Toshikazu Adachi

Fast data acquisition system of a non-destructive profile monitor for a synchrotron beam by using a microchannel plate with multi-anodes

A microchannel plate (MCP) is a good sensor for the head of a non-destructive profile monitor (NDPM) in a synchrotron ring. The gain of the sensor can be controlled from 1 to 104 by adjusting the bias voltage on the MCP. If the gain of the MCP is not sufficient for observing a polarized beam with an intensity which is about one thousandth of the normal beam intensity, two MCPs in series (tandem type) should be used for the sensor. The conventional type of NDPM takes data by moving an MCP with a narrow window from the end of the beam size to the other end during many acceleration periods. Therefore, the measured beam profile is the average of the beam dynamics over many acceleration periods, and data taking requires a long time. The fast NDPM data acquisition system introduced in this article can obtain a beam profile from injection into a synchrotron to extraction only for one acceleration period. The head of the NDPM is a large rectangular MCP having multi-anodes of a strip line. Each anode has an independent electric system for data taking into a computer. In a parallel data acquisition system, such as this monitor system, the calibration of the whole gain of each channel from the MCP to the analog-to-digital converter (ADC) is the most important. In our system, this is done by longitudinally rotating the MCP by 90° (i.e., the direction of the anode strips is set perpendicular to the beam direction).

Recent beam studies of the PoP FFAG proton synchrotron

The PoP (Proof of Principle) FFAG accelerator, which was the world first FFAG proton synchrotron, was constructed at KEK. After the first proton beam acceleration of FFAG, we studied various aspects of the PoP FFAG. The observed beam orbit shift during the acceleration was consistent with the simulation result. It was confirmed that the beam intensity increased about five times with multi-bunch injection. The horizontal acceptance of the PoP FFAG was estimated at about 4000 /spl pi/ mm.mrad experimentally.

Eddy Current Effects of the J-PARC RCS Sextupole Magnets

Sextupole magnets for the chromaticity correction of the rapid-cycling synchrotron of the Japan Proton Accelerator Research Complex have a large bore of 330 mm and a relatively short length of 320 mm. The end effect, therefore, was not negligible and a three-dimensional magnetic field calculation was necessary to achieve the required field quality of inside the radius of 141.2 mm for the designed maximum field gradient of 18.6 T/m. Eddy current effect on the field quality and temperature rise was considered because the magnets were to be excited with a current pattern of a frequency of 25 Hz. Measurement using harmonic coils confirmed that the required field quality was achieved. Measurement results of the sextupole component and 18-pole component field were reproduced with the magnetic field calculation program OPERA3d/ELEKTRA.

Multi-orbit synchrotron with FFAG focusing for acceleration of high intensity hadron beams

A multi-orbit synchrotron (MOS) with fixed field alternating gradient (FFAG) focusing is attractive for acceleration of high intensity hadron beams because acceleration cycle could be increased. The magnetic field of MOS is static, therefore, the repetition rate of acceleration could be increased more than 10 times larger than that of ordinary rapid cycling synchrotron (RCS) if an efficient high voltage RF accelerating system becomes available. Recently, a new type of high gradient RF cavity (HGC) using high permeability magnetic alloy (MA) has been developed and MOS with FFAG focusing becomes very promising. In order to clarify the feasibility of rapid cycling MOS (RCMOS) experimentally, proof-of-principle (POP) machine, which accelerates protons up to 1 MeV with 1 kHz repetition, is under development. We have also made several designs on high intensity proton accelerators with RCMOS for various applications such as an accelerator driven system (ADS) as an energy breeder, a spallation neutron source and a proton driver for a muon collider.

Response of a large CsI(Tl) crystal to electrons and pions below 1.5 GeV/c

Abstract A CsI(Tl) crystal of 9.5 cm diameter and 30 cm length was tested with electrons and pions in the momentum range from 0.2 to 1.5 GeV/ c . Photodiode and photomultiplier readouts were used for comparison. In the photodiode readout, the fwhm energy resolution for electrons was 6.7% at 1 GeV in agreement with the EGS simulation. The e/π separation for momentum analyzed particles was found to be 1/1000 at 1 GeV/ c with a simple energy cut. The pulse heith nonuniformity along the longitudinal position, scanned with a pencial beam of 1 GeV/ c pions, was smaller than ±4% between 4 and 27 cm from photomultiplier.

Full-Scale Prototype Power Supply for SuperKEKB Final Focus Superconducting Magnets

A full-scale prototype power supply for the SuperKEKB final focus superconducting magnets was developed. The aiming specifications of the power supply are a dc rated output of 2 kA-10 V, a current setting resolution of <; 0.1 ppm, current stability of <; 2 ppm/8 h, a temperature coefficient of <; 0.01 ppm/ degree, and a current ripple of <; 1 ppm, where the assumed magnet inductance and cable resistance are 0.88-13.28 mH and 5 mΩ, respectively. High-power tests were performed, and expected results were obtained.

Intensity dependent emittance-exchange in a high intensity proton synchrotron

The acceptance of the KEK booster has large side value (272 /spl pi/ nm mrad in the horizontal plane and 61/spl pi/ mm mrad in the vertical plane). To increase the beam intensity we have been trying to achieve painting injection in the horizontal plane. The intensity-dependent emittance exchanges in the horizontal and vertical plane were measured by a method using a scraper and bump magnets method. In order to clarify the experimental results, multiparticle tracking was performed with self-consistent space-charge forces. The experimental and simulation results imply that a space-charge potential of a beam-induced coupling exists between the horizontal and vertical planes.

Beam extraction of the PoP FFAG with a massless septum

We propose a new extraction scheme with a massless septum magnet in FFAG accelerator, with which the DC beam can be extracted. The system consists of a combination of massless and ordinary septa without kickers. After passing through the massless septum, the beam tail is stretched by the field gradient of the massless septum magnet, and that can be extracted with an ordinary septum. From the result of the tracking simulation, the principle of the extraction scheme is verified. The result of the performance test of the massless septum indicates that the magnet works well as designed, and this scheme is feasible.

SuperKEKB Main Ring Power Supply System

The power supplies for magnets of KEKB main ring were recycled into SuperKEKB main ring. Several tests were performed for all of the power supplies to check the soundness. Some of the power supplies were improved to satisfy the requirements of optical design, and some of them were replaced by new power supplies. Most of the trim-coils were arranged with one of power supply per a coil in SuperKEKB. The total number of the power supplies is over 2000. INTRODUCTION SuperKEKB [1] have been started to upgrade aiming 40 times higher luminosity than KEKB had achieved the peak of 21.083 × 10 cm s . New components and reused ones are installed in the KEKB tunnel or in the buildings during 5 and a half years. The installation has finished and then a beam commissioning of Phase-1 has started in February 1st [2]. Huge number of power supplies for electro-magnets was used in KEKB and almost the same number of ones is used in SuperKEKB continuously. The oldest power supplies are replaced, and a part of the others are overhauled. The number of power supplies which are new ones or reused ones is shown in Table 1. Table 1: The Number of Power Supplies new reuse BM, Wiggler (0.4 1 MW) 13 0 QM: large (0.1 0.5 MW) 0 18 QM, SM: medium (2 105 kW)) 204 335 Steer., etc.: small (0.3 2.4 kW) 138 1681 QCS steering magnets (70 A, 10 V) 49 0 QCS main magnets (<2 kA, <15 V) 11 0

A Compact Hadron Driver for Cancer Therapies with Continuous Energy Sweep Scanning

The compact hadron driver for future cancer therapies based on the induction synchrotron concept, which has been proposed recently, is discussed. This is a fast cycling synchrotron that allows the energy sweep beam scanning. Assuming a 1.5 T bending magnet, the ring can deliver heavy ions of 200 MeV/au at 10 Hz. A beam fraction is dropped from the barrier bucket at the desired timing and the increasing negative momentum deviation of this beam fraction becomes enough large for the fraction to fall in the electrostatic septum extraction gap, which is placed at the large D(s) region. The programmed energy sweeping extraction makes spot scanning beam irradiation on a cancer area in depth possible.