JJAP Conference Proceedings

JJAP Conf. Proc. 2, 011102 (2014) doi:10.7567/JJAPCP.2.011102

Annealing of a pre-assembled tungsten positron moderator by direct electron bombardment

Atsushi Yabuuchi, Nagayasu Oshima, Hidetoshi Kato, Brian E. O’Rourke, Atsushi Kinomura, Toshiyuki Ohdaira, Yoshinori Kobayashi, Ryoichi Suzuki

  1. Research Institute of Instrumentation Frontier (RIIF), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
  • Received June 08, 2014
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Abstract

We have developed a positron moderator annealing system with a handmade electron gun which allows the pre-assembled moderator temperature to be monitored directly during heating. The moderator, composed of strips of tungsten arranged in a regular lattice, was heated by bombarding electrons emitted from a hot tungsten filament. Moderator annealing was successfully achieved up to a temperature of 2600 °C in the central region of the moderator with a thermionic power of about 1200 W. Positron annihilation lifetimemeasurements of as-received and annealed tungsten foils were performed using a pulsed slow positron beam. As a result, it was confirmed that residual defects contained in the as-received tungsten foil were eliminated by conducting the annealing process.

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