From: IRBY@CMOD.PFC.MIT.EDU
Date: Mon, 2 Mar 1998 13:40:02 -0500
Reply-To: IRBY@PSFC.MIT.EDU
Message-ID: <980302134002.510138aa@CMOD.PFC.MIT.EDU>
Subject: Alcator C-Mod Weekly Highlights
Organization: MIT Plasma Fusion Center
Newsgroups: sci.physics.plasma


Alcator C-Mod Weekly Highlights
March 2, 1998


Operation of Alcator C-Mod was stopped last tuesday when a short
across the TF bus occurred early in the ramp-up phase of shot 15. Since
that time we have been warming up the machine so that we can open
the bus tunnel and determine the location of the damage. We estimate
access will be possible tomorrow morning, March 3rd. The protective
crowbar circuit operated properly, and the short cleared quickly.
However, up to 1.5 MJ of energy was dissipated in the arc before it
cleared. In view of the time needed to warm up and inspect the tokamak to
determine and correct the cause of the fault, it is probable that we shall
decide to stop the winter plasma campaign and move into our scheduled
maintenance and upgrade phase.
Part of the run plan from last Tuesday was completed before the
fault. The machine was boronized over the weekend and helium ECDC was
run until Monday morning. Deuterium ECDC was then run overnight. It was
hoped that a period of deuterium ECDC would help post boronization startup.
Fiducial discharges were readily obtained on Tuesday morning and
were of very good quality. We then began work on mp194, ICRF
Reversed Shear Mode with 3He Minority at 80 MHz. One 8T H-mode was obtained
(150 kJ) which will be very useful for power absorption analysis. Early
heating during the current ramp-up was also begun. The initial guess on He
concentration was probably too high, but we did not have time to reduce the
concentration before the end of the run. Preliminary break-in-slope
analysis indicated some off_axis mode conversion electron heating.
Work on the DNB last week included improvements to the MOD/REG
120 VAC service, installation of the computer interface connections to
the secondary emission/thermocouple chassis, fabrication of the first
five optical transmitter and receiver boards, and installation of the
fast isolation amplifier boards. Work continues on the HV supplies,
MOD/REG system, and master control logic system.
Professor Cy MacLatchy from Acadia University, Nova Scotia,
met with Brian LaBombard and the C-Mod edge group on monday and tuesday
to discuss experimental plans during the next year. Cy will be
spending part of his upcoming sabbatical leave (august 98 - july 99)
participating in divertor/edge experiments on C-Mod. Possible
areas of research include: video image-capture and tomographic
reconstructions of impurity injection "plumes", analysis of divertor
plate probes data, operation and analysis of Omegatron-probe
ion-mass spectrometry.
Gerd Schilling and Gary Taylor from PPPL continued to work at C-Mod
last week on RF analysis and the new ECE polychromator. Roger Bengtson
and his graduate student David Winslow were here from the University of Texas,
Austin, to work on their scanning probe.