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in creator/contributor: "Hsieh, C. L."

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The multipulse Thomson scattering diagnostic on the DIII-D tokamak

This paper describes the design and operation of a 40-spatial channel Thomson scattering system that uses multiple 20 Hz Nd:YAG lasers to measure the electron temperature and density profiles periodically throughout an entire plasma discharge. Interference filter polychromators disperse the scattered light which is detected by silicon avalanche photodiodes. The measurable temperature range from 10 eV to 20 keV and the minimum detectable density is about 2 {times} 10{sup 18} m{sup {minus}3}. Las… more

Date: September 1, 1991

Creator: Carlstrom, T. N.; Campbell, G. L.; DeBoo, J. C.; Evanko, R. G.; Evans, J.; Greenfield, C. M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Design and operation of the multipulse Thomson scattering diagnostic on DIII-D

This paper describes the design and operation of a 40 spatial channel Thomson scattering system that uses multiple 20 Hz Nd:YAG lasers to measure the electron temperature and density profiles periodically throughout an entire plasma discharge. As many as eight lasers may be fired alternately for an average measurement frequency of 160 Hz, or they may be fired in rapid succession (< 10 kHz), producing a burst of pulses for measuring transient events. The high spatial resolution (1.3 cm) and wide… more

Date: March 1, 1992

Creator: Carlstrom, T. N.; Campbell, G. L.; DeBoo, J. C.; Evanko, R.; Greenfield, C. M.; Haskovec, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Recent results from DIII-D and their implications for next generation tokamaks

Recent results from the DIII-D tokamak have provided significant contributions to the understanding of many of the elements of tokamak physics and the application of this understanding to the design of next generation devices including ITER and CIT. The limitations of magnetohydrodynamics stability on the values of plasma beta (the ratio of kinetic pressure to the containing pressure of the magnetic field) that can be attained has been experimentally demonstrated and found to be described by ex… more

Date: July 1, 1990

Creator: Luxon, J. L.; Bramson, G.; Burrell, K. H.; Brooks, N. H.; Callis, R. W.; Carlstrom, T. N. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A multi-laser system for a fast sampling Thomson scattering diagnostic

A multi-laser system is being developed for the DIII-D Thomson scattering diagnostic. This system combines the beams from up to eight Nd:YAG lasers onto a common beamline in which the beams are nearly parallel and are all focused into a small, common area within the desired scattering volume. Each laser can be fired at a constant rate (20 Hz per laser) for a high average repetition rate, or together in a burst,'' which will give very high sampling rates (10--20 kHz) for short periods. The burst… more

Date: October 1, 1990

Creator: Trost, P. K.; Carlstrom, T. N.; DeBoo, J. C.; Greenfield, C. M.; Hsieh, C. L. & Snider, R. T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

New Thomson scattering Laser Control for DIII-D

A Laser Control system has been built for the DIII-D Scattering Diagnostic. This new system has provided the capability to place the laser probe pulses with one microsecond timing precision throughout the DIII-D shot. The new system fires the eight lasers with a programmable sequence which repeats ever 50 ms. If one wants to probe the plasma at a higher rate to study a fast paced event, the new control circuit can fire all charged lasers in rapid succession (BURST MODE). This burst rate is prog… more

Date: October 1, 1993

Creator: Makariou, C. C.; Stockdale, R. E.; Carlstrom, T. N.; Hsieh, C. L. & Bramson, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Confinement and stability of VH-mode discharges in the DIII-D tokamak

A regime of very high confinement (VH-mode) has been observed in neutral beam-heated deuterium discharges in the DIII-D tokamak with thermal energy confinement times up to {approx}3.6 times that predicted by the ITER-89P L-mode scaling and 2 times that predicted by ELM-free H-mode thermal confinement scalings. This high confinement has led to increased plasma performance, n{sub D} (0)T{sub i}(0){tau}{sub E} = 2 {times} 10{sup 20} m{sup {minus}3} keV sec with I{sub p} = 1.6 MA, B{sub T} = 2.1 T,… more

Date: October 1, 1992

Creator: Taylor, T. S.; Osborne, T. H.; Burrell, K. H.; Carlstrom, T. N.; Chan, V. S.; Chu, M. S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Design and operation of the multipulse Thomson scattering diagnostic on DIII-D

Date: March 1992

Creator: Carlstrom, T. N.; Campbell, G. L.; DeBoo, J. C.; Evanko, R.; Greenfield, C. M.; Haskovec, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Progress on the multipulse Thomson Scattering diagnostic on DIII-D

The DIII-D Thomson scattering diagnostic, operational since 1990, uses 8 Nd: YAG 20 Hz lasers to measure electron temperature and density profiles (40 spatial points) throughout the plasma discharge. Recent progress has enabled a new set of operating modes to better fullfill varying plasma physics requirements. Custom circuitry for laser control (programmable with los precision) has successfully replaced a previous scheme which used real-time 68030 software. Two new modes of operation have been… more

Date: May 1, 1994

Creator: Stockdale, R. E.; Carlstrom, T. N.; Hsieh, C. L. & Makariou, C. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Long-Pulse, High-Performance Discharges in the DIII-D Tokamak

Significant progress in obtaining high performance discharges for many energy confinement times in the DIII-D tokamak has been realized since the previous IAEA meeting. In relation to previous discharges, normalized performance {approx}10 has been sustained for >5 {tau}{sub E} with q{sub min} >1.5. (The normalized performance is measured by the product {beta}{sub N} H{sub 89} indicating the proximity to the conventional {beta} limits and energy confinement quality, respectively.) These H-… more

Date: October 1, 2000

Creator: Luce, T. C.; Wade, M. R.; Politzer, P. A.; Allen, S. L.; Austin, M. E.; Baker, D. R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Confinement and stability of VH-mode discharges in the DIII-D tokamak

A regime of very high confinement (VH-mode) has been observed in neutral beam-heated deuterium discharges in the DIII-D tokamak with thermal energy confinement times up to [approx]3.6 times that predicted by the ITER-89P L-mode scaling and 2 times that predicted by ELM-free H-mode thermal confinement scalings. This high confinement has led to increased plasma performance, n[sub D] (0)T[sub i](0)[tau][sub E] = 2 [times] 10[sup 20] m[sup [minus]3] keV sec with I[sub p] = 1.6 MA, B[sub T] = 2.1 T,… more

Date: October 1, 1992

Creator: Taylor, T. S.; Osborne, T. H.; Burrell, K. H.; Carlstrom, T. N.; Chan, V. S.; Chu, M. S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A silicon avalanche photodiode detector circuit for Nd:YAG laser scattering

A silicon avalanche photodiode with an internal gain of about 50 to 100 is used in a temperature controlled environment to measure the Nd:YAG laser Thomson scattered spectrum in the wavelength range from 700 to 1150 nm. A charge sensitive preamplifier has been developed for minimizing the noise contribution from the detector electronics. Signal levels as low as 20 photoelectrons (S/N = 1) can be detected. Measurements show that both the signal and the variance of the signal vary linearly with t… more

Date: June 1, 1990

Creator: Hsieh, C. L.; Haskovec, J.; Carlstrom, T. N.; DeBoo, J. C.; Greenfield, C. M.; Snider, R. T. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Central Thomson scattering upgrade on DIII-D

The existing 36 channel Thomson scattering system on the DIII-D tokamak measures the plasma temperature and density in the core region. However, with the recent interest in core peaked density profiles, coverage needs to be extended into the magnetic axis. This paper addresses the technical issues involved with extending the viewing region from a major radius of 194 cm to 165 cm. At least one of the existing seven core laser beams will be rerouted to probe the plasma horizontally instead of ver… more

Date: November 1, 1997

Creator: Nilson, D. G.; Stallard, B. W.; Carlstrom, T. N.; Hsieh, C. L. & Stockdale, R. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

DIII-D Thomson Scattering Diagnostic Data Acquisition, Processing, and Analysis Software

One of the diagnostic systems critical to the success of the DIII-D tokamak experiment is the Thomson scattering diagnostic. This diagnostic is unique in that it measures local electron temperature and density: (1) at multiple locations within the tokamak plasma; and (2) at different times throughout the plasma duration. Thomson ''raw'' data are digitized signals of scattered light, measured at different times and locations, from the laser beam paths fired into the plasma. Real-time acquisition… more

Date: June 1, 1999

Creator: Middaugh, K. R.; Bray, B. D.; Hsieh, C. L.; McHarg, B. B., Jr. & Penaflor, B. G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Horizontal Thomson Scattering Systems for DIII-D and SSPX

DIII-D--Three of the seven existing core Thomson scattering laser beams were redirected to probe the previously unmeasured central region of the DIII-D plasma. Modifications to the existing collection optics system and support tower were made to inject the lasers and collect scattered light in this new extended region. Stray light levels were reduced to acceptable levels to permit Rayleigh scattering calibration on five of the six new channels, indicating that the new in-vessel dump operates we… more

Date: August 1, 1999

Creator: Nilson, D. G.; Hill, D. N.; Wood, R. D.; McClean, H.; Moeller, J. M.; Labik, G. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department