The Motional Stark Effect Diagnostic for NSTX-U

Technical Report · Thu Jan 27 04:00:00 EST 2022

DOI:https://doi.org/10.2172/1842458· OSTI ID:1842458

Levinton, Fred M. ^[1]

---

1. Nova Photonics, Inc., Princeton, NJ (United States); Nova Photonics, Inc.

This report describes the development of the motional Stark Effect diagnostic for NSTX. The MSE concept relies upon observation of the Balmer-alpha (n=3 to n=2) emission from a neutral hydrogen beam traversing a plasma. As a beam at high velocity, $$\vec{ν}$$, passes through the magnetic field in the plasma, $$\vec{B}$$, it experiences in its reference frame a Lorentz electric field, $$\vec{E}$$ = $$\vec{ν}$$ x $$\vec{B}$$. This electric field causes the spectral emission to be split and polarized as described by the Stark effect. The transition is separated into a set of lines in which the line spacing is linearly proportional to the electric field magnitude, and the line polarization is dependent on the electric field direction. Traditionally, MSE has used polarimetry to determine the polarization angle of the light, and related that to the magnetic field pitch angle in the plasma. The MSE diagnostic was developed under high magnetic field ($$>$$ 1~T) conditions, and the lower fields of recent high-beta experiments such as NSTX posed challenges to the technique. At low magnetic fields Doppler broadening effects mask the Stark effect. With the use of a narrow bandwidth filter MSE measurements at very low magnetic fields have been obtained.

• Research Organization: Nova Photonics, Inc., Princeton, NJ (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• DOE Contract Number: FG02-99ER54520
• OSTI ID: 1842458
• Report Number(s): DOE/ER54520-1
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
MSE
magnetic field
NSTX-U