The Average Energy Required to Produce an Ion Pair in Argon, Nitrogen, and Air for 1- to 5-MeV Alpha Particles

An analytical model is presented that facilitates the calculation of the mean energy W expended to produce an ion pair upon complete slow-down for heavy particles in gases. This model is applied to the calculation of the W values for helium beams of energies from 10 keV to 10 MeV in argon and nitrogen gas. Good agreement of the theoretical W values with the experimental ones is found in the case of nitrogen. The theoretical results for argon are about 15% higher than the experimental values throughout the entire energy range. However, they show a similar energy dependence. The theoretical and the experimental W values for nitrogen exhibit an extraordinary energy dependence at energies around 300 keV, at which the cross-section for charge exchange cycles reaches the maximal value. Such a phenomenon was also observed in the case of the W values for protons, which show a clear minimum at the energy of the maximal cross-section for charge exchange cycles.

Section: Discussionsupporting

confidence: 84%

W values for helium particles in nitrogen and argon in the energy range from 10 keV to 10 MeV

Baek

Großwendt²

1995

“…Compilation of data on w/e values in air for protons, α-particles and light ions. Full circles refer to proton data(Huber et al 1985, Willems et al 1983, Gerthsen 1930, Larson 1958, Thomas and Burke 1985, Jentschke 1940, Hiraoka et al 1989, Siebers et al 1995, Denis et al 1990, Petti et al 1986, Bakker and Segrè 1951 compiled byGrosswendt and Baek (1998), plusses refer to alphas(ICRU 1979, Chapell and Sparrow 1967, Ishiwari et al 1956 and open squares refer to light ions(Kanai et al 1993, Hiraoka et al 1989, Schimmerling et al 1982, Thomas et al 1980, Stephens et al 1976. The full line is the value of 34.8 recommended for protons by ICRU 59 (1998), the dotted lines represent a ±4% uncertainty interval.…”

mentioning

confidence: 99%

Determination of water absorbed dose in a carbon ion beam using thimble ionization chambers

Hartmann¹,

Jäkel²,

Heeg³

et al. 1999

The method to measure absorbed dose to water in a field of carbon ions as applied for the heavy ion therapy project at the Heavy Ion Research Laboratory in Darmstadt (GSI), Germany, is described in detail. Thimble ionization chambers with a water absorbed calibration factor are applied. The dose obtained with this method was compared with that obtained at the heavy ion therapy facility HIMAC at the National Institute of Radiological Sciences in Chiba, Japan, using the Japanese code of practice. The agreement found was better than 1%. The combined uncertainty of the determination of absorbed dose to water was estimated to amount to 5%.

“…Agreement with the value given by Varma and Baum is good at about 1.1 MeV but it differs by as much as 1.8% at higher energies. The values given by Chappell and Sparrow (1967) have a very much flatter distribution and differences vary from 4.6 to 1.4% with increasing energy.…”

Section: Discussionmentioning

confidence: 96%

Determination of W values for tissue-equivalent gas and its constituents using alpha particles in the range 1.1-3.9 MeV

Whillock

Edwards

1983

values are of considerable interest in the determination of absorbed dose by gas filled detectors, particularly in the fields of radiobiology and radiation protection. This paper describes experimental work undertaken in the measurement of @-values for Rossi-Failla type tissue-equivalent gas and its constituents using alpha particles in the range 1.1-3.9 MeV. Descriptions are given of the ionisation chamber used and the procedure adopted. Results and uncertainties are shown together with results of other workers for comparison. It is concluded that in general there is good agreement among the values quoted by different authors and that the experimental data available provides a reasonable basis for dose assessment.