin gold target on the beam line, and a fraction of the scattered protons comes into a small cavity. After deflected by a rf electric field in the cavity, the protons finally reach a position sensitive detector (PSD). The PSD gives the information of the energy and position of the individual scattered proton, which enables us to reconstruct the longitudinal distribution of the beam before colliding with the target. The phase and energy resolution of the system are estimated to be 13° and 23 keV full width at half‐maximum, respectively. The longitudinal rms emittance measured was 0.39±0.07 π deg MeV under the nominal operating condition of the linac.

Matching section to the RFQ using permanent magnet symmetric lens

A permanent magnet symmetric (PMS) lens is considered as the final focusing element for the RFQ linac at ICR. The PMS lens, which produces strong axial magnetic field like a solenoid lens, is composed of radially magnetized permanent magnet rings. Because of the low injection energy (50 keV) and a relatively high beam current intended (20 mA), space-charge effects should be taken into account. The beam tracking code PARM-SYL is developed for the purpose, which first reads an output file from PANDIRA for the PMS field and then numerically integrates the equation of motion including the space-charge force The matching section to the RFQ is designed using this code and TRACE-3D.

The monitor system of the 7 MeV proton linac at ICR

The beam monitor system at ICR 7 MeV proton linac is described. Because of the pulsed beam (<1% duty) and the simplicity, fluorescence on a screen plate is observed for the beam profile monitoring. To clear the beam line, the screen can be flipped away by an electromagnetic actuator installed in the vacuum vessel. With this view screen, an emittance monitor is constructed. The beam current can be measured non‐destructively by a core monitor. Because the pulse length is rather long (∼50 μs), a special preamplifier using Negative Impedance Converter is designed. Very thin steering magnet with eight poles is also developed to compensate the deflection of the output beam.

Measurement of the Beam Distribution of 433 MHz Proton Linac in Longitudinal Phase Space

We measured the longitudinal phase space distribution of the proton beams provided by the 433 MHz linac at ICR, Kyoto University, by means of a new monitor which consists mainly of a thin gold target, a deflector cavity, a position sensitive detector (PSD) and three permanent magnet quadrupole lenses. Protons are scattered by the target are guided into cavity, then focused by the PMQs, deflected by the cavity, then focused by the deflector electrodes, and finally reach the PSD. The position and energy data from the PSD are employed to reconstruct the phase space configuration of the beam before hitting the target. The longitudinal emittance of the ICR linac was measured with the present monitor system under some different operating conditions. The obtained measurement results were used to optimize the RF condition. Introduction At the Institute for Chemical Research, Kyoto University, a 433 MHz proton linac has been operated. The linac mainly consists of 50 keV Ion source, and low energy beam transport, 2 MeV Radio Frequency Quadrupole (RFQ) linac, Beam Matching Section (BMS), and 7 MeV Drift Tube Linac (DTL)[1]. In order to measure the longitudinal beam emittance of the 7 MeV proton beam, we developed a new beam monitor [2]. The monitor enables us to measure the beam distribution in the longitudinal beam phase space. The longitudinal beam distribution of the proton linac is obtained by measuring the position and energy of the protons which are scattered at the target and then deflected by an rf field whose frequency is the same as those of RFQ linac and DTL. The figure of the longitudinal emittance monitor is shown in Fig.1. The position and energy of a proton measured by Position Sensitive Detector (PSD) depend on the phase and energy when it is scattered at the target. By calculating the orbit of the deflected proton, the coordinates of the proton in the phase space can be obtained. In this way, a beam distribution in the longitudinal phase space is reconstructed from the measured position and energy distribution. When we accelerate the proton beams, how we control the rf condition is large problem. Then the variations of the longitudinal beam distribution at different rf conditions were measured, in order to examine the effect of the rf condition to the longitudinal beam dynamics. Target PMQ 2 PMQ 1 Baffle Slit Proton Beam