• Y. Takeda, Y. Irie, H. Kawakami, M. Oyaizu, I. Sugai, A. Takagi
  KEK, Ibaraki
• T. Hattori, K.K. Kawasaki
  TIT, Tokyo

Japan Proton Accelerator Research Complex (J-PARC) requires thick carbon stripper foils (200-500 ug/cm²) to strip electrons from the H^- beam supplied by the linac before injection into the Rapid Cyclic Synchrotron. A H^- beam of 181MeV energy is injected into the 3 GeV Rapid Cycling Synchrotron (RCS) with a pulse length of 0.5 ms, a repetition rate of 25 Hz, and an average beam current of 200 μA. The H^- ions are stripped into protons by a charge stripper foil in the injection section. For this high-energy and high-intensity beam, the conventional carbon stripper foils will be ruptured in a very short time. Thus, long-lived thick carbon stripper foils are needed to this high-power accelerator. For this purpose, we are described R and D of long-lived Hybrid Boron-mixed Carbon foils (HBC-foils) of 100 - 500 μg/cm² by arc discharge method. The preparation procedure is described and lifetime measurement by using a 3.2MeV Ne⁺ DC beam of 2-3 μA are reported.

• H. Fujimori, Z. Igarashi, Y. Irie, Y. Sato, M.J. Shirakata, I. Sugai, A. Takagi, Y. Takeda
  KEK, Ibaraki

The carbon stripping foil is the key element for the high-intensity proton accelerator. At KEK, the foil test system using the 650keV H^- Cockcroft-Walton accelerator is in operation, which can simulate the energy depositions to the foil with the same amount in the J-PARC. In order to quantatively observe the foil degradations (such as foil thinning, pin-hole production) during irradiation, online energy and particle analyzing system is under construction. This report outlines the design detail of the analyzing system including the detectors.

• T. Fujinaka, T. Matsunaga, S. Mochizuki, H. Takase
  Kyushu University, Center for Accelerator and Beam Applied Science, Fukuoka
• H. Arima, T. Hasuo, N. Ikeda, K. Ishibashi, T. Korenaga, K. Maehata, N. Shigyo, Y. Uozumi, G. Wakabayashi, Y. Yonemura
  Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka
• K. Fujita, T. Morikawa, T. Noro, T. Wakasa
  Kyushu University, Fukuoka
• Y. Mori
  KURRI, Osaka
• H. Nakayama, A. Takagi
  KEK, Ibaraki
• T. Tomimasu
  SAGA, Tosu

150 MeV FFAG accelerator is under construction at Center for Accelerator and Beam Applied Science on Ito Campus to promote activities in all related scientific, medical, engineering and educational field at Kyushu University. In this paper, status of the development of hardware and the results of the beam commissioning of the injector are described.

• K. Takayama, T. Adachi, T. Arai, Y. Arakida, M. Hasimoto, T. Iwashita, E. Kadokura, M. Kawai, T. Kawakubo, K. Koyama, T. Kubo, T. Kubo, H. Nakanishi, K. Okamura, H. Someya, A. Takagi, M. Wake
  KEK, Ibaraki
• T. Kikuchi, T. Yoshii
  Nagaoka University of Technology, Nagaoka, Niigata
• K.W. Leo
  Sokendai, Ibaraki
• K. Mochiki, T. Sano
  Tokyo City University, Tokyo
• M. Okamura
  RBRC, Upton, Long Island, New York
• K. Okazaki
  Nippon Advanced Technology Co. Ltd., Ibaraki-prefecture
• H. Tanaka
  Iwate university, Morioka, Iwate

A novel circular accelerator capable of accelerating any ions from an extremely low energy to relativistic energy is discussed. A digital accelerator (DA)* is based on the induction synchrotron concept, which had been demonstrated in 2006. All ions are captured and accelerated with pulse voltages generated by induction acceleration cell (IAC). The IAC is energized by the switching power supply, in which power solid-state conductors are employed as switching elements and their tuning on/off is maneuvered by gate signals digitally manipulated from the circulating signal of an ion beam. Acceleration synchronized with the revolution of the ion beam is always guaranteed. The concept is realized by renovating the KEK 500 MeV booster into the DA, introducing a laser ablation ion source. Ion energy of 85-140 MeV/au and intensity of 10⁺⁹ - 10⁺¹⁰ /sec are estimated and these ions will be delivered without any large-scale injector. Companion papers** will discuss more details of instruments of DA. Applications for innovative material sciences and life sciences will be briefly introduced as well as the outline of DA.

*K. Takayam, J. of Appl. Phys. 101 (2007) 063304.
**K.Takayama "Ion source and LEBT", T.Adachi "Injection and extraction system", T.Iwashita "Induction acceleration system" in this conference.

• K. Takayama, T. Adachi, T. Arai, Y. Arakida, M. Hasimoto, T. Kawakubo, K. Koyama, T. Kubo, T. Kubo, H. Nakanishi, A. Takagi, K. Zhang
  KEK, Ibaraki
• T. Kikuchi
  Nagaoka University of Technology, Nagaoka, Niigata
• K.W. Leo
  Sokendai, Ibaraki
• K. Okazaki
  Nippon Advanced Technology Co. Ltd., Ibaraki-prefecture

KEK digital accelerator (DA) capable of accelerating all species of ion* is an induction synchrotron employing no large scale injectors. At the beginning of its operation, Ar ions from the ECR ion source (ECRIS) embedded in the 200 kV high voltage terminal (HVT) are directly injected into KEK-DA though the low energy BT line (LEBT). The permanent magnet ECRIS was assembled at KEK. Its characteristics such as a charge-state spectrum, emittance, and intensity are presented. The 200 kV HVT has been also assembled at KEK. Its voltage stability in the pulse mode operation, where a plasma of 1 msec is created by x-band microwaves at 10 Hz, is discussed. The LEBT consists of the Eintzel lens, momentum analyzer, B magnets with edge focusing, electrostatic chopper**, and a combination of Q magnets. In the upper LEBT from the ion extraction hall to the entrance of the analyzer, possible charge-state ions are contaminated in the space-charge limit and beam focusing is realized through the Eintzel lens and tandem acceleration gaps. In the lower LEBT from the analyzer to the KEK-DA injection point, the lattice has been optimized so as to meet optics matching at the injection point.

*K. Takayama, J. of Appl. Phys. 101 063304(2007), "KEK digital accelerator for material and biological sciences" in this conference
**T.Adachi, "Injection and extraction system" in this conference

• Y. Irie, S. Fukumoto, K. Muto, H. Nakanishi, A. Takagi
  KEK, Ibaraki
• D. Bayley, I.S.K. Gardner, R.J. Mathieson, A. Seville, J.W.G. Thomason
  STFC/RAL/ISIS, Chilton, Didcot, Oxon
• J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf
  ANL, Argonne
• T. Oki
  Tsukuba University, Ibaraki

A low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron has been developed by collaboration between Argonne National Laboratory (US), KEK (Japan) and Rutherford Appleton Laboratory (UK). The system has less than 30 Ω of output impedance over wide frequency range of 2.7-6.2 MHz. However, distortions of voltage waveform in the driver stage have been a long-standing issue. It was found such distortions were generated depending upon the higher-order-modes of the anode-choke impedance. In this report, method to realize the smooth sinusoidal waveform in the wideband system is presented.

• M. Yoshii, K. Hara, C. Ohmori, T. Shimada, H. Suzuki, M. Tada
  KEK/JAEA, Ibaraki-Ken
• E. Ezura, K. Hasegawa, A. Takagi, K. Takata
  KEK, Ibaraki
• M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

The Japan Proton Accelerator Complex includes the 3GeV rapid cycling synchrotron (RCS) and the 50GeV main ring synchrotron (MR). Both synchrotrons use the high field gradient magnetic alloy (MA) loaded cavities. In RCS, 11 RF systems have been fully operational since December 2008. The RCS RF systems are operated with dual-harmonic acceleration voltages. Beam acceleration and bunch shape manipulation are efficiently taking place. 120kW of the neutron user operation was started at the Material and Life science facilities in November 2009. In MR synchrotron, the 5th RF system were installed in August 2009, and therefore 5 RF systems are now in operation. Beam commissioning for delivering protons to the hadron facility and neutrino beam experimental facility are under way. The neutrino user experiment is intended to start January 2010. Proton beam operation with more than 100kW is required. The approaches to realizing high intensity operation and the MR upgrade plan will be presented.

• M. Yamamoto, M. Nomura, A. Schnase, T. Shimada, H. Suzuki, F. Tamura
  JAEA/J-PARC, Tokai-mura
• E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, M. Tada, A. Takagi, K. Takata, M. Yoshii
  KEK, Ibaraki

The Longitudinal emittance in J-PARC RCS should be controlled to accelerate a high intensity proton beam with minimal beam loss. In order to study and minimize the beam loss during acceleration, the optimized way to add the 2nd higher harmonic rf has been calculated by a particle tracking code. Furthermore, the bunch shape at RCS extraction should be controlled and optimized for the MR injection. For this purpose, the optimum RCS acceleration pattern has been calculated. We describe the simulation results and the comparison with the beam test.

• C. Ohmori, K. Hasegawa, A. Takagi
  KEK, Ibaraki
• K. Hara, T. Shimada, H. Suzuki, M. Tada, M. Yoshii
  KEK/JAEA, Ibaraki-Ken
• M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

Magnetic alloy cavities are successfully used for J-PARC synchrotrons. These cavities generate much higher RF voltage than ordinary ferrite cavities. For future upgrades of J-PARC facilities, a higher field gradient is necessary. It was found that the characteristics of magnetic alloy is improved by a new annealing scheme under magnetic field. A large production system using an old cyclotron magnet is under construction for the J-PARC upgrade. The status of core development will be reported.

• A. Takagi, Y. Irie, I. Sugai, Y. Takeda
  KEK, Ibaraki

Thick carbon foils (>300ug/cm²) has been used for stripping of H^- ion beam into protons at the injection stage of the 3GeV Rapid Cycling Synchrotron (3GeV-RCS) in J-PARC. The carbon stripping foils with high durability at high temperature >1800K are strongly required. We have recently developed a new irradiation system for lifetime measurement of the stripping foils using the KEK 650keV Cockcroft-Walton type of high voltage accelerator with high current pulsed negative hydrogen ion beam, which can simulate the high energy-depositions upon foils in the RCS. It is found that, by adjusting the peak intensity and the pulse length of the hydrogen ion beams appropriately, the energy deposition becomes equivalent to that exerted by the incoming hydrogen ions and the circulating protons at the injection process of the RCS. The most important factor that affects the foil lifetime is the foil temperature. During lifetime tests by this system, the temperature of foil is measured by a fast thermometer and by using a phototransistor in a pulsed mode (650keV, 10mA, 0.25msec, 25Hz). The new irradiation system and some preliminary results on lifetime of the carbon stripping foil will be presented.