• A. Toyoda, A. Agari, E. Hirose, M. Ieiri, Y. Katoh, A. Kiyomichi, M. Minakawa, T.M. Mitsuhashi, R. Muto, M. Naruki, Y. Sato, S. Sawada, Y. Suzuki, H. Takahashi, M. Takasaki, K.H. Tanaka, H. Watanabe, Y. Yamanoi
  KEK, Tsukuba
• H. Noumi
  RCNP, Osaka

Optical beam measurement such as OTR(Optical Transition Radiation), ODR(Optical Diffraction Radiation), gas Cerenkov, and so on is a powerful tool to observe a two-dimensional information of high intensity beam profile, so that this method is widely used at various electron and hadron accelerators. However, high radiation field to damage an optical system gradually becomes a major issue with increasing the beam intensity to explore new physics. Our present effort is devoted to develop a high efficient optical system to resist such high radiation field. We newly designed an optical system composed of two spherical mirrors which do not have any lenses vulnerable to radiation. Detailed optics design and a result of optical performance test will be presented. Also we will report a result of a beam test experiment of this optics system combined with an OTR screen performed at high intensity proton extraction beamline of the J-PARC.

• S. Onuma, K. Mochiki
  Tokyo City University, Tokyo
• T. Adachi, A. Kiyomichi, R. Muto, H. Nakagawa, H. Someya, M. Tomizawa
  KEK, Ibaraki
• T. Kimura
  Miyazaki University, Miyazaki
• K. Noda
  NIRS, Chiba-shi
• H. Sato
  Tsukuba University, Ibaraki

J-PARC is a new accelerator facility to produce MW-class high power proton beams. From the main ring (MR) high energy protons are extracted in a slow extracted mode for hadron experiments. The beam is required with as small ripple as possible to prevent pileup events in particle detectors or data acquisition systems. We took beam tests at HIMAC using a prototype signal processing unit. In these beam tests we had recognized the improvement of the extracted beam structure by using the feedback algorithm whose parameters were changed according to the beam characteristics. We have developed a new signal processing unit for the spill feedback control of J-PARC. The unit consists of three signal input ports (gate, spill intensity and residual beam intensity), three signal output ports (spill control magnets), two DSPs (power spectrum analysis and spill feedback control), dual port memories, FPGAs and a LAN interface (remote control with SUZAKU-EPICS). From October 2009, this unit is being used in the beam study of J-PARC MR to check the performance of digital filtering, phase-shift processing, servo feedback control, real-time power spectrum analysis and adoptive control.

• M. Tomizawa, T. Adachi, Y. Arakaki, A. Kiyomichi, S. Murasugi, R. Muto, H. Nakagawa, K. Niki, K. Okamura, Y. Sato, S. Sawada, Y. Shirakabe, H. Someya, K.H. Tanaka, T. Toyama, E. Yanaoka
  KEK, Ibaraki
• A. Ando, Y. Hashimoto, T. Koseki, J. Takano
  J-PARC, KEK & JAEA, Ibaraki-ken
• D. Horikawa, I. Sakai
  University of Fukui, Faculty of Engineering, Fukui
• K. Mochiki, S. Onuma
  Tokyo City University, Tokyo
• H. Sato
  Tsukuba University, Ibaraki
• A. Schnase
  JAEA/J-PARC, Tokai-mura

High power protons from the J-PARC main ring is slowly extracted using the third integer resonance and delivered to the experimental hall for various nuclear and particle physics experiments. The slow extraction device comprises two electro static septa (ESS),ten magnetic septa, four bump magnets, eight resonant sextupole magnets and their power supply. One of the critical issue of the slow extraction is radiation caused by the beam loss during the slow extraction. We have developed the electrostatic and magnetic septa with thin septum thickness. A unique scheme with large step size and small angular spread of the extracted beam enables hit rate on the ESS less than 1% level. In January 2009, first 30 GeV proton beam has been successfully delivered to the fixed target. Quadrupole magnets and a DSP feedback control system to obtain a uniform beam spill structure were implemented in 2009 summer shutdown period. We will report the extraction efficiency, extracted beam profiles and spill structure obtained by the beam commissioning so far. We will also mention a upgrade plan based on some new ideas to aim a higher performance.

• A. Kiyomichi, T. Adachi, A. Akiyama, S. Murasugi, R. Muto, H. Nakagawa, J.-I. Odagiri, K. Okamura, H. Sato, Y. Sato, S. Sawada, H. Someya, K.H. Tanaka, M. Tomizawa, A. Toyoda
  KEK, Tsukuba
• T. Kimura
  Miyazaki University, Miyazaki
• K. Mochiki, S. Onuma
  Tokyo City University, Tokyo
• K. Noda
  NIRS, Chiba-shi

The slow extraction beam from the J-PARC Main Ring (MR) to the Hadron Experimental Facility is used in various nuclear and particle physics experiments. A flat structure and low ripple noise are required for the spills of the slow extraction. The spill control system has been developed for the J-PARC slow extraction to make a flat structure and small ripple. It consists of the extraction quadrupole magnets and feedback device. The extraction magnets consist of two kinds of quadrupole magnets, EQ (Extraction Q-magnet) which make flat beam and RQ (Ripple Q-magnet) which reject the high frequent ripple noise. The feedback system, which is using Digital Signal Processor (DSP), makes a ramping pattern for EQ and RQ from spill beam monitor. The extraction magnets and feedback device were installed in September 2009, and spill feedback study were successfully started from the beam time in October 2009. Here we report the operation status of magnets and first study of beam commissioning with spill feedback.