From: irby@PSFC.MIT.EDU
Reply-To: IRBY@PSFC.MIT.EDU
Subject: Alcator C-Mod Weekly Highlights
Newsgroups: sci.physics.plasma
Organization: MIT


Alcator C-Mod Weekly Highlights
March 22, 2002


Reassembly of Alcator C-Mod continued this week. Work on the new RFX
DNB and the LH MIE Project continued as did work on diagnostics.


Physics
-------

A faster (non-parallel, out-of-core) version of the 2-D full-wave ICRF
code, TORIC, has been successfully configured to run locally on the new
Linux workstations (CMODWS01, 02 and 03). Up to 161 poloidal modes have
been run with CPU time of about 400 minutes, which is comparable to run time
on the CRAY. Runs with higher mode number appears to be limited by
available scratch disk space on the Linux stations. Some preliminary
physics runs have shown the mode conversion process in D:He3
and H mixture may be much more complicated than previously thought.

J. Snipes, M. Greenwald, and T. Fredian attended the ITPA Confinement
Threshold and Modeling Database meeting at PPPL the week of 11 - 14 March.
The latest results of the Confinement and Threshold Database Working Groups
were presented. The L-mode database has moved from Garching to Cadarache
where it will be managed by G. T. Hoang. New low aspect ratio MAST data has
just been added to the database and initial regression fits indicate that the
data do not change the density, toroidal field, and plasma surface area
dependencies very much, but add an aspect ratio dependence of (a/R)^0.46.
Joseph Snipes was asked to present the latest results from the Confinement
and Threshold Database Groups at the IAEA meeting.


Operations
----------

Following installation of all the upper TF springplates, another successful
hi-pot of the TF was done. This test was required before installation of the
TF legs could proceed. However, reassembly of the machine was delayed
somewhat this week when the boots that seal the cryostat were found to need
modifications to allow for more insulation and more space around the vacuum
flange. These new boots have to be installed before the TF vertical legs.
Five of the ten required new boots have been fabricated, and two of the
TF legs have been installed. Pumpdown is now scheduled for the week of
April 22, approximately 4 weeks later than indicated on the original schedule
generated in August 2001.


Lower Hybrid MIE Project
------------------------

The transmitter wiring is progressing. Only one more wiring harness is
needed to complete transmitter #3. Connections to Cart #2 are approximately
50%, and those to cart #1 are about 20% complete. The klystron high voltage
cable is also being installed. The nitrogen waveguide pressurization plenum
is being fabricated. Termination of fiber-optic data and control cables is
nearly complete. Both cooling water pumps for the LH system are now
operational.


ICRF Systems
------------

Work continued on the testing and calibration of the approximately
35 demodulator boards required for the ICRF diagnostic and protection
systems.

Peter Koert was in Germany this week working with the vendor who will supply
the fast ferrite tuners. He hopes to procure sufficient documentation
to allow control and protection circuitry to be designed and fabricated at
MIT for the prototype unit.


DNB and Related Diagnostics
---------------------------

Operation of the RFX DNB injector began last week, 20 days after the Budker
team arrived from Novosibirsk. Beam parameters were rapidly brought up to the
full specification operating values of 50 kV, >50 ms pulse duration, and >4.5
amps of ion current (simultaneously). About 500 pulses have been fired during
the first week of operation, and the injector reliability is extremely high.
Calorimetry measurements show that the beam has a 1/e diameter of 6 cm at the
exit of the injector, and should be even smaller at its focus inside the
tokamak. Comparisons of calorimetry data with the dump magnet on and off
indicate that full-energy neutrals are the predominant beam component.
Spectroscopic measurements of the component fractions are in progress. The
beam is now routinely fired remotely under MDSplus control, and work continues
this week on interfacing the data acquisition directly to our MDSplus trees.


Diagnostics:
------------

At PPPL, the 140 GHz reflectometer channel has successfully been changed into
a fixed frequency channel, bypassing the malfunctioning Gunn diode.
This modification now gives us two fixed-frequency channels, at 140
and 130 GHz, for edge pedestal fluctuation measurements. Also at PPPL,
fabrication of the remaining BES/MSE fiber optics ferrules continued this
week; they should be completed next week. EDM machining of a new
BES/MSE image bisector block has begun, with completion expected by
the end of April. Schott Glass USA has been contacted about new SFL6
glass vacuum windows for this diagnostic.

At MIT, we continue to work on the MSE optics, CXRS telescope and shutter
system, new wide angle cameras, Penning gauges, and divertor probes.


Travel and Visits
-----------------

Martha Redi, PPPL, was here this week as part of the PPPL collaboration on
investigating the gyrokinetic stability of the Alcator C-Mod ITBs. This
work will be presented at the upcoming Transport Task Force meeting. Stew
Zweben, PPPL, was also at MIT for the week, working on upgrades to the Gas
Puff Imaging diagnostic.

Martin Greenwald attended the ESnet steering committee meeting at
the Jefferson Lab, Newport News, Virginia this week.