skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Impurity levels and power loading in the PDX tokamak with high power neutral beam injection

Abstract

The PDX tokamak provides an experimental facility for the direct comparison of various impurity control techniques under reactor-like conditions. Four neutral beam lines can inject up to 6 MW for 300 ms. Carbon rail limiter discharges have been used to test the effectiveness of perpendicular injection, but non-disruptive full power operation for > 100 ms is difficult without extensive conditioning. Initial tests of a toroidal bumper limiter indicate reduced power loading and roughly similar impurity levels compared to the carbon rail limiter discharges. Poloidal divertor discharges with up to 5 MW of injected power are cleaner than similar circular discharges, and the power is deposited in a remote divertor chamber. High density divertor operation indicates a reduction of impurity flow velocity in the divertor and enhanced recycling in the divertor region during neutral injection.

Authors:
; ;
Publication Date:
Research Org.:
Princeton Univ., NJ (USA). Plasma Physics Lab.
OSTI Identifier:
6778902
Report Number(s):
PPPL-1932
ON: DE83001394
DOE Contract Number:
AC02-76CH03073
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; LIMITERS; PDX DEVICES; IMPURITIES; CARBON; GRAPHITE; NEUTRAL ATOM BEAM INJECTION; POLOIDAL DIVERTORS; BEAM INJECTION; DIVERTORS; ELEMENTAL MINERALS; ELEMENTS; MINERALS; NONMETALS 700209* -- Fusion Power Plant Technology-- Component Development & Materials Testing

Citation Formats

Fonck, R.J., Bell, M., and Bol, K. Impurity levels and power loading in the PDX tokamak with high power neutral beam injection. United States: N. p., 1982. Web. doi:10.2172/6778902.
Fonck, R.J., Bell, M., & Bol, K. Impurity levels and power loading in the PDX tokamak with high power neutral beam injection. United States. doi:10.2172/6778902.
Fonck, R.J., Bell, M., and Bol, K. 1982. "Impurity levels and power loading in the PDX tokamak with high power neutral beam injection". United States. doi:10.2172/6778902. https://www.osti.gov/servlets/purl/6778902.
@article{osti_6778902,
title = {Impurity levels and power loading in the PDX tokamak with high power neutral beam injection},
author = {Fonck, R.J. and Bell, M. and Bol, K.},
abstractNote = {The PDX tokamak provides an experimental facility for the direct comparison of various impurity control techniques under reactor-like conditions. Four neutral beam lines can inject up to 6 MW for 300 ms. Carbon rail limiter discharges have been used to test the effectiveness of perpendicular injection, but non-disruptive full power operation for > 100 ms is difficult without extensive conditioning. Initial tests of a toroidal bumper limiter indicate reduced power loading and roughly similar impurity levels compared to the carbon rail limiter discharges. Poloidal divertor discharges with up to 5 MW of injected power are cleaner than similar circular discharges, and the power is deposited in a remote divertor chamber. High density divertor operation indicates a reduction of impurity flow velocity in the divertor and enhanced recycling in the divertor region during neutral injection.},
doi = {10.2172/6778902},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1982,
month =
}

Technical Report:

Save / Share:
  • In ohmically heated ISX-B discharges, both the intrinsic iron impurity ions and small amounts of argon introduced as a test gas accumulate at the center of the plasma. But during certain beam-heated discharges, it appears that this accumulation does not take place. These results may reflect the conclusion of Stacey and Sigmar that momentum transferred from the beams to the plasma can inhibit inward impurity transport.
  • We have extended our previous collisional-regime theory for rotation and impurity transport in a tokamak plasma with strong, directed NBI and strong rotation (v/sub phi/ approx. v/sub th/) to the plateau regime. We present a kinetic theory derivation of the parallel viscous force in the strong rotation ordering and a self-consistent formalism for calculating ion and impurity rotation velocities and radial transport fluxes, as well as the radial electric field and the poloidal variation of the impurity density upon which the former strongly depend. Calculations for model problems representative of ISX-B and PLT are presented. The predicted impurity transport exhibitsmore » features in agreement with experimental observations.« less
  • The carbon concentration in the central region of TFTR discharges with high power neutral beam heating has been measured by charge-extracted recombination spectroscopy (CXRS) of the C{sup +5} n = 3--4 transition in the extreme ultraviolet region. The carbon concentrations were deduced from absolute measurements of the line brightness using a calculation of the beam attenuation and the appropriate cascade-corrected line excitation rates. As a result of the high ion temperatures in most of the discharges, the contribution of beam halo neutrals to the line brightness was significant and therefore had to be included in the modeling of the data.more » Carbon concentrations have been measured in discharges with I{sub p} = 1.0-1.6 MA and beam power in the range of 2.6-30 MW, including a number of supershots. The results are in good agreement with carbon concentrations deduced from the visible bremsstrahlung Z{sub eff} and metallic impurity concentrations measured by x-ray pulse-height analysis, demonstrating the reliability of the atomic rates used in the beam attenuation and line excitation calculations. Carbon is the dominant impurity species in these discharges; the oxygen concentration measured via CXRS in a high beam power case was 0.0006 of n{sub e}, compard to 0.04 for carbon. Trends with I{sub p} and beam power in the carbon concentration and the inferred deuteron concentration are presented. The carbon concentration is independent of I{sub p} and decreases from 0.13 at 2.6 MW beam power to 0.04 at 30 MW, while the deuteron concentration increases from 0.25 to 0.75 over the same range of beam power. These changes are primarily the result of beam particle fueling, as the carbon density did not vary significantly with beam power. The time evolutions of the carbon and deuteron concentrations during two high power beam pulses, one which exhibited a carbon bloom and one which did not, are compared. 30 refs., 12 figs., 2 tabs.« less
  • The heating efficiency of high power (up to 7.2 MW) near-perpendicular neutral beam injection in the PDX tokamak is comparable to that of tangential injection in PLT. Collisionless plasmas with central ion temperatures up to 6.5 keV and central electron temperatures greater than 2.5 keV have been obtained. The plasma pressure, including the contribution from the beam particles, increases with increasing beam power and does not appear to saturate, although the parametric dependence of the energy confinement time is different from that observed in ohmic discharges.
  • A compilation and analysis of charge exchange ion temperature measurements obtained duriang recent high power neutral beam heating experiments on PLT is presented. For titanium gettered discharges using water-cooled carbon limiters (a = 40 cm), PLT produced ion temperatures up to 6.6 keV (T/sub e/ = 3.5 - 4.0 keV) with 2.4 MW-level neutral deuterium injection into low density hydrogen and deuterium plasmas. Over the beam power (P/sub B/ approx. 0.7 - 2.4 MW) and line average electron density (anti n/sub e/ approx. 1.6 - 3.6 x 10/sup 13/ cm/sup -3/) parameter space thus far explored, the ion temperature increase,more » ..delta..T/sub i/, is observed to scale according to the empirical relation: ..delta..T/sub i/ (keV) = 4.5 +- 0.5 P/sub B/ (MW)/anti n/sub e/(x 10/sup 13/ cm/sup -3/), where anti n/sub e/ is the line average electron density at peak ion temperature.« less