[en] Two magnetic horns have been designed and constructed for the long-baseline neutrino oscillation experiment from KEK to SuperKamiokande. The horns, which produce the toroidal magnetic field along the beam axis, are used to enhance the neutrino flux. Pulsed current of 250 kA (2 msec) which is synchronized with a fast extracted proton beam from the accelerator will be supplied every 2 sec. for both horns. A trial run of horns has been started. (author)

[en] When the hadrons of high energy are collided with relatively heavy nuclei, the intermediate mass fragments (IMF) heavier than alpha particles are released. This reaction is called target nucleus fragmentation reaction. The IMF formed by the nuclear reacted in the region where the total energy of motion of incident particle exceeds several GeV is considered to arise by target multi-fragmentation (TMF). By examining this TMF reaction in detail, it is expected that the information on the nuclear system in high excitation state formed before IMF was released can be obtained. Particularly in this energy region, the possibility that the phase transition from liquid drops to gas of nuclear substances occurs is high. If the particles sufficiently lighter than target nuclei can be used as incident particles, only the IMF originated in target nuclei can be observed. Such experiment carried out so far is summarized. The purpose of this research is the precise, high accuracy observation of the information on TMF. This is the preliminary measurement of TMF using 12 GeV proton beam of the KEK-PS. A coaxial Bragg curve counter is used for the measurement of IMF. The results of measurement are reported. (K.I.)

[en] We have constructed the new counter experimental hall at the KEK 12 GeV Proton Synchrotron (KEK-PS) in order to handle high intensity primary proton beams of up to 1x10³ pps (protons per second), which is one order of magnitude greater than the present beam intensity of the KEK-PS, 1x10¹² pps. New technologies for handling high-intensity beams have, then, been developed and employed in the construction of the new hall. A part of our R/D work on handling high intensity beams will be reported. (author)

[en] High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Agency (JAEA) constructed Japan Proton Accelerator Research Complex (J-PARC) in Tokai, Ibaraki. It succeeded in the slow extraction beam at 19:35 January 27, 2009 to the hadron beam line, and the observation of Kaon in the K1.8BR beam line. The secondary particle generation target of the hadron beam line adopts the rotating disk method of water-cooled directly. It is necessary to become interrupted the vacuum line at the rotating disk target because of water-cooled. Therefore the beam window was needed in the design that considered similar thermal loading, corrosion to the target, and the exchange function. (author)

[en] The new counter experimental hall was constructed at the KEK 12 GeV Proton Synchrotron (the KEK-PS) in order to handle high-intensity primary proton beams of up to 1 x 10¹³ pps (protons per second), which is one order of magnitude greater than the present beam intensity of the KEK-PS, 1 x 10¹² pps. New technologies for handling high-intensity beams have, then, been developed and employed in the new hall construction. A part of our R/D work on handling high intensity beam is briefly reported. (author)

[en] The experiments of the hadron facility were operated with a slow extraction beam for 2 cycles after the great east Japan earthquake on 2011. The maximum intensity was 6 kW for RUN no.40, 14 kW for RUN no.43 on 2012. The indirect water-cooling Pt fixed target (50% of beam loss) was designed based on the last report, and it was used for these experiments. The thermo couples with high speed response were installed for a preliminary target design of high intensity beam. The distribution and the rapid transition of temperature were measured successfully. As a result of analyzed with transient temperature data, the heat transfer coefficient is 11293[W/m² K] between Pt target and Cu base block, 9282[W/m² K] between Cu base block and the SUS pipe of cooling water. FEM analysis which replaced the target material with Au from Pt was executed at 25 kW of beam intensity conditions. The shear stress is reduced one half with replaced the target material, therefore Au target can use to under 70 kW within the stress analysis. Au target case also needs to design for the pipe arrangement of cooling water without boiling, for a target not to melt. (author)

[en] K1.1 beam line is joined in the hadron experimental hall in this year, and it becomes four beam lines (K1.8, K1.8BR, and KL) in total. It is scheduled that slow extraction is restarted in October, 2010 and the beam power will be increased up to 5 kW. T1 target is the first production target in hadron experimental hall. To obtain the amount of the maximum Kaon for this primary beam intensity, operation plan of T1 target was examined. As a result, air-cooling fixed target is used for the beam power of 5 kW. Moreover, use water-cooling fixed target made of the platinum for 30 kW. The rotating target made of the nickel will be used in 30 kW or more. (author)

[en] In order to verify presence of neutrino oscillation at present, the K2K experiment is carried out. The K2K is an abbreviation of 'KEK to Kamiokande', where KEK is a place forming neutrino and Kamiokande is an elementary particle observation apparatus with 40 m in diameter, 42 m in height, and 50,000 ton of pure water, and situated at 1,000 m in depth of the old Kamioka mine in Gifu prefecture. For formation of neutrino, proton beam by 12 GeV accelerator at KEK was used. The proton beam passed through 400 m of neutrino beam line, and was charged into a target in a horn situated at it downstream to form particle and pi meson constituting origin of neutrino formation. The pulse source was flown 250 kA of pulse current into a horn electromagnet synchronously with taking out of proton beam from an accelerator (two seconds in period) in order to focus pi meson to a direction of the Kamiokande. Here were reported on design to operation results on the apparatus comprising of capacitor, high voltage capacitor, thyristor switch, and pulse transformer. (G.K.)

[en] Noxious gases, produced by the radiolysis of air during accelerator operation, finally formed HNO₃ and caused the corrosion of the accelerator components. Then the production rate of noxious gases in the tunnel of PS beam line is the important information for J-PARC accelerator. In order to obtain the information of noxious gases in the accelerator tunnel, the production rate of noxious gases in gas systems mixed with N₂ and O₂ gases were measured in the neutrino beam line at KEK. The experimental results were agreement within about factor 4 with the estimation values which were calculated using Monte Carlo code MARS and G-value of ozone. The production rate in O₂ gas is lowest among various gas systems. Production rates of tritium in O₂ gas, N₂ gas and air for 12 GeV protons and secondary neutrons were measured using 12 GeV Proton Accelerator Facility. The tritium production rates in those gases were good agreement with the results of the calculation using MARS code. (author)

[en] A liquid argon TPC is a very useful detector for the next generation physics to search for “CP violation in lepton sector”, “nucleon decay” and “dark matter”. The hundred kton liquid argon TPC in the Okinoshima island has been proposed to perform such physics in future. To check the detector performance of liquid argon TPC, especially particle IDs, we performed test beam in October 2010 using K1.1BR beamline in J-PARC hadron hall, so called T32 test-experiment. In last T32 experiment, the prototype cryostat with size of 250 L was borrowed from MEG (Mu → E+gamma) experiment, but we had to bring it back to Europe, therefore we started to design and have produced a new cryostat for the next possible test-beam from September 2010. For the R and D on the liquid argon TPC, the good purity is indispensable, therefore the liquid circulation system and good pre-cooling system is crucial. We added the materials for those R and D improvements to the new cryostat. We report the results of the various performance tests on the cryostat which has been performed at present in this article. (author)