Magnetic and Electric Field Diagnostic for High Temperature Plasmas
Abstract
A Transient Internal Probe (TIP) diagnostic has been developed for precise (<= 15 G), high resolution (1 cm, 1 MHz) measurements of magnetic fields in plasmas, and has been used to determine the internal field in the Helicity Injected Torus where T <= 80 eV.( T.R. Jarboe, M.A. Bohnet, A.T. Mattick, B.A. Nelson, and D.J. Orvis, ``Results from current drive on the Helicity Injected Torus,'' Phys. Plasmas 5, 1807 (1998) ) The basis of measurement is the rotation of polarization of laser light by a magneto-optic probe launched through the plasma at ~ 2 km/sec. In order to survive and provide useful information in higher temperature plasmas, the probe must be protected by a refractory cladding. This paper discusses design of a TIP probe clad with sapphire, and presents results of measurements of B-fields using a clad probe traversing a static magnetic field at 2 km/sec. Unlike previous designs, the probe utilizes ``catseye'' optics to retroreflect the illuminating laser beam back to an ellipsometer for polarization analysis. The design incorporates an MgO lens to eliminate polarization effects, and is expected to be capable of measuring B-fields over a ~ 1/2 meter chord in plasmas with temperatures up to 300 eV. Design and preliminary tests of an electro-optic probe for measuring plasma E-fields will also be discussed.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2000
- Bibcode:
- 2000APS..DPPCP1082K