Alcator C-Mod Weekly Highlights
			November 29, 1999



The maintenance period continued on Alcator C-Mod last week with the
completion of the first neutron calibration, edge Thomson scattering
alignment checks, power system maintenance, and work on the RF and DNB
systems.


Engineering:

Good progress was made on the DNB last week in spite of the holiday.
Anode and cathode HV dividers in the MOD/REG cabinet were compensated.
These 120 kV dividers have been borrowed from PPPL until our units are
in house. MOD/REG anode current signals and crowbar test circuits were
tested and calibrated.  Low end electronics (analog board) calibration and
testing were started.  PLC control of the HV supply was established, first
with no 480VAC and then with main power applied.  Kirk Key system interlocks
for the HV supply and MOD/REG were tested and are now in operation and
required for operation.  The MOD/REG cabinet door interlocks were tested and
a modification was required to prevent the switch covers from bypassing the
door switches.  The PLC functions related to door switches and dump switches
were tested.  Some wiring mistakes had to be corrected.  A test PLC program
to allow timing pulses for HV supply, MOD/REG, and crowbar command
was tested and used to pulse the HV supply into a dummy load located
inside the MOD/REG cabinet.  The MOD/REG tube cage circuits were not in place
for this test.  The cathode and anode voltage monitoring circuits and crowbar
circuits were in the test circuit as were the anode current monitoring
circuits.  The supply was successfully operated at up to 30 kV at several
amps.  Some of the protection circuits for the MOD/REG low end electronics
and high voltage supply were also tested.  Work in the cell on the HV cage
and access doors continued.  HV cables have been pulled onto the platform and
terminated at the cell wall.

We also continued work on the RF systems last week.  Screen crowbar units were
bench tested to verify current trip level and transformer saturation.
The trip level required decreasing the turn ratio from ~300:1 to 300:3 and
was verified to be 18-25 A.  The transformer did not saturate up to the trip
level, which is sufficient for our purposes. The crowbar units will be
reinstalled and tested in-situ this week.

Preliminary analysis of J-port antenna performance suggested that we need to 
eliminate the strong correlation of impurity influx with RF power. Large
injections associated with Prf > 1.3 MW total or 0.6 MW/strap pairs,  and
arcing at high (>1.0 x 10^20 m^-2) target line density was observed during the
last run campaign.  Our current suspects are the top/bottom protection tiles
and poor contact between back plane elements for the impurity source.  The
arcing is suspected at the center ground of the antenna at high target
densities.  Invessel inspection will be possible this week.  Boron
nitride is being considered as a possible tile replacement material, at least
for the j-port antenna.  Vacuum outgassing tests of this material have
already been conducted to qualify it for C-Mod.  Mechanical and thermal tests
are planned for this week.

General maintenance of the C-Mod power systems has also begun.  All the
power supply cabinets, inside and out, are being cleaned and inspected.
Ross relay contacts in various systems including the commutation charging
supply and bus instrumentation system are being cleaned and tested.
Similar activities are also ongoing in the alternator.

The bus tunnel, LN2 manifold box, and LN2 sump are all being readied for
inspections, filter replacements, and pressure checks.


Physics:

The Alcator C-Mod Ideas Forum will be held Dec. 7-8, 1999, at the MIT Plasma 
Science & Fusion Center. The purpose of the forum is to obtain input from a
wide range of interested parties regarding possible experiments to be carried
out  on C-Mod during the 2000 operating campaign. Information can be obtained
on the Web at  http://www.psfc.mit.edu/cmod/forum2000/forum2000.html