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In order to handle high intensity primary proton beam provided by Japan Proton Accelerator Research Complex (J-PARC), radiation-resistant beam lines have been constructed at Hadron Experimental Hall of J-PARC. The key technology of the radiation-resistant beam line is the radiation-resistant magnets. However all the peripheral devices of the magnets were designed and assembled as radiation-resistant ones since peripherals as well as magnets should be operated in very high radiation environment. In addition a safe operation and maintenance scheme of high intensity beam lines has been established based on the Chimney technology of radiation-resistant magnets including their peripherals. Then the beam lines in the Hadron Experimental Hall have been constructed with “radiation-resistant magnet system”. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

More than 50 radiation-resistant electromagnets were constructed for the primary proton and the secondary particle beam lines of the Hadron Experimental Hall of Japan Proton Accelerator Research Complex (J-PARC). The main radiation- resistant technologies we employed were the Polyimide-resin Insulation conductor for magnets at the relatively low radiation exposure and the Mineral Insulation Cable for magnets at the seriously high radiation environment. The remote handling and maintenance scheme of radiation-resistant magnets for seriously high radiation environment was developed also based on the Chimney magnet technology and applied to magnets near the production target in the Hadron Hall. On January 27th 2009, the first proton beam was successfully introduced to the Hadron Hall from the main accelerator of J-PARC, i.e. 50 GeV Proton Synchrotron. On February 10th, the secondary particles were extracted to the experimental area of the Hadron Hall through the secondary particle beam line. No serious problem happened on magnets of both primary proton and the secondary particle beam lines until the end of the beam operation scheduled on February 26th. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The high intensity proton accelerator facility J-PARC is now in its final stage of construction. Soon intense primary proton beams will be slowly extracted to an experimental hall (HD-hall) and transported to a production target. Since the radiation level around the target will be very high, the beam line tunnel needs to be surrounded by 2.5 m-5 m thick concrete shields in the HD-hall. Radiation resistant magnets for handling high intensity beams are buried inside these thick concrete shields. This structure, however, brought us a problem of leading electric power lines to the magnets. For a solution to this problem, we have developed water cooled bus ducts penetrating radiation shield. These bus ducts enable us to connect the power supplies placed outside the shields to the magnets in the shortest power line length without any deterioration of protection ability of radiation shielding. The maximum power capacity of the bus duct is over 5000 A. The bus ducts plays an important part in our radiation resistant magnet system. [ABSTRACT FROM AUTHOR]

A series of construction works of the radiation resistant magnets for the Japan Proton Accelerator Research Complex (J-PARC) external beam facilities is now at the production and installation stage. The main accelerator of J-PARC is the 50 GeV proton synchrotron (50 GeV-PS). The designed intensity of the extracted proton beam from the 50 GeV-PS is 15 μA, i.e. a beam power of 750 kW. Then the radiation-resistant magnets are the key apparatus to construct the external beam lines and experimental facilities of the J-PARC 50 GeV-PS. The radiation-resistant magnets we have foreseen are approximately 50 magnets with Polyimide resin Insulation (P1) for radiation dose up to 108 Gy, and 20 magnets with completely Mineral Insulation Cable (MIC) for higher radiation dose up to 1011 Gy. Most of those magnets have already been fabricated and are waiting for being installed in primary and secondary beam lines. The installation will be completed by the middle of 2008. All the magnets are placed on the plug-in base assembled with water and electricpower quick disconnect devices. A new remote handling system of beam line magnets named "Chimney" has been developed and employed for magnets placed at the highest radiation area near the production target. The first beam will be introduced to the experimental area by the end of 2008. [ABSTRACT FROM AUTHOR]

The facility of the long baseline neutrino oscillation experiment using the J-PARC's 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 [1]. 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Continuity R&D work is reported here on the radiation resistant magnets for the Japan Proton Accelerator Research Complex (J-PARC). The main accelerator Of the J-PARC is the 50 GeV-15 mA proton synchrotron (50 GeV-PS) with beam power of 750 kW. The radiation resistant magnet is the key technology to realize the external beam lines and experimental facilities of the J-PARC 50 GeV-PS. The radiation resistant technologies we have selected for the J-PARC are; (1) Polyimide Resin Insulation (PI) for up to 108 Gy and, (2) Mineral Insulation magnet Cables (MICs) with larger cross sections for higher radiation dose up to 1011 Gy. Approximately 20 polyimide insulation magnets and 10 MIC magnets are designed for the external beam lines of the 50 GeV-PS. The fabrication of those magnets has already started in 2005 and will continue until the end of 2007. [ABSTRACT FROM AUTHOR]