From:
WOLFE@PSFC.MIT.EDU
Reply-To: WOLFE@PSFC.MIT.EDU
Subject: Alcator
C-Mod Weekly Highlights
Newsgroups: sci.physics.plasma
Organization:
MIT
Alcator
C-Mod Weekly Highlights
April
18, 2000
Operations:
-----------
Last week was
a maintenance week at Alcator C-Mod. No plasma runs were
scheduled.
During
testing last Friday, a stainless steel shutter used to protect a mirror
during
discharge cleaning became detached and had to be removed from the
vessel.
A brief up-to-helium vent was carried out, following which the machine
was
pumped back down and ECDC in deuterium carried out over the weekend.
Vacuum
conditions appeared to be acceptable as of Monday.
Plasma
operations are scheduled to resume this week.
Physics and
Diagnostic Systems
------------------------------
An absolute
calibration of the Michelson interferometer was carried out over two
days. The measured sensitivity vs frequency proved
very stable, when compared to
measurements over a year ago. All of the other ECE diagnostics (GPC, GPC2,
radiometers) are cross-calibrated to this instrument during plasma
operation.
We have now installed a total of six TV cameras viewing
the plasma and
in-vessel hardware. When the data acquistion is fully
operational, we will be
digitizing the images from all six cameras. The
views include a wide angle
view inside the vessel, a view of the J port
antenna, a view of the D port
antenna, a view of the E port antenna, and
two nearly indentical, tangential
views of the divertor region. Presently
the E port antenna is being viewed by
the LANL-supplied fast-framing,
gated, visible camera. The digitized frames
from the cameras are also
being compressed and made available on the
WEB, allowing after-shot access
by operators, diagnosticians, and any other
interested parties. The site
for these images is
http://www.psfc.mit.edu/cmod/PlasmaVideo/imagedir.plx
which
can also be reached by clicking on the "Plasma Videos from Recent
Shots"
line in the C-Mod "Experimental Operations" page of
the PSFC WEB-site.
ICRF Systems:
-------------
The
C-Mod ICRF transmitters #2, #3 and #4 have been retuned to provide 2 MW
output
power each into a dummy load. Control logic issues that are common to
all
four transmitters have been discovered and still need to be fixed before
operation
is resumed.
Diagnostic Neutral Beam
-----------------------
Progress
on the DNB continued. Paralleling the
filament cables was
finished. The
additional cabling reduced the total resistance by approx.
10 milliohms,
adding another volt at 100 A. A new,
isolated current
measurement system was installed to improve the
measurement of the
accelerator current.
The vacuum instrumentation was fixed, with 2 new ion
gauges and a
replacement gauge controller installed, and a new monitor for
the RGA
connected. The sticky source gas valve
was replaced with a new
valve.
Travel and Visitors
--------------------
Bill
Dorland visited the PSFC for 2 days.
The main activity was working with
Martin Greenwald and Howard Yuh
on the adaptation of the gyrokinetic stability
code (GS2) to use MDSplus
data structures. A standard gs2 tree
was agreed on
and built. We expect
to have the I/O modules and a GUI for setting control
values and entering
data within a month or two. Bill also
delivered a seminar
which discussed the difference between gyrokinetic and
gyrofluid simulations
of ITG turbulence.
Chris Brunkhorst came
to MIT for the week to help with the transmitter
retuning. Norton Bretz came on 4/14 and will stay over
the weekend working on
MSE software.
Matthias Groth visited MIT
last week and presented a seminar on 'Measurements
and modeling of helium
and neon enrichment in the JET divertor'. He also spent
considerable time
in discussions with C-Mod staff regarding similarities and
differences
between C-Mod and JET results in this area. Models of compression
and
enrichment were also discussed.
David Winslow (UT-FRC) and Keith
Carter (UT-FRC) visited the PSFC to work
on the Texas probe system and
attend the EPC meeting. Alignment of the
probe drive, installation of the
vacuum system, and installation of the PLC
electronics were
completed.