Date: Tue, 17 Mar 1998 8:16:10 -0500
From: IRBY@CMOD.PFC.MIT.EDU
Reply-To: IRBY@PSFC.MIT.EDU
Message-ID: <980317081610.51013586@CMOD.PFC.MIT.EDU>
Subject: Alcator C-Mod Weekly Highlights
Newsgroups: sci.physics.plasma
Organization: MIT Plasma Fusion center


Alcator C-Mod Weekly Highlights
March 16, 1998



The Alcator C-Mod maintenance period continued last week as
we concentrated on disassembling the machine. More igloo blocks,
cabling, diagnostics, and ports were removed as we prepared to lift
the cylinder. The top dome cover was removed on thursday giving us access
to the top TF arms and core. Small amounts of copper and carbon tracking
radiating out from the A-right TF leg were found. However, most of the
debris is probably contained within the cylinder. We hope to have
the cylinder off early this week, at which point we will also be able
to remove TF arms and legs for detailed inspections. We have also found
a small crack on one of the TF core fingers which we cannot properly
inspect until the spring-plates and upper arm are removed.
First invessel access occurred last Tuesday after a several
day long room-air purge to eliminate the effects of residual
boron compounds. Detailed radiation and video surveys were done before
general access was allowed. Following the surveys, calibrations of several
of the invessel diagnostics were performed. An extensive set of digital
pictures detailing hardware on the outer wall was also taken. These pictures
will appear on our WEB site soon.
The development of the diagnostic neutral beam continued with
progress on the Mod/reg system, PLC control, data acquisition, and diagnostics.
The crowbar trigger and control system isolation transformer/power
distribution for the Mod/Red is now complete. Design began for the grid drive
circuits for the power tetrode, and HV cables were installed to the test cell.
PLC programming for control of the DNB waveform generators was completed.
These waveform generators provide timing for power supplies and process
gas feed during the interval in which the beam is generated. The
two camac crates, one for timing and acquisition of engineering data,
the other for beam diagnostics, were connected to their buses and
successfully tested. The camac data acquisition modules for the DNB
profile diagnostics were installed in their final locations and
provided with triggers and clocks that are distributed from the master
DNB decoder. DNB diagnosticians completed their optical designs for
MSE and CXRS. The optics were developed using commercial optical
design packages. The diagnosticians are now involved in arbitrating
the use of space on the flange and in recommending modification of
structures near the machine to provide adequate access for the
diagnostics.
Work in the power systems group last week included continued
development of new over-voltage protection boards. Checks on the
calibration of the bus instrumentation continued. Power systems
group personnel also began to work on DNB related projects last week.
This change will certainly move this major project along more quickly.
The RF group has continued working on exploring the upper frequency
limit of FMIT#3, antenna disassembly, porting ACCOME to the VAX, and
advanced tokamak scenario modelling. The maximum frequency obtained
to date is 76.9 MHz. Approximately half of the ACCOME modules have been
modified to compile properly on a VAX Alpha machine. Advanced tokamak
scenario developmental work has been done for a single null, high
beta, high q equilibrium.
Last week Boyd Blackwell from Australian National University visited Tom
Fredian and Josh Stillerman to discuss plans for upgrading their MDS data
acquisition system to MDSplus. Romik Chatterjee from the University
of Texas visited on Friday to work on some hardware for the O-mode
radiometer.
Dave Johnson from PPPL visited last week to direct calibrations
of the X-point Thomson scattering system. Ben Welch visited from the
University of Maryland to direct calibrations of various visible
light spectroscopic systems.