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
March
1, 2002
Work continued on reassembly of Alcator this
week. The installation of the
inner
divertor, milestone 78, was
completed. Work also continued on
ICRF,
DNB, and Lower Hybrid MIE Project systems.
Physics
-------
Dmitri
Mossessian made a presentation at the
ITPA pedestal group meeting at
GA, February 26 - 28, on "Recent
results of pedestal studies at
Alcator C-Mod". He showed scaling studies of pedestal
parameters with
plasma parameters, talked about the operational region of
EDA H-mode, and the
conditions for obtaining small ELMs on C-Mod. He also
presented the results
of ideal MHD stability analysis for both EDA and
ELMing discharges and
showed that the small ELMs can be associated with
medium n coupled
peeling/ballooning modes that are unstable in the pedestal region.
David
Mikkelsen, PPPL, visited GA this week
to gain experience with the GYRO
turbulence simulation code and the vuGYRO analysis tool. These codes
will
be applied to simulations of transport in C-Mod plasmas.
The
Alcator C-Mod FY2004 work proposal has been submitted to DoE OFES.
It can
be found online at
www.psfc.mit.edu/people/censabella/C_Mod_Work_Proposal.pdf
Inner
Divertor
--------------
Milestone 78 was completed on Friday,
March 8th. This milestone
states
that:
All components of the
inner wall modifications will be installed
and made ready for operation.
These modifications will strengthen
the inner divertor and wall, allowing for operation at higher
plasma
currents, while
simultaneously increasing plasma shaping flexibility
for our standard lower single-null divertor
configurations.
All twenty interlocking inner wall girdle plates
have been installed along
with the over 1000 moly tiles, tile support
plates, and tile keeper
hardware.
The number of inner wall studs was tripled to better hold these
new
components. New eddy and halo Rogowski
coils, thermocouples, and
retro-reflectors have also been installed behind
the divertor.
Simulations indicate that not only will the new divertor
easily survive high
current, high field disruptions, but it will also add
strength to the inner
wall and provide a substantial increase in the heat
load capacity of the
inner divertor during long pulse AT discharges. A
picture of the
completed inner divertor installation can be seen at
http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/Machine_assembly_A/DCP_0254.JPG
Operations
----------
The
last port on the cylinder needing modification will be completed
by
Tuesday of next week. Final cleanup
and testing will then be done,
followed by installation of the cylinder on
the machine. The upper wedge
plate
was installed and carefully aligned this week, and the installation of
the
top TF arms was begun. Each arm goes
through a process of cleaning,
hi-potting, and coating of the feltmetal
with graphite before installation.
Lower Hybrid MIE
Project
------------------------
Fiber-optic cables from the
transmitter to the pump controller and HV junction
box are installed and
ready for termination. Wiring on the
TPS systems
continues. The
electrical panel for the transmitter racks is installed.
More components
were machined for the LH low power microwave rack, including
the master
oscillator chassis.
PPPL continued to focus on launcher prototype
testing and the
preparation of drawing packages and specifications for
early procurement
of long-lead components.
ICRF
Systems
------------
We have checked crowbars and protection
circuits, tuned, and brought up both
transmitter #1 and #2 to
approximately 1.8 MW into a dummy load.
We have
also run the #1 and 2 transmitters at 200 kW into a dummy
load with a 4 second
pulse length.
With this test we have begun to qualify the rf system for
long
pulse operation. Control, fault, and data system hardware performed
properly
on this initial test.
The final version of the new phase demodulator
board has been tested and
has now been put into production. This board uses a programmable
local
oscillator and PIC controller to mix signals from 40 to 85 MHz into
a 10
MHz IF band. Standard operating
frequencies can be loaded into and
easily selected from a lookup
table. Besides providing very
accurate
measurements of signal phase and amplitude, over a broad power
input range,
the board also generates fault signals to protect the
transmitters. The
response time of
the fault circuitry is approximately 1 us.
A picture of
the board can be found at
http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/Machine_assembly_A/DCP_0257.JPG
DNB
and Related Diagnostics
---------------------------
The RFX
beam is now installed in the cell along with the new power supplies
and
the pulse transformer. Utilities and
control systems are being
hooked up.
Some redesign of the DNB duct was necessitated by last
minute
changes in the beam location. We expect
to pump down the beamline
early next week.
Ron Bravenec,
UT-FRC, visited MIT to work on noise reduction in the BES data
acquisition
electronics and to work on the final design of the
MSE/BES
fiber-holder.
Diagnostics:
------------
Perry
Phillips, UT-FRC, is currently visiting MIT and will be here through
next
week. He met with Josh Stillerman to get the PC data acquisition system
for
FRC ECE system up and running. He also met with Robert Childs to work out
any
possible conflicts on the modified ECE mirror system on F-port. He plans
to test fit the ECE mirror to
the F-port flange. Matt Sampsell,
UT-FRC, is
visiting MIT this week to repair any damaged BES optical fibers.
Travel
and Visits
-----------------
John Rice and Catherine Fiore were
in San Diego last week to participate in
the ITPA ITB/T session, which
reviewed ITB results in an attempt to develop
a definition of what an ITB
is, and discussed implementation of an ITB
database.