The ionization method of measuring neutron energy

Abstract

The absolute measurement of neutron flux density by ionization methods is discussed.The relation Eυ = JυW ρ between the energy Eυ absorbed per unit volume of a solid medium and the ionization Jυ produced in a gas-filled cavity in the medium, the average energy W expended by the ionizing particles in producing a pair of ions in the gas, and ρ the stopping power of the solid relative to the gas for these particles, is critically examined from the point of view of the measurement of the rate of absorption of neutron energy at any point in a hydrogenous medium. The accuracy attainable is assessed, in so far as it depends on our knowledge of the quantities ρ and W.

The w-value in air for proton therapy beams

“…Table 2). The Verhey and Lyman (1992) data at 2, 10, 20, 50, 100 and 200 MeV and the Gray (1944) datum at 7.5 MeV have been offset to slightly higher energies for clarity, while the Grosswendt and Back (1998) datum at 10 MeV has been offset to a slightly lower energy.…”

“…Gray (Gray, 1944) assessed proton and a-particle (W air ) pvalues from previous measurements (Jentschke, 1940) and calculations based on a modified formalism proposed by Gerbes (1935). He estimated constant values of (36.070.4) J C À1 between proton energies of 2.5 and 7.5 MeV increasing to 38.8 J C À1 at 0.25 MeV.…”

Measurement of the Ionization Yield of Low Energy Atomic Particles in Gases

“…I n the 1 9 u review by Gray (13) t h e works of Jentschke (32) and Gerthsen (33) were t h e most p e r t i n e n t t o the present experiment. Jent schke i n v e s t igated the s p e c i f i c ionization-range r e l a t i o n i n nitrogen f o r individual pro-, t o n s with ranges between 1 0 and 70 cm.…”

Ionization Chamber Study of the Disintegration ofHe3andN14by Th

“…(Helium is assumed to be similar to argon in its ionization properties in accordance with the conclusions of Gray. 15 ) The polonium alpha-particles were assumed to have an energy of 5298.4 kev. 16 (It should be emphasized that the indicated uncertainties in the Q-values for the (n,p) reactions do not reflect any possible systematic errors arising from the method of calibration.)…”