Measurement of Tritium as Water Vapor

When Geiger or proportional counters are used for the assay of tritiated water, the sample is usually converted into hydrogen or methane which is included in the counter filling. Measurement of the sample itself as water vapor would appear to be a more direct method which avoids possible uncertainties in the chemical conversion, and this technique has been used recently [1,2]. It will be shown, however, that although counters containing water vapor may have satisfactory characteristics, adsorption effects can introduce large errors

Proportional Counters for Demonstration Experiments

Proportional counters suitable for demonstration purposes are described, and some experiments to illustrate counter operation are discussed. The charge carried by the positive ions produced in the multiplication process, and the localization of the avalanche, is revealed in a special proportional counter whose cathode is covered by a layer of polythene. Other properties of this type of counter, such as its ability to work for a considerable period of time without a high-voltage supply, are pointed out

Operation of Proportional Counters at High Temperatures

The operation of proportional counters at temperatures up to 900°C has been investigated and it is shown that the factors determining the maximum working temperature are thermal emission of electrons from the cathode, and the conductivity of heated insulating materials. Several types of proportional tubes are discussed and the advantages of counters with external cathodes are pointed out. Pulse spectra from quartz and glass counters containing K‐capture A^(37) sources indicate satisfactory operation at temperatures of 810°C in the case of quartz and 450°C in the case of glass

CXLIV. K-capture in the decay of chlorine 36

A search for the existence of K-capture in ^(36)C1 has been made using a proportional tube spectrometer with labelled methyl chloride as a gaseous source. A peak which was observed in the beta spectrum corresponded to the K-radiation of sulphur and indicated the presence of K-capture. The branching ratio K/β^- was found to be (l·7±0·1)%. A scintillation spectrometer failed to detect any gamma-ray lines above 20 kev with intensity greater than 10^(-4) of the beta intensity, so the observed K-capture transition goes to the ground state of ^(36)S

XCVII. The ratio of K-capture to positron emission in fluorine 18

The existence of electron capture in the decay of ^(18)F has been revealed by the detection of K-radiations of oxygen in a proportional tube spectrometer containing a gaseous BF, source. The K/β^+ ratio determined from the number of counts in the observed K-peak and the total number in the positron spectrum is 0·030, with an estimated accuracy of 6%. A scintillation spectrometer investigation showed the absence of any gamma rays with intensity greater than 0·5% of the positrons, suggesting that both K-capture and beta decay are ground state to ground state transitions. A comparison between theoretical and measured values of the K/β^+ ratio gives, for the ratio of the axial vector and tensor coupling constants, C_A/C_T=(0·4±2)%

The l/k-capture ratio of germanium 71

A direct measurement of the L/K-capture ratio of ^(71)Ge has been made using a special proportional counter system which avoids the effects of x-ray escape. One proportional counter is effectively enclosed by another, without any intermediate wall. With a gaseous source of germanium hydride and an argon filling at 6 atmospheres, the ratio of the L- and K-peaks from the central counter, in anticoincidence with the surrounding counter, was determined. The LjK-capture ratio was found to be 0·128^(+0·005)_(−0·003). In addition, in a separate measurement, a value of 0·53 ± 0·03 was obtained for the K-fluorescence yield of gallium