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Title: A combined phase contrast imaging and heterodyne interferometer system for multiscale fluctuation measurements (invited)

Journal Article · · Review of Scientific Instruments
DOI:https://doi.org/10.1063/1.5035413· OSTI ID:1609192

In this work, a novel combined diagnostic capable of measuring multiscale density fluctuations that extend from magnetohydrodynamic (MHD) to the lower range of electron temperature gradient turbulence has been designed, installed, and operated at DIII-D. The combined diagnostic was constructed by adding a heterodyne interferometer to the pre-existing phase contrast imaging (PCI) system, both of which measure line-integrated electron density fluctuations. The port-space footprint is minimized via use of a single 10.6 μm probe beam. With temporal bandwidths in excess of 1 MHz, the PCI measures high-k (1.5 cm-1 < |kR| ≤ 25 cm-1) fluctuations with sensitivity 3×1013 m-2/$$\sqrt{kHz}$$, while the interferometer simultaneously measures low-k (|kR| < 5 cm-1) fluctuations with sensitivity 3×1014 m-2/$$\sqrt{kHz}$$. The intentional mid-k overlap has been empirically verified with sound-wave calibrations and allows quantitative investigation of multiscale effects that are predicted to be significant in the reactor-relevant Te ~ Ti regime. Lastly, via correlation with the primary DIII-D interferometer, the toroidal mode numbers of core-localized MHD can be measured.

Research Organization:
General Atomics, San Diego, CA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Grant/Contract Number:
FC02-04ER54698; FC02-99ER54512; FG02-94ER54235; NA002135
OSTI ID:
1609192
Alternate ID(s):
OSTI ID: 1461728
Journal Information:
Review of Scientific Instruments, Vol. 89, Issue 10; ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 6 works
Citation information provided by
Web of Science

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