Alcator C-Mod Weekly Highlights
			Feb. 16, 2004

Research operations resumed at Alcator C-Mod last week. Five run days were
scheduled and completed. Experiments were carried out in support of the
research in the MHD, Edge, Transport, and RF Physics areas. The FMIT#3 and 4
ICRF transmitters were successfully returned to service. Progress also
continued on the Lower Hybrid project.

Plasma operations are scheduled to continue this week.

Operations
-----------

C-Mod was operated for five days last week. A total of 123 plasma discharges
were produced with a startup reliability of over 85%. A fresh boronization was
carried out on Wednesday evening.

Monday's run was in support of MP#359, to investigate the damping of Alfven
Eigenmodes as a function of elongation using the C-Mod Active MHD Spectroscopy
antennas and the newly installed Active MHD Amplifier system. This
miniproposal is part of a collaboration with Ambrogio Fasoli of CRPP
(Lausanne).  Resonance data were obtained over the range 1.2<kappa<1.7, and
analysis is ongoing.

Tuesday's run, MP#387, investigated scaling of the locked mode threshold in
C-Mod lower single null discharges as a function of safety factor in the range
2.8< q_95 < 4.2. Data were obtained at constant current by varying B and at
constant B by varying the plasma current. The density at which locking occurs
was found to be at most a weak function of q in each dataset. More detailed
analysis is in progress.

On Wednesday and Thursday a series of experiments (MP#388) investigating the
impact of early fueling and impurity puffing on plasma performance in pre- and
post-boronization discharges was carried out. The impetus for this experiment
was the observation of a historical trend which seemed to point to a
correlation between a higher level of early fueling, during the first 100msec
of the discharge, before the plasma is diverted, and subsequent plasma
cleanliness and performance. Operation in recent years has typcally featured a
reduced early fueling level. In these controlled experiments no significant
correlation between the early gas puff and subsequent confinement could be
confirmed. Nevertheless, the post-boronization run on Thursday resulted in
some of the highest H-mode performance levels yet obtained on C-Mod, with
stored energies above 225kJ and H-factors of 1.7-2.3 in H-mode plasmas.

The run on Friday (MP#384) continued our investigations of the relationship
between edge and core rotation and the L-H transition threshold. Upper and
lower null discharges were run at a relatively low density of ~1e20/m^3, for
which the intrinsic core rotation speeds are similar, and the difference in
threshold was documented. In addition, the effect of strong inboard and
outboard gas puffs, and of enhanced recycling from the inboard divertor plate,
on the rotation speed and on thresholds was investigated.

ICRF System
-----------

FMIT#3 and #4 were returned to service and operated with up to 3 MW into
plasmas through the 4-strap J-port antenna.  The ferrite repair in FMIT#3 has
improved the overall screen current and further analysis indicates that the
reflected power has a significant impact on screen current (plate impedance
rises resulting in higher screen currents) for this transmitter.  The behavior
of FMIT#4 appears to a bit more robust.  We plan to investigate this
difference in the coming weeks.


Lower Hybrid System
-------------------

Each of the three windows of a copper-plated three window prototype have been
tested to 72 kW with half-second long pulses.  This power level is
approximately three times that expected at the coupler windows during
operation on C-Mod.  In addition, network analyzer measurements of the
prototype windows indicated very low reflection coefficients of -26db.

The Forward Wave Guide assembly is now complete and ready to be
installed onto the C-Mod vacuum test stand.  The port extension rails
and bushings are installed and have been adjusted to provide the
proper fit.  The port extension slides along the FWG assembly as
designed without resistance.  The radial motion mechanism has been
tested (in air) and is also working properly. Installation of the
fwg on the vacuum test stand will begin this week.

An additional 86 ceramic brick windows have been received from PPPL.
Brazing tests continued on sample windows with Ni strike, and 0.2 and 0.5 mil
Cu plating. Braze flowed best on the 0.5 mil Cu sample, least well on the Ni
strike.

One klystron developed high body current during high power testing, and will
probably need to be sent out for refurbishment.

DNB Systems
------------

The CXRS System acquired Ti data on several days of operation.  This was done
remotely by W. Rowan, UT-FRC, who was in Hefei, China at the time.  Remote
operation included adjusting the control of the detector via remote access to
the local Windows machine, monitoring and doing limited analysis of data as it
was taken, and interacting with other group members to select a firing time
for the beam.  Operation of the CXRS shutters was accomplished by onsite
personnel.

Meeting Submissions
--------------------

Eleven abstracts concerning C-Mod research were accepted for  presentation at 
the 16th
International Conference on Plasma Surface Interactions in Controlled Fusion
Devices, Portland ME, May 24-28, 2004.

Eight abstracts and extended synopses dealing with C-Mod research work have
been submitted to the U.S. Selection Committee for the IAEA Fusion Energy
Conference 2004 (FEC2004) to be held at Vilamoura, Portugal on November 1-6,
2004.


Travel and Visitors
--------------------

Alan Lynn (U. Texas) traveled to MIT to install the repaired ECE radiometer
receiver. The installation was completed over the weekend and all channels are
now working.

Ron Bravenec (U. Texas) was on site to help with acquisition of CXRS data
(communicating with Bill Rowan who was in China), run the DNB one afternoon,
and repair the restraint of the BES fiber corrlok.  He also talked with Darin
Ernst about his code GS2_PREP that generates GS2 input files from C-Mod TRANSP
runs.  Ron is learning to use it to generate GYRO input files for simulations
of C-Mod discharges.

Joe Frangipani, Larry Guttadora and Dave Miller (PPPL) were at MIT from 2/9 to
2/12, and Doug Loesser (PPPL), was at MIT 2/11 and 2/12, working on the lower
hybrid system.

Ron Parker, Bruce Lipschultz and Amanda Hubbard were at GA for the DIII-D PAC
meeting last week.  Ron chairs the committee, and Bruce and Amanda are also
members of the PAC. Bruce Lipschultz also spent time working on a proposed
experiment with Tony Leonard (GA).