NDLI: Five second helium neutral beam injection using argon-frost cryopumping techniques

Content Provider	IEEE Xplore Digital Library
Author	Philips, J.C. Kellman, D.H. Hong, R. Kim, J. Laughon, G.M.
Copyright Year	1995
Description	Author affiliation: Gen. Atomics, San Diego, CA, USA (Philips, J.C.; Kellman, D.H.; Hong, R.; Kim, J.; Laughon, G.M.)
Abstract	High power helium neutral beams for the heating of tokamak discharges can now be provided for 5 s by using argon cryopumping (of the helium gas) in the beamlines. The DIII-D neutral beam system has routinely provided up to 20 MW of deuterium neutral beam heating in support of experiments on the DIII-D tokamak. During normal operation each of the eight DIII-D neutral beams produces from 20-30 Torr/spl middot/l/s of deuterium gas for periods of up to 8 s per discharge. This gas is effectively pumped by the 4.3 K cryopanels present in each beamline, and only a small fraction is conducted into the DIII-D tokamak. Operation of neutral beams with helium has historically presented a problem in that pulse lengths have been limited to 500 ms due to reliance solely on volume pumping of the helium gas. Helium is not condensed on the cryopanels. A system has now been installed to deposit a layer of argon frost on the DIII-D neutral beam cryopanels, between tokamak injection pulses. The layer serves to trap helium on the cryopanels providing sufficient pumping speed for 5 s helium beam extraction. The argon frosting hardware is now present on two of four DIII-D neutral beamlines, allowing injection of up to 6 MW of helium neutral beams per discharge, with pulse lengths of up to 5 s. The argon frosting system is described, along with experimental results demonstrating its effectiveness as a method of economically extending the capabilities of cryogenic pumping panels to allow multi-second helium neutral beam injection.
Starting Page	852
Ending Page	855
File Size	390231
Page Count	4
File Format	PDF
ISBN	0780329694
DOI	10.1109/FUSION.1995.534356
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1995-09-30
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Helium Argon Laser excitation Deuterium Tokamaks Particle beam injection Particle beams Plasma simulation Heating Plasma devices
Content Type	Text
Resource Type	Article

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