Cylindrical Counter Research Articles

531. 高速中性子束測定用<SUP>232</SUP>Th小型核分裂計数管

A 232Th miniature fission counter probe was perfected with use of the Th depositing technique. A sensitivity of approximately 1×10-6 counts/n/cmcm2 was obtained for reactor fast neutron flux with a typical cylindrical counter (6mm O.D., 10mm sensitive length). The counter was applied to the measurement of the fast neutron flux distribution within a research reactor core. The fast neutron flux distribution thus measured with the counter provided results identical with that obtained from the activation of threshold foils. Depleted U fission counters with Cd-cover have in the past been used for fast neutron flux measurements. The 232Th fission counter can, however, be used without Cd-filter, with excellent resolution of thermal and epithermal neutrons.

Muon-pair production by cosmic-ray muons

Thirty-three examples of muon pair production by muons were observed in a large cosmic-ray detector comprised of cylindrical spark counters and water Cerenkov counters having an automatic digitized data-handling system. These events were found in the analysis of 2 060 000 incident cosmic-ray muon trajectories recorded for study during 837 hours of running time between March and August 1966. Backgrounds from all sources contribute, at most, three events to this sample. The measured cross-section agrees qualitatively with the theory of Murotaet al. Experimental uncertainties prevent a more accurate comparison of theory and experiment.

Wall effect corrections in proportional counter spectrometers

The measurement of neutron spectra using proton recoil spectrometers sometimes requires wall effect corrections. This article presents an accurate method of calculating the wall effect, when measuring an isotropic neutron flux, for a spherical counter without a dead region and for a finite-length cylindrical counter either with or without a dead region at each end. Analytical expressions are obtained for four path length probability functions, in which the geometric aspects are handled in an exact manner. The path length probability functions and range data are applied to proton recoil spectrometers to determine the energy lost in the sensitive region by protons starting in either the dead region or the sensitive region and stopping in the gas or hitting the wall.

Neutron Detection by Corrugated-Plate Spark Counters

Corrugated plates as spark counter electrodes provide well-defined discharge gaps with low operating voltages, analogous to the conditions more usually obtained in multiwire arrays. By inserting boric acid or a hydrogenous material into the grooves, sensitivity to thermal or fast neutrons may be obtained. For a more sensitive counter geometry, plastic strips have been mounted between the grooves of adjoining plates, and coated with boric acid for slow neutron detection. A cylindrical counter consisting of a heavy threaded aluminum rod mounted in a matching threaded aluminum tube has been constructed with a set of plastic boron-coated washers as neutron converters. Good sensitivity has been obtained with this device as a detector of reactor neutrons without appreciable interference from background gamma-rays.

Calculation of the detection efficiency of a cylindrical counter for X-rays from an internal source

This paper describes detailed calculations of the efficiency of a long cylindrical proportional counter for detection of X-rays from an isotropic point source placed centrally in the wall of the counter. The results are applicable to counters of varied length and radius for a range of X-ray energies and are presented in both analytic and graphical forms.

Focussing gaseous Cherenkov counters for particle identification at the Brookhaven AGS

Two gaseous Cherenkov counters used at Brookhaven are described, and schematic diagrams of both are shown. One is a small (9 in. long) lens type focusing counter originally designed and used for Cosmotron K/sup +/ production experiments. The second is a much higher resolution cylindrical mirror counter, which was used for most of the high momentum particle separation work at the AGS. TYpical CO/sub 2/ pressure curves for both counters show successive pion, kaon, and antiproton peaks as the pressure is increased. (A.G.W.)

Thin-walled cylindrical counter for Geiger-M ller counting of low energy beta radiation

A cylindrical thin-walled counter, 22 mm in diameter, 15 cm long, suitable for counting carbon-14 β particles is described. The window thickness is 4.54 mg cm-2, operating voltage 1600 v, plateaux 400 v, slope less than 2%. The efficiency of counting for particles arriving at the counter is 6-8%.

Counting Efficiency of Gamma Rays in Counter Tubes

The counting efficiency of gamma rays in cylindrical counters and end window counters is examined by means of a very thin sheet and a collimated fine pencil beam of gamma rays. The distribution of the number of gamma rays emitted from the thin slit is measured by means of a end-window counter or by the effect of the fine anode wire of the cylindrical counter. When the plane of thin sheet of gamma rays reaching from side to a cylindrical counter is parallel to the axis, the counting efficiency registers a maximum value at the position where the sheet of gamma rays is in contact with the inner surface of the counter, and a smaller value near the central wire, but when the pencil beam of gamma rays is parallel to the anode wire and the gamma rays entering the counter through the end-window plate, the counting efficiency gives a maximum value at the anode wire and the inner surface of the counter. An average efficiency for a sheet of gamma rays which are in a plane perpendicular to the counter axis is also in...

天然産カリウムの放射能測定

Radioactivities of the solutions of potassium salt of different liquid thickness were measured with a thin walled cylindrical counter. It was found that the ratio of counting rate of γ to that of β depends on the sample thickness. Therefore when the sample thicknesses are much different with each other, the counting rate should not be regarded as a linear function of potassium content.In order to estimate the counting rate regardless of the liquid thickness, the following two equations were derived.A=2la∫rRx⋅exp{-μ(x-r)}arc tg⋅((r'l)/(2√x2-r'2√l2/4+x2-2'2))dx (1)N=A·ε·{-μ'(r-r')} (2)where A is the number of the particles incident on counter window, N the counting rate, r and r' the outer and inner radius of counter respectively, l its length, R the radius of cylindrical sample, a the number of disintegration rate occuring per unit volume of sample, x the distance from central axis of the counter to any point in sample, μ and μ' linear absorption coefficients of sample and wall material of counter respectively, and ε the intrinsic efficiency of counter.Counting rates thus estimated were in good agreement with the observation. With these equations the absolute radioactivity can be estimated from observed counting rate.

Characteristic parameters of gas-tube proportional counters

The gas multiplication factorA 0 was determined in cylindrical counters at specific counter wire voltages and varied pressures, wire radii and counter shell radii for methane and various methane-argon mixtures, as used in proportional counters. It is seen that the Rose-Korff and the Curran-Craggsmodified Rose-Korff theory do not agree with the experimental results. Use of the Diethorn expression is made in presenting the results in terms of two parameters $$\overline {\Delta V} $$ and $$\overline K $$ , characteristic of the gas filling. The meaning and values of $$\overline {\Delta V} $$ and $$\overline K $$ are discussed, and the recent results of van Duuren and Sizoo for an ethanol-argon mixtire are reinterpreted in terms of these characteristic parameters.

Measurements on halogen-quenched counters

Measurements have been made of the gas amplification factor of a cylindrical counter filled with neon-bromine and argon-bromine mixtures. Information has been obtained as to the mechanism of gas multiplication when the gas amplification is less than 100. The transit time of electrons across a tube of average dimensions operated in the proportional region was found to be less then 0.2 microseconds. The duration and the mechanism of the discharge build-up was found to change with the amount of bromine present in the counter.

Corona Threshold and the Range of Velocities of Pulse Spread in Geiger Counters

By using the writer's expression for a self-sustaining burst pulse corona and Alder, Baldinger, Huber, and Metzger's expression for the propagation of a Geiger pulse along the anode wire in coaxial cylindrical counter geometry, the limits of the velocity of spread of counter pulses can clearly be delineated. The interpretations resulting clarify the significance of the previously assumed fictive average distance of spread. These relations are illustrated in terms of the observations of E. Huber on ${\mathrm{O}}_{2}$-${\mathrm{N}}_{2}$ mixtures.

Geometric Efficiency of Cylindrical Counters

Counting experiments were made with cylindrical counters fitted with geometry ``definers'' in order to ascertain whether it is possible to find an area of constant sensitivity in these counters. These measurements are similar to those made by Gleason et al. with end-window counters. It is possible to achieve this result by means of a careful choice of the dimensions of these definers. The definers also allow a great simplification of the calculation of counter efficiency for a point source. We present a formula for sources placed in any position with respect to the counter. This formula is compared with experiment and the agreement is found to be good. A comparison of absolute beta counting between one of our cylindrical counters (with definer) and an end-window counter (with definer) is made. The agreement obtained is satisfactory.

Proportional Counters in Corona Region

The behavior of cylindrical counters filled with argon of various purities has been studied in the corona discharge zone. In this zone the counters act in a normal proportional manner with regard to the detection of α-particles. The amplitude of pulses obtained is found to be independent of applied voltage over an interval of about 1000 volts. The discharge mechanism is briefly discussed.

Some Geiger-Müller and Proportional Counters of Spherical Shape

A Geiger-Müller counter with a spherically shaped cathode is described. The pulse shape from this counter is similar to that of cylindrical counters. It may be used satisfactorily in ordinary coincidence work. Some of the counters, slightly modified to avoid spurious discharge, were filled with boron trifluoride and used as proportional counters for detection of neutrons.

Some Experiments with Geiger-M ller Counters

The paper describes a simple counting circuit and various types of Geiger-Muller counter. Representative plateau curves are shown for normal cylindrical counters and for parallel plate/wire counters. The latter are shown to have directional response if a suitable thin window is provided. A simple method for the suppression of delayed cathode emission (Paetow effect) is also outlined.