Thermally Stimulated Exoelectron Emission Research Articles

Measuring tritium with exoelectron dosimeters

Small disks of ceramic BeO, called Thermalox 995, are sensitive detectors of tritium when read for thermally stimulated exoelectron emission (TSEE). An additional reading of the thermoluminescence provides a means for estimating the exposure to tritium in the presence of other penetrating radiations. Weakly contaminated surfaces, <1 nCi/cm 2, which are small, curved, or difficult to reach, can be monitored accurately. While the detector sensitivity is sufficient to measure tritium gas or tritiated water vapor at allowable, occupational exposure levels, the sensitivity of this particular detector is insufficient for monitoring members of the public exposed continuously to HTO vapor at the MPC. The TSEE peak location and shape are useful features for identifying an exposure to tritium. Prior to reading, rinsing the detector in alcohol is desirable to prevent spurious electron emissions.

Thermally Stimulated Exo-Electron Emission (TSEE) from the Gamma Irradiated Aluminium

Thermally Stimulated Exo-Electron Emission (TSEE) from the Gamma Irradiated Aluminium

ベリリウム青銅の表面酸化層からの熱刺激エキソエレクトロン放射

It is well known that the protective film on beryllium bronze consists of beryllium oxide BeO. In the present study this was confirmed by means of TSEE (thermally stimulated exoelectron emission). The surface of beryllium bronze oxidized and irradiated with γ-ray gave glow curves identical with those of beryllium oxide having the characteristic emission peak at 230°C. The pattern of glow curves for specimens treated in the same manner was identical, but the height of the glow peaks varied with specimens. It was also found that the emission for the same specimen decreased as the irradiation and measurement of the emission were repeated. In order to improve the reproducibility of the emission, the specimens were aged in vacuum. They were examined in the same way as described above. The aging effect did not always exert favourable influences upon the reproducibility.

Fast-neutron response characteristics of TSEE dosimeters

Further applications are described of the previously reported technique of fast neutron dosimetry with combinations of hydrogenous radiators and ceramic BeO, to be evaluated by thermally stimulated exoelectron emission (TSEE). For example, a pronounced directional response has been minimized with a dosimeter-radiator-dosimeter sandwich; and information on the effective neutron energy can be obtained by varying either the radiator thickness, or the thickness of an absorber layer between radiator and TSEE dosimeter.

Adsorbed gases, atmospheric, and temperature effects on TSEE from BeO

Abstract 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.

The radiation-induced increase of thermoluminescence sensitivity of the dosimetry phosphor LiF(TLD-100)

Thermoluminescence (TL) and optical absorption measurements on LiF(TLD-100) show that the radiation- induced increase of TL sensitivity of this phosphor occurs in the luminescence process. New data are presented on thermally stimulated exoelectron emission (TSEE), photoluminescence (PL) and radioluminescence (RL). The TSEE results confirm that some of the TL traps in LiF(TLD-100) capture electrons. The PL behaviour suggests that the increased TL sensitivity does not arise from an increase in the number of luminescence centres which participate in the TL process, and that the most likely cause of the increased TL sensitivity is the removal of competitors with the luminescence centres. The RL data indicate that the TL traps are localized near the luminescence centres, especially those centres from which there is increased photon emission.

The radiation-induced increase of the 100 C thermoluminescence sensitivity of fired quartz

The 100 degrees C thermoluminescence (TL) sensitivity of fired quartz is increased greatly by beta irradiation and subsequent heating (eg by an order of magnitude following a 1 krad dose and heating to 500 degrees C). Its radioluminescence response increases similarly, implying that the increase of TL sensitivity arises from an increased probability of photon emission per thermally released charge. This implication is confirmed by the decrease of thermally stimulated exoelectron emission (TSEE) sensitivity which accompanies the increase of the TL sensitivity. Furthermore, the decrease of TSEE sensitivity shows that the increased TL sensitivity arises from an intrinsic change in the luminescence centres themselves, rather than from some cause external to the luminescence centres. The increase of TL sensitivity is reduced by uv irradiation, and restored by subsequent heating to 500 degrees C. These results indicate that the increase of TL sensitivity results primarily from an increase in the number of activated luminescence centres participating in TL emission, the centres being activated by charge capture.

Thermally stimulated exoelectron emission (TSEE) caused by pressure loads on BeO ceramic

Thermally stimulated exoelectron emission (TSEE) caused by pressure loads on BeO ceramic

Thermally stimulated exoelectron emission, thermoluminescence, and impurities in LiF and BeO.

In order to obtain more information on the relation between thermally stimulated exoelectron emission (TSEE), thermoluminescence (TL), and the impurity content in different TL grade, analytical and technical grade samples of LiF and BeO, a number of experiments have been carried out, in particular (a) semi-quantitative spectroanalysis and mass spectrography, (b) an investigation of the TL sensitivities and glow curves for different dose levels and LET of the radiation, and (c) studies on TSEE sensitivity and peak locations (including their dependence on LET and heating rate). Sintered BeO samples exhibit the highest TSEE sensitivity, in particular after their work function has been reduced by the partial diffusion of inert metals into the surface. The results are discussed on the basis of the existing information on TSEE and TL in LiF and BeO.