E 1 T, BST and binary scaler made for experimental use are examined concerning the influences of anode voltage and input pulse on their performance. For BST, the beam switching action in particular is looked into. For E 1 T, the region of stable operation is determined by the relation of decay time of input pulse to discharging time of anode capacity. The decrease of source voltage and the increase of both the accelerating voltage and grid voltage shortens the discharging time, and as long as the discharging time remains shorter than the decay time, the operation of E 1 T is stable even if the input pulse height is raised and operating frequency is lowered. As for BST, if the input pulse frequency is raised, the pulse height and bias voltage become lower, which is favorable to operation in the region of high frequency up to a certain limit, for which determination the tolerable limits of spade, target and pulse circuit static capacities and their voltage varia-tions are examined. From the experimental data obtained, the switching mechanism of electron beam is investigated. As for the binary scaler, an empirical formula for the relation between the figure of merit of the tube used and the time resolution of the scaler is derived.
The ratio of target current to incident electron beam current is studied for thick targets of Al, Fe, Sn, Pb and U in the, energy range 4_??_14 MeV. In consideration of practical use, the target is placed in air at about 10 cm from the output window of an electron linear accelerator. The effect of ion current on target current and other errors expected under this experimental condition are verified to be negligible. Therefore, the difference of the observed ratio from unity can be inter-preted as the backscattering coefficient of electrons. The backscattering coefficient for a target placed perpendicularly to the beam is found to decrease exponentially with increasing energy in this region. While it increases with the atomic number Z of the target also in the present energy region, the curve of the relation between them does not show such a large change of gradient as observable at Z_??_30 in keV region.
Molecular motion in gamma-irradiated polytetrafluoroethylene is investigated with the nuclear magnetic resonance method. With 60Co as radiation source and 108R as total exposure dose, irradiation effects on the line shape of F19 nuclei are investigated, whereby change of motional narrowing in the narrow line width, room temperature transition in the second moment, and increase in crystallinity were observed. Especially, a specimen, heated at 300°C for four hours after irradiation, showed a remarkable increase of crystallinity. These results are discussed in some detail. The increase in crystallinity is ascribed to the decrease in molecular weight, and the change in molecular motions to the change in molecular arrangement.
A time-of-flight neutron spectrometer is assembled for radiation researches. It simply consists of a horizontal Van de Graaff accelerator, a deflector, an analyzing magnet, a strong focusing magnet and usual electronic components used widely in time-of-flight system. The post-acceleration pulsing device provides bursts of neutrons. Alternative voltage supplied at deflection plates deflects the accelerated beam with 0.5, 1.0, 2.5 and 5.0 Mc/sec in frequency. The beam slit defines the beam pulse of less than 1.5 nsec in duration and the resultant resolution of the flight time of about 2 MeV neutron in full width at half maximum is 2.2 nsec due to broadenings from plastic scintillator of 3cm in thickness and electronic circuitry, etc. Supplying about 200μA of the analyzed beam current of the accelerator, it results in an average beam of about 1μA on the target at the pulse length of 1.5 nsec in 2.5Mc pulsing.
By the use of a parallel plate ionization chamber with laboratory air and a 60Co γ-ray source that gives the ion density of 0.02_??_1.2 e.s.u./cc, sec, volume recombination characteristics are in-vestigated. With perspex, aluminum, graphite and copper as the wall material, 0.5_??_5000 volt/cm as the field intensity and 2_??_15mm as the plate spacing, the m-value is observed to vary from 39.0 to 27.5 as the collection factor ƒ increases from about 0.2 to nearly 1.0. The m-value seems dependent not on the wall material, plate spacing or ion density, but on the field intensity alone. Since the m-value remains steady when ƒ<0.5, intentional use of the intensity range in which the ionization current is not saturated seems of advantage to obtain the saturation current with high accuracy. Treating of the m-value as a constant as has customarily been done is proved meaningless. In this paper, some of stem effects are also investigated.