Development of a tritium compatible mass spectrometer.

氚暴露使质谱仪的噪声大大增加。为了避免这种损害，并将质谱仪应用于D-T燃烧聚变装置的氚处理系统，我们开发了一种氚兼容的四极杆质谱仪，并配备了氚去污装置。质谱仪的可能部分涂有金以减少对氚的吸附。观察到，随着氚的暴露，质谱计的噪声级和宽度增大：即，由于氚的累积暴露为0.1 Torr.sec，噪声级和宽度分别增加到1E-9和5E-11安培。噪声水平增加了约100倍，宽度增加了约30倍。证实了噪声的增加是由于氚吸附在真空系统内壁表面、四极杆表面和检测器本身，气相中的氚只起很小的作用。在室温下，通过简单的疏散不能有效地降低噪声的声级和宽度。另一方面，卤素灯的光子照射使噪声的声级和宽度分别降低到2E-10和1.5E-11安培。它们大约是传统四极杆质谱仪用类似程序去污后的1/15。水银灯的光子照射也有类似的作用。去污不是由于热效应，而是由于光子引起的脱附。这些结果表明，虽然需要改进泵浦系统和光子辐照装置，但由于光子辐照可以原位去除氚污染，从而减少了质谱仪的机头，因此本研究开发的质谱仪与无载流子氚兼容。

Tritium exposure gives rise to considerable increase in the noise of mass spectrometers. To avoid this imparirment and apply the mass spectrometer to tritium handling system for D-T burning fusion devices, we developed a tritium compatible quadrupole mass spectrometer equipped with tritium decontamination devices< Possible parts of the mass spectrometer were coated with gold to reduce the adsorption of tritium.It was observed that the noise level and width of the mass spectrometer increased with tritium exposure: namely, the noise level and width increased to 1E-9 and 5E-11 Amp., respectively, owing to cumulative tritium exposure of 0.1 Torr.sec. The increase in the noise level was about 100 times and that in the width was about 30 times of the initial one. It was confirmed that the increase in the noised due to the tritium adsorbed on the surfaces of inner wall of the vacuum system, quadrupole and detector itself: the tritium in gasphase playd only a minor role. The noise level and width could not be effectivly reduced by simple evacuation at room temperature. On the other hand, it was revealed that photon irradiation by halogen lamp caused to reduce both of the noise level and width to 2E-10 and 1.5E-11 Amp., respectively. They were about 1/15 or those of a conventional quadrupole mass spec- trometer after decontamination with similar procedures. The photon irradiation by mercury lamp acted similarly. The decontamination is not due to thermal effect but to photon induced desorption. These results indicate the mass spectrometer developed in the present study is compatible to carrier free tritium because the tritium contamination can be removed in-situ by photon irradiation to reduce the nose of the mass speqtrometer, although the improvement of the pumpling system and photon irradiation device should be required.