Thomson scattering at 250 kHz

Young, W. C.; Hartog, D. J. Den

doi:10.1088/1748-0221/10/12/c12021

Cited by 2 publications

(2 citation statements)

References 7 publications

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“…A two-dimensional view of the T e structure is captured in a single discharge for the first time in an RFP by the new high-repetition-rate Thomson scattering (TS) laser. [25][26][27] We demonstrate that peaked island-shaped T e structures do not necessarily imply remnant islands in which closed flux surfaces fill the majority of the island volume.…”

Section: Introductionmentioning

confidence: 80%

Electron thermal confinement in a partially stochastic magnetic structure

et al. 2018

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Using a high-repetition-rate Thomson scattering diagnostic, we observe a peak in electron temperature T e coinciding with the location of a large magnetic island in the Madison Symmetric Torus. Magnetohydrodynamic modeling of this quasi-single helicity plasma indicates that smaller adjacent islands overlap with and destroy the large island flux surfaces. The estimated stochastic electron thermal conductivity (%30 m 2 =s) is consistent with the conductivity inferred from the observed T e gradient and ohmic heating power. Island-shaped T e peaks can result from partially stochastic magnetic islands.

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Section: Introductionmentioning

confidence: 80%

Electron thermal confinement in a partially stochastic magnetic structure

et al. 2018

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“…About a decade ago we built a pulse-burst laser system that produced acceptable 100 kHz bursts, and could be operated up to 333 kHz with substantial pulse energy variation during the burst [10]. This laser system was overly complex and had compromises that made it impractical to further improve and to continue operation long term.…”

Section: Jinst 18 C10023mentioning

confidence: 99%

Next steps in high-repetition-rate laser development for Thomson scattering

Den Hartog,

Holly,

Thomas

2023

J. Inst.

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Design of a next generation high-rep-rate laser system is underway, aiming for a maximum rep rate of 100 kHz for 1 ms. This will be a “pulse-burst” laser, which is a type of heat-capacity laser. Heat-capacity laser operation is characterized by a burst of pulses of limited duration, with burst length ≤100 ms and pulse rep rate ≥1 kHz. Waste heat accumulates in the laser rod during the burst. This heat is deposited evenly throughout the rod volume, with very little heat removed during the burst, such that temperature rises evenly across the rod radius. Thus beam distortion due to thermal gradients is small. Heat is removed from the rod after the burst, with typically tens of seconds between bursts. Pulse-burst operation of flashlamp pumped Nd:YAG lasers is a cost-effective route to high-rep-rate capability. Pulse-burst laser systems with “fast burst” rep rates in the range of 10–20 kHz have been built for the Thomson scattering diagnostics on MST, NSTX-U, and LHD. For Thomson scattering diagnostic application, the typical requirements are 1064 nm, 1–2 J/pulse, ≤30 ns FWHM pulse, with a top-hat beam profile. A major requirement for this next generation laser system is flexibility in burst sequence programs, ranging from 1 kHz for 100 ms to 100 kHz for 1 ms, and a variety of scenarios in between so that operation can be tailored to plasma experiment requirements. Flashlamp pumping will be used for this next generation laser because it is inexpensive and flexible. A new switch-regulated flashlamp driver will provide improved flashlamp control at lower cost. Additional design issues such as the optimum flashlamp pumping spectrum and optimum Nd doping will be addressed. The use of commercial off-the-shelf components will be maximized in this laser system so that pulse-burst systems can be developed and built by others for new applications.

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Thomson scattering at 250 kHz

Cited by 2 publications

References 7 publications

Electron thermal confinement in a partially stochastic magnetic structure

Electron thermal confinement in a partially stochastic magnetic structure

Next steps in high-repetition-rate laser development for Thomson scattering

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