Determination of the stopping cross-sections of N2, H2, CH4, C4H10 and C3H6 using alpha particles in the range 1 . 3--4 . 2 MeV.

The stopping cross-sections of N2, H2, CH4, C4H10 and C3H6 have been measured using natural alpha particles from a 238Pu source, with facilities to vary the energy in the range 1.3--4.2 MeV. The work is the extension of measurements made earlier, using C2H4 as the absorber, which showed discrepancies in comparison with results of other authors. The comparison is continued with the results presented here and brief comments made on the degree of agreement obtained.

Comparison of the stopping cross-sections of ethylene and polyethylene using alpha particles in the energy range 1.5--4.2 MeV.

In order to design reliable gas-filled dosemeters it is necessary to have knowledge of the ratios of the stopping powers of various solids and their gaseous equivalents. This paper describes the measurement of the stopping cross-sections of ethylene and its polymer polyethylene using alpha particles, and compares the measurements with results published by other workers. The results indicate that there is no difference between the two sets of values, within the quoted errors. Reasons are suggested to account for part of the discrepancy between our results and those of others for thin solid sample measurements.

A preliminary study on photoaddition and erythema due to UVB radiation.

The spectral irradiance of narrow band and broad spectrum radiation sources have been measured and the erythemally effective irradiance calculated by weighting the spectral irradiance of each source by an erythema action spectrum for human skin and integrating over the range of wavelengths in each spectrum. The ratio of the erythemally effective irradiances determined in this manner have been compared with the ratio of exposure times necessary to produce a delayed minimal perceptible erythema on the trunk skin of fair-skinned subjects irradiated with the two different sources. There was close agreement between the two ratios, supporting the notion of photoaddition applied to erythema elicited by UVB radiation.