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Cold-pressed pellets of unfired BeO, called Thermalox 995, have been fired at temperatures between 400° and 1900°C. The thermally stimulated exoelectron emission (TSEE), thermoluminescence (TL), and electron paramagnetism (EPR) have been measured and correlated with sintering and grain growth. Changes in TL and TSEE sensitivity are as much as five, and two and a half orders in magnitude, respectively. The changes in concentration of the paramagnetic trapping centers correlate fairly well with the changes in TL sensitivity showing that the two are intimately related. The TSEE data show a markedly different trend; the traps are of a different type from those producing TL and are not detected by EPR. The most satisfactory radiation dosimeters are obtained after firing at 1300°C when the mean grain size is about 7 μm. The commercially available ceramic disks of Thermalox 995, with grains about double this size, are close to being in an optimum condition for TL-TSEE dosimetry. Dosimeters with a mean g...

Oxygen, water vapor and/or carbon dioxide adsorbed on ceramic BeO before or after irradiation profoundly affect the thermally stimulated exoelectron emission (TSEE). In their presence the TSEE is dominated by a single peak at a surface temperature of ∼275°C. Removal of these adsorbates by outgassing during read-out causes the exoelectron emission to intensify with the TSEE curve becoming more complex. Apparently, sorption layers render inoperative certain traps effective for TSEE. Increased temperature during irradiation reduces the response (20% between 22° to 150°C). The influence of the gas surrounding the sample during irradiation was tested for the inert gases helium, nitrogen, neon, argon and krypton using 5.6 keV, 22 keV and 0.66 MeV photons. The enhancement in sensitivity for argon and krypton was much less than expected, which indicates that absorption of radiation in the volume of the solid is more important for excitation of the dosimeter than hitherto assumed.