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
2, 2001
We continued
to maintain transmitters, develop Lower Hybrid systems,
fabricate new
J-port antenna components, and work on the DNB this week.
Physics
-------
The
first Active MHD Antenna that will be installed on the upper, outer
vessel
wall has been completed and initial tests indicate that it can
stand off at
least 2.5 kV in air, which greatly exceeds expected voltages
induced by
disruptions and by driven currents. Photos of the antenna are available at
http://www.psfc.mit.edu/cmod/operations/EngImages/CmodImages.asp?ref=/DIAGNOSTIC
S/Active_MHD/
Power
tests of the Active MHD Antenna with a 400 W high frequency amplifier
will
be performed next week.
Ken Gentle, University of Texas, presented
via video conference at our
physics meeting his analysis of density
peaking in core barrier experiments
from last December. His conclusion was that there was a change
in the
V/D ratio relative to the non-peaking cases, but that it was not
possible
to determine whether the improvement is in the pinch term, or
the
diffusivity, or both.
ICRF Systems
------------
Fabrication
has begun on the inconel stripline components for the J-Port
antenna
modifications. The EDM process had to
be stopped briefly
because of voids/cracks in the inconel billet. New inconel has been
supplied and
machining is proceeding. Straight
sections of the stripline
are being machined using conventional techniques
in our shop. The
stainless steel
ground return plates have been completed and are ready
to be plated. Modifications to and reassembly of the
Faraday screen
continue.
Maintenance
of FMIT #4 has been completed and the transmitter has been
tested into a
dummy load at 2 MW. Maintenance work
continues on FMIT #3.
All PC boards for the J-Port antenna control
upgrade have been
fabricated. One board (fault indicator) has been tested
and is
operational. Two more
boards (phase balance) remain to be tested and
debugged.
All
meters for FMIT #3 and #4 have been installed and calibrated.
Meters
connected to Driver #3 will be re-calibrated when the driver is
reinstalled.
The
board layout files for the new demodulator board have been sent to the
manufacturer
for prototype fabrication.
We continue development of an acoustic
arc detection system. Shielded
boxes
were installed around the piezoelectric detectors that greatly
reduced
electrical pickup and allowed acoustic delays to be
measured.
DNB
---
During this week, the
mechanical design for the H-alpha detectors
to monitor wall/beam
interactions in the DNB duct was completed
and parts ordered. The CXRS shutter design moved forward, and
is nearly
complete. This includes
both the cable runs from outside the machine as
well as the modification
to the in-vessel optical holder. A
design
review of this shutter is planned for next week.
Lower
Hybrid Project
--------------------
A test panel with splitter,
vector modulator, I/Q detector, amplifier,
isolator and directional
couplers was assembled.
Characterization
of vector modulator and I/Q detector operation is
now underway.
New arc detection schemes and test plans were
discussed in some detail
this week.
We are addressing concerns by the review committee that
the
planned detection system will miss arcs at the launcher.
The four klystron carts will be
installed on a new mezzanine in the cell
following the next run
campaign. A meeting was held this
week
to discuss safety issues during testing of the klystrons and
HVPS.
Procedures will be developed and safety indicators in the cell will
be
specified.
We have received updated HVPS container
foundation drawing from Thomcast.
The drawing was reviewed and some
suggested changes or modifications were
prepared to submit back to
Thomcast. The suggestion are mainly to
simplify
the construction process and add stability and strength to the
container
anchoring.
Requisitions for LH transmitter instrumentation
and control electronics
were prepared and released.
The
mechanical configuration of LH transmitter instrumentation and control
cabinets
has been designed. This design was
required before
connectors could be selected and detailed pin outs could
be specified.
Modification and wiring of the klystron carts
continues.
Responses to comments from the Lower Hybrid Review
committee have been
prepared.
Inner Divertor
--------------
The
inner divertor C and backing plate fabrication continues on
schedule. Tiles continue to be produced and checked
through QA.
Travel and Visits
-----------------
Sergei
Mirnov (TRINITI) and Igor Semenov (Kurchatov) visited the PSFC on
Monday.
They accompanied Leonid Zakharov who
gave the Monday Nuclear
Engineering
seminar, and spent time in discussions with several C-Mod staff
members,
on topics ranging from disruption dynamics to the possibility of
using
MDSplus for data acquisition on T-10. Following the regular weekly
C-Mod
Physics Meeting, Dr. Mirnov gave an informal seminar on recent Lithium
limiter
experiments on T11-M tokamak at Troitsk.
David Mikkelsen and Stewart
Zweben from PPPL spent the week at MIT.
David worked on transport
modeling, and Stewart worked on his
edge turbulence imaging
diagnostic. Mike Zarnstorff also
visited from
PPPL on Friday and gave the PSFC seminar.
Rejean
Boivin gave a colloquium to the Physics department at the University
of
Montreal on C-Mod and fusion in general.
He also met with representatives
who were present at the APS-DPP teacher's
day (Quebec city -- October) to
discuss feedback from the meeting, and
plans for the future. He also
made contact with officials from the
Montreal Science Museum who wanted
to learn more about plasmas and fusion
and had heard about the teacher's day.
Miklos Porkolab attended the
VLT-PAC meeting in San Diego, on Feb 22,23.
He also gave a talk at the
US-Japan Workshop on Plasma Control and Sustainment
Using RF Waves. The
title of the talk was "Progress in ICRF Experiments on
Alcator C-Mod
and Future Plans". This workshop was held at General Atomics
on Feb.
22,23 also. Subsequently, Miklos attended the FESAC meeting in
Gaithersburg,
MD, on Feb 27,28, and participated in the March 1st Fusion
Congressional
Outreach Day activities.
Earl Marmar went to a JET collaboration
discussion at OFES in Germantown
on Feb 26.