Y. Katoh

Precision positioning of SuperKamiokande with GPS for a long-baseline neutrino oscillation experiment

Abstract A positioning of the neutrino detector SuperKamiokande (SK) was made for a long-baseline neutrino oscillation experiment planned at KEK. For positioning, Global Positioning System (GPS) was employed. It has been demonstrated that GPS is of practical use for measuring the positions of SK and KEK, being 250 km distance from each other, to a better resolution. The geodetic coordinates at the SK center were obtained to be Lat. 36°25′32.5862″ N., Long. 137°18′37.1241″ E., H. 371.839 m in the global ellipsoidal coordinate system, WGS-84. The obtained coordinates are based on the coordinates given at a triangulation point at the KEK site. The present work will be fed back for constructing the neutrino beam line.

Development of Indirect-Cooling Radiation-Resistant Magnets

In a high-intensity proton beam facility, beam line elements downstream of a production target are exposed to a huge amount of radiation and heat. Beam pipes are closer to the beam than the magnet poles and more difficult to cool sufficiently without tritium production. Therefore, the magnets are placed in a large vacuum chamber, instead of using vacuum pipes located within the pole gaps. We have adopted indirect-cooling mineral-insulation-cable (MIC) coils for these magnets. They have a great advantage that the mechanical strength and the insulation performance can be significantly improved by avoiding the use of ceramic insulation pipes, because electric circuits are completely separated from water passages. We have made coils using 1000-A-class solid-conductor MICs and stainless-steel pipes, and tested magnet operation in vacuum. By improving the structure of end parts of MICs and increasing their emissivity, we have successfully fed the current of DC 1000 A to the solid-conductor MIC coils in vacuum.

The Beam-Handling Magnet System for the J-PARC Neutrino Beam Line

The facility of the long baseline neutrino oscillation experiment using the J-PARCs 50 GeV-0.75 MW proton beam is now under way. The primary proton beam line consists of three sections, i.e. the first preparation (PP) section with normal conducting magnets, the second arc (ARC) section with superconducting magnets and the third final focus (FF) section with normal conducting magnets. In the PP section, we have to clean the primary proton beam extracted from the 50 GeV-PS and transport halo-less pure beam only to the ARC section. In the FF section the magnets have to be placed very close to the pion production target and horns. Therefore the normal conducting magnets have to work in the very high radioactive environment. The R&D works on the radiation resistant magnets for handling a high-intensity proton beam have already been continued at KEK as reported in . Another important point regarding high-intensity beam handling is to realize easy maintenance of the beam line. Any magnet experiencing trouble can be easily removed from beam line and repaired remotely. For this purpose, we developed new tools for the magnet maintenance. These are automatic sling apparatus, quick alignment and installation guide, and the quick disconnect devices of cooling water and electric power. In this paper, we will report the beam line maintenance scheme developed for the neutrino beam line, as well as the design of normal conducting magnet sections

Development of radiation-resistant magnets for the JHF project

In connection with the Japan Hadron Facility (JHF) Project, R&D work on the radiation-resistant magnets has continued at KEK. JHF is the next-generation high-intensity accelerator project of Japan and aims to provide 1 MW 3 GeV/50 GeV proton beams for various fields of science.

Magnet Operation in Vacuum for High Radiation Environment Near Production Target

In a high-intensity proton beam facility, beam line elements downstream of a production target are exposed to a huge amount of radiation and heat. A water-cooled beam collimator must be located between the target and the magnets, and the iron yokes of the magnets also have to be cooled by water. Moreover, beam pipes are closer to the beam than the magnet poles and more difficult to cool sufficiently without tritium production. Therefore, the magnets are placed in a large vacuum chamber, instead of using vacuum pipes located within the pole gaps. In order to reduce the residual radiation dose during maintenance, the chamber lid and feedthroughs are 4 meter above the beam line, and radiation-shielding blocks are also stacked in the chamber. We have tested magnet operation in vacuum using a dipole magnet with mineral-insulation-cable (MIC) coils and a nickel-coated yoke. A magnet with 2500-A-class hollow-conductor MIC coils has worked successfully with the current of DC 3000 A. The stability of operation in vacuum was confirmed by measuring the temperature with thermocouples and the magnetic field with a NMR probe. We have also succeeded in operating a 1000-A-class solid-conductor MIC coil in vacuum

Indirectly Cooled Radiation-Resistant Magnets for Hadron Target Station at J-PARC

The target station in the hadron experimental facility at J-PARC consists of a production target and a huge vacuum chamber in which several secondary-beam-line magnets can work. This vacuum chamber system aims to remove the vacuum beam pipe from the magnet gap, because the cooling of the beam pipe is the most serious problem in the high intensity beam facility. We have developed indirectly cooled radiation-resistant magnets for the hadron target station. Their coils are made of solid-conductor type mineral-insulation cables and stainless-steel water pipes. They have the great advantages that electric circuits can be completely independent of water pass. The mechanical strength and the insulation performance of the coil are significantly improved also because the insulation water pipes can be avoided from the water pass. A C-type sector dipole and a figure-8-type quadrupole magnet have been fabricated by using indirectly cooled radiation-resistant magnet technology, and installed in the vacuum chamber. We have succeeded to operate them in vacuum stably with the current of DC 1000 A by improving the end structure of the MIC coils and increasing their emissivity. These magnets have been used for the real beam operation without any serious problems.

Radiation-Resistant Magnets for J-PARC

Several species of radiation-resistant magnets were developed for J-PARC, a Japanese brand-new high-intensity accelerator complex, whose maximum beam power reaches 1 MW. The first development was polyimide insulation magnets. The ordinal epoxy resin was replaced by polyimide resin in order to improve its radiation lifetime up to 4 × 108 Gy. Most accelerator magnets of J-PARC were assembled with polyimide insulation coils. Peripherals of polyimide insulation magnets, such as insulation water tubes, water valves, water gaskets, etc., were replaced also by ones made of inorganic materials. The second development was mineral insulation magnets. Magnet excitation coils were made of “Mineral Insulation Cable (MIC).” The copper conductor of MIC was surrounded by a thin MgO insulation layer, and the MgO layer was covered by a copper sheath. Several sizes of MIC cross section were developed for large and small magnets with various maximum currents from 1000 to 3000 A. Peripherals of magnets assembled with MIC coils were also made of completely inorganic materials. These MIC magnets were used at the downstream part of beam loss points such as the secondary particle production target of Hadron Experimental Facility. The R&D stories of the radiation-resistant magnets, including the present status of the magnet operation, are briefly summarized.

Development of radiation resistant magnets for JHF/J-PARC project

A series of the R&D works on the radiation resistant magnets for the Japan Hadron Facility (JHF) project has been continued at the High Energy Accelerator Research Organization (KEK). The JHF is a high-energy part of the Japanese high intensity Particle Accelerator Research Complex (J-PARC), which is Japanese next-generation high-intensity accelerator project. The main JHF accelerator is the 50 GeV proton synchrotron and will provide high intensity 15/spl mu/A proton beam for various nuclear and particle physics experiments. This time, the actual sized completely-inorganic radiation-resistant quadrupole magnet, designed for the 50 GeV proton beam transportation, was manufactured successfully by using mineral insulation magnet cable (MIC). The assembling procedure and the test results are presented in this issue.

Indirectly Cooled Radiation-Resistant Magnet With Slanting Saddle Shape Coils for New Secondary Beam Extraction at J-PARC Hadron Facility

We have developed the most upstream dipole magnet K1.1D1 for a new secondary beam line at the hadron experimental hall in J-PARC. It is placed downstream of a production target and is close to the K1.8D1 magnet. Indirectly cooled coils using mineral insulation cables have been adopted for high radiation resistance. The coils have a slanting saddle shape in order to minimize the interference of the magnetic field between the two magnets. It has been operated during the beam time in the autumn of 2010 without any problems.

Construction and beam commissioning of Hadron Experimental Hall at J-PARC

The new facility J-PARC has been constructed in Tokai, Japan. It aims at providing intense proton beams of 750 kW for next-generation particle and nuclear physics experiments. The Hadron Experimental Hall (HD-hall) is one of the two facilities at the J-PARC Main Ring and utilizes various secondary particles produced by the slowly extracted primary proton beam. We have constructed two charged and one neutral secondary beam lines. The K1.8 beam line transports separated charged secondaries with the maximum momentum of 2 GeV/c. Secondary particles are purified by two electrostatic separators (ESSs). The K1.8BR beam line is branched from the K1.8 at the bending magnet downstream of the first ESS. The K1.8BR delivers separated charged beams with the momentum up to 1.2 GeV/c. On January 27th, 2009, the first beam was successfully extracted to the HD-hall and transported to the beam dump. The first secondary beam extraction to the K1.8BR beam line succeeded in February 2009. The beam commissioning of the K1.8 and KL beam lines started in October 2009.