title: A phase contrast imaging-interferometer system for detection of multiscale electron density fluctuations on DIII-D.
abstract: Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI-interferometer. The combined system uses a single 10.6 μm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz <f < 5 MHz and 0 cm-1≤k ≤ 20 cm-1), allowing simultaneous measurement of ion- and electron-scale instabilities. Further, correlating our interferometer's measurements with those from DIII-D's pre-existing, toroidally separated interferometer allows core-localized, low-n MHD studies that may otherwise be inaccessible via external magnetic measurements. The combined diagnostic's small port requirements and minimal access restrictions make it well-suited to the harsh neutron environments and limited port space expected in next-step devices.
authors.affiliation: MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: Davis
authors.affiliation: MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Rost
authors.affiliation: MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA.
authors.forename: M
authors.initials: M
authors.lastname: Porkolab
authors.affiliation: MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA.
authors.forename: A
authors.initials: A
authors.lastname: Marinoni
authors.affiliation: General Atomics, San Diego, California 92121, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Van Zeeland