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 9, 2001


We continued to maintain transmitters and power systems, develop Lower Hybrid
systems, and fabricate new J-port antenna components. Work is proceeding
on improvements to the ICRF control system. A design review was
held on a new CXRS shutter.


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

Inconel stripline components for the J-Port antenna modification are being
produced both in our shop and by two EDM vendors. We expect to have all
components complete and ready for plating within the next two weeks.
Modifications to the Faraday shield are complete, and the shield has been
assembled successfully on the test stand. Work on the new dB/dt RF probes
for the antenna also proceeded this week. Four of the six probes are
ready for calibration. Fabrication of the remaining two that will be
mounted on the antenna septum is nearly complete.

A change to the IPA drive point location and installation of a
matching transformer greatly reduced the drive power required for
this stage of the transmitter. Saturation of the IPA stage limited
transmitter performance somewhat during the last run period. Similar
improvements will be made as needed to the other transmitters.

We have modified the new demodulator board layout per manufacturer
recommendations and are awaiting new quotations for these boards.
The RF components and modules used in our fault detection system are being
carefully tested and parameterized. These systems currently require very
time consuming recalibrations for each frequency change. We are investigating
both programmable modules to make automatic gain adjustments, and changes
to the electronics and cabling to increase bandwidth so that manual
recalibration is not required.

A PCI based data acquisition system has been setup. This system will provide
very fast data logging of forward and reflected power and other fault
indication signals. Testing has begun to verify that all channels are
working. Work has started on the auto-tune system which links CAMAC analog
outputs with PLC inputs. Software is in progress and the associated patch
panel installation and wiring has started.


DNB
---

A design review was held for shutters to be installed invessel to protect
CXRS optics. It was strongly suggested by the DNB Review Committee that this
work be done during the current up to air. The basic design was approved.
A number of suggestions for improvement were made during the review and
are being implemented.


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

We finalized the design of the anti-alias filters for the D-Traq digitizers
to be used as part of the lower hybrid data acquisition system.
The SFOL transmitter was completed, and we have begun testing the SFOL receiver.
The SFOL link must be operational soon so that closed loop tests of the
active feedback system can begin. Programming of the active feedback loop
is proceeding. As we approach a control program with realistic input, output,
and processing modules, an assessment of the ultimate control system speed
will be made. A network problem with the PXI chassis was resolved this
week.

Data characterizing operation of the vector modulator and I/Q detector
operation has been taken. Both the vector modulator and the I/Q detector
are performing as expected. The network analyzer will be used to make more
accurate measurements for comparison with our test program results.

Representatives from C-Mod, MIT, and SMMA (the contractor hired by
MIT), met this week to discuss the electrical work that will be needed
during lower hybrid site modifications. The proper breakers to use,
cabling required, and cable runs have been agreed upon.

Electro-Mechanical design of the transmitter equipment rack is nearing
completion. We have been notified by the vendor that the contract for the
klystron circulators is in place. Work is proceeding on klystron cart
modifications and wiring, and work has also begun on modifications to the
equipment racks. We have ordered the EMI/RFI protected cabinets for
the transmitter racks.


Power Systems
-------------

The work on the EF1 commutation switch capacitor bank continues. The
machining of the extrand supports is in progress.

Preventative maintenance of power supply control boards continued.


Inner Divertor
--------------

Over 150 upper transition tiles were received from our vendor this week.
A successful test fit of these new tiles into our rear and c-plate mockups
was done shortly after their arrival. Dimensions of ten tiles will be
computer checked as part of the QA process developed for the tiles.
The vendors supplying the rear and c girdle plates are still on
schedule. A picture of one of the rear backing plates can be seen at:

http://www.psfc.mit.edu/cmod/operations/EngImages/MACHINE/Divertor/Rear_girdle_02.jpg

Note that none of the ribs that will lock the tiles into position have been
machined into the plate as yet.


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

Phil Ryan visited from Oak Ridge this week to look at J-port antenna
components and get drawings and measurements needed to model the
antenna.