Double Ionization Chamber Research Articles

A radon exposure experiment of rats and mice.

The exposure experiment of experimental animals was carried at a level of about 0.01 μCi radon/ml of chamber air. The concentration of radon was measured by a double screen ionization chamber. The concentration of dust free daughters in the chamber is decreased by radioactive decay, attachment to dust particles and deposition to the chamber wall. To express the rate of decrease, the attachment constant kp and the deposition constant kw were introduced in addition to the radioactive decay constant. The values of kp and kw were experimentally obtained by using a semiconductor detector installed on the chamber wall. The diffusion constant of daughter atoms estimated from the deposition constant kw was in good agreement with those obtained by other methods. The absorbed lung doses given to rat and mouse were 8.0 and 18.9 rads respectively, when radon was introduced into the test chamber at a level of 0.01 μCi/ml. The retention efficiency of the lung was approximately 2%9 for rat and mouse.

Photoelectron spectroscopy and partial photoionization cross sections for iodine and bromine

A hemispherical retarding potential analyser has been used in conjunction with a vacuum monochromotor to record photoelectron spectra from iodine and bromine. The photoelectron spectra were recorded at wavelength intervals of 5 Å over the range from 584 to 1245 Å in the case of iodine and from 584 to 1180 Å in the case of bromine. Total photoionization cross sections for these molecules were measured over the same wavelength ranges using a double ion chamber technique. The relative populations of the electronic states resolved in the photoelectron spectra have been combined with the total photoionization cross section measurements in order to determine the corresponding partial cross sections.

Electron detachment in oxygen

Using a double ionization chamber in one half of which negative ions are formed and in the other half of which they suffer detachment, experiments on the collisional detachment from O3-and O2-in oxygen at E/p at 20 degrees C equal to 45-50 V cm-1torr-1give values for the detachment coefficient per unit pressure delta /p approximately 0.01. Pressure variations (20-60 torr) are discussed. For Townsend discharges in these circumstances in oxygen detachment is thus relatively unimportant, in that delta << eta (the attachment coefficient).

A transistorized linear gate for use with a double grid ionization chamber

Transistorized circuit details and performance characteristics of a linear gate with increased stability and lesser power consumption is described. The circuit operates on signal levels between 0.2 ∼ 5.0 V. A novel constant-delay sampling method assures an overall integral linearity of better than 0.5% between slow input pulses and narrow square output pulses of a linear gate. An application of the circuit to the measurement of alpha particle angular distributions from a thin Po 210 source is also given.

Fine Structure Effects in the Fission ofU235

By the use of a Frisch-gridded double ionization chamber the energy and mass distribution of U/sup 235/ fission fragments under thermal neutron fission were studied in coincidence with relatively high-energy prompt-fission gamma rays. The data were electronically analyzed and the results printed on paper tape, transferred to IBM cards, and analyzed by an IBM 7074 computer. Runs were taken for fission fragments in coincidence with prompt-fission gamma 's> 2 Mev and gamma 's> 3 Mev and the results were compared with fission fragments corresponding to all gamma rays. Pronounced structural effects were noted in the kineticenergy distribution and in the mass ratio, the magicnumber nucleus N = 82, Z = 50 preferentially emitting higher energy gamma rays. The symmetric fission yield was found to increase the gamma -ray energy, thus offering the possibility that the extra excitation energy of symmetric fission fragments may be carried off in the form of higher energy gamma rays. (auth)

Kinetic energy and angular distribution of the fragments from neutron and photon fission of U238

Angular and energy distribution measurements obtained by means of a gridded, double pulse ionization chamber are reported for fragments from the fission of U238 by 14 MeV neutrons and by photons with Eγmax=85 MeV. A study was made of the behavior of the most probable total kinetic energy for fixed mass ratios, mH/mL, of the fragments in five ranges of the angle between the direction of fragment emission and the direction of the neutron or photon beam.

Precision comparison of the mean kinetic energy of U235 fission fragments from thermal neutrons and neutrons with a mean energy of 5 Mev

A double ionization chamber containing a grid has been used to investigate how the mean kinetic energy of U235 fission fragments depends on the excitation energy of the fission nucleus. It has been found that the mean kinetic energies of the fragments from fission by thermal neutrons and neutrons with a mean energy of 5 Mev are the same to within ∼0.1%.

High-Energy Interference Effect of Bremsstrahlung Production in a Single Crystal of Silicon

In an experiment performed at Stanford to look for the interference effect of the bremsstrahlung production by 575-Mev electrons in a single crystal of silicon, the ratio of the charges collected in the two halves of a double ion chamber were used to detect the enhancement of the soft component of the bremsstrahlung. The data, presented in the form of a three-dimensional plot of the ratio vs the angles of rotation between the lattice normal and the electron beam about the horizontal and the vertical axes, clearly showed the enhancement. Comparison of the experimental result and the theory showed good agreement. The resolution of this experiment was poor; hence the central minimum predicted by the theory could not be observed. This minimum, however, has been observed by Bologna et al. at Frascati.

Anisotropy of the 14 mev neutron induced fission of 238U

A double ionization chamber has been used to record the angular distribution of 238U fission fragments produced by 14-4 MeV neutrons. It is found that to within 3 per cent the light and heavy fragments are distributed symmetrically about a direction normal to the axis of the neutron beam. The directions in which the light and heavy fragments are emitted are of equal probability, whether the fission is symmetric or otherwise. If the mass ratio is less than 1·7·1·8, the angular anisotropy increases with the mass asymmetry. The results are discussed in terms of STRUFINSKII'S statistical theory.

Investigation of the statistical distribution of spontaneous U238 fission acts according to the energies of the two fragments

Using an apparatus consisting of a double pulse ionization chamber, two amplifying channels, a coincidence circuit and a two-beam pulsed oscillograph, we measured the kinetic energy of each of the two fragments formed during nuclear fission. 780 cases of spontaneous U238 fission and about 4500 cases of U235 fission by slow neutrons were recorded. Using these data we plotted the statistical distributions of acts of spontaneous fission and fission with slow neutrons according to the energies of the two fragments. These distributions gave the following curves for the two fission methods: a) the energy spectrum of all fragments and that of light and heavy fragments separately; b) the distribution of acts according to the total kinetic energy of the two nuclear fragments; c) the distribution of fission fragments according to mass; d) the relation of the average total kinetic energy of the two fragments to the ratio of their masses; and e) the relation of the average kinetic energy of light and heavy fragments to their total kinetic energy. The results of the two methods of fission are quite similar. It was found that the total kinetic energy of the two fragments in spontaneous U238 fission was, on the average, 4 Mev less than the energy in U235 fission by slow neutrons.

Spontaneous Fission Kinetics ofCf252

A double ionization chamber is used to determine the spontaneous fission modes of ${\mathrm{Cf}}^{252}$ [${\ensuremath{\tau}}_{\frac{1}{2}}(\mathrm{fission})=66$ years]. The most probable energies of the light and heavy fragments are measured to be 107 and 79 Mev, respectively. The asymmetry of the process is found to agree with chemical mass-yield determinations. The results of the experiment are compared with the kinetics of other fission processes.

Correspondence

In an attempt to produce a water-equivalent medium, Jones and Raine (1949) have suggested a recipe for a phantom material (Mix D) consisting of a paraffin wax and polyethylene base loaded with magnesium and titanium oxides. They reported that measurements on the mixture, using the double ionization chamber and differential filter apparatus described by Spiers (1946), gave a linear absorption coefficient corresponding to an atomic number of 7·47, in good agreement with the calculated value of 7·42.

Relative Intensities and Transition Probabilities of theK-Series Lines of the Elements 24 to 52 by the Ionization Chamber Method

Experiments on the ionization currents produced by x-ray lines of wave-lengths 2.29, 1.93 and 1.66A entering a double ionization chamber filled with methyl iodide, methyl bromide, argon, air, and sulphur dioxide have been carried out. The current ratios obtained when corrected for the fraction of the direct beam absorbed in the front chamber were found not to vary by more than 1.5 percent in these gases. The conclusion is reached that the ionization chamber is a suitable instrument for measuring relative intensities of x-ray lines of different wave-lengths in the region 0.4 to 2.3A. The relative intensities of the $K$-series lines of twenty elements from Cr (24) to Te (52) were examined under controlled conditions and on correction for various factors yield a variation of relative intensity with atomic number. $\frac{{\ensuremath{\alpha}}_{2}}{{\ensuremath{\alpha}}_{1}}$ remains constant at approximately 0.50 throughout the range. $\frac{{\ensuremath{\beta}}_{1}}{{\ensuremath{\alpha}}_{1}}$ rises steeply from a value of 0.161 at Co (27) to 0.274 at Sr (38) then less rapidly to 0.306 at Te (52). $\frac{{\ensuremath{\beta}}_{2}}{{\ensuremath{\alpha}}_{1}}$ rises steeply from a value of 0.0036 at Zn (30) to 0.0450 at Zr (40) and then in a more linear fashion to 0.0735 at Te. Equations obtained from measurements on the absorption coefficients of various materials are: $\mathrm{Mica} \ensuremath{\mu}=36.56{\ensuremath{\lambda}}^{2.76} \mathrm{from}0.4\mathrm{to}2.3\mathrm{A}$ $\mathrm{Cellophane} \ensuremath{\mu}=3.52{\ensuremath{\lambda}}^{2.66} \mathrm{from}0.6\mathrm{to}2.3\mathrm{A}$ $\mathrm{C}{\mathrm{H}}_{3}\mathrm{Br} \frac{\ensuremath{\mu}}{\ensuremath{\rho}}=19.2{\ensuremath{\lambda}}^{2.79} \mathrm{from}1.1\mathrm{to}2.3\mathrm{A}$ $\mathrm{C}{\mathrm{H}}_{3}\mathrm{I} \frac{\ensuremath{\mu}}{\ensuremath{\rho}}=65.46{\ensuremath{\lambda}}^{2.62} \mathrm{from}0.4\mathrm{to}0.9\mathrm{A}.$ A treatment is given and discussed for the absorption of the x-rays within the target. The resultant correction is small and on application to the observed relative intensities the ratio of the transition probabilities for the $K$-series lines of these elements is obtained.

Effect of Chemical Combination on the Absorption of X-Rays at Wave-Lengths on Each Side of The K Discontinuity

The difference in the absorption of x-rays by iodine in the free state as compared to that of iodine in the chemically combined state, was investigated for wave-length bands on each side of the $K$ absorption limit of this element. The method used was the double ionization chamber method, with the x-ray bands obtained by voltage control and filters. The results indicate that on the long wave-length side of the $K$ limit, the absorption coefficient of the chemically free iodine atom is about 0.3 percent greater than that of the combined atom, while on the short wave-length side of the $K$ limit, the reverse is indicated with a difference of about 0.5 percent. Silver was also investigated, but from the few measurements obtained, the absorption coefficient of the chemically free silver atom as reduced from AgCl by sunlight, seems to be greater than that of the combined silver atom in the AgCl before reduction, for wave-length bands on each side of the $K$ limit of silver.