Isao Sugai

Plastic scintillator produced by the injection-molding technique

Abstract Plastic scintillators based on polystrene and a polystyrene derivative (MS resin) have been produced by the injection-molding technique, and the light yield, transmission, fluorescence, sunshine hardness and radiation hardness were compared with those of casting scintillators. It was also investigated whether or not a fluorescent lamp affected the transparency.

Analysis of Hybrid Type Boron-Doped Carbon Stripper Foils in J-PARC RCS

J-PARC (Japan-Proton Accelerator Research Complex) requires a carbon stripper foil to strip electrons from the H− beam supplied by the linac before injection into the Rapid Cycling Synchrotron (RCS) [1]. The foil thickness is about μm (200μg/cm2) corresponding to conversion efficiency of 99.7% from the primary H− beams of 181MeV energy to H+. We have successfully developed the Hybrid type thick Boron-doped Carbon (HBC) stripper foil, which showed a drastic improvement the lifetime without thickness reduction and shrinkage at the irradiated area. We started to study carbon stripper foils microscopically why carbon foils have considerable endurance for the beam impact by boron-doped. At first step, we made a comparison of ion irradiation effect between normal carbon and HBC by the electric microscope, ion-induced analysis. In particular, it seems that grain size of boron-rich area became much larger by irradiation for HBC. It was also observed that the boron-rich grain grew up by taking around material and generated pinholes more than 100 nm near itself consequently.

Spallation neutron source (SNS) diamond stripper foil development

Diamond stripping foils are under development for the SNS. Freestanding, flat 300 to 500 mug/cm2 foils as large as 17 x 25 mm2 have been prepared. These nano-textured polycrystalline foils are grown by microwave plasma- assisted chemical vapor deposition in a corrugated format to maintain their flatness. They are mechanically supported on a single edge by a residual portion of their silicon growth substrate; fine foil supporting wires are not required for diamond foils. Six foils were mounted on the SNS foil changer in early 2006 and have performed well in commissioning experiments at reduced operating power. A diamond foil was used during a recent experiment where 15 muC of protons, approximately 64% of the design value, were stored in the ring. A few diamond foils have been tested at LANSCE/PSR, where one foil was in service for a period of five months (820 C of integrated injected charge) before it was replaced. Diamond foils have also been tested in Japan at KEK (640 keV H) where their lifetimes slightly surpassed those of evaporated carbon foils, but fell short of those for Sugais new hybrid boron carbon (HBC) foils.

Lifetime of charge stripping foils and transmission of heavy ions in 12UD-pelletron tandem accelerator

Abstract The lifetime of charge stripping foils produced by means of new arc-discharge method developed by Sugai was measured for the bombardment of 10 MeV Au ions. Transmission of Au ions through 12UD-pelletron tandem accelerator was also measured. The lifetime of tested charge stripping foils for 10–15 μg/cm 2 thick and 3.8–5.0 μg/cm 2 thick, respectively, demonstrated to be longer than that of usual arc-discharge method by more than 30 times and 20 times, meanwhile, the transmission of 3.8–5.0 μg/cm 2 thick foils was about 4 times higher than that of 10–15 μg/cm 2 thick foils.

A New and Versatile Coating Method of Particles at Room Temperature

We have discovered a new coating method, which is based on the vibrational motion of microparticles in the electrostatic field between parallel electrodes. The metallic elements of Mn, Mo, W, Os, Ir, Cr and Pb and the nonmetallic elements of B, C, Si and Ge were successfully coated on to Fe, Cu, Al and brass substrates. The coated thicknesses were from 1 µg/cm2 to 30 mg/cm2 and the thickness is easily controllable. Threshold voltages of 3 and 5 kV for metallic and nonmetallic materials, respectively, exist. The particle sizes examined were larger than 0.1 µm. This method requires a minimum one hour to complete. The uniformity in thickness is fairly good, compared to that obtained using a vacuum-evaporation method. It is a dry method used at room temperature, and is very simple to use. Furthermore, the coated materials show strong adhesion and the used remnants are recyclable.

Preparation of Low-Energy Reference Electron Source with 169Yb

Large sized and uniformly deposited 169Yb sources were prepared with the following properties: the intensity variation and the deposited thickness were <±8% and ~0.4 µg/cm2, respectively, for the source sizes of 35×45 mm2 and 20×100 mm2 with the deposited activity of 20-50 µCi, as an energy reference source for the neutrino mass measurement at INS. The technical details of the preparation: the processes of chemical separation and purification, and vacuum-deposition, are here reported.

Fabrication of Boron-Mixed Carbon Stripper and Target Backing Foils for High-Power Accelerators

We have succeeded, for the first time, in making long-lifetime boron-mixed carbon stripper foils for high-power accelerators. Foils of 10–1000 µg/cm2 thickness were made by controlled DC arc discharge. The lifetime of the foils was tested using 3.2 MeV Ne+ DC beams of 2.5 µA, by which a significant amount of energy was deposited in the foils. The maximum lifetime was found to be extremely long, 110 and 450 times longer than those of diamond and commercially available carbon foils, respectively. The foils turned out to be free from any shrinkage, and showed an extremely low thickness reduction rate, even at a high temperature of 1800 K.

Electron Energy Loss Spectrum in Adsorbed Residual Gas on Cooled Arachidic Acid Langmuir-Blodgett Film and Its Adsorbed Gas Amount

The energy-loss spectra of 18 keV electrons in adsorbed residual gas on Langmuir-Blodgett film, made from arachidic acid (C20H40O2) and cooled at temperatures of -10°C, -35°C and -60°C, were measured through use of an electron source that also acted as an adsorbent. In addition, the amount of adsorbed residual gas was estimated from the energy-loss probability.

Comparative study on lifetime of stripper foil using 650 keV H- Ion beam

Thick carbon stripper foils of >300 mug/cm2 will be used as a stripping of H-ion beam for 3 GeV rapid cycling synchrotron (3 GeV-RCS) of the J-PARC. The carbon foils with long lifetime even at >1800degK are required. For this purpose, we have developed a new irradiation system for the lifetime measurement using high current pulsed and dc H- beams of the KEK Cockcroft-Walton accelerator. These high power 750 keV H- Ion beams can simulate the high energy deposition in carbon stripper foils at the J-PARC RCS. An automatic data acquisition system is also developed for recording the data of foil temperature and irradiated beam current. The hybrid boron mixed carbon (HBC) stripper foils, which are developed at KEK are irradiated by high current H- ion beam up to 2000degK. A few SNS-diamond and commercially available carbon (CM) foils are also tested for comparing with HBC-foils. The results of the lifetime measurement of HBC and SNS-diamond including CM stripper foils are reported.

Development of hybrid type carbon stripper foils with high durability at >1800K for RCS of J-PARC

The Japan-Proton Accelerator Research Complexes (J-PARC) requires thick carbon stripper foils (200-300 mug/cm2) to strip electrons from the H- beam supplied by the linac before injection into the RCS of J-PARC. High-intensity H- beam and circulating bunched beam give much energy depositions to conventional carbon stripper foils. Thus carbon stripper foils with high durability at 1800 K are urgent and indispensable for this accelerator. Recently, we have developed hybrid type boron mixed carbon stripper foils (HBC-foil). Namely, the lifetime measurement of the foils was tested by using a 3.2 MeV, Ne+ DC beams of 2.5 muA, in which a significant amount of energy was deposited in the foils. We have investigated double- layered effects on the lifetime of the HBC-foils. The maximum lifetime was found to be extremely long , 30- and 250-times longer than those of diamond and commercially available best carbon foils (CM-foil). It was also found that the foils show free from shrinkage, and an extremely low thickness reduction rate even at a high temperature of 1800 K. In this poster the foil preparation procedure and lifetime measurements with a 3.2 MeV Ne+ beam is reported.