Alcator C-Mod Weekly Highlights
				June 16, 1997

Last week was a maintenance week at Alcator C-Mod. The major activity during
this period was removal of the 40MHz transmission lines and re-installation of
the 80 MHz ICRF system, which will be used for the majority of the physics
runs in the current experimental campaign. 

The ICRF dipole antennas at D- and E-port have been re-plumbed for 80 MHz
operation, and the Uptegraff DC power supply which had been moved to connect to
the 40MHz transmitter #4 has now been switched back to the 80MHz
transmitter #2. Transmitter #1 was tuned and tested into the dummy load (2.2
MW for 0.3 sec). Transmitter #2 was also tested into the dummy load (2MW for
0.1 sec). 

Additional work carried out during the maintenance period included checkout of
the boronization system, including all interlocks, after which the diborane
bottle was installed in the cell. The tangential two-color interferometer
(TTCI), which will provide density information based on a midplane view, was
installed. The final components of the new pre-ionization system were
installed. Electronics and cabling for two out of four of the OH position
sensors were installed.  The LN2 pump used to circulate coolant from the sump
was replaced; this pump had been showing indications of worn bearings during
runs the previous week.

The core and x-point Thomson scattering systems were re-aligned. A new ECE
calibration was completed. The cryopump prototype, which had difficulty
cooling down due to a transfer line problem the previous week, was made
operational. The lithium pellet injector (LPI) system was installed and is
nearly ready for operation. The LPI was relocated from K to C port, in
anticipation of the installation of the new ICRF antenna next year.


The machine was baked at 60 to 80 C and ECDC run for several days during the
week. The H/D ratio, as monitored on residual gas analyzer, was observed to
be decreasing.

Ken Takase began working with Paul Bonoli on incorporating a current drive
package into Marco Brambilla's TORIC code.

Development of the crowbar to protect the DNB beamline during arcs continued.
The crowbar will be based on an existing sparkgap and its associated trigger
hardware.  This system was successfully tested, and modifications for the new
installation were devised.  The remaining acceptance tests of the spark gap
and the trigger assembly will be carried out to the anticipated maximum
operating voltage of the DNB modulator regulator in the coming week.  The
fabrication drawings for the high voltage transmission line are in progress
based on the conceptual design mentioned in a previous report.  The PLC
interface circuitry design continued.  Custom replacement vacuum feedthroughs
for the vacuum system were received so that reassembly of the vacuum system
can continue.  Installation of the utilities for the DNB test lab (water,
electricity, air and hydrogen vent) are now complete.

Don Patterson of UT-FRC was on-site to set-up additional data acquistion
software and to assist MIT personnel in the installation of the UT alpha
workstation.

Chris Watts of Auburn was on-site to assist with the UT-FRC ECE heterodyne
system that is being operated in a collaboration between Auburn, UT, and
MIT. The heterodyne ECE system has been expanded to include 6 more channels
(in addition to the original 8).  The new channels are set up as "fast"
channels and are 3 coupled channels that can be digitized up to 2 MHz.  The
frequencies of the coupled channels are 117.8 & 118.0 GHz, 123.2 &123.4 GHz,
and 125.8 &126.0 GHz.  At 5.3 T, these frequency pairs correspond to r/a=
0.77, 0.62, and 0.53,respectively.  The original 8 channels are now set up as
"slow" channels digitized @ 50 kHz to cover the entire plasma pulse from 113
GHz to 128 GHz (4.0 T to 4.5 T, for a 5.3 T discharge the channels correspond
to r/a range of 0.94,0.92,0.90.0.87,0.83,0.70,0.59,0.50).  All channels should
be working by the end of the week.  Presently only the "slow" channels are
connected.

A new diagnostic, the omegatron ion mass spectrometer, recorded its
first ion spectrum during operation the week of June 2. The omegatron
combines a gridded energy analyzer with an ion mass spectrometer.  The
ion mass spectrometer exploits the local magnetic field (approximately
the toroidal field on axis); RF potentials applied to a cavity
separate ions with resonant cyclotron frequency.

Yuichi Takase, Miklos Porkolab, Ian Hutchinson, Spencer Pitcher, Joe Snipes,
and Jim Terry participated in the 24th EPS Conference on Cont.
Fusion and Plasma Physics in Berchtesgaden, Germany.

Physics operations are scheduled to resume this week.