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We developed a Lambertson magnet and two septum magnets as the splitting devices for the new beamline at the Hadron Experimental Facility in J-PARC. This new beamline, now under construction, is called high-p/COMET beamline, and the experiments using 30- and 8-GeV proton beams are planned. The required functions of the splitting devices are as follows: to split a small fraction (around 10−4) of the 30-GeV proton beam into the high-p/COMET beamline (30-GeV mode) and to bend all of the 8-GeV proton beam into the high-p/COMET beamline (8-GeV mode). These two requirements are met by adjusting the vertical beam position at the entrance of the Lambertson magnet. In 30-GeV mode, the Lambertson magnet is used to scrape the beam halo of the proton beam and bend the beam into the high-p/COMET beamline. The beam loss at the Lambertson magnet is inevitable; thus, the magnet must be resistant to the radiation and heat caused by the beam loss. The magnet is composed of nonorganic materials only and equipped with two water pipes to remove the heat induced by the beam loss. The branched beam is bent further by two septum magnets at the downstream of the Lambertson magnet. The construction and the magnetic field measurements of these devices were completed in March 2015, and the installation into the beamline is planned for the summer of year 2017.

An electrostatic separator is one of the key elements of a secondary beam line at the Hadron experimental hall of J-PARC. It generates a transverse electric field along the beam axis to separate particles of the same momentum by their mass differences. Two beam lines for charged secondary particles, K1.8 and K1.1BR, are constructed, to provide kaon beams with less contamination of pions. Three experimental areas, K1.8, K1.8BR and K1.1BR are available for nuclear and particle physics experiments. Two 6-m-separators and a 2-m-separator of a Wien filter type are installed for the K1.8 and the K1.1BR beam lines.

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.

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 .

The new electrostatic (ES) separator to select and deliver 1–2 GeV/c kaon beams is made for the secondary beam line at the high intensity proton accelerator facility. The ES separator will generate a 75 kV/cm electrostatic field between parallel electrodes of 10 cm gap and 6 m in length along the beam direction. The K − /π − ratio of the line is expected to have a larger value than 1. It is designed so as to be radiation-proof and to lower spark rate comparing with the present separators.

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.

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

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 . 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

At the Japan Proton Accelerator Research Complex (J-PARC), the world highest intensity secondary beams of kaons, pions, anti-protons, muons, and neutrinos will be produced by irradiating a target with the 50 GeV primary proton beam of 0.75 MW. Utilizing such high intensity secondary beams, various unique and interesting experimental studies in nuclear and particle physics can be carried out. We will describe the current R&D status of the target systems to be constructed in the Nuclear and Particle Physics Experimental Hall (NP-Hall) and the neutrino beam line of J-PARC. Some experimental studies proposed there will be also introduced.

We made a series of surveys to obtain neutrino beam line direction toward SuperKamiokande (SK) at a distance of 250 km for the long-baseline neutrino oscillation experiment at KEK. We found that the beam line is directed to SK within 0.03 mr and 0.09 mr (in sigma) in the horizontal and vertical directions, respectively. During beam operation, we monitored the muon distribution from secondary pions produced at the target and collected by a magnetic horn system. We found that the horn system functions like a lens of a point-to-parallel optics with magnification of approximately -100 and the focal length of 2.3 m. Namely, a small displacement of the primary beam position at the target is magnified about a factor -100 at the muon centroid, while the centroid position is almost stable against a change of the incident angle of the primary beam. Therefore, the muon centroid can be a useful monitor of the neutrino beam direction. We could determine the muon centroid within 6 mm and 12 mm in horizontal and vertical directions, respectively. This means that the neutrino beam direction could be controlled within 0.03 mr and 0.06 mr (in sigma) in the horizontal and vertical directions, respectively. We confirmed the beam direction with the neutrino distribution reconstructed at the near detector in KEK.

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.

As a part of the Japan Hadron Facility (JHF) Project, R&D on radiation-resistant magnets is being carried out at the High Energy Accelerator Research Organization (KEK). JHF is the Japanese next-generation high-intensity accelerator project, which will provide 1-MW proton beams of 3 GeV and 50 GeV for various fields of science.

A neutron beam line has been constructed at the KEK-proton synchrotron. Neutrons have been produced by the disintegration reactions of deuterons in a 6 cm thick beryllium target. Deuteron beams of 2–6 GeV have provided neutron beams of 1–3 GeV. The neutron flux increases with the deuteron energy. The typical beam intensities obtained were 1 × 108, 2 × 108, and 3 × 108 neutrons per 1011 deuterons of 2, 4, and 6 GeV, respectively. The neutron-momentum width, Δpp, was measured to be (4 ± 1) % in sigma at 1 GeV.

In April 1994, 4 He ions were accelerated at the KEK proton synchrotron for the first time. Subthreshold antiproton productions with α beams in the incident energy range between 2.0 and 5.0 GeV/nucleon were measured for antiproton momenta between 1.0 and 2.5 GeV/c. The data are compared with the p production cross sections in pA and dA collisions measured previously by our group as well as those in heavy ion collisions.

Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4 mrad from the measured profile center. The normalized event rate is measured with 4% precision., Comment: 32 pages, 27 figures, submitted to Nucl. Instr. and Meth. A

A brief description of the primary beam line at the hadron experimental facility at the Japan Proton Accelerator Research Complex (J-PARC) is presented. The facility has been constructed in Tokai, Japan, and the first beam was successfully introduced into the experimental hall in January 2009. The facility utilizes a high-intensity proton beam with an energy of 50 GeV and a power of 750 kW and provides various secondary beams such as pions, kaons, and antiprotons for nuclear and particle physics experiments. We have developed beam-line components with sufficient radiation hardness and heat resistance to handle the high-power proton beam.

J‐PARC Hadron Experimental Facility is designed as a multi‐purpose experimental facility for particle and nuclear physics experiments using high‐intensity secondary particles (Kaons, pions, and so on) produced by 50 GeV‐15 μA (750 kW) primary proton beams. Currently, three secondary beam lines (K 1.8 BR, K 1.8, and KL) have been constructed. The first beam extraction from 50 GeV proton synchrotron was on January 27th, 2009, and the beam commissioning of the primary and secondary beam lines are on going. The present article reports construction status and beam commissioning of Hadron Experimental Facility in detail.

We developed beam diagnosis devices, a residual gas ionization beam profile monitor (RGIPM) and an optical transition radiation (OTR) monitor, for a high power proton beam transfer line at the 50-GeV proton synchrotron (PS) of the Japan Proton Accelerator Research Complex (J-PARC). The RGIPM collects electrons produced by beam ionizing a residual gas in the vacuum beam pipe. Since the RGIPM is operated at a vacuum level of 1 Pa, a magnetic field is required to confine electrons around the magnetic field against the diffusion effect due to interactions of drift electrons to residual gas molecules. We, therefore, developed a magnet-built-in type of RGIPM. The OTR monitor observes OTR photons emitted at beam particles crossing a screen with a video camera. We demonstrated that the OTR can be measured even at the KEK 12-GeV proton synchrotron. In order to maintain radiation doses to imaging devices small, the devices are located at a distance of 5 m from the beam line. The OTR photons are collected by a Newtonian reflecting telescope.

Nondestructive beam profile monitor utilizing ionizations of residual gas has been developed for continuous monitoring of 3/spl times/10/sup 14/ protons at Japan Proton Accelerator Research Complex (J-PARC). Knock-on electrons produced in the ionizations of residual gas vacuumed to 1 Pa are collected with a uniform electric field applied between electrodes. Applying a uniform electric field parallel to the electric field is essential to reduce diffusion of electrons crossing over magnetic flux. A prototype monitor has been constructed and installed in EP2-C beam line at KEK 12 GeV proton synchrotron (12 GeV-PS). The profiles measured with the present monitor agree with the ones measured with the existing destructive profile monitor. The present monitor shows sufficient performances as a candidate of the profile monitor at J-PARC. In the present article, the working principle of the present monitor, the results of test experiments, and further developments are described in detail.

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”.

The construction of the facility of the long baseline neutrino oscillation experiment using the J-PARC's 50 GeV-0.75 MW proton beam [1] was completed at the end of 2008. The number of radiation-resistant magnets we have prepared for the neutrino beamline of J-PARC were 15 with Polyimide resin Insulation (PI) against up to 108 Gy, and 4 magnets with completely Mineral Insulation Cable (MIC) for higher radiation dose up to 1011 Gy, and 2 magnets with Epoxy resin Insulation. All magnets were equipped with remote handling system, i.e. automated magnet lifts, quick alignment guides, water connectors, electric power connectors and interlock-signal connectors. On April 23rd 2009, the first proton beam was successfully introduced to the neutrino beamline from the main accelerator of J-PARC and the long baseline oscillation experiment, T2K, started. Now the beamline is operated with 135 kW (30 GeV-4.5 ) primary proton beam. No serious problem happened on magnets until the great East Japan earthquake on March 11th.

A new counter experimental hall [K.H. Tanaka et al., IEEE Trans. Magn. 28 (1992) 697] was designed and constructed at the KEK 12-GeV Proton Synchrotron (KEK-PS). The extracted proton beam from the KEK-PS is introduced to the new hall through the newly-prepared primary beam line, EP1, and hits two production targets in cascade. The upstream target provides secondary particles to the low momentum ( 0.4–0.6 GeV c ) separated beam line, K5, and the downstream target is connected to the medium momentum (0.6–2.0 GeV/c) separated beam line, K6. Several new ideas were employed in the beam optical designs of EP1, K5 and K6 in order to increase the number and the purity of the short-lived secondary particles, such as kaons and pions, under the limited energy and intensity of the primary protons provided by the KEK-PS. These new ideas are described in this paper as well as the first commissioning results.

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.

Construction work on the new counter experimental hall of the KEK 12-GeV Proton Synchrotron (KEK-PS) was completed in December 1990. The new hall was planned to be a mini kaon factory from the start. The beam-handling magnet system of the hall was thus equipped with newly developed radiation-resistant magnets in order to handle a high-intensity proton beam. Another important point regarding high-intensity beam handling is to realize easy maintenance of the beam line. For this purpose, all magnets of the primary proton beam line were mounted on special base plates on which quick-disconnect devices for electric power, cooling water, and interlock signals were assembled. The vacuum connections of the beam ducts located at both ends of the magnet are also operated remotely. Any magnet experiencing trouble can thus be easily removed from the beam line and repaired remotely. >

This paper describes the control system for magnet power supplies and many beam lines in two experimental halls at the 12 GeV proton synchrotron at KEK. In the experimental halls, many beam lines have been constructed, cleared away or modified every year since 1974. With this experience, in order to reduce construction time, cost, maintenance and manpower, we are now using a distributed control system, with the following features: - each power supply is equipped with a microprocessor and communications interface, - each beam line has an independent control system, - each beam line controller is connected to a central controller, providing a unified system.

J-PARC Hadron Experimental Facility is designed to carry out a variety of particle and nuclear physics experiments with intense secondary particles generated by 750 kW proton beams. The first construction stage including the experimental hall, the primary beam line, and one secondary beam line (K1.8BR) has been completed at the end of December 2008. In order to handle the high intensity primary beam safely, we have developed many special devices working under severe radiation environment. The present article reports the current status of the Hadron Experimental Facility in detail.