J. Vincent

The energy dependence of lifetime damage constants in GaAs LEDs for 1-500 MeV protons

The energy dependence of lifetime damage constants have been measured in GaAs LEDs for 1-500 MeV protons. At energies below about 100 MeV, the dependence is close to that expected based on proportionality between non-ionizing energy loss (NIEL) and damage constants. In the 150-500 MeV range, however, a monotonic decrease in damage constant is found, at variance with published calculations which show an increase with energy. Two possible explanations are suggested; an inadequate model for the calculated energy dependence of NIEL, or the creation of damage clusters which have less effect than the deposition of an equivalent energy in the form of point defects.

MEASUREMENT OF PROTON PRODUCTION CROSS SECTIONS OF 10BE AND 26AL FROM ELEMENTS FOUND IN LUNAR ROCKS

Cosmic rays penetrate the lunar surface and interact with the lunar rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in lunar rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in lunar rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and {similar_to}87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of lunar rocks. We have reported already {sup 14}C production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x){sup 10}Be from 58 160 MeV[6]. Here we present new measurements for the cross sections O(p,x){sup 10}Be,O(p,x){sup 7}Be, Si(p,x){sup 7}Be,Si(p,x){sup 26}Al, and Si(p,x){sup 22}Na from {approximately}30 - 500 MeV.

Manufacture of strontium-82/rubidium-82 generators and quality control of rubidium-82 chloride for myocardial perfusion imaging in patients using positron emission tomography

We describe a protocol to manufacture 82Sr/82Rb generators and 82RbCl for myocardial imaging with PET. The generators are manufactured in 3 stages: (1) preparation of a tin oxide column, (2) leak test of the generator column and (3) loading of the generator with 82Sr. The generators produced sterile and non-pyrogenic 82RbCl for i.v. injection. No significant 82Sr/85Sr breakthroughs were observed after elution with 20 1 of saline. The automated system delivered human doses of 82RbCl accurately.

Target and ion source development at the TISOL facility at TRIUMF

Abstract This paper presents recent developments on the TISOL (test on-line isotope separator) facility at TRIUMF with details on the ongoing work with the surface ion source as well as the newly developed ECR (electron cyclotron resonance) ion source. First measurements using the ECR ion source on-line with a thick-target isotope separator are presented. Release properties of several targets for isotope production have been measured and will be reported.

Proton production cross sections for 14C from silicon and oxygen: implications for cosmic-ray studies

Abstract The production rates of 14 C from proton spallation of silicon and oxygen have been measured over a wide range of energies from 31 to 450 MeV. 14 C was measured by accelerator mass spectrometry (AMS) after extraction of carbon from the samples by melting in a flow of oxygen.

82Sr production from metallic Rb targets and development of an 82Rb generator system

Abstract A complete procedure for producing 82Sr/Rb generators is described. 82Sr was produced by bombarding metallic rubidium targets with 60 MeV protons with beam currents as high as 80 μA. The experimentally determined cross section for a thick target (61–48 MeV) agrees with the literature value of 100 mb. Production rates of about 0.2 mCi/μA-h with a 1.8 g/cm2 target were achieved. The 82Sr was separated from the target by dissolving the rubidium metal in n-butanol then separating the strontium isotopes on a Chelex-100 column. A SnO2 generator system was built from readily available components. Factors affecting generator design, performance and limitations included SnO2 particle size, column length and eluant flow-rate.

A design of an ECR ion source for radioactive ion beams for ISAC on-line facility at TRIUMF

A 2.45 GHz ECR ion source for the ISAC on-line operation is being tested at the TRIUMF ion source test stand prior to its installation in the radioactive ion beam production target module. Steps were taken at the design stage to ensure short transient time and high ionization efficiency for single charged ions. Further considerations were given to radiation hardness, reliability, and remote handling capabilities. Transient time was measured using an ultrafast piezoelectric valve. Efficiencies were measured using calibrated gas leaks of stable and radioactive isotopes such as 127Xe. This article describes the overall characteristics of the source.

Photoluminescence study of gallium vacancy defects in gallium arsenide irradiated by relativistic protons

Epitaxially grown n-type gallium arsenide films, doped with silicon to concentrations of 2/spl times/10/sup 15/ and 2/spl times/10/sup 16/ cm/sup -3/ were exposed at room temperature to 200, 350, and 500 MeV proton irradiation at fluences of 3/spl times/10/sup 11/, 10/sup 12/, 10/sup 13/, 3/spl times/10/sup 13/ 10/sup 14/ and 10/sup 15/ cm/sup -2/. The effects of the irradiation were determined through low temperature continuous photoluminescence spectroscopy. Two radiation-induced donor-to-acceptor transitions were observed. The one at 1.476 eV has been associated to the gallium vacancy acceptor (V/sub Ga/) and the other at 1.482 eV to the silicon at the arsenic site acceptor (Si/sub As/). The relative introduction rate of these two defects has been measured in the irradiated samples before and after annealing at 550/spl deg/C for 30 minutes. The introduction rates are higher than those predicted by relativistic elastic scattering cross-section theory in the energy range studied here. We conclude that inelastic scattering contributes to the cross-section. The introduction rates are lower than non-ionizing energy loss (NIEL) calculations in the 200 to 500 MeV energy range. We suggest that the proton inelastic scattering parameter used in NIEL needs revision. The relativistic inelastic scattering formula is closer to experiment than present NIEL calculations.

The ECR ion source at the TRIUMF isotope separator, TISOL

Abstract The installation at the isotope separator TISOL of a single staged ECR (electron cyclotron resonance) ion source has been completed. The source can now routinely deliver radioactive species extracted from the production target when bombarded by 500 MeV protons. Among the radioactive species detected so far are isotopes of He, C, N, O, Ne, Cl, Ar, Kr, and Xe including multiply charged states and with yields exceeding in some cases those of the ISOLDE facility at CERN. The effect of varying parameters on the operation of the source are discussed.

The UofA/TRIUMF radioactive beam ECR ion source

One of the objectives of the TISOL (Test Isotope Separator On Line) facility at TRIUMF is the production of low Z radioactive isotopes, with a special interest in those related to nuclear astrophysics. A part of experimental objectives is the installation of an electron cyclotron resonance ion source on‐line to test its suitability for this use. In collaboration with TISOL, the University of Alberta has designed, built, and tested off‐line a single stage ECRIS. As part of the source, testing measurements were carried out to determine the efficiency of the source; some preliminary results indicate efficiencies of 20% for Ne+ and 30% for Ar+. In general, it was attempted to test the source under as wide as possible a set of operating conditions. The final off‐line testing is completed. It is hoped that the source will go on‐line in the early summer of 1989.