The ionization rate in a thin air film sandwiched between a large area β-active plaque of phosphorous-bakelite and a thick layer of inactive material has been examined by McInally and Neary (1953). They denoted by R the ratio of the increase in ionization rate caused by the presence of the inactive material, to the rate with no material present. Values of (1 + R) for a number of materials relative to acrylic resin were tabulated, and it was suggested that the results could be used to correct the “contact” readings of a β-ray ionization chamber having a solid base of material significantly different from tissue. This is true provided that the dimensions of the chamber approximate to the conditions mentioned above, i.e. that its depth h is very much less than its radius a. In cases where this is not so the correction factors will be less as is shown by the following considerations. Suppose a plane β emitter is at a distance h0 from a thick layer of inactive material. Let J0 be the ionization rate at the sur...
[1]
R. Muller.
Interaction of Beta Particles with Matter
,
1954
.
[2]
G. Neary,et al.
Investigations on beta-ray dosimetry for A 32P enclosure.
,
1953,
The British journal of radiology.
[3]
D. P. Cole,et al.
The phosphor-phototube radiation detector
,
1952,
Electrical Engineering.
[4]
G. Swindell,et al.
Measurement of skin dose in radium therapy.
,
1951,
The British journal of radiology.
[5]
R. W. Engstrom.
Multiplier photo-tube characteristics: application to low light levels (Journal of the Optical Society of America 1947)
,
1947
.
[6]
J. M. Sturtevant.
A stable selective audio amplifier.
,
1947,
The Review of scientific instruments.
[7]
H. Parker,et al.
A Radium Implant Reconstructor
,
1939
.