Yutaka Yamanoi

Radiation hardness of cerium-doped gadolinium silicate Gd2SiO5:Ce against high energy protons, fast and thermal neutrons

Abstract Degradation of Gd 2 SiO 5 :Ce in optical transmittance due to proton irradiation was negligibly small below 10 6 rad, smaller than 2%/cm at 10 7 rad and large at 10 8 rad. The radiation hardness of 10 7 rad against protons is by two orders of magnitude smaller than against low energy γ-rays. Long term spontaneous recovery of the proton-induced damage is not large (10–20% of the initial degradation in 84 days). Recovery upon exposure to UV light occurs to some extent. Degradation due to thermal neutrons was negligibly small for a fluence of 10 14 n/cm 2 . No degradation was observed for exposure to fast neutrons of about 10 13 n/cm 2 during one year in the extracted beam tunnel of proton synchrotron.

Radiation hardness of undoped CsI crystals against high energy protons

Abstract We compared radiation damages of undoped CsI for 12 GeV protons and for 60Co γ-rays between 104 and 108 rad. Degradation in optical transmission was similar in magnitude both for protons and γ-rays; it is as small as 1–3% per 1 cm thickness at 104 rad, while it is as large as or larger than 5% above 105 rad. The above feature is different for BGO or GSO:Ce, whose radiation hardness is roughly two orders of magnitude smaller regarding protons than regarding γ-rays. Recovery of damage is qualitatively similar both for proton and γ-ray irradiations; spontaneous recovery is only partial and the annealing effect of UV exposure is negligibly small.

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

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

The K1.8BR spectrometer system at J-PARC

A new spectrometer system was designed and constructed at the secondary beam line K1.8BR in the hadron hall of J-PARC to investigate

Radiation-Resistant Magnets for J-PARC

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

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Radiation-Resistant Magnets for Hadron Experimental Hall of J-PARC

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ADSORPTION BEHAVIOR OF RADIONUCLIDES ON ION-EXCHANGE RESIN FROM COOLING WATER FOR THE K2K TARGET AND MAGNETIC HORNS

-nuclear bound systems. The spectrometer consists of a high precision beam line spectrometer, a liquid