The Production and Use of Proton-Induced Ultrasoft X-rays
Abstract
A 700 keV Van de Graaff accelerator was used to accelerate protons
onto solid targets of different light elements to produce ultrasoft,
characteristic X-rays (< 5 keV). The proton energies were calibrated
using the (p, y) resonances at 633 keV in Aluminium and at 340 and
483 keV in Fluorine.
The X-ray emission characteristics of Aluminium, Carbon, Gold,
Silicon/Carbon, Silicon/Nitrogen and Titanium/Boron were studied as
a function of incident proton energy, angle of inclination of the
target (30° - 60° to the proton beam) and angle of detection of the
X-rays (40° - 130° to the beam). Detection of the X-rays was achieved
using a gas-flow proportional counter directly coupled to a low-noise
pre-amplifier. The resulting spectra, recorded on a multichannel
analyser, were well fitted by linear combinations of single Gaussian
curves to give peak position (X-ray energy), width and area (X-ray
intensity).
Carbon contamination of the target surface was studied in detail
for the Aluminium target. A number of low beam currents onto the
target (10 - 70 nA) were used for total irradiation times of up to
17 hours in order to establish the degree of overall X-ray energy
mixing.
The information gained from the study of both the Carbon
contamination and the X-ray emission characteristics was used to
propose practical optimum conditions for the production of ultrasoft
X-rays by proton bombardment in their application to biological and
biochemical irradiations.
A computer code, capable of following the electron track histories
resulting from ultrasoft X-ray interactions has been used to compare
the details of such energy deposition with the results of mammalian
cell irradiations made at the M. R. C. Radiobiology Unit for a number,
of different ultrasoft X-ray energies. Such a-comparison has been used
to try to identify the mechanisms of radiation action. Included in this
work is the application of the computer code to a variety of. characteristic
X-ray photon energies, thus extending the available, calculated data.
Authors
Jones, Elizabeth AnneCollections
- Theses [4504]