Asao Kusumegi

An electrostatic separator with built-in high-voltage generators

An electrostatic separator with high-voltage generators mounted directly onto the separator chamber is described together with the present performance of the separator of this type. A maximum voltage of 900 kV was obtained with the 3 m separator and of 800 kV with the 9 m separator for an interelectrode spacing of 10 cm.

Photoproduction of πΔ(1236) from protons below 1.1 GeV

Abstract The π + and π − momentum spectrum of the reaction γ p → ππ N have been measured at lab angles 20°, 40°, 60° and 90° and photon energies 0.744, 0.844, 0.944 and 1.044 GeV with a magnetic spectrometer using the photon subtraction method. Both spectra show a peak corresponding to the production of the πΔ(1236) state. The analysis has been carried out with amplitudes for the quasi two-body process γ p → πΔ (1236) and a phase-space background so as to reproduce both π + and π − spectra. The ratio of cross sections σ ( γ p → π + Δ 0 )/ ( γ p → π − Δ ++ ) is found to vary 0.0 to 1.8, depending on kinematical conditions.

Investigation of Voltage Breakdown in the Vacuum of DC Electrostatic Separator

A small rectangular dc electrostatic separator with the dimensions 1×1×2m3 is used to investigate the voltage breakdown in the vacuum of a dc electrostatic separator with the electrodes 400 mm in diameter. The electrodes are made of several materials to which voltages are applied up to 400 kV. The chamber is evacuated to 1×10-6 Torr with a turbo-molecular pump and an ion pump. A gas is fed to the chamber to obtain a curve of maximum voltage as a function of the pressure, a P-V curve. The P-V curves are obtained by varying the kind of gas, the material of the cathode and the gap spacing etc. Speculations are given for the voltage breakdown mechanism in the vacuum of the separator, and condition for the optimization of the design of dc electrostatic separators are also given.

Absolute Calibration of Bremsstrahlung Beam Monitors

The absolute calibration of the bremsstrahlung beam monitors of the INS electron synchrotron is made by using a Faraday cup and converters of known thicknesses with external electrons. The results show that the calibration constant of the quantameter is independent of the maximum photon energies from 302 MeV to 1102 MeV and the average value is (4.69±0.14)×1018 MeV/C. The calibration constant of the thick-walled ionization chamber varies slowly with the maximum photon energy and the results are consistent with the previous measurement. At the same time, the effects of saturation were investigated for these bremsstrahlung beam monitors at a maximum photon energy 1000 MeV by varying the intensity, the beam spill length and the bias voltage to the monitor, as the parameters. The results of the measurements are given and discussed in connection with the ion recombination effect.

Heavy liquid total absorption counter “helicon”

Abstract The results of a test using heavy liquid counters (HELICONs) as a total absorption counter (calorimeter) for electrons or photons are reported. The results indicate that some of them are already equivalent or even superior to an SF-5 lead glass counter with high resistivities against radiation damage. Discussions are given for using them as a practical calorimeter as well as for further development of HELICONs.

Thallium formate heavy liquid counter “Helicon” as a total absorption calorimeter

Abstract The results of tests using a thallium formate Tl(HCO2) heavy liquid counter “HELICON” as a total absorption calorimeter are reported. The results indicate that the thallium formate HELICON can be used with characteristics equivalent or even superior to those of an SF-5 lead glass Cherenkov counter. In particular it possesses a high resistance to radiation damage.

Possibilities of using heavy liquid materials as a radiator of total absorption calorimeters

Abstract We propose to use heavy liquids of chemical compounds as a radiator for total absorption calorimeters in high-energy physics experiments. Preliminary results of the optical properties of ZnI 2 solution are presented together with the pulse-height distribution obtained with 1.0 GeV / c electrons.

Total Absorption Measurements for 250-1000 MeV Photons in Carbon, Aluminium and Titanium

Total absorption cross sections of photons in carbon, aluminium and titanium have been studied for photon energies at 250, 450, 700 and 1000MeV. The bremsstrahlung beam produced by the 1.3 GeV electron synchrotron at the Institute for Nuclear Study was used as the source of high energy photons. The detection of high energy photons was made by a magnetic pair spectrometer. Experimental results agree with theoretical calculations on the total absorption cross section for photons within experimental errors.

Flexible Adiabatic Light Guide of Silicon Rubber

A certain type of silicon rubber (KE103RTV) is found to be a useful material as an adiabatic light guide for scintillation counters because of its mechanical flexibility. The refractive index of KE103RTV is measured to be 1.410±0.006. The transmission and the resolution of scintillation light pulses through it are comarable with those through acrylic resin light guides. This RTV has the resistivity against high dose of radiation.

Double-pion photoproduction off protons below 1 GeV

SummaryMeasurements of the energy spectra and the excitation yields of π− and π+, from the reactions γ+p → π−+π++p and γ+p → → π++π0+n together, were done at a laboratory angle 58.2° with bremstrahlung maximum energies up to around 1 GeV, using the 1.3 GeV electron synchrotron. The differential cross-sections were derived and compared with a simple isobar model. The results show that, while the energy spectra and the excitation yields ofπ− agree with the model of theT=1/2 isobar excitation decaying into Δ+π as well as with the existing data, those of π+ show some discrepancy with the same model. Discussions are given to explain the particular feature of π+ distributions observed in the present experiment.RiassuntoPer mezzo dell’elettrosincrotrone di 1.3 GeV si sono eseguite misure degli spettri di energia e delle rese di eccitazione di π− e π+ dalle reazioni combinate γ+p → → π−+π++p e γ+p → π++π0+n, ad un angolo di 58.2° nel sistema del laboratorio con energie di bremsstrahlung massime sino a circa 1 GeV. Si sono dedotte le sezioni d’urto e le si è confrontate con un semplice modello isobarico. I risultati mostrano che, mentre gli spettri di energia e le rese di eccitazione del π− concordano col modello della eccitazione dell’isobaroT=1/2 che decade in Δ+π e con i dati esistenti, quelli del π+ presentano qualche discordanza con il suddetto modello. Si discute il modo di spiegare il particolare comportamento delle distribuzioni dei π+ osservate in questo esperimento.РеэюмеИспольэуя злектронный синхротрон 1.3 ГзВ, были проведены иэмерения знергетических спектров и выходных воэбуждений π− и π+ иэ реакций ρ+p → → π−+π++p и ρ+p → π++πo+n при лабораторном угле 58.2°, с максимальными знергиями тормоэного иэлучения вплоть до 1 ГзВ. Выводятся дифференциальные поперечные сечения, которые сравниваются с простой иэобарной моделью. Полученные реэультаты покаэывают, что хотя знергетические спектры и выходные воэбуждения для π− согласуются с моделью иэобарного воэбужденияT=1/2, которое распадается на Δ+π, а так же с сушествуюшими данными, то знергетические спектры и выходные воэбуждения для π+ обнаруживают некоторое расхождение с той же моделью. Проводятся обсуждения, чтобы общяснить особенность π+ распределений, наблюденных в настояшем зксперименте.