Subject: Alcator C-Mod Weekly Highlights
Alcator C-Mod Weekly Highlights
January 25, 2002
Assembly of C-Mod continued this week with installation of the lower
TF arms. Work continued on ICRF, LH MIE, DNB, and diagnostic systems.
At the weekly physics meeting, Robert Granetz presented some initial
results involving analysis of x-ray tomography of ITB plasmas on C-Mod.
It may be possible to use the shapes of the reconstructed x-ray emissivity
contours to measure the q-profile near the axis. Recent ITB plasmas on
C-Mod exhibit extremely peaked x-ray emissivity profiles, which
makes this technique feasible near the magnetic axis (in an earlier study,
on ohmic L-Mode plasmas, the technique was found not to be applicable).
These new preliminary results appear to determine elongation near the center
to an accuracy of +/-0.03, which would correspond to an error in q0 of +/-0.1.
Tomographic analysis of high performance eda H-Mode plasmas also shows promise.
Assembly of C-Mod continued this week with the installation of 6 out of the
20 lower TF arms. All arms are inspected carefully, hi-potted, and
thermocouple and voltage tap instrumentation is checked before installation.
Fitup and testing of the new springplate insertion tool has begun.
We continued setting up for machining the cylinder this week. Fabrication of
the new cryostat ports by an outside vendor is on track for a late Feb
Development of the drive amplifier and some small machining operations for
the new MHD antennas continued.
Lower Hybrid MIE Project
Commissioning of the HVPS is well underway. The primary power supply
transformers were energized to 13.8 kV this week with the modules initially
disconnected. Following this initial test, the modules were reconnected
and testing continued. The snubber, voltage divider, and triax inner conductor
were hi-potted successfully to 60 kV with low leakage current. Testing of
the high voltage dummy load wiring is in progress.
Fabrication of control and protection circuit boards, development of PLC
software, preparations for installation of the remaining klystron carts,
development of the phase and amplitude control software, and work on the
water cooling system all continued this week.
After achieving very good results with the phase measurements, careful tests
of the amplitude detection section of the new demodulator board are in
progress. Both the amplitude and arc detector step response is less
than 1 us. These fast response times will limit the damage done by
any antenna or transmission line fault condition to harmless levels.
Machining of the D and E-Port antenna Faraday shield and the J-Port antenna
straps are continuing in house.
DNB and Related Diagnostics
Planning and design for the initial installation and commissioning of
the RFX beam is largely complete. We are ready to start
modifications to the beam support frame to accommodate the new beam.
Though not required for beam commissioning, the F-port flange has
been approved for machining. Information has arrived from the Budker
Institute team regarding the interface of the beam control software
with MDSPlus. This information will be used to begin work on the software
that will transfer the beam parameters to MDSPlus on a shot by shot basis.
The PLC rack has been cleared of all old cabling, and new wiring is in
progress. Once the PLC is wired to the cross connect blocks, we can begin
installation of the vacuum controllers and other rack mounted equipment.
At PPPL, mechanical/optical work continued on the MSE diagnostic in
preparation for reassembly and testing next week.
Travel and Visits
Steve Wukitch, Jim Zaks, Dave Terry, and Montgomery Grimes attended
SOFE this week in Atlantic City, NJ. Steve presented an invited talk
on C-Mod with an accompanying paper. Jim, Dave, and Montgomery
all presented posters, also with accompanying papers. Peter Titus,
PSFC Fusion Engineering and Technology Division, also discussed analysis
results of our divertor and antennas.
"Results and Status of the Alcator C-Mod Tokamak", S. Wukitch, B. Beck,
E. Fitzgerald, R. Granetz, D. Gwinn, M. Grimes, J. Irby, D. Terry, P. Titus,
R. Vieira, S. Wolfe, J. Zaks, and the Alcator C-Mod Group, MIT-PSFC, and
S. Bernabei, R. Ellis, L. Gehrig, J. Hosea, D. Loesser, G. Schilling,
J.R. Wilson, PPPL
"Inner Divertor Detailed Design and Manufacturing", J. Zaks, M. DeMaria,
B. LaBombard, R. Granetz, E. Fitzgerald, H. Savelli, P. Stahle
"The Alcator C-Mod Lower Hybrid Current Drive Experiment Transmitter
and Power System", M. Grimes, D. Gwinn, R. Parker, D. Terry, MIT-PSFC,
and J. Alex, Thales AG
"The Alcator C-Mod Lower Hybrid Current Drive Experiment Low Power
Microwave and Active Control System", D. Terry, W. Burke, M. Grimes,
D. Gwinn, J. Irby, N. Kambouchev, R. Parker, P. Woskov
"Disruption Load Calculations Using ANSYS Transient Electromagnetic
Simulations for the Alcator C-Mod Antenna", P. Titus
"Alcator C-Mod Inner Divertor Upgrade Design and Analysis", P. Titus,
J. Zaks, M. DeMaria, B. LaBombard, R. Granetz, J. Irby, B. Lipschultz,
E. Fitzgerald, R. Childs, W. Beck, W. Burke, E. Marmar, D. Gwinn,
I. Hutchinson, R. Boivin
In addition, work on the Lower Hybrid system being done at PPPL was
discussed in three papers:
Design and Engineering of teh Alcator C-Mod Lower Hybrid Current Drive
System", G.D. Loesser, J. Rushinski, S. Bernabei, J.C. Hosea, J.R.
Wilson, PPPL, and B. Beck, R. Parker, MIT-PSFC
"A Third Generation Lower Hybrid Coupler", S. Bernabei, J. Hosea, C. Kung,
D. Loesser, J. Rushinski, J.R. Wilson, PPPL, and M. Grimes, R. Parker,
"Compact Probe Design for the Power Monitoring Fromt he Narrow Side of
the Reduced Waveguide", C. Kung, S. Bernabei, J. Gumbas, N. Greenough,
E. Fredd, PPPL