Calorimetric, method of determining the total energy of high energy electron beams is discussed. The measurements made with 1_??_3 MeV and 10_??_100 μA electron beams proved that the use of calorimeter is a method that gives satisfactory results. The relations of calorimetrically determined total backscattered energy from targets Al, Cu, Ag and Au to the atomic number and incident beam energy are described. The corrections of 32% to the observed value when Au with 1 MeV beam was used, 6.8%, 3.7% and 2.3% when Al with 1 MeV, 2 MeV and 3 MeV respectively was used were found necessary.
A compensation type water flow calorimeter has been constructed to measure the power of intense electron beams. Many kinds of energy loss, such as leakage of bremsstrahlung, thermal radiation loss from the bottom surface of the beam catcher, beam absorption by the window foil and cutting-out of the beam from the aperture due to spreading by the window are discussed. Maximum temperature rise of water is also estimated. The results obtained with this instrument show a good linearity with electron power in the case of medium beam power over the energy range 1_??_21 MeV and this system seems useful to measure the power of electron beams, which have arbitrary shape of energy spectrum, within an. error 1_??_2%. There remain some problems in the measurement of high output power owing to the spreading of beam flux by the water cooled window. Pulsed beam has no special effect on these measurements.
As to the electron linear accelerator, a large number of parameters, such as electron energy, electron beam current, microwave frequency and power, hole diameter of loading disks, length of accelerator tubes, Q of cavities, and conversion efficiency of the accelerator, are essential for its design, and the relations among these parameters are very much complicated. In this article, charts which show numerical relations among these parameters are given and a nomogram of accelerator tubes is designed. These charts are prepared on the assumptions that: the beam loading characteristics can be represented as, dP/dz=-2IP-2iE, the group velocity is proportional to the fourth power of the ratio of hole diameter of disks to wave length, and the ratio of fundamental special waves to total waves in the electric field can be express as a function of hole diameter of disks. In general, comparatively high conversion efficiency can be acquired at PL/PO=0.04.
The absolute disintegration rate of sources of radioisotopes that decay by electron capture is determined by the X-gamma ray coincidence counting method. The counting system consists of an X-ray and a gamma-ray detector, two single channel pulse height analyzers, a fast-slow coincidence circuit and three scalers. The detectors are of scintillation type with a NaI crystal; the crystal for the gamma-ray detector is 13/4"φ×2" and that for the X-ray detector is 2 mm thick to minimize the background effect caused by energetic gamma-rays, this effect being measured by inserting a copper plate of 0.5 mm thick as an X-ray filter between the detector and the source. An A-1 type low noise preamplifier with a gain of 25 is used to amplify output signals from the X-ray detector. The X-rays and the gamma-rays, which are to be coincided, are selected by the respective pulse height analyzers. The resolving times of the fast and slow coincidence circuits. are 2 and 6 μsec. respectively. The normality of operation of the system is examined by the absolute measurement of disintegration rate of a 88Y source, the characteristic X-rays and 1.83 MeV gamma-rays emitted from 88Y are coincided. The absolute disintegration rate of this source is. also measured by the gamma-ray scintillation spectrometrical method with a 3"φ×3" NaI crystal scintillation detector and a TMC 256 channel pulse height analyzer. The photopeak efficiency of this spectrometer is determined by the use of 137Cs, 60Co and 24Na sources, the absolute disintegration rates of which are determined in advance by the 4πβ counting or 4πβ-γ coincidence method. The disintegration rate of 99Y sources obtained by the X-gamma ray coincidence method is in good agreement with that obtained by the scintillation spectrometrical method.
A new analysing method of radiation spectrum has been developed by the use of the technique of the information theory whereby the resolving power is effectively increased about ten times. The reliability of this method is proved by numerical simulation and the increase of the resolving power is confirmed. This method is applied to gamma-ray spectrometry and a small energy difference between two gamma-rays from Zr95 is exactly determined. It is also successfully applied to the identification of Nd141m and Ce139m in their mixture, this identification being otherwise impossible on account of a small energy difference, short life times and similarity of chemical property.
Thermal neutron radiography by the use of Toshiba Training Reactor (max. output 100 kW) has been studied concerning its possibility of being used as an industrial testing device of low cost. A neutron beam of Cd-ratio 3.5 (In) from the reactor core is satisfactorily collimated with a col-limator of simple design, which gives fairly good pictures by the image transfer method with In screen. The effectiveness of the collimator for imaging is discussed with relation to energy spec-trum of neutron in the reactor. Several neutron radiographs and ordinary X-ray radiographs are shown for comparison. Cadmium shadowing method is newly introduced for sensitive detection of hair cracks and porous portions in the sample. Heavily irradiated radioactive nuclear fuel in the form of UO2 pellet is radiographed to prove that the thermal neutron radiography is free from γ-ray fogging. The effects of scattering of neutrons in sample materials on the resolving power are briefly discussed.
Heat of about 100μW released from 3c tritiated water is measured with a twin differential type microcalorimeter within the error of 1%. This calorimeter consists of two identical copper cylinders as heat absorber, one holding the sample, the other a measuring coil, both suspended in a vacuum jacket which is kept immersed in an oil bath, the temperature of which is controlled to 1/1000 deg. C by a thermostat. The measuring coil is heated by a d. c. current, whereby the input to the coil to raise the cylinder temperature to the temperature of the sample cylinder determines the heat given off by the sample, the balancing of the two cylinder temperatures being checked with 25 pairs of thermojunctions bridging the cylinders. To avoid the error that arises from thermal inequality between the two cylinders, another heating coil is placed in the sample cylinder, by which means accurate determination of the sought-for heat quantity is succeeded by a devised method. The disintegration of tritium in the sample is calculated by assuming the mean β-ray energy of this nuclide. To check the correctness of the result, the sample is diluted to the con-centration of NBS standard sample and, by the use of a liquid scintillation counter and on the assumption of the same mean β-ray energy, a comparison is made with an NBS sample. The twoare in good agreement with the difference of less than 0.1%.
A multi-anode 2rr gas flow counter for the absolute determination of radioactivity of large area sources, 14cm×18cm for one, is described. The cathode comprises two parallel brass plates which are parts of the counter casing. Five equally 30mm-spaced anode wires of stainless steel and 0.05 mmø are stretched in a plane parallel to, and at 15.5mm from each of, the cathode plates. A large area source of the thickness of up to several mm is put on the lower cathode plate. Usually, methane gas is used as the proportional region counting gas. In the proportional region, the prrallel plate type cathode has advantages over other types. Narrowing of the anode wire spacing does not very much improve the counter characteristics. Even in the GM region, the mutual interference of anode wires has no significant effect on the measurement.
A new solid-state single channel pulse-height analyzer of high stability over a wide temperature, range is desced. A stable bipoler standard pulse of equal positive and negative areas is generated for every input pulse. This pulse is attenuated according to the channel width, and is added to the input pulse which is also shaped to a bipoler pulse by a double delay line clipping circuit. Since these pulses have zero d-c level, an adder consisting of a stable feedback a-c ampli-fier can be employed. The pulse delivered from the adder is applied to a pulse-height discriminator, in which circuit Esaki diodes are used. The system employs only one discriminator. In the temperature range from 0° to 40°C, the threshold level of the discriminator drifts 2 percent of the maximum pulse-height accepted by the discriminator, while the stability of the chan-nel width is better than 1 percent and does not depend on the values of the channel width. Hence, by the use of the system with a very narrow channel width, energy measurements of nuclear radiations are achieved with high accuracy. The time resolution of the PHA is about 2μs, for the system has been designed for NaI (Tl) scintillators. For fast scintillators, it is possible to design the system so as to obtain a good per-formance for input pulse rates of higher than 2 Mc.