Thermocurrent dosimetry with high purity aluminum oxide

Technical Report · Thu Jan 01 04:00:00 EST 1976

DOI:https://doi.org/10.2172/7190627· OSTI ID:7190627

Fullerton, G. D.; Cameron, J. R.; Moran, P. R.

The application of thermocurrent (TC) to ionizing radiation dosimetry was studied. It was shown that TC in alumina (Al/sub 2/O/sub 3/) has properties that are suited to personnel dosimetry and environmental monitoring. TC dosimeters were made from thin disks of alumina. Aluminum electrodes were evaporated on each side: on one face a high voltage electrode and on the opposite face a measuring electrode encircled by a guard ring. Exposure to ionizing radiation resulted in stored electrons and holes in metastable trapping sites. The signal was read-out by heating the dosimeter with a voltage source and picnometer connected in series between the opposite electrodes. The thermally remobilized charge caused a transient TC. The thermogram, TC versus time or temperature, is similar to a TL glow curve. Either the peak current or the integrated current is a measure of absorbed dose. Six grades of alumina were studied from a total of four commercial suppliers. All six materials displayed radiation induced TC signals. Sapphire of uv-grade quality from the Adolf Meller Co. (AM) had the best dosimetry properties of those investigated. Sources of interference were studied. Thermal fading, residual signal and radiation damage do not limit TC dosimetry. Ultraviolet light can induce a TC response but it is readily excluded with uv-opaque cladding. Improper surface preparation prior to electrode evaporation was shown to cause interference. A spurious TC signal resulted from polarization of surface contaminants. Spurious TC was reduced by improved cleaning prior to electrode application. Polished surfaces resulted in blocking electrodes and caused a sensitivity shift due to radiation induced thermally activated polarization. This was not observed with rough cut surfaces.

• Research Organization: Wisconsin Univ., Madison (USA). Medical Physics Labs.
• OSTI ID: 7190627
• Report Number(s): COO-1105-217
• Country of Publication: United States
• Language: English

Related Subjects

440102* -- Radiation Instrumentation-- Radiation Dosemeters
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
COOLING SYSTEMS
CORUNDUM
DOSEMETERS
DOSIMETRY
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
HEATING
HOLES
INTERFERENCE
LEPTONS
MEASURING INSTRUMENTS
MINERALS
OXIDES
OXYGEN COMPOUNDS
PERFORMANCE
PERSONNEL DOSIMETRY
READOUT SYSTEMS
RITAC DOSEMETERS
SAMPLE PREPARATION
SAPPHIRE
SURFACE TREATMENTS
TRAPPING