End Window Research Articles

Dip counting of aqueous solutions of tritiated sodium dodecyl sulfate using a thin end window poly(mono-chloro-p-xylylene) flow proportional counter

This investigation describes the determination of the adsorption of tritiated sodium dodecyl sulfate (TNaDDS) from aqueous solutions at the poly(monochloro-p-xylylene) interface by dip counting. The TNaDDS used in this study has a high chemical and radiochemical purity. The areas occupied at the surface per adsorbed TNaDDS molecule decrease as the bulk TNaDDS concentration is increased. At and above the critical micelle concentration (c.m.c.) the areas per adsorbed molecule computed from our radiotracer measurements are essentially constant in agreement with earlier measurements at solution-air and solution-hydrocarbon interfaces. No experimental evidence is found to confirm the observations of others that an essentially constant area per adsorbed molecule is attained when the bulk surfactant concentration is about half the c.m.c.

Direct Measurement of Radioactivity Contents in Radioactive Selfluminous Paint which is Used for watches and Clocks in the State of Painted on the Plate

In 1967, A Recomendation of IAEA, concernning Radiation Protection Standard for Radioluminous Timepiece was issued.Accordingly checking method become necessary for control radioactivity which is used for timep ece. After studied about the method of direct measurement, the following have been concluded.I. The method of measurement for Pm-147 radioactive selfluminous Paint.(1) To convert all beta emission to bremsstrahlung, Samples were covered with acryl resin plate, thickness 1mm, (2) Measurement of bremsstrahlung was made by wide end window GM tube. (3mg/cm2, 50mm dia)(3) To eliminate the geometrical effect, the GM tube was set at 10cm far from the source and measurable area was restricted under 60mm diameter.(4) The cpm of samples were compared with cpm of standard Pm-147 radioactive selfluminous paint which was measured by the same method. As the results, the inspection of radioactivity used was able to achieve under the error of 10%.II. The method of measurement for H-3 radioactive selfluminous paint.(1) Total luminousity of H-3 radioactive paint was measured by photomultiplier tube.(2) To eliminate the geometrical effect, the height of PM from source was fixed 25mm and the measurable area was restricted under 25mm diameter.(3) The luminousity of Samples were compared with the standard H-3 radioactive selfluminous paint which was the similar product as samples, and its decay of luminousity was well controled. As the result, the error of this measurement will be about 10%.

The polar substorm and electron ‘islands’ in the Earth's magnetic tail

The behaviour of energetic electrons in the distant magnetosphere near the midnight meridian during polar substorms has been studied for the period March 5th–April 4th, 1965, using data from two end window Geiger counters flown on the IMP 2 satellite (apogee 15.8 Earth radii) and magnetic records from a chain of auroral zone stations around the world at magnetic latitudes equivalent to L = 7.4 ± 2.0. When the satellite was in the distant radiation zone or in the plasma sheet which extends down the Earth's magnetic tail, sudden decreases in the horizontal magnetic field component at ground stations near the midnight meridian (negative magnetic bays) were followed by sudden increases in 40 keV electron fluxes (electron islands) at the satellite. When the satellite was at high latitudes in the magnetic tail ‘bays’ often were not followed by ‘islands.’ When the satellite was near the centre of the plasma sheet, energetic electron fluxes were observed even during magnetically quiet periods. The time delay between the sharp onset of magnetic bays in the auroral zone and the corresponding rapid increase in energetic electron intensity at the satellite, typically some tens of minutes, was least when the satellite was close to the Earth and increased with its increasing radial distance from the Earth. The delay was also a function of distance of the satellite from the centre of the plasma sheet, and of the magnitude of the intensity increase (smaller delays for larger intensity increases). We deduce that the disturbance producing the magnetic bays and associated particle acceleration originates fairly deep in the magnetosphere and propagates outward to higher L values, and down the plasma sheet in the Earth's magnetic tail on the dark side of the Earth. It is unlikely that the accelerated electrons are themselves drifting away from the Earth, because the apparent velocity with which the islands move away from the Earth decreases with increasing distance from the Earth. It is suggested that the polar substorm and the associated particle acceleration are part of an impulsive ejection mechanism of magnetospheric energy into the ionosphere, rather than an impulsive injection mechanism of solar wind energy into the magnetosphere.

Liquid scintillation counting techniques for the radioassay of [14C] melanin

AbstractThe radioactive melanin used in this study was extracted from the cell walls of the fungus Aspergillus nidulans after growth in the presence of 14C‐labelled precursors. The counting systems investigated comprised solid samples suspended in a liquid scintillator with or without silica gel, solubilized samples blended in a liquid scintillator and solubilized samples adsorbed on to glass‐fibre discs wich were suspended in a liquid scintillator. Results obtained by counting solid samples with an end window detector are compared with the liquid scintillation data. High counting efficiencies were realized with the glass‐fibre disc method which is recommended for the assay of soluble samples. Liquid scintillation counting of silica gel suspensions was vastly superior to end window counting for the assay of solid samples. The data suggest that 14C‐labelled materials of a particulate or highly pigmented nature can be counted with high efficiency in a liquid scintillation system.

Principles of Nutrient Uptake from Fertilizer Bands. VII. P32 Uptake by Brace Roots of Maize and Its Distribution Within the Leaves1

AbstractThe influence on phosphorus uptake of area of roots in the fertilized soil and the rate of fertilization was investigated using aerial brace roots of maize. Either 1 or 2 brace roots were directed into soil containing 0.62 or 3.10 g of phosphorus labeled with P32. The radioactivity of the tip and/or basal portions of all leaves was measured by wrapping one thickness of leaf around a long G–M tube. The distribution of P32 in several leaves was mapped with an end window G–M tube.The P32 accumulation measured by the in‐situ technique was highly correlated with that of the standard briquet method. Phosphorus uptake varied with the rate of fertilization and the number of fed brace roots. The proportion of total phosphorus derived from the fertilizer ranged from 1–37%.The P32 distribution in the leaves depended upon their position relative to the fertilized brace roots. The leaves on the brace root side had higher P32 activity in their tip portions than in their basal portions. This distribution is explained by limited connections between vascular bundles of the stem and the diverging of the leaf veins from the midrib.

Radiotracer Studies of Metal-Detergent Interaction by Means of a Dip Counter with an Evaporated Metal Film Window

Abstract The accumulation of solute on metal surfaces has been studied using a radiotracer technique. A dip GM-counter with an end window covered with an evaporated metal film was immersed in an aqueous solution of 35S-labeled sodium dodecyl sulfate, and the change in counting rate due to the accumulation of solute on the metal surface was traced with time for various metals and pH values of the solution. The accumulation curves obtained turned out to be composed of an initial plateau, representing the region of the physical adsorption of the detergent onto the the metal surface, and/or a rising portion of the accumulation curve, indicative of chemisorption. Assuming the closely packed adsorption of solute, the roughness factors of various metal surfaces have been calculated from these plateau characteristics. The rising portion of the curve corresponds to the formation of a thick metallic soap film. The rate of film growth is controlled by the migration of the detergent or metal ions through the film, and this rate decreases as the thickness of the surface film increases. This leads to the parabolic formula for the surface film growth, which is in good agreement with the experimental results. The effect of the pH of the solution on the rate of the uptake of dodecyl sulfate has also been measured for both copper and lead surfaces. For copper surfaces the rate of the uptake of a detergent shows a maximum at pH 7 and decreases in both acid and alkaline regions. For lead surfaces, the rate is large in the acid region and gradually decreases twoards the alkaline region.

Neutron dosimetry using gold and sulphur: the calibration of a Geiger-M ller counter

The efficiency of an end window Geiger-Müller counter has been determined for the measurement of gold foil and sulphur disk beta activities to enable slow and fast neutron fluxes to be estimated from a personnel dosimeter, designed at the Atomic Energy Research Establishment, Harwell, for general use in the Atomic Energy Authority.

Remarks on the Efficiencies of Geiger, Proportional, and Cintillation Counters with Application to the Absolute Intensity of Characteristic X-Radiation

The measurements of the absolute intensities of Ou Ka radiation, isolated by means of balanced nickel and iron filters,. necessitated the determination of the quantum counting efficiency of three types of detectors: an end� window argon-filled Geiger counter, a two side-window, xenon-filled proportional counter, and a scintillation counter with NaITI crystal. It is shown that, provided the necessary corrections are made, results of absolute intensity measurements obtained with these three detectors show good agreement.

Energy Resolution of CsI (T1) Scintillation Counter for 12.5- to 100-keV Protons

The energy resolution of a CsI(Tl) scintillation counter for protons with energies of 12.5 to 100 kev is described. rhe crystal edge was beveled to 45 deg and the crystal was attached to the end window by a thin film of paraffin wax instead of silicon grease. The mounting arrangement of photomultiplier and crystal and the circuit used to define the dynode potentials is shown. (R.E.U.)

Point anode proportional counters

An experimental investigation of point anode proportional counters is described. The point to end-window distance is found to be an important parameter in determining counter performance. A resolution of 21% at 6 kev can be achieved with an end window 7/8 in. in diameter in a counter of internal dimensions only 1 in. × 1 3/8 in. Data concerning gas multiplication, efficiency and sensitive volume are given. A possible operating mechanism is discussed qualitatively.

Fluorescence and Pre-Ionization in Nitrogen Excited by Vacuum Ultraviolet Radiation

Fluorescence in nitrogen following absorption of vacuum ultraviolet radiation has been found to begin at a wavelength of 661.3 Å and to extend to at least 580 Å, the shortest wavelength available in this experiment. The energy of the longest wavelength at which the fluorescence appears is almost exactly equal to the energy required to excite the N2 molecule from the ground state, X1Σg+, to the B2Σu+ state of the N2+ ion. It is thought that the first negative bands of N2+, B2Σu+→X2Σ g+, are responsible for the observed fluorescence. The fluorescence is excited by dispersed radiation from a stabilized helium gas discharge which produces the Hopfield continuum in the region 580–1100 Å. Fluorescence is also detected in carbon monoxide and in oxygen, but it is too weak for accurate measurements of the appearance wavelength. Experiments with a quartz cell window, in the presence of the electric field from the end window of the photomultiplier, enabled the pre-ionized bands of nitrogen to be observed.

Optical Properties of a Continuous Helium–Neon Optical Maser

A continuous optical maser has been operated at five wavelengths in the near infrared. Such a maser oscillator consists of a medium having optical amplification at the wavelength of interest and a Fabry-Perot interferometer as a resonant cavity. The optical amplification is provided by maser action in a discharge through a mixture of helium and neon gas. The Fabry-Perot interferometer is constructed within the gas volume using two very flat, and highly reflecting, parallel, silica plates. The transmission of the Fabry-Perot plates, although small, allows a beam to pass through each end window, with four milliwatts of continuous output power in the strongest transition at 1.153-μ wavelength. Examination of the beam shows that it is almost diffraction limited for its one-centimeter diameter. The spectral line shape at each transition is made up of three or more components each less than a few hundred cycles in width separated by the spacing of orders in the interferometer.

Optical Properties of a Continuous Helium-Neon Optical Maser*

A continuous optical maser has been operated at five wavelengths in the near infrared. Such a maser oscillator consists of a medium having optical amplification at the wavelength of interest and a Fabry-Perot interferometer as a resonant cavity.The optical amplification is provided by maser action in a discharge through a mixture of helium and neon gas. The Fabry-Perot interferometer is constructed within the gas volume using two very flat, and highly reflecting, parallel, silica plates.The transmission of the Fabry-Perot plates, although small, allows a beam to pass through each end window, with four milliwatts of continuous output power in the strongest transition at 1.153-μ wavelength.Examination of the beam shows that it is almost diffraction limited for its one-centimeter diameter. The spectral line shape at each transition is made up of three or more components each less than a few hundred cycles in width separated by the spacing of orders in the interferometer.

Radiant Flux from a Cylindrical Distributed Source*

Of the total radiant flux produced in a right-circular cylindrical cell containing a uniformly distributed isotropic source of radiant energy, the fraction emanating from the end window is computed both for a cell with ideal, perfectly reflecting mirror surfaces and for a cell with ideal, totally absorbing surfaces. Graphs are presented of the calculated radiant-flux fractions from the cylinder as a function of the absorbance of the contents. Also presented are results of measurements of the radiant flux emitted from a cylindrical cell containing an externally excited scintillating solution when the inner reflecting surfaces of the cell are (1) polished aluminum, (2) aluminum evaporated on glass, (3) aluminum oxide, and (4) Teflon. These results are expressed relative to the radiant flux emitted by the same cell-solution combination with blackened inner cell surfaces. The actual radiant-flux fractions emitted by the cells are estimated by using the calculation for a cell possessing ideal, totally absorbing surfaces.

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...

Simplified Procedures for Radioassay and Autoradiography of Plant Materials1

SynopsisCompared with the conventional end window Geiger tube, the jacketed counter for the radioassay of liquids had higher precision and counting efficiency, eliminated the need for pipetting and evaporating samples prior to radioassay, and was suitable for counting digested plant samples.The autoradiographic technique was considerably simplified through the use of individually packed film, thus eliminating the need for light‐proof equipment. Autoradiograms of corn, soybeans, tobacco, and tomato plants are presented.

A machine for the automatic chromatography and assay of mixtures of radioactive substances

The construction and operation of a machine, used for the automatic chromatography and estimation of mixtures of radioactive substances, are described. The apparatus is designed to collect effluent fractions of equal volume from a chromatographic column, evaporate them to dryness, count them in turn beneath an end window G.M. counter and provide a record of the counts obtained. Some typical results are given, and the performance and versatility of the machine are discussed. On décrit la construction et le fonctionnement d'une machine servant à la chromatographie automatique et au dosage de mélanges de matières radioactives. L'appareil est destiné à recevoir d'une colonne chromatographique des portions de l'effluent de quantité fixe, à les faire évaporer à sec, à les compter à tour de ròle sous un compteur Geiger ayant la feneêtre au bout, et à enregistrer les comptes ainsi obtenus. On donne quelques résultats typiques, et on discute l'exécution et les capabilitiés variées de la machine. Die Konstruktion und das Funktionieren einer Maschine werden beschrieben, welche für automatische Chromatographie und zur Bestimmung von Gemischen radioaktiver Substanzen verwendet wird. Der Apparat sammelt ausfliessende Fraktionen gleichen Volumens von einer chromatographischen Säule, verdampft sie bis zur Trockenheit, zählt sie der Reihe nach unter dem Fenster eines Geiger Müller Zählers und liefert die erhaltenen Messresultate auf einem Schreiber. Einige typische Resultate werden angeführt. Das Funktionieren und die vielseitige Verwendungsfähigkeit der Maschine werden diskutiert.

Investigation of the decay of polonium-210

Conversion coefficient of 800 keV γ-rays from the decay of Polonium-210 has been measured using scintillation method to be 0.039 ± 0.01. The value of conversion coefficient has also been obtained by the measurement of conversion electrons with an end window type G.M. counter. The absorption curve for electrons is given and its shape has been interpreted in the light of the results ofAlphonse Lagasse andJacqueline Doyeb (Compt. Rend.,239, (11), 670 (1954)). The value of conversion coefficient obtained in this way is 0.014 ± 0.005. The discrepancy between the two values has been explained as due toK andL shell ionization by α-particles. No coincidences were found between the different parts of γ-ray spectrum.

Half-Life of 2.7-Day Au-198

The half-life of 2.7-day Au198 has been measured, using end window Geiger counters, over a period of 24 days, and found to be 2.694 ± 0.006 days.The half-life of 2.7-day Au198 has been reported lat...

Unusual radioactivity observed in the athmospherical precipitation in Debrecen (Hungary) between Apr. 22–Dec. 31, 1952

The authors investigated, by means of an end window β-counter tube Geiger-Muller equipment the activity of precipitation fallen in Debrecen between April 22–December 31, 1952. At times the precipitations showed radioactivity, which proved to be due to fission products deriving from atomic explosions. These anomalous activities, with a lag of a few days, were in correlation of time with the atomic explosions published during the same period. The order of magnitude of the activity calculated for a precipitation of an area of 1/50 sq. metres was 10−11 Curie. Calculating this figure to the whole surface of earth it appears obvious that this activity refers to the average value of activity of the whole surface or possibly of the northern hemisphere of the earth rather than to the activity of air masses incidentally drifted here. It appears from the investigations that by using an equipment of adequate sensitivity the fission products of an atomic bomb may be registered even at very considerable distances. The authors are of the opinion that by systematical and internationally organised observations of air masses which were imparted activity by way of atomic explosions or in any other way, the problems of general circulation, the movement of air masses and their-interchange between the two hemispheres could be most efficiently studied and thereby the solution of the most recent problems of meteorology approached.