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
April 12, 2002


Reassembly of Alcator C-Mod proceeded this week with installation of the
retaining cylinder and dome. Work continues on Lower Hybrid, ICRF, and
RFX DNB systems. We continue to refurbish and test power system components
for the next run period.


Physics
_______

Robert Granetz presented further analysis on the possibility of obtaining
information about the internal q-profile from the elongation of x-ray
emissivity contours. Tomographic reconstructions were done throughout the
evolution of large sawteeth in highly-peaked ITB discharges. The
elongation of emission contours located near the sawtooth inversion radius
consistently showed a gradual decrease during the sawtooth ramps, implying
a slow decrease in q by 0.01-0.03, which is quite plausible. However, the
x-ray contours very close to the magnetic axis did not behave as expected.
Analysis is continuing.


Operations
----------

Installation of the remaining springplates was completed early this week.
Following successful hi-pot and resistance checks on the TF magnet, and
a complete checkout of thermocouples, heaters, and diagnostic instrumentation,
we installed the retaining cylinder. Pictures of this operation can be
found at

http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/Machine_assembly_A/DCP_0436.JPG

and

http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/Machine_assembly_A/DCP_0441.JPG

On Friday we installed the retaining dome, approximately 65,000 lbs of
stainless steel. A picture of the machine during this last major machine
component installation can be found at

http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/Machine_assembly_A/DCP_0454.JPG

Installation of cooling lines and horizontal ports has begun.

Preparations for operations continued on the alternator this week with
work on the water cooling systems, while the inspection of all magnet bus
work was begun in the power room. Some bus work joints near the transitions
from aluminum to copper bus are being re-plated.


Lower Hybrid MIE Project
------------------------

At PPPL, Lower Hybrid launcher drawing packages are being assembled for rear
waveguide components to be procured. An RFQ will go out in within two
months. The remainder of antenna detailing and RFQ packages will be
sent in August. We are awaiting samples of the ceramic window billet
to re-measure and verify its electrical properties prior to final
window machining. The following LH launcher hardware items have been
delivered to PPPL: couplers, coupler flanges, vacuum shroud,
interface flange, and flange heaters. The remaining "Phase 1
Components" have received RFQ responses, and purchase orders have
been awarded.

At MIT, Wiring of transmitter #3 is now very close to complete. The following
power-up tests of transmitter #3 were performed this week. A closed-loop
communication between the operator interface computer, the HVPS, and the
transmitter #3 PLC was established. This closed loop communication
allowed for remote control of the HVPS. An enabling of the HV,
which includes raising the HV relays on cart #3, raising the HV relay in the
HV junction box, and enabling the HVPS was performed. Now that the flow
meters and other water-related instrumentation are operating on transmitter
#3, testing of the PLC ladder-logic software was able to proceed. Many of
the scaling and fault logic routines were updated and pre-tested. Design and
layout of the TPS optical interface board #2 was completed this week.
The PCB layout was sent out for bids. The requisition for these boards will
be placed soon. Parts to populate this board have been ordered.

Commissioning of the LH HVPS was stopped late in the week by the vendor when
timing problems appeared in the new controller software. Commissioning
is expected to resume again in two to three weeks.


ICRF Systems
------------

The current straps for the ICRF antenna have been re-plated with copper
and are currently being baked. The Faraday screens are being prepared
for baking early next week. New boron nitride tiles for the antennas will
also be ready for an extended high temperature bake early next week.

Work continues on the new diagnostic, fault, and control system electronics.
Printed circuit boards are being populated, new racks fabricated, and
power supplies installed.


RFX DNB
-------

To verify proper operation of the DNB controls, we operated the beam
remotely this week. With the exception of the initial power
supply turn-on, the beam was operated from outside the cell, and the
data describing the beam pulse was also displayed at the remote site.
The beam was operated from Austin in these tests, though during
C-Mod operation the beam will be operated from the C-Mod
control room.

The assembly of F-port was completed this week. The final assembly
consisted of installing the cleaned and baked components of the ECE
High Resolution mirror, as well as installation of various periscopes
that are attached on the radial port. It is ready for installation
at the first opportunity.


Diagnostics
-----------

The new low Verdet constant glass (SFL6) windows for the MSE
diagnostic were received by PPPL from Schott and were forwarded to MIT
for installation on C-Mod. These components are now at MIT and the
window port design is being finalized.

Work continued on the CXRS edge system, MHD antenna components and
power supplies and amplifiers, and new periscopes. Horizontal ports
and the components associated with them are being prepared for installation.


Travel and Visits
-----------------

David Mikkelsen, PPPL, gave an invited talk on his transport simulations of
C-Mod plasmas at the IAEA Technical Meeting on Theory of Plasma
Instabilities at Kloster Seeon, April 10-12.

Stefano Bernabei and Remi Dumont, PPPL, were at C-Mod on 4/10 for discussions
on the future Lower Hybrid experiments on C-Mod and the associated
modeling effort. They communicated with Paul Bonoli, Amanda Hubbard,
John Liptac, Ron Parker, Miklos Porkolab, and John Wright.