Alcator C-Mod Weekly HIghlights
				July 21, 1997

The maintenance period on Alcator C-Mod continued last weeks. No runs were
scheduled. Next week will also be a maintenance week. 

A quick up-to-helium vent was carried out on Thursday to remove several
internal components for repair and upgrading.  Diagnostic systems involved
include the fast scanning probe with gas injection capability, the Omegatron
probe, and the 2 pi bolometer.  The opening was completed in a few hours and
the machine pumped back down. A second vent will be performed later for
re-installation. 

Maintenance work on the RF system is progressing.  Calibration and testing of
the PPPL demodulators is about 50% complete.  Power has been connected to the
RF racks in the power room.  Work has begun to repair a leak on the E-port
resonant loop (external to the tokamak) and complete the control system for
transmitters #3 and #4.

Intensive efforts have been devoted to implementing the repair of the
alternator rotor. Estimates from competent contractors indicate about a
ten week schedule. Assuming a prompt start can be made, it ought therefore
to be possible to restart operation in October.

Preparation of the DNB power supplies continued with power and control
wiring.  Remaining aspects of the low capacitance transmission line design,
fabrication, and installation await the results of the consultation on
truss loading.  A contact with the consultant resulted in additional
information being supplied by PSFC staff.  Development of the PLC
programming for the DNB continued principally with operator interface and
variac control programming so that this part of the system should soon be
ready for test with the hardware.

Those responsible for DNB diagnostics met on Monday, July 14, to discuss
capabilities and requirements of proposed diagnostics and to get ideas and
criticism from members of the C-Mod staff.  Details of the CXRS diagnostic
were presented by Bill Rowan (UT-FRC); BES, by Ron Bravenec (UT-FRC); MSE
by Norton Bretz (PPPL); Poloidal Rotation by Ron Bell (PPPL).

UT-FRC continued to cycle staff and students in and out of Cambridge.  David
Storek, a UT staff member, completed installation of the BES spectrometer.
Matt Sampsell, a UT-FRC graduate student, arrived to begin the on-site
electronics and CAMAC tests of the BES system.  These will be conducted with
the assistance of UT staff located in Austin.  Xavier Bonnin, a UT-FRC
graduate student, ended his month-long visit and returned to Austin where he
will complete a B2-Eirene simulations of the C-Mod SOL.  Ashley Shugart, a
UT-FRC graduate student, continued to assist PSFC staff in the installation of
the PCI diagnostic system.

Wayne Houlberg visited from ORNL for 3 days to begin adapting his neoclassical
code "FORCEBAL" to analyze C-Mod data.  This code uses the latest formulations
of the neo-classical theory, including off-diagonal terms and orbit squeezing
effects.  We will be using the code to calculate the electric field from
radial force balance and to compare measured impurity fluxes with those
calculated from neoclassical theory.

Two collaborators from Japan have arrived at C-Mod.  Dr. K Kondo, from the
University of Kyoto and Dr. Y. Yamauchi from the Hokkiado University are
visiting for two and four weeks respectively.  Dr. Kondo will be working on
molybdenum spectroscopy, while Dr. Yamauchi will be working on surface physics.

Peter Beiersdorfer from LLNL visited to discuss C-Mod and EBIT observations
of the forbidden line and inner shell satellites from helium-like nitrogen.

Qian Peng of General Atomics visited on Friday for discussions relating to the
MDSplus data acquisition system, and the interfacing of the EFIT code to
MDSplus, as implemented at C-Mod. 

King-lap Wong of PPPL spent several days at C-Mod last week, examining the
data from the high frequency MHD activity observed on reversed-shear startup
experiments (see last week's report). His preliminary analysis indicates the
"streak" feature, whose frequency chirps from about 200kHz to about 400kHz in
less than 20msec, is consistent with a core-localized TAE mode, with the
rapidly evolving frequency corresponding to a rapid change in central q near
the end of the reversed shear phase. The frequency values would seem to
indicate a higher q0 at the time of the observation than previously
estimated. Further analysis is underway. 

Dr. K.C. Shaing, from IFS, University of Texas, visited on July 17 and 18 and
gave a seminar on bootstrap current driven tokamaks.  Dr. Shaing showed that
when the neo-classical theory is done correctly it indicates that a current
will be driven on axis, which eliminates the need for a seed current. Dr.
Shaing's predictions for the C-mod parameter range indicate a possibility of
testing this theory on C-mod.