From:
irby@PSFC.MIT.EDU
Subject: Alcator C-Mod Weekly Highlights
Newsgroups:
sci.physics.plasma
Alcator C-Mod Weekly
Highlights
October 13, 2003
Alcator
C-Mod resumed plasma operation last week.
Work continued on
Lower Hybrid and ICRF systems and
diagnostics.
Operations
----------
After
extensive consultation with GE, the MIT alternator was brought
back into
operation on Wednesday and C-Mod power tests were begun. By
Thursday afternoon all supplies and
support systems had been tested
and one plasma discharge was
produced. On Friday, plasma
cleanup
continued, with the first full length plasmas of the
campaign.
Following successful vacuum conditioning, plasma conditioning of
the
D- and E-Port ICRF antennas was also begun.
Diagnostic
Neutral Beam
-----------------------
We have continued to
prepare the beam for plasma operation.
Conditioning of the beam has
resulted in reliably obtained peak beam
currents of over 4 A, at voltages
of 48 kV.
ICRF Systems
------------
Both
FMIT#3 and #4 (J-Port antenna transmitters) have been tested at
50 MHz to
greater than 1.5 MW for 500 ms into a dummy load. The
mechanical measurements of the cavities were taken for
future
reference and for inclusion in the cavity models. The tuning of the
J-Port antenna, with
the new external matching components needed for
50 MHz operation, has been
found to be a very sensitive operation.
This effect has caused some
faulting of the J-Port antenna during
plasma operation. We are addressing this issue.
Lower
Hybrid Systems
--------------------
A design review was held at
PPPL on 10/10 for the brazing of new
ceramic windows into the Lower Hybrid
coupler. Attending from MIT
were
Bob Childs, Jim Irby, Ron Parker, Rui Vieira, and Steve Wukitch.
Attending
from PPPL were Larry Dudek (chairman), Bob Ellis, Joel
Hosea, Steve
Jurczynski, Jay Kung, George Labik, Doug Loesser, Steve
Raftopoulos, Gerd
Schilling, Skip Schoen, and Randy Wilson.
The
review went extremely well, with comprehensive discussions of
the
relevant technical issues. We
have agreed to begin preparing the
couplers for brazing, including a
modification to the coupler wall at
each end to reduce the tensile force
on the ceramic. Two of the
three-window
prototypes using the Gapasil brazing compound have been
taken to MIT for
additional tests.
We continue to test the two reconditioned
klystrons and prepare them
for operation.
NSTX X-Ray
Spectrometer
-----------------------
The NSTX X-Ray
Spectrometer was installed and operated on C-Mod during
the last run period. The X-Ray spectrometer is now operational
again
at C-Mod with several improvements. The spectrometer has been
equipped
with a new spherically bent quartz crystal, and a new 2D
position
sensitive detector with a spatial resolution of 0.1 mm will
be
installed this week. Due to
these changes, the spectral resolution
will be increased by a factor of 2
and the uncertainty for the ion
temperature measurement will be reduced by
a factor of 4 (from
presently 600 eV to 150 eV). Brass plates with rectangular apertures
were installed at
the entrance and exit ports of the crystal housing
to reduce the hard
X-rays and bremsstrahlung background. A support for
additional lead
shielding of the detector has been fabricated and was
installed last
weekend.
Travel and Visits
-----------------
Marco
Valisa is visiting from RFX, and has been able to run the beam
and become
familiar with day-to-day beam operation. Matt Sampsell and
Bill Rowan,
UT-FRC, assisted Marco in acquiring and analyzing the
initial beam
spectral measurements which will be used to determine the
beam divergence
and the acceleration voltage which produces the
optimum component mix for
the diagnostics.
Stewart Zweben, PPPL, was at C-Mod last week to
work on analysis of
edge minority heating and edge turbulence
experiments.
Alan Lynn, UT-FRC, was at MIT last week to reassemble
the FRCECE
diagnostic. He returned
it to operation in time for the first plasma
shots on 10/9.
Joe
Snipes attended the IAEA Technical Meeting on Energetic Particles
from
10/6 to 10/9 at General Atomics in San Diego where he presented
a talk on
Active and Passive MHD Spectroscopy on Alcator C-Mod. Paul
Bonoli also traveled to General Atomics last week where
he attended
an ITPA meeting of the Steady-State and Energetic Particles Group.
Jim
Irby was at PPPL from 10/7 to 10/9 to serve on the NCSX
Preliminary Design
Review committee. Along with Bob
Childs, Ron
Parker, Rui Vieira, and Steve Wukitch, he also attended the
Lower
Hybrid Coupler Brazing Review on 10/10.
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