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
January
11, 2002
Reassembly of
Alcator C-Mod has begun. In addition,
work continued
on the ICRF systems, Lower Hybrid MIE project, and Inner
Divertor Upgrade.
Physics
-------
We continued
our remote collaboration with ASDEX Upgrade on matching pedestal
conditions. Dedicated C-Mod experiments were run in July
2001. AUG has
resumed operation
after a maintenance period. On Friday,
Jan 11, they began
the first part of their comparison experiments,
focussed mainly on shape
development.
They obtained a good match to the dedicated C-Mod shots and
also,
unexpectedly, were able to closely match the shape of our more typical
EDA
discharges. Both NBI and RF heating
were used. Further experiments
aimed
at matching dimensionless plasma parameters and comparing ELM behaviour
will
continue later in their winter campaign.
Operations
----------
With
the installation of the OH2L coax early this week, reassembly of Alcator
C-Mod
was begun. Torque checks will be
complete on the coax early
next week at which point the installation of
cover plates, the lower
wedge plate, and lower TF arms can be staged. Hi-Pot and ringing tests of
all the EF
magnets were successfully completed this week, as were
similar tests on
the OH2L magnet. The OH1 and OH2U
magnets will
be tested as soon as installation of their respective coaxes
is
complete. Hi-Pot turn-to-turn
tests of the TF core were also completed
successfully.
We
continue work on the TF and Thermocouple scanner upgrades. A controller
PC has been selected for
purchase. Communication links are
being
defined and tested for speed.
Work on the drive amplifier
for the MHD antennas continued this week.
The
prototype amplifier is now operating over a DC to 1 MHz band at
the 10 Amp,
60 Volt level. We
expect to push up these parameters somewhat next week.
Lower Hybrid MIE Project
------------------------
Three
of the four klystrons on CART3 have been installed
in the cell. A picture of the klystrons and cart can be
found at
http://www.psfc.mit.edu/cmod/operations/EngImages/RF/lower_hybrid/DCP_0117.JPG
Final
testing has begun on cart2 in preparation for its move to the cell.
Wiring
of the HV Junction Box that interfaces the transmission line from
the HVPS
to the cell has been completed. Two
engineers from the vendor that
supplied the HVPS are on-site and preparing
for the supply acceptance tests.
At PPPL, procurements have now been placed for many of the
LHCD components
(items within vacuum boundary): couplers, flanges, shroud,
interface
flange, and ceramic windows.
The remaining "Phase 1 Components" have
been sent to
vendors for RFQ, and awards are expected shortly. These
include the forward wave guides, and those parts
required for the completion
of "front end & vacuum
components." Procurement of
further components
is presently limited by available funding.
ICRF
Systems
------------
Machining of the D&E Faraday screens
has begun in our shop.
Modifications
are being made so that the metal to boron nitride
interface can be
shielded from interaction with the edge plasma. During the last campaign
these regions
sometimes limited plasma performance with impurity injections.
In
addition, the D and E-port current
straps sustained some arc damage and
required some reconditioning. We have deburred the straps and are
preparing
them for brush plating.
Also during the last campaign, we found the power handling capability
of
the J-Port antenna was limited by development of a discharge where
the
current strap passed under a grounding bridge that terminated the end
of
the strap. Detailed analysis of
this region indicates that changes to its
width and contouring will
increase the power handling capability by more
than 50%. We are proceeding with the modifications
required.
The first demodulator PC board has been populated and
testing has begun.
The PLL synthesized LO section of the board is working
extremely well.
Initial tests of the phase detector also indicate proper
operation.
DNB and Related Diagnostics
---------------------------
The
DNB layout for the cell was forwarded to Budker Institute with
addition of
cable tray details to allow interconnect cables to be
fabricated. The fueling system design was completed and
made
available for fabrication.
PLC software is now in progress along
with associated PLC and
vacuum rack modifications. Initial
tests of
the C-Mod shot synchronization software were successful. The output
signals for the beam will be
verified next week and results made
available for comment. Fabrication of the beam and pulse
transformer
supports has not yet begun.
Matt Sampsell, UTexas, visited
MIT to begin
preparing the beam diagnostics area so that diagnostic
assembly can begin
for the next campaign.
During the last week
and a half a lot of work has been done on the
MSE/BES canister. Two machinists at PPPL are working in
parallel on this
project. The
modifications to L2, L3, M2 and M3 designed by Paul LaMarche,
PPPL, are
nearly complete. Final ray trace
evaluations are being supplied by
Ron Bravenec at the University of Texas
after which cutting of the M2 mirror
can begin. Other modifications are proceeding as well. A new more rugged
mount for the M1
mirror is nearly complete and will be sent to MIT to be
blackened and then
sent back to PPPL for final assembly.
The canister
split, and addition of new flanges to allow this
vertical section to
be rotated and removed, will begin January 14. Work has also begun on
modifying the
external polarizer sheet holder; it will now be
removable rather than
fixed. We expect to begin assembly of
the
canister by late January.
Inner Divertor
--------------
All studs and high strength bolts have
been torqued to specification.
Tiles installation will resume next
week. We continue installation
of
new diagnostic cable runs. The new
probe arrays for the inner divertor
are on schedule for installation late
this month.
Travel and Visits
-----------------
Matt
Sampsell visited from UTexas to work on the DNB diagnostic installation.