• 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.

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

In the hadron experimental hall at the 50-GeV Proton Synchrotron (PS) of J-PARC, the secondary beam line K1.8 with double stage separator is expected to provide 1-2 GeV/c kaon beams with less contamination of pions mainly for hadron and nuclear physics experiments with strangeness. An electrostatic (ES) separator is one of key elements of this secondary beam line. The ES separator will generate a 75kV/cm electrostatic field between parallel electrodes of 10cm gap and 6m in length along the beam direction. It is designed so as to be radiation-proof and to lower spark rate at the high intensity proton accelerator facility. The K1.8 line has two 6m ES separators with the intermediate focal point upstream of separators to reduce the pion backgrounds from the production target. The K-/π- ratio of the line is expected to have a larger value than 1 at the experimental target. Beam commissioning of the K1.8 has just started. We will report separator performance, optics design of the K1.8 beam line and the first result of the beam commissioning.