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

Alcator C-Mod Weekly Highlights
February 22, 2002


Alcator C-Mod was moved from the assembly area to the center of the
Cell this week. Work also continues on the new DNB installation, ICRF
systems, and the Lower Hybrid MIE Project.


Physics
-------

At the Physics meeting, Catherine Fiore presented preliminary calculations of
the electrostatic potential and radial electric fields in CMOD ITB shots,
generated by the input of central toroidal rotation measurements into TRANSP.
The highest value of the resulting EXB shearing rate peaked at 8e4/s in the
ITB region after the ITB was fully developed. Further work is needed to
compare this result with the ITG growth rates.

Joe Snipes presented a preview of the talk he will give at the ITPA Confinement
and Threshold Database meeting in Princeton 11 - 14 March on the Latest H-mode
Threshold Results and Future Plans. The talk covered the inner gap scan
experiments that were presented by C. S. Pitcher at the APS meeting in Long
Beach. There does not appear to be an increase in threshold down to a 3 mm
inner gap within the measurement errors. Closing the gap still further to
produce inner wall limited plasmas, however, increased the threshold
dramatically to the point where 2.7 MW of launched ICRF power was
insufficient to get into H-mode. More experiments on this topic are planned
during the next run campaign when more ICRF power will be available.


Operations and Power Systems
----------------------------

All lower TF springplates were installed and carefully documented for proper
operation this week. TF joint resistances were measured and turn-to-turn
hi-pots were conducted. All measurements indicated successful completion of
the lower TF arm installation, and the machine was moved from the assembly
stand to the lower dome at the center of the Cell on Friday. A picture of
the "big lift" can be found at

http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/Machine_assembly_A/DCP_0196.JPG

We continued maintenance work on the alternator this week in preparation for
the next run campaign. Cooling water pumps are being refurbished as is the
varistor bank that protects the rotor from over-voltage.


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

We have stopped the commissioning activity on the HVPS until several issues
with the control system can be addressed by the vendor. We expect to resume
the commissioning process late March to early April. Though the supply has
reached current, voltage, and pulse length specifications, the control system
as it currently programmed will not allow safe operation of the supply with
our klystrons. We continued installing the cabling between the klystron
carts and the various control and protection cabinets this week. Waveguide
is being prepared for installation on the klystrons.


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

Chris Brunkhorst (PPPL) visited this week to participate in
commissioning of FMIT#3 and #4 in preparation for the upcoming campaign.
Transmitter and screen crowbars were tested. FMIT#3 was successfully tested
to 1.8 MW into a dummy load. FMIT#4 was limited by a low power problem that
will be addressed next week.


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

The first contingent of Russian engineers from the Budker Institute arrived
this week to begin assembling the diagnostic neutral beam, which has been
loaned to us by Consortium RFX in Italy. Over the next four weeks, a total
of eleven Russian scientists and engineers will assemble, install, and
commission the DNB. Completion is scheduled for 24 March, in time for the
beginning of tokamak conditioning operations.

The new spectrometer for the CXRS is being ordered this week. A design
review for the new high-resolution edge CXRS in-vessel optical system was
held this week. No significant problems were found, and final drawings for
construction will be ready next week.

Russel Feder, PPPL, continued to work on the new ferrules and ferrule
holder for the MSE/BES Image Dissector with Ron Bravenec, U. of Texas, and
Howard Yuh, MIT. The ferrules for MSE have been merged into larger
rectangular ferrules, and the new design should be generally easier
to work with.


Other Diagnostics
-----------------

Work at PPPL continued on the 130/140 GHz TFTR reflectometer upgrade
for C-Mod. Power supplies have been built and tested. During microwave
circuitry checkout two of the Gunn oscillators were found not to be
in proper working condition, and have been returned to the
manufacturer for further testing.


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

Martha Redi, PPPL, was here this week, doing further exploration of the
stability of dual frequency heated ITBs on CMOD.

David Mikkelsen gathered information relevant to transport
simulations at MIT February 18-22, and began to use the MIT Beowulf
cluster. He also spoke with Joe Snipes about the possibility of using
PPPL codes to analyze Alcator C-Mod plasmas with locked modes.

Miklos Porkolab gave a talk at the AAAS meeting in Boston last Sunday,
Feb. 17, as part of a panel discussion on the future of Nuclear Energy
entitled "Recent Progress in Fusion Research and Future Prospects."
The lecture was well attended and covered by the news media.