Institute For Nuclear Study Research Articles

Horizontal Air Showers of Energies Above 1013 eV

An observation of horizontal air showers has been continued during these four years with the air shower array at the Institute for Nuclear Study, University of Tokyo. The integral size spectrum is expressed by (4.9±0.7)×10 -13 ( N /10 4 ) -2.8±0.3 cm -2 sec -1 ster -1 for the showers of sizes 10 3 to 10 5 and zenith angles above 70°. The zenith angle distributions for three size regions (0.5∼1)×10 4 , (1∼2)×10 4 and (2∼4)×10 4 indicate that the intensities are proportional to sec θ from 60° to 75° and decrease at above 75°±5° with attenuation mean free path of 5,000 to 10,000 g/cm 2 . The proportion of nuclear cascade showers to the total showers is estimated to be (20∼70)% in the range of size 3×10 3 to 6×10 4 . The implications of an effect of possible anomalous muon interactions and of, as an alternative, a possibility of heavy mass particles being the parent particles of the horizontal air showers are discussed.

Cl − L 23 absorption spectra of alkali chlorides obtained at 80°K with synchrotron radiation

Cl - L 23 absorption spectra of alkali chlorides have been obtained at 80°K with a 2 m grazing incidence spectrograph. Synchrotron radiation emitted from a 1.3 GeV electron synchrotron at INS ∗ ∗ The Institute for Nuclear Study, Tokyo, Japan. has been used as a continuum background. The experimental results are interpreted in terms of X-ray exciton, electronic band structure, and two electron excitation.

Cryostat for a Polarized Target

This short note describes briefly on a cryostat of the polarized hydrogen target by means of so-called dynamic nuclear orientation, which was constructed for proton-proton scattering experiment with the 50MeV synchrocyclotron at Institute for Nuclear Study, University of Tokyo. The entire system consisted of a liquid helium dewar at the top and a cryostat part involving a target cavity. Liquid helium stored in the dewar was guided downwards through a thin pipe and spurted out continuously at the target cavity. Temperature of the target was easily adjusted by changing flow of liquid helium with a needle valve. The lowest temperature obtained was about 1.2°K and 1.5°K with and without the microwave power (about 75mW, 70kMc/s). The average helium loss was approximately 1.2l/hour., not involving losses during transfer of liquid helium to the dewar from outside. Average polarization obtained through 300 hours' experimental run was about 30%.

Cryogenic Facilities for 75cm Hydrogen Bubble Chamber

A hydrogen bubble chamber with 200 liters of liquid, 78cm in diameter is under construction at Institute of Nuclear Study, University of Tokyo. A simple Linde refrigeration cycle is provided, as such a system meets the design considerations of this chamber. In order to establish the required capacity of the refrigerator, the static and dynamic heat loads were analyzed. Designing for a cycling rate of two expansions per second gives an estimated total heat load of 920 watt, including safety factors. A refrigerator with a capacity of 1, 000 watt at 26°K, therefore, was designed for this chamber, and brief descriptions of this refrigerator are given. For the precise control of the temperature of the chamber liquid, an elaborate temperature control loop configuration was considered, and the hydrogen temperature circuit schematic is shown.

University of Chicago, Institute for Nuclear Studies

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Soft X-Ray Absorption Spectra of Metals and Alloys. I. Be, Al, Sb, Bi and Al-Mg Alloys

Soft X-ray absorption spectra of Be, Al, Sb and Bi, and Al-Mg alloys have been obtained by the use of synchrotron radiation emitted from the 750 MeV electron synchrotron at the Institute for Nuclear Study, Tokyo, as a continuous light source. The K-absorption structure of beryllium was found to agree with the density of states calculated by Loucks and Cutler. Some correspondence was found between the maxima in the L 2,3 -absorption spectrum and the K-absorption spectrum of aluminum. A remarkable band was observed in the L 2,3 -absorption spectrum of aluminum at 23 eV above the edge. This band is not attributable to the singularity in the state density of the conduction band. A tentative interpretation based on the delayed onset of transitions 2 p -∞ d is proposed. The L 2,3 -absorption spectrum of aluminum in Al-Mg alloy shows a remarkable degeneration of the edge, while the L 2,3 -absorption edge of magnesium in the same alloy seems relatively unaffected. This behavior is similar to the effect reported b...

Soft X-Ray Absorption Spectra of Alkali Halides. I. KCl and NaCl

Soft X-ray absorption spectra of typical alkali chlorides, KCl and NaCl, were observed by using as a continuous background the synchrotron radiation from the 750 MeV electron synchrotron in the Institute for Nuclear Study, Tokyo. The L 2,3 -absorption spectrum of Cl - in these chlorides has been obtained. The spectrum shows one or two sharp absorption maxima at the long wavelength limit and a rapid increase in absorption at about 9 eV above the limit. A shoulder-like structure is observed at the foot of the second absorption band. A tentative X-ray energy level diagram suggests that the shoulder corresponds to the onset of interband transition from L 3 to the conduction band. The first absorption maximum is accordingly interpreted as the excitation of a stable X-ray exciton; a metastable X-ray exciton seems to be involved in the second maximum. The spectral behavior of the L 2,3 -absorption near the long wavelength limit has some similarity to the optical absorption spectrum in the vacuum ultraviolet regi...

Some cryogenic developments at the joint institute for nuclear studies

Some cryogenic developments at the joint institute for nuclear studies

Some cryogenic developments at the joint institute for nuclear studies

Some cryogenic developments at the joint institute for nuclear studies

On the Design of the Vacuum System of Tokyo Electron Synchrotron

Design and operation of the vacuum system of the electron synchrotron at the Institute for Nuclear Study, University of Tokyo are described. The number of pumps to be installed around the donut ring of the electron synchrotron was determined by a quantitative estimation based on experimental data. Eight pumping units are installed around the donut ring. These units are all linked at the backside, and are backed by one fore-pump system consisting of an oil diffusion pump and a rotary pump. The role of the diffusion pump in the fore-pump system is discussed with results of pressure distribution measurement in the vacuum system under various conditions. Each pump unit used in the vacuum system of the synchrotron is operated without any cold trap.

A new broad range spectrometer with a uniform-field sectorial magnet and a preceding quadrupole-magnet doublet

Theoretical basis of constructing a high-resolution and high-transmission spectrometer of a broad range type for charged-particle nuclear reactions is given by the use of a uniform-field sectorial magnet and a preceding quadrupole-magnet doublet. Formulae for various ion-optical parameters in the spectrometer are obtained. The parameters are given as the explicit functions of fractional momentum changes over a range of ±10%. The spectrometer can analyse and detect particles over an energy range from E max to 0.67 E max. The application of a quadrupole-magnet doublet does not only increase the solid angle but also improve the momentum resolution. Applying our theory to a practical example, a product-particle spectrometer is designed for the 55 MeV proton beam which is available by a synchrocyclotron in our Institute for Nuclear Study. An energy resolution of 0.1% and a solid angle of 3×10 −3 steradian can be obtained in the above-mentioned energy range.

The oscillator for the variable energy cyclotron

A new type of oscillator for the cylotron has been developed, by which the frequency can be changed over a wide range. The cavity of the oscillator is of a shielded Lecher-wire type. The shorting device, the plate loop and the cathode loop are carefully designed so as to enable a very easy change in the resonant frequency. The oscillator is used for the “variable energy” cyclotron at the Institute for Nuclear Study.

On the Operation of Electron Synchrotron at the Institute for Nuclear Study, Tokyo

The present characteristics of the electron synchrotron are tabulated. Operation was initiated in Nov. and Dec. 1961, and an electron energy of 750 Mev was obtained. A maximum intensity of 1.2 x 109 electrons/pulse or 2.5 x 1011 electrons/sec was also obtained.

A Thermistor Gauge of Temperature Contraled Type

A new type thermistor vacuum gauge is described. In a thermistor, the electric resistance changes largely with its temperature, so that it can be used as a pressure sensitive elenent in a thermal vacuum gauge. Owing to a nonlinear relation between the temperature and electric resistance in a thermistor, however, the problem of the ambient temperature compensation in a thermistor gauge is very difficult. So a gauge of new type was designed, emploging two thermistors one of which is a monitor of gauge head temperature. The signal from the temperature monitoring thermistor drives a vacuum tube and control its plate current, the load of which is a nichrome wire winding around the gauge head. If the temperature of the gauge head is lower than the setting point, the plate current increases so that the temperature will be raised and vice versa, thus the gauge head is hold at a constant temperature irrespective of the ambient temperature. Some theoretical discussions concerning thermal vacuum gauge designs are presented. The measureable pressure range is 10 torr to 10-3 torr. Thermistor gauges of this type, together with Penning gauges and hot cathode ionization gauges, are now being used as pressure monitors in a vacuum system of a 1 Bev electron synchrotron at the Institute for Nuclear Study, University of Tokyo.

Five years of activity of the Joint Institute for nuclear studies

In March of this year, the Joint Institute for Nuclear Studies, the international scientific organization of the socialist countries, completed five years of existence. On this occasion, the Editorial Board publishes an abridged text of the main report delivered by the Institute's Director Prof. D. I. Blokhintsev to the Committee of Authorized Representatives of the Member Nations in November, 1960.

Investigation of the energy characteristics of the external proton beam in the six-meter synchrocyclotron

The energy spectrum and the average energy of the external proton beam of the six-meter synchrocyclotron of the Joint Institute for Nuclear Studies have been investigated under various operating conditions. The spectrum is described by a Gaussian curve with a dispersion of (2.8±0.3) Mev. The mean energy has been determined to within an accuracy of 0.1%.

The energy distribution of the proton beam from the six-metre synchrocyclotron

The energy distribution and mean energy are given for the proton beam from the six-metre synchrocyclotron at the Joint Institute for Nuclear Studies, for various modes of acceleration. The energy spectrum is Gaussian, with a dispersion of 2.8 ± 0.3 MeV. The mean energy is accurate to 0.1 per cent.

New positron activities in neutron-deficient isotopes of lutetium, ytterbium, and holmium

A 10-minute irradiation of a tantalum target by 660-Mev protons was carried out in the synehrocyclotron of the Laboratory of Nuclear Problems in the Joint Institute for Nuclear Studies. A magnetic ~ spectrometer was used to measure the end-point of the positron spectrum and half life of htet ium, ytterbium, and holmium, which were separated by a chemical method from the target. Positrons with an energy of 1.7 + 0.2 Mev and a half life of 43 rain were found in the lutetium fraction. Within the limits of our experimental accuracy, the h a l f life is the same as the half life of Lu 167 (55 min [1]), and the end-point energy agrees well with the value of the end-point energy of Lu Is7 (1.76 Mev) predicted by Levy on the basis of a semiempirical rule [2]. In comparing the experimental values of the end-point energies of positron spectra with predicted values, it was assumed that a transition to the ground state of the daughter nucleus occurs in the positron decay. A positron spectrum with an energy of 2.9 9 0.15 Mev and a half life of 82 ~ 4 min was detected in the Yb fraction. This value of energy agrees very well with the end-point energy value of 3.0 Mev which Levy calculated for Yb 161.

Carrier-free Separation of Rhodium-102 from Ruthenium Target

The carrier- and salt-free separation of Rh/sup 102/ from the ruthenium target was investigated. Rh/sup 102/ was produced by bombarding the ruthenium metal with 12.5-Mev protons using the 63-in. cyclotron at the Institute for Nuclear Study, University of Tokyo. After addition of iron as the collector for rhodium, the bombarded target was fused with KOH and KNO/sub 3/. Ruthenium comes to the aqueous solution, and rhodium remains in the residue. The residue was fused with KHSO/sub 4/ to make rhodium completely soluble in an aqueous solution. Foreign ions were separated with the ion exchange resin column. A great difference in the chemical behavior of rhodium was found in the presence or absence of the stable rhodium carrier. Applying this separation method, sources for the beta spectrometry and for the measurement of gamma - gamma angular correlation were prepared. The separation is made rapidly and completely, and is useful for the study of the short-lived isotopes of rhodium. (auth)

INS Isotope Separator

The general aspect of an isotope separator, installed in the Institute for Nuclear Study, University of Tokyo, is described. Several operational characteristics as well as the working conditions for the separation of A, Zn, Sb, Mg and Ge are presented. The separated ion out-put was found to be several mA in every case . It was demon strated that the focusing point could be changed by means of a heterogeneous electric field. In the last part the method of direct traget preparation by using decelerating field at the traget is described.