37th Annual Meeting, APS Division of Plasma Physics

6-10 November 1995, Louisville, KY

Abstract

LA-UR-95-2298

Subject Classification   5.1.1.5  Experimental    
 

Neutron Irradiation Testing (on TFTR) of Hall Probes for Steady-State Magnetic Field Measurements*.

G. A. Wurden, C. W. Barnes, Irina Vlaicu, Los Alamos National Laboratory, and G. LeMunyan, Princeton Plasma Physics Laboratory.

We have installed two indium arsenide Hall effect magnetic field sensors on the midplane of TFTR, in order to test their sensitivity to neutron damage in a DT fusion environment. The system has been online since April 1995, and has already been exposed to a fluence of greater than 5x10^13neutrons/cm^2. The so-called "HST" material (oriented to pickup the toroidal field) is more highly doped, and should be less sensitive to neutron damage than the more sensitive "HSE" material, which is oriented to measure the vertical field. Both are being monitored for instantaneous and/or long term neutron damage. The units are commercial Lakeshore Cryogenic Model 450 Hall effect gaussmeters, and we read them in real-time at 18 Hz over a GPIB fiber optic link to the control room, using a WindowsNT PC and LabViewNT software. Thermal compensation appears to be unnecessary on the outer midplane location for TFTR. The units work without problem in discharges with 2x1018 DT neutrons/second, and we are building a long-term database, comparing the Hall signals to conventional torodial and vertical field magnetic sensors.

*Work supported by U.S. D.o.E. Contract W-7405-ENG-36 & DE-AC02-76CH03073