Yoshida Masafumi, Hanada Masaya, Kojima Atsushi, Kashiwagi Mieko, Grisham Larry R, Akino Noboru, Endo Yasuei, Komata Masao, Mogaki Kazuhiko, Nemoto Shuji, Ohzeki Masahiro, Seki Norikazu, Sasaki Shunichi, Shimizu Tatsuo, Terunuma Yuto
Japan Atomic Energy Agency, 801-1, Mukoyama, Naka 311-0193, Japan.
Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA.
Rev Sci Instrum. 2014 Feb;85(2):02B314. doi: 10.1063/1.4830365.
Non-uniformity of the negative ion beams in the JT-60 negative ion source with the world-largest ion extraction area was improved by modifying the magnetic filter in the source from the plasma grid (PG) filter to a tent-shaped filter. The magnetic design via electron trajectory calculation showed that the tent-shaped filter was expected to suppress the localization of the primary electrons emitted from the filaments and created uniform plasma with positive ions and atoms of the parent particles for the negative ions. By modifying the magnetic filter to the tent-shaped filter, the uniformity defined as the deviation from the averaged beam intensity was reduced from 14% of the PG filter to ∼10% without a reduction of the negative ion production.
