Initial results from the scoop limiter experiment in PDX

R Budny,K Mcguire,D Mueller,R Kaita,D Slusher,D Mccune,M Ulrickson,F Tenney,D Heifetz,H Takahashi,B Grek,A Cavallo,M Okabayashi,H Kugel,K Bol,M.G Bell,E Mazzucato,D Buchenauer,T Mcbride,R Mccann,M.f Reusch ,G L Schmidt ,Kunihiko Okano ,T P Crowley ,S Šesnić ,R J Fonck ,D K Owens ,D M Manos ,D A Boyd ,D S Darrow ,W W Heidbrink ,D W Johnson ,D K Mansfield ,Kurt P Jaehnig ,R J Knize ,Pierre Couture ,H F Dylla ,B.p Leblanc ,J.d Strachan ,C M Surko ,S M Kaye ,Robert Gilpin ,H H Towner ,D Post ,Robert James Goldston ,J F Valley

doi:10.1016/0022-3115(84)90137-5

R Budny, K Mcguire + Show 44 more

Open Access

https://doi.org/10.1016/0022-3115(84)90137-5

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Abstract

A particle scoop limiter with a graphite face backed by a 50 liter volume for collecting particles was used in PDX. Experiments were performed to test its particle control and power handling capabilities with up to 5 MW of D° power injected into D + plasmas. Line average plasma densities of up to 8 × 10 13 cm −3 and currents up to 450 kA were obtained. Plasma densities in the scoop channels greater than 2 × 10 13 cm −3 and neutral densities in the scoop volume greater than 5 × 10 14 cm −3 were observed. There is evidence that recycling may have occurred in the scoop channels for several discharges with large line-averaged plasma density. At beam powers up to 2.5 MW, energy confinement times above 40 ms were deduced from magnetics measurements and from transport analysis. Pressures in the vacuum vessel were in the 10 −5 Torr range, and recycling source neutral densities in the central plasma were low.

Highlights

Limiters equipped with various means for particle removal have been proposed for control of recycling, reduction of impurity, and ash removal in fusion reactors
Pi specially designed pump limiter called a scoop limiter was installed in PDX in 1982 (Fig. 1)
It consisted of a box with an internal volume of 50 liters rigidly mounted on the PDX vacuum vessel wall

Summary

INTRODUCTION

Limiters equipped with various means for particle removal have been proposed for control of recycling, reduction of impurity, and ash removal in fusion reactors. The two sides of the entrances approximated arcs with radii 120 and 40 cm separated by 2 cm at the midplane Particles flowing into these entrances could continue- in a short channel to a neutralizer made of copper and clad with 1/2 mm of vanadium (Fig. 2b). Calculations indicate that as the density or temperature of the plasma in the scoop channels increases, the probability of neutrals being ionized in the channels will increase. When this probability is high, there is a hypothetical mode of operation where the neutral flow oat of the plenum is throttled, resulting in high scoop pressures.

CONDITIONS IN THE SCOOP

CONCLUSIONS

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