Newsgroups: sci.physics.plasma
From WOLFE@CMOD2.PFC.MIT.EDU Tue Feb 28 13:26:05 1995
From: WOLFE@CMOD2.PFC.MIT.EDU
Organization: MIT
Subject: Alcator C-MOD weekly Highlights

Alcator C-MOD Weekly Highlights
Feb. 27, 1994

Last week was a scheduled maintenance week on Alcator C-MOD. A "clean" vent
was completed on Tuesday, following re-installation of the fast-scanning probe
and installation of new windows on the reflectometer diagnostic. Additional
maintenance and upgrade activities were performed on several diagnostics,
power systems, ICRF system, and computer and data acquisition systems. Plasma
operation will resume this week.

After the machine was pumped down on Tuesday, a bake to 110C was run until
Saturday morning. Discharge cleaning (ECDC) in helium was carried out for 32
hours at a wall temperature of 60C, followed by a cooldown to 45C and a final
leak check on Monday. ECDC in D2 will be carried out on Tuesday morning. The
feedback control algorithm used to maintain the coil temperatures during
bakeout was improved. This modification resulted in better control and lower
LN2 usage during the present bake.

The HV supply for ICRF transmitter #4, which had been out for modification,
was returned from the vendor and installed in the high-yard. This supply will
be used with the tunable FMIT transmitters which are being brought from
PPPL as part of the Princeton collaboration on the C-MOD project. In other
ICRF activities this week, arc paths were located and repaired in the
transmission line to the D-port antenna. These had been restricting the power
available through this antenna in the last week of operation before the
maintenance period. A Conceptual Design Review for the new 4-strap antenna
being provided by PPPL as part of the Princeton collaboration is being held at
MIT today. This antenna will be installed in 1996.

Maintenance was performed on the ECE diagnostic, the Thomson scattering
and TCI interferometer windows, the charge exchange system, and the UV
spectrometer diagnostics.

Modifications were made to the control boards of the OH2 power supplies to
improve performance and limit the slew rate. Testing of these modifications
was carried out on Monday.

The VAX computers in the C-Mod cluster were all brought up to the latest
release of OpenVMS operating system, version 6.1. A new disk caching feature
in this release should result in a performance increase of the data
acquisition and analysis systems. In addition to the operating system upgrade,
the collection of disks used for the storage of C-Mod MDSplus data and RDB
databases were converted to a RAID (Redundant Array of Independent Disks) set.
This should provide additional reliability and speed to the on-line storage
facility. Using RAID technology, the data is spread evenly across the entire
set of disks along with error correction information. Increased speed is
obtained by spreading the disk activity across all of the disks. Prior to
converting to RAID, all new C-Mod data was contained on one disk and all I/O
requests from analysis and display programs had to be serviced by a single
drive.

Drs. C.H. Ma, Roger Richards, and Don Hutchinson from ORNL were working
on-site last week, readying their experiments for operation on C-MOD.

Dr. Rob Pinsker is visiting from GA this week. He will be participating in the
C-MOD ICRF experiments.

Dr. Katsumi Kondo from the Heliotron E group at the Institute of Plasma
Physics at Kyoto University has begun a two-month visit to Alcator C-MOD.
He will be working on VUV and x-ray spectroscopy.