A combined phase contrast imaging and heterodyne interferometer system for multiscale fluctuation measurements (invited)
- MIT Plasma Science and Fusion Center, Cambridge, MA (United States)
- General Atomics, San Diego, CA (United States)
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
Web of Science
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