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J L Tom

Publications and source records attributed to J L Tom.

6 recordsLinked to original sources
PubMed1978

Dosimetry measurements of 26, 35 and 45 MeV p-Be and p-Li neutron beams.

Dosimetric properties of neutron beams produced by stopping 26, 35 and 45 MeV protons in beryllium and lithium have been measured. The effects of filtering the p-Be beam with 6 cm of polyethylene have been investigated. The tissue kerma rate in air exhibited an energy dependence of approximately E3 and the rate for p-Be beams was approximately one-fifth of the rate for d-Be beams. The penetrability of the neutrons was significnatly enhanced by the use of the filter, but with a 50% attentuation in tissue kerma rate. The tissue kerma rate for the p-Li beam was nearly the same as that for the p-Be beam.

Beryllium↗
PubMed1978

Dosimetric properties of neutron beams from the D--D reaction in the energy range from 6.8 to 11.1 MeV.

The tissue kerma in air, the tissue dose at maximum build-up, the relative depth dose on the central axis and the dose build-up characteristics were measured for neutrons produced by 6.8, 8.9 and 11.1 MeV deuterons on deuterium. The neutron beams were produced by a variable-energy cyclotron with a fully stopping deuterium gas target 20 cm long. Measurements were made in a 11.1cm x 11.1 cm field 126 cm from the target entrance window. The dose rate was found to increase rapidly with energy from 0.07 rad min-1 microamperemeter-1 at 6.8MeV to 0.35 rad min-1 muA-1 at 11.1 MeV. The entrance dose is about 50% of the dose maximum for each bombarding energy. The depth of the 95% dose level in the build-up region increased from 50 mg cm-2 at 6.8 MeV to 90 mg cm-2 at 11.1 MeV. The penetration was independent of the bombarding energy in the region investigated. Attenuation of the total dose to 50% of the maximum occurred at 10.2 +/- 0.1 g cm-2 for all three bombarding energies. The dose at the maximum is typically 14% higher than the tissue kerma in air.

Atmosphere↗
PubMedDate not supplied

The influence of target thickness and backstop material on proton-produced neutron beams for radiotherapy.

Results are presented of measurements of skin sparing, penetration and total dose per unit of incident charge for various target thicknesses and filtrations for a neutron beam generated by 42 MeV protons on beryllium. These results are contrasted to predictions outlined in a previous paper. The differences from these predictions are attributed to the contribution of low-energy neutrons produced by the residual proton beam in the thick copper target backstop.

Activation Analysis↗
PubMedDate not supplied

p(42)Be neutron therapy beams: dose rate and penetration as a function of target thickness and beam filtration.

It is shown that, in the production of p(42)Be neutron beams for clinical use, the use of semithick targets leads to more desirable beam characteristics when appropriate backstop materials are used. Furthermore, an algebraic representation of beam penetration and of dose per unit charge on target, including hardening by polyethylene filters, provides a method for target optimization.

Beryllium↗