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Polarized deuteron acceleration tests were performed at the KEK-PS. There is one weak intrinsic resonance at 8 GeV. The polarization was measured by an external polarimeter at 2 GeV following two patterns. The beam was extracted after deceleration to 2 GeV from 10.2 GeV in pattern 1 and just after acceleration up to 2 GeV in pattern 2. The polarization was almost the same in the two patterns, meaning that a polarized deuteron beam has been successfully accelerated up to 10.2 GeV at the KEK-PS.

The test operation were started from this January. During this operation some debugings of the software program and hardware circuit were carried out and the construction of this system was successifully completed by this April.

The beam commissioning of J-PARC LINAC has been started in November 2006. Beam position monitors (BPMs) which had been calibrated on the bench setup with a scanning wire, take beam-based-calibration method in order to enable the beam to pass at the centre of a quadrupole magnet (Q-magnet). In this presentation, the installed BPMs and their calibration methods are described.

In the beam commissioning of J-PARC (Japan Proton Accelerator Research Complex) Linac, the RF amplitude and phase tuning has been performed for its DTL (Drift Tube Linac). The tuning has been performed with a "phase- scan" method, monitoring the output beam energy from each DTL tank. Comparing the obtained phase dependence of the output beam energy with those from the modeling, we have tuned the RF phase and amplitude for DTL tanks mostly within the required tuning accuracy of 1 deg in phase and 1 % in amplitude, although further analysis is required to quantitatively evaluate the achieved tuning accuracy.

Beam commissioning of J-PARC linac has been performed since November 2006. We have developed wire scanners in order to measure beam profile and perform transverse matching. Four wire scanners are installed at each matching section. We report the result of measurement of beam profile.

A transverse matching scheme has been planned for the J-PARC linac beam commissioning with use of wire scanners. The beam diagnosis layout has been determined to realize the planned matching scheme. Continuous monitoring of the matching with beam position monitors is also discussed.

In the J-PARC LINAC, there are mainly two requirements for calibration of beam position monitors (BPMs). One is that BPMs need to be calibrated with the accuracy of less than about a hundred micrometers to minimize beam loss for the world highest class of proton intensity. The other is that about a hundred of BPMs need to be calibrated and maintained consistently. To achieve these requirements, the calibration tools are being developed. During development, experiences on real beam in a MEBT line set for the DTL commissioning are utilized. The status of the development of calibration tools is described in this paper.

A direct fast‐chopped beam extracted from a surface‐plasma H− ion source is proposed and a preliminary test has been examined. The converter bias voltage is modulated by rf pulses and the extracted H− beam is observed. The direct fast‐chopped H− beam extracted from the ion source has a good response to the modulation of the converter bias voltage, as expected. The chopped H− beam extracted by this method has been injected into the 500 MeV booster synchrotron at KEK‐PS.

The construction of the initial part of the J-PARC linac has been started at KEK for beam tests before moving to the JAERI Tokai campus, where J-PARC facility is finally to be constructed. The RFQ and MEBT (Medium Energy Beam Transport) have already been installed at KEK, and the beam test has been performed successfully. In this paper, the experimental results of the beam tests are presented together with simulation results with a 3D PIC (Particle-In-Cell) code.

The construction of the initial part of the J-PARC linac has been started at KEK for beam tests before moving to the JAERI Tokai campus, where J-PARC facility is finally to be constructed. The RFQ and MEBT (Medium Energy Beam Transport) has already been installed at KEK, and the beam test has been performed successfully. In this paper, the experimental results of the beam test are compared with simulation results with a 3D PIC (Particle-In-Cell) code, IMPACT. Copyright 2003 American Institute of Physics

A high duty UHF (432-MHz) RF source for the intense proton linac of the Japanese Hadron Project (JHP) has been constructed at KEK. A test-linac consisting of a RFQ and a drift-tube (DTL) structures is under construction. The UHF RF power generated by 2-MW peak power klystron will be fed into these structures with 650 /spl mu/sec pulse-duration and 50 Hz repetition-rate through an waveguide system with a Y-junction circulator. A dc high voltage (max. 95 kV) is applied to a cathode of the klystron and a beam current is modulated up to 40 A by a pulsed high voltage (max. 80 kV) applied to a modulating anode. The klystron power supply can operate two such klystrons simultaneously with two individual anode modulators. The first operation of this RF power source and the preliminary test of an RF signal processing such as PLL and ALC are reported. >

A fast beam chopping directly in a surface-plasma H/sup -/ ion source was proposed and a preliminary test has been examined. The converter bias voltage is modulated and the extracted H/sup -/ beam is observed. The direct fast chopped H/sup -/ beam extracted from the ion source responds to the modulated converter bias voltage as expected. The extracted beam using this method has been accelerated by the 40 MeV linac.

In order to measure the transverse beam emittance non-destructively, we have developed a new method using profile monitors. The usual assumption of Gaussian distribution is not necessary for it to measure the percent emittance. So, even if the profile is far from Gaussian, the percent emittance can be measured accurately. This method was applied to the 20 MeV KEK beam transport line and resulted in horizontal and vertical emittances of ϵh = 85 mm mrad and ϵv = 25 mm mrad containing 85% of the particles.

Depolarization of the polarized proton beam accelerated in the 500 MeV booster was investigated as the first step of polarized proton acceleration in the KEK proton synchrotron. Beam polarization was measured in the 20 MeV beam transport line from the linac to the booster and in the main ring at the injection energy of 500 MeV. About 40 % of the linac beam polarization was kept in the main ring.

An RFQ model linac of 62 cm long at a frequency of 200 MHz was constructed using a computer program "QKEK" developed at KEK. QKEK generates an RFQ linac, calculates beam dynamics, and provides geometrical data of vanes for a numerically controlled milling machine. A detailed study of rf characteristics was performed. The accelerating and focusing fields measured by the bead perturbation method on axis agree well with the design values. An RFQ linac, which accelerates protons from 50 keV to 750 keV, is designed.

The KEK GeV Proton Synchrotron aims at an intensity as high as 10/sup 13/ protons/pulse. For instance, a combination of a 50 MeV linac and 8 to 10 GeV separated function type synchrotron with reasonable aperture planned in the early stage of designing gives the space charge limit of 1.8 x 10/sup 12/ protons/pulse. By inserting a 500 MeV booster synchrotron and replacing with a 20 MeV linac, the incoherent space charge limit of the main synchrotron is raised to 2.0 x 10/sup 13/ protons/pulse. The 500 MeV booster is a fast-cycling combined-function type AG synchrotron with a repetition rate of 20 Hz. The mean radius of the booster is 6 m, which corresponds to one ninth of the main ring. Nine beam pulses from the booster every two seconds are stacked into the main ring longitudinally. Synchronization between the rf accelerating systems of the booster and the main ring requires the transition energy of the booster as far as possible from the ejection energy of the booster. Several candidates for the lattice structure of the booster synchrotron were studied, and triplet lattice of FDFO was chosen from the view point of the high transition energy.

Various beam profile monitor systems provide an invaluable tool for studying beam behavior throughout the acceleration cycle in the main ring and booster. Non-destructive slow profile monitors are used for injection, magnet, rf, internal target and fast extraction studies. The time resolution of the slow profile monitor is 30 ..mu..sec. A multiwire secondary emission profile monitor which is sensitive enough to work with single bunch is used for injection tuning. Single wire secondary emission scanners are used for the circulating beam. These profile monitors are cross-checked in precision. As an application of non-destructive profile monitoring, a position monitor is installed in main ring and booster.

A simple, and rich in information, method for Q-measurement is developed. The method is essentially Fourier analysis, using a transient recorder and minicomputers. The word "simple" is for electronic circuit, though the program of computer is not so complicated. We use the revolution frequency of bunched protons as a "clock", so our method is free from recalibration or elimination of revolution frequency. We were able to measure Q-value even in the case that betatron oscillation was very rapidly damped.

The high speed orbit display capable of following one bunch during one turn was built for KEK 12 GeV proton synchroton and has been used during the present running in period. The information on the beam orbit and its variations during one turn is very helpful for a systematic tune up at the injection of the cycle and steering the beam on to target and ejection channels. In order to follow betatron amplitudes, 56 pick-up electrodes (28 horizontal, 28 vertical), 4 per betatron wave length, are distributed around the main ring of about 300 m circumference. The position signals obtained from pick-up electrodes are sent to two local control rooms via low loss coaxial cables. These signals are digitized by specially designed analogue-to-digital converter and then sent to the satellite computers upon request. The computers are connected to the KEK control computer network. The central computer collects the data from two satellite computers and calculates the beam position at each electrode and displays the results on graphic terminal. The system was intended to be economical, ease of maintenance and wide dynamic range with high accuracy. The overall accuracy of the position measurement, including electrode alignment, is expected to be 1more » mm +- 3% of the distance from center.« less

An Alvarez linac is being built to increase the injection energy of the booster synchrotron from 20 MeV to 40 MeV. Its drift tubes are equipped with quadrupole permanent magnets. It has post couplers and still inherits the two feed system. Two TH 516 RF high power amplifiers, which have excited the 20 MeV linac, are modified so that one excites the old linac and the other the new one. 40 MeV H- beams will be supplied to the booster in November of 1985.

The second 750 kV Cockcroft preaccelerator is being built for polarized H- ions. The accelerating column is similar to the present one. The accelerated ions will be transported by a 40 m beam line. At the beginning of the line, the spin is rotated from parallel to the beam to vertical. An ordinary H- ion source is also developed and 20 mA is achieved.

A stepping motor control for a fast beam scraper in high vacuum is described. High speed (5 degrees /ms) and smooth angular velocity are obtained by using inertia motion within 270 degrees in one revolution.

An optically pumped polarized H− ion source which uses an electron pick‐up reaction of low energy HT ion from optically pumped sodium atoms has been developed for the acceleration of a polarized proton beam in the 12 GeV synchrotron at KEK. In this polarized ion source, a 16.5 GHz ECR ion source is used as a H+ ion source. In a preliminary experiment, we have obtained about 10∼25 μA H ion beam of 83±27∼39±21% polarization.

A multi‐cusp H− ion source was built for the charge‐exchange multiturn injection project in the KEK 500 MeV booster proton synchrotron. More than 20 mA H− ion beam was extracted from the ion source, 18 mA was injected in the linac and 8.5 mA was accelerated up to 20 MeV. Beam was successfully injected in the booster and a new intensity record of 500 MeV proton beam was obtained.

Optically pumped polarized H− ion source has been developed for the 12 GeV proton synchrotron at KEK. Sodium atoms are electron‐spin polarized by two single frequency dye lasers. Protons, which are yielded by an ECR ion source, receive the polarized electrons from the sodium atoms and are polarized by conventional zero‐crossing method. The hydrogen atoms become H− ions by charge‐exchange reaction with sodium vapor. Beam intensities and polarizations so far achieved are 15 μA with 60 % and 25 μA with 40 % at 350 keV. The intensity increases recently to 30 μA and the beam is accelerated to 20 MeV by the linac and injected in the 500 MeV booster synchrotron. The polarization is 45∼56 % at 20 MeV.