Speaker
Prof.
Daniel Den Hartog
(University of Wisconsin-Madison)
Description
A pulse-burst laser system has been built for Thomson scattering on NSTX-U, and is currently being integrated into the NSTX-U Thomson scattering diagnostic system. The laser is Nd:YAG operated at 1064 nm, *q*-switched to produce ≥1.5 J pulses with $\sim$20 ns FWHM. It is flashlamp pumped, with dual-rod oscillator (9 mm) and dual-rod amplifier (12 mm). Variable pulse-width drive of the flashlamps is accomplished by IGBT (insulated gate bipolar transistor) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction. The laser will be operated in three modes. The specified base mode is continuous 30 Hz rep rate, and is the standard operating mode of the laser. The base mode will be interrupted to produce a “slow burst” (specified 1 kHz rep rate for 50 ms) or a “fast burst” (specified 10 kHz rep rate for 5 ms). Laser pulsing is halted for a set period (a few minutes) following a burst to allow the YAG rods to cool; this type of operation is called a heat-capacity laser. The laser system has demonstrated compliance with all specified operating modes, and is capable of exceeding design specifications by significant margins, e.g., higher rep rates for longer burst periods. Burst operation of this laser system will be used to capture fast time evolution of the electron temperature and density profiles during events such as ELMs, the L-H transition, and various MHD modes.
The material in this presentation is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences under Award Number DE-SC0015474.
Primary author
Prof.
Daniel Den Hartog
(University of Wisconsin-Madison)
Co-authors
Dr
Ahmed Diallo
(Princeton Plasma Physics Laboratory)
Dr
Benoit LeBlanc
(Princeton Plasma Physics Laboratory)
Dr
Donald Holly
(University of Wisconsin-Madison)
Mr
Michael Borchardt
(University of Wisconsin-Madison)
