Alcator C-Mod Run 990915 Information

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Miniproposals
Miniproposal:239
Date Filed: 3/9/1999
Title:Determination of Critical Exponents for L to H Transitions and
First Author:Amanda Hubbard
Session Leader:Amanda Hubbard (shots 1-27)

Operators
Session leader(s):Amanda Hubbard
Physics operator(s):Robert Granetz
Engineering operator(s):Gary Dekow,Frank Silva

Engineering Operator Run Comment
MP#239/Granetz, Silva

Session Leader Plans

Physics Operators Plans

Session Leader Summaries
Entered: Jul 7 2004 03:49:21:100PM
Author: To Be Determined
Summary:

Post boronization conditioning of D and E-port antennas went well.
EDA H-modes were readily obtained with moderate power. We identified
a limitation with the screen current, but found that detuning the
antenna match improved the screen voltage without too much reflected
power. (see below) A maximum power of 2.5 MW was obtained.

FMIT#1 and #2 Screen current problem

The major limitation today was the screen current. We found that the
screen current overloaded more readily at better matches than shots
with the antenna detuned capacitively. For FMIT#1, shots 016 and 018
show that detuning (10% reflected power) reduces the screen current
from 4 A to < 2 A. With FMIT#2, we were less successful, but the
screen current from shot 016 to 021 reduced from 2 A to 1 A. The root
of the problem is the dummy load impedance. It was measured earlier
and it was 50 ohms with about 8 omhs capacitive. This imaginary
component results in low screen currents for impedances other than 50
ohm real - this is what the tuning program suggested solutions are
optimized for.

In investigating the optimum screen voltage, the gain of the FPA
increases with screen voltage approaching -1500 V ( the supply is
limited to 1700 V). From the tube curves, the screen current is
changes little with more negative (-1500 V) screen current. As
mentioned earlier, the high frequency oscillations we observe decrease
with increasing screen voltage. By raising the screen voltage we
increase the gain and decrease the unwanted oscillations. Providing a
screen regulator should keep the voltage high without increasing the
screen current beyond the limit. We need to install a voltage
regulator - should improve the oscillation problem by keeping the
screen voltage steady. In fact, when the voltage is steady -1.4 kV,
the oscillation monitor measured < 50 mV!

We are also going to insert a stub in the dummy load circuit to allow
for some fine tuning of the dummy load impedance. This should allow
us to tune the antenna to a good match and have the screen current
remain within limits. Presently, we are allowing about a 10% mismatch
on #1 and the screen current is a managable 1-2 A. For FMIT#2, a 5%
mismatch drops the screen current to 2 A. This mistune cost in higher
VSWR in the "matched" line section and the tube efficiency is lower.

Screen current limit:

The dissipated power limit for a 2274 is 20 kW. If the screen voltage
is 1.5 kV, the screen current limit ought to be 13.3 A. Our present
limit is 8 A, so we should reset our overload threshold to at least
12.5 A (leaving some head room).

Entered: Jul 7 2004 03:49:21:117PM
Author: To Be Determined
Run Plan 990915
Session Leader: Amanda Hubbard
Phys. Op: Bob Granetz
Eng. Ops: Frank and Gary
RF experts: Steve Wukitch and Rejean Boivin

This run is in support of MP 239, Hubbard Carreras et al, on
"Critical Exponents for L-H transitions and Pedestal Widths"
The basic idea is to test some ideas on the input power dependence of
the edge pedestal parameters; particularly the Te pedestal in the MP, but
also density pedestals.

The main technique for doing the will be power ramps, of various levels and
durations, to measure the response of pedestal params as a function of P-Rrad.
There will also be shots with
constant power (or long steps) and Bt ramps to measure the Pe pedestal width
in more detail. The nominal conditions are 5.4 T, 800 kA and nel~9e19 m-2.

Given the limited RF power available today, we will be able to explore only
the regime close to the threshold (P/Pthresh < 2). This corresponds to part
(a) of the MPs. The regime P >> Pthress will await another day. On the other
hand, since this will require fewer ramp shots, we may have more time
available for the second part of the MP; varying the density/gas puffing rate.
Now that ionization rate and ne pedestal diagnostics are working well, it seems
interesting to test the part of the Carreras/Diamond model which predicts a
dependence of pedestal widths (esp ne) on the ionization rate. This will
involve power ramps at both higher and lower ne.

Run Summary:

We actually accomplished much of what we set out to today. The machine ran
very well, as did the RF systems. Half of the run was power ramps and scans
at the nominal 800 kA, 9e19 m-2 EDA condition (Shots 1-15). Most had an
initial power rampup, with varying ramp rates. From shot 6, we ended the
ramp with a steady period and did a Bt sweep to get the ne pedestal. Good
shots were:
6 - 2.4 MW
7 - 2.7 MW
8 - 2.0 MW
9 - 1.6 MW
10 - 1.15 MW
11 - 0.98 MW
12 - 0.86 MW (Right at Pthresh)
Steady EDA with constant Prad was obtained even at the lowest H-mode power.

On shots 13 and 14 we ramped the power DOWN. Strong hysteresis was found; EDA
H-modes were maintained down to ~ 150 kW. They went dithery at ~ 600 kW (#13).
On shot 14 we got a good Te sweep at 700 kW (ie P < Pthresh)
Temperature pedestals got very small at the low powers (~ 200 eV vs ~ 400 with
high power). The widths increased at high power, but the dependence was less
clear at low P. Bremstrahlung widths may have been responding to P too; this
needs to be checked.
Shot 15 was used for RF steps so that Pabs can be calculated.

Shots 16 to 24 had higher density and power ramps. The highest ne was shot 19,
which stayed in L-mode at 1.9 MW. Shots 18-24 had nel=1.5e20 (L-H) and
1.8-2.0e20 in EDA. 23 was a power rampdown shot, again showing big hysteresis.
Te pedestals were measured at 2.0 and 1.0 MW. They were rather cold, and the
width was not notably different than at lower ne. The bremsstrahlung widths
did seem wider, up to 3 cm(?).

Shots 25 to 27 had progressively lower starting ne, and power ramps. 26 and 27
started as ELM-free, and then went to EDA at higher power (nice comparison
shots of the two modes, fluctuations widths etc.) The low and high ne
transitions should provide interesting data on neutral effects etc, once
Rejean's Lyman alpha data are analysed.

Many thanks to the operators, esp the much maligned RF group for supplying
constantly changing power waveforms to request all day. We should have some
interesting data for our theory collaborators to chew on!


Physics Operator Summaries
Entered: Jul 7 2004 04:37:09:287PM
Author: To Be Determined
Physics operator summary for run 990915:

MP 239 -- Determination of Critical Exponents for L-to-H Transitions and
Pedestal Widths

SL: A. Hubbard
PO: R. Granetz

The goal for today:

Determine exponent of Te dependence on power flux around the L-H and
H-L transitions (critical transition, critical exponent). Determine
whether this exponent is independent of density.

Summary: Everything worked incredibly well today, including the D and E ICRF
systems. We had excellent quality RF power ramps (both upward-going
and downward-going) through the L-H and H-L transitions, as well as
good 2-2.5 MW flattops, producing long steady EDA H-modes. Btor jogs
allowed for several good Te pedestal profile measurements. Te
measurements during the transitions were done at three different
densities. See the session leader's report for information on the
critical exponent physics. All shots had plasma, with all but one
going the full length (up to 1.97 s)!.

Note: from shot 12 on, the fizzle detector was moved to t=1.9 s (from
2.2 s).

Scorecard: 27 plasmas
0 fizzles
0 dud (0 due to lack of one or more power supplies)
0 tests
0 aborted
----------
27 total

------------------------------------------------------------------------------

Engineering Setup for Wednesday, 990915:

Run will begin at 09:00.
Setup power supplies from shot 990914021 (1 MA, 5.4 T, flattop to 1.5 s)

Two hours of ECDC in D2 prior to the run.

Gas setup - fill B-top with 6 psi of D2 Hybrid enabled
fill B-side lower with 1 psi of Ar Hybrid enabled
fill B-side upper with 6 psi of H2 Hybrid DISABLED
fill C-side with 30 psi of D2 Hybrid enabled
leave J-bottom as is Hybrid DISABLED

The following gate valves should be enabled, assuming no vacuum problems:
ECE, VUV

-------------------------------------------------------------------------------

Run Plan for Wednesday, 990915:

MP 239 -- Determination of Critical Exponents for L-to-H Transitions and
Pedestal Widths

Session leader: A. Hubbard
Physics operator: R. Granetz

Load shot 990914021, and make the following changes for the first shot:
1) Remove the small Bt ramp at t=1 s,
2) Lower the plasma current to 0.8 MA, and
3) Reduce the density to nl=0.9e20 m-2.

Most of the run involves ramping the RF power with various timings and
power levels. Later in the run we will probably put the Bt ramp back in
in order to get edge Te profiles.

-------------------------------------------------------------------------------

Note: There were two hours of ECDC in D2 prior to this run.

Hybrid coldstart done; no errors found
($set default cmod$models:[hybrid.tcl]
$@hybinit_dispatch
$@show_bitbus_log
Use editor search to verify no occurrences of "error" nor
"not respond")

Load 990914021 and make the changes specified above.

Shot 01 -- Plasma. Good shot. Ip=0.8 MA, nl_04=0.95e20 m-2 (target),
Bt=5.4 T. Prf=1.2-1.7 MW. Long EDA H-mode. Outer gap=10-12 mm.

Next shot: no PCS changes. RF will be ramped linearly through
the H-mode threshold.

Shot 02 -- Plasma. Good shot. Beautiful RF power ramp! There was a huge
brick at 0.1 s which nearly killed the plasma.

Next shot: no PCS changes. Same RF ramp. Flappers will be open
for the next shot.

Shot 03 -- Plasma. Good shot. Another beautiful RF ramp! The time of the
L-H transition is delayed by 100 ms compared to the previous
shot (with closed bypass flaps), but the F-side pressure is lower
on this shot... conflicting results.

Next shot: no PCS changes. Ramp RF power faster, and to a higher
max value (2.5 MW?). Bypass flaps will be closed.

Shot 04 -- Plasma. Good shot. Gorgeous RF ramp at twice the previous ramp
rate, and to 2.2-2.3 MW max.

Next shot: insert a small Bt up/down ramp starting at t=1.05 s,
and ramp the RF up like the previous shot, but then hold it steady
starting at t=1.00 s. Flappers will be open on the next shot.

Shot 05 -- Plasma. Disrupted at 0.61 s due to an OH2L crowbar fault at 0.56 s.
I_halo_L=106 kA.

Next shot: try again, but flappers will be closed.

Shot 06 -- Plasma. Good shot. RF control is fantastic! Prf ramps up to 2.3 MW
at t=1.0 s and then holds steady until t=1.35. Got the Bt blip.

Next shot: ramp RF a little faster, in order to get 0.2 MW higher
power at t=1.0 s, and then hold steady.

Shot 07 -- Plasma. Good shot. Max Prf=2.6 MW. Excellent power ramp control.
H/D down to 2.7% (has been low all day). Thermal energy has been
drooping slightly during the RF flattops.

Next shot: extend fast ZCUR feedback by another 9 ms (from 1.86 to
1.95 s). RF will ramp at the same rate, but start flattopping at
t=0.9 s, at a lower value of 2.1 MW.

Shot 08 -- Plasma. Good shot. RF flattopped at 1.9-2.0 MW. Shot duration was
extended to 1.91 s. Some kind of impurity injection occurred at
t=1.34 s.

Next shot: tweak Ip late in the shot to extend rampdown slightly.
Move Bt bump earlier by 50 ms (will start at t=1.000 s.) RF will
keep the ramp timing the same, but decrease the ramp rate. This
will result in a lower flattop power of 1.6 MW.

Shot 09 -- Plasma. Good shot. RF flattops at 1.6 MW. Plasma lasted to
1.92+ s. H/D=3.1%. Good Bt blip for Te pedestal profiles.

Next shot: tweak Ip some more at end of rampdown. Decrease Prf
flattop value some more.

Shot 10 -- Plasma. Good shot. Prf flattop value = 1.15 MW. Still getting
a good steady EDA H-mode. Plasma only lasted 1 ms longer.

Next shot: increase Ip significantly at tail end of rampdown, and
extend fast ZCUR feedback to 2.00 s. Decrease Prf flattop value
some still more.

Shot 11 -- Plasma. Good shot. Prf flattops at 0.95 MW. Still getting a
long steady EDA H-mode. Discharge lasted to t=1.97+ s (a new
record).

Next shot: reduce flattop Prf to 0.9 MW. Move fizzle detector
from back from 2.2 to 1.9 s. Extend high frequency (5 kHz)
magnetics sampling to 2.0 s, and store 1K more samples.

Shot 12 -- Plasma. Good shot. Prf flattops at 0.85 MW. Got an EDA H-mode,
but something kicked it back to L-mode at t=1.24 s. (RF stayed
on.) The shot terminated at 1.95 s, which is a little earlier
than the previous one.

Next shot: ramp Prf up quickly to 2 MW, and then ramp it down
slowly. Remove Bt blip.

Shot 13 -- Plasma. Good shot. Prf ramps up quickly to 2 MW, and then ramps
down slowly to zero. The H-L back transition doesn't happen until
the RF power is down to 0.12 MW... a clear example of strong
hysteresis. Plasma lasted until t=1.96+ s.

Next shot: add Bt blip starting at 1.20 s. Prf will have similar
waveform, except it will flattop at t=1.15 s, at a power of 0.75 MW.
Extend CLEARIN feedback slightly to 2.0 s.

Shot 14 -- Plasma. Good shot. Excellent Prf waveform control. Plasma stays
in EDA H-mode for 50 ms after RF turns off.

Next shot: increase CLEARIN slightly towards end of shot (to try
and keep EF2U from turning off, as suggested by Steve Wolfe).
RF will be doing on/off waveform to measure absorption.

Shot 15 -- Plasma. Good shot. RF got the data it needed to determine
absorption. Steve Wukitch's quick estimate gives at least 50%.

Next shot: various miniscule tweaks to RXL, ZXL, RXU, ZXU, and
EF2xEF4, and their gains, late in the rampdown. Increase density
to nl_04=1.1e20 m-2. RF will reload the ramp from the beginning
of today's run (slow ramp up to 2 MW).

Shot 16 -- Plasma. Good shot. Target density was 1.05e20 m-2. Excellent
RF ramp. Good long steady EDA H-mode. Shot duration was unchanged.

Next shot: increase nl_04 to 1.25e20 m-2.

Shot 17 -- Plasma. Good shot. Target density was 1.2-1.25e20 m-2. There was
a big impurity injection at 1.27 s which causes the plasma to
revert to L-mode momentarily.

Next shot: increase density to nl_04=1.4e20 m-2. RF is adjusting
tuning as the density is stepped up.

Shot 18 -- Plasma. Good shot. Target density was 1.4e20 m-2. H-mode power
threshold was 1.4 MW.

Next shot: increase nl_04 to 1.5e20 m-2.

Shot 19 -- Plasma. Good shot. Target density was 1.45e20 m-2. No H-modes.

Next shot: decrease nl_04 back to 1.4e20 m-2 to recover the EDA
H-mode.

Shot 20 -- Plasma. Good shot. Target density was 1.4-1.45e20 m-2. E-port
antenna faulted at t=1.1 s. Got an EDA H-mode.

Next shot: repeat with no changes; re-tune RF.

Shot 21 -- Plasma. Good shot. Similar to previous shot, including the
antenna fault.

Next shot: repeat, no PCS changes; re-tune RF.

Shot 22 -- Plasma. Good shot. One RF antenna faulted early on.

Next shot: do an RF rampdown shot. Remove Bt blip.

Shot 23 -- Plasma. Good shot. RF had good rampdown. Extreme hysteresis
on H-L back transition.

Next shot: flattop RF at 1.8-2 MW. Turn on Bt blip starting at
t=0.90 s.

Shot 24 -- Plasma. Good shot. RF had a good flattop at 2 MW.

Next shot: lower the density to nl_04=0.7e20 m-2. Ramp the RF.

Shot 25 -- Plasma. Good shot. RF ramped up to nearly 2 MW. Density was
nl_04=0.85e20 m-2, which is somewhat higher than we wanted.

Next shot: reduce density programming to nl_04=0.6e20 m-2. Add in
Bt blip starting at t=1.15 s.

Shot 26 -- Plasma. Good shot. Density came down to nl_04=0.7e20 m-2. There
was actually a finite-duration ELM-free H-mode, followed by an EDA
H-mode. RF ramped up to 2.5 MW, but then one antenna faulted.
Edge and core x-ray emissivities were much higher on this shot than
on previous shots today.

Next shot: repeat, trying for no RF faults.

Shot 27 -- Plasma. Good shot. Again there was an ELMfree period followed by
a brief L period and then an EDA. RF didn't do as well as earlier
today. Probably didn't get a good Te pedestal profile.

End of run.

Session Leader Comments
Sep 15 1999 01:55:07:060PM990915016Amanda HubbardThis was the start if a density scan. RF has a slow rampup 0.5-2.0 MW, flat from 1.15 secs.

Bt sweep at 1.2 secs.

Ne only slightly higher, 1.05 e20 (L), 1.6e20 (H). Good RF, increase ne more next shot.
Sep 15 1999 02:49:36:263PM990915019Amanda HubbardL-mode, despite 1.9 MW RF. Looks like we are too high in ne.

Go back to 1.4e20, as on shot 18, and repeat with re-tuned RF.

Physics Operator Comments
Sep 14 1999 05:53:42:577PMRobert GranetzEngineering Setup for Wednesday, 990915:

Run will begin at 09:00.
Setup power supplies from shot 990914021 (1 MA, 5.4 T, flattop to 1.5 s)

Two hours of ECDC in D2 prior to the run.

Gas setup - fill B-top with 6 psi of D2 Hybrid enabled
fill B-side lower with 1 psi of Ar Hybrid enabled
fill B-side upper with 6 psi of H2 Hybrid DISABLED
fill C-side with 30 psi of D2 Hybrid enabled
leave J-bottom as is Hybrid DISABLED

The following gate valves should be enabled, assuming no vacuum problems:
ECE, VUV
Sep 14 1999 05:54:10:140PMRobert GranetzRun Plan for Wednesday, 990915:

MP 239 -- Determination of Critical Exponents for L-to-H Transitions and
Pedestal Widths

Session leader: A. Hubbard
Physics operator: R. Granetz

Load shot 990914021, and make the following changes for the first shot:
1) Remove the small Bt ramp at t=1 s,
2) Lower the plasma current to 0.8 MA, and
3) Reduce the density to nl=0.9e20 m-2.

Most of the run involves ramping the RF power with various timings and
power levels. Later in the run we will probably put the Bt ramp back in
in order to get edge Te profiles.
Sep 15 1999 08:50:40:107AMRobert Granetz Note: There were two hours of ECDC in D2 prior to this run.

Hybrid coldstart done; no errors found
($set default cmod$models:[hybrid.tcl]
$@hybinit_dispatch
$@show_bitbus_log
Use editor search to verify no occurrences of "error" nor
"not respond")

Load 990914021 and make the changes specified above.
Sep 15 1999 09:16:18:793AM990915001Robert GranetzShot 01 -- Plasma. Good shot. Ip=0.8 MA, nl_04=0.95e20 m-2 (target),
Bt=5.4 T. Prf=1.2-1.7 MW. Long EDA H-mode. Outer gap=10-12 mm.

Next shot: no PCS changes. RF will be ramped linearly through
the H-mode threshold.
Sep 15 1999 09:35:42:000AM990915002Robert GranetzShot 02 -- Plasma. Good shot. Beautiful RF power ramp! There was a huge
brick at 0.1 s which nearly killed the plasma.

Next shot: no PCS changes. Same RF ramp. Flappers will be open
for the next shot.
Sep 15 1999 10:00:37:090AM990915003Robert GranetzShot 03 -- Plasma. Good shot. Another beautiful RF ramp! The time of the
L-H transition is delayed by 100 ms compared to the previous
shot (with closed bypass flaps), but the F-side pressure is lower
on this shot... conflicting results.

Next shot: no PCS changes. Ramp RF power faster, and to a higher
max value (2.5 MW?). Bypass flaps will be closed.
Sep 15 1999 10:20:44:670AM990915004Robert GranetzShot 04 -- Plasma. Good shot. Gorgeous RF ramp at twice the previous ramp
rate, and to 2.2-2.3 MW max.

Next shot: insert a small Bt up/down ramp starting at t=1.05 s,
and ramp the RF up like the previous shot, but then hold it steady
starting at t=1.00 s. Flappers will be open on the next shot.
Sep 15 1999 10:39:33:750AM990915005Robert GranetzShot 05 -- Plasma. Disrupted at 0.61 s due to an OH2L crowbar fault at 0.56 s.
I_halo_L=106 kA.

Next shot: try again, but flappers will be closed.
Sep 15 1999 10:53:51:123AM990915006Robert GranetzShot 06 -- Plasma. Good shot. RF control is fantastic! Prf ramps up to 2.3 MW
at t=1.0 s and then holds steady until t=1.35. Got the Bt blip.

Next shot: ramp RF a little faster, in order to get 0.2 MW higher
power at t=1.0 s, and then hold steady.
Sep 15 1999 11:07:58:013AM990915007Robert GranetzShot 07 -- Plasma. Good shot. Max Prf=2.6 MW. Excellent power ramp control.
H/D down to 2.7% (has been low all day). Thermal energy has been
drooping slightly during the RF flattops.

Next shot: extend fast ZCUR feedback by another 9 ms (from 1.86 to
1.95 s). RF will ramp at the same rate, but start flattopping at
t=0.9 s, at a lower value of 2.1 MW.
Sep 15 1999 11:28:28:263AM990915008Robert GranetzShot 08 -- Plasma. Good shot. RF flattopped at 1.9-2.0 MW. Shot duration was
extended to 1.91 s. Some kind of impurity injection occurred at
t=1.34 s.

Next shot: tweak Ip late in the shot to extend rampdown slightly.
Move Bt bump earlier by 50 ms (will start at t=1.000 s.) RF will
keep the ramp timing the same, but decrease the ramp rate. This
will result in a lower flattop power of 1.6 MW.
Sep 15 1999 12:48:26:623PM990915009Robert GranetzShot 09 -- Plasma. Good shot. RF flattops at 1.6 MW. Plasma lasted to
1.92+ s. H/D=3.1%. Good Bt blip for Te pedestal profiles.

Next shot: tweak Ip some more at end of rampdown. Decrease Prf
flattop value some more.
Sep 15 1999 12:03:18:310PM990915010Robert GranetzShot 10 -- Plasma. Good shot. Prf flattop value = 1.15 MW. Still getting
a good steady EDA H-mode. Plasma only lasted 1 ms longer.

Next shot: increase Ip significantly at tail end of rampdown, and
extend fast ZCUR feedback to 2.00 s. Decrease Prf flattop value
some still more.
Sep 15 1999 12:27:47:687PM990915011Robert GranetzShot 11 -- Plasma. Good shot. Prf flattops at 0.95 MW. Still getting a
long steady EDA H-mode. Discharge lasted to t=1.97+ s (a new
record).

Next shot: reduce flattop Prf to 0.9 MW. Move fizzle detector
from back from 2.2 to 1.9 s. Extend high frequency (5 kHz)
magnetics sampling to 2.0 s, and store 1K more samples.
Sep 15 1999 12:41:52:140PM990915012Robert GranetzShot 12 -- Plasma. Good shot. Prf flattops at 0.85 MW. Got an EDA H-mode,
but something kicked it back to L-mode at t=1.24 s. (RF stayed
on.) The shot terminated at 1.95 s, which is a little earlier
than the previous one.

Next shot: ramp Prf up quickly to 2 MW, and then ramp it down
slowly. Remove Bt blip.
Sep 15 1999 01:04:03:340PM990915013Robert GranetzShot 13 -- Plasma. Good shot. Prf ramps up quickly to 2 MW, and then ramps
down slowly to zero. The H-L back transition doesn't happen until
the RF power is down to 0.12 MW... a clear example of strong
hysteresis. Plasma lasted until t=1.96+ s.

Next shot: add Bt blip starting at 1.20 s. Prf will have similar
waveform, except it will flattop at t=1.15 s, at a power of 0.75 MW.
Extend CLEARIN feedback slightly to 2.0 s.
Sep 15 1999 01:18:52:340PM990915014Robert GranetzShot 14 -- Plasma. Good shot. Excellent Prf waveform control. Plasma stays
in EDA H-mode for 50 ms after RF turns off.

Next shot: increase CLEARIN slightly towards end of shot (to try
and keep EF2U from turning off, as suggested by Steve Wolfe).
RF will be doing on/off waveform to measure absorption.
Sep 15 1999 01:37:27:310PM990915015Robert GranetzShot 15 -- Plasma. Good shot. RF got the data it needed to determine
absorption. Steve Wukitch's quick estimate gives at least 50%.

Next shot: various miniscule tweaks to RXL, ZXL, RXU, ZXU, and
EF2xEF4, and their gains, late in the rampdown. Increase density
to nl_04=1.1e20 m-2. RF will reload the ramp from the beginning
of today's run (slow ramp up to 2 MW).
Sep 15 1999 01:52:54:263PM990915016Robert GranetzShot 16 -- Plasma. Good shot. Target density was 1.05e20 m-2. Excellent
RF ramp. Good long steady EDA H-mode. Shot duration was unchanged.

Next shot: increase nl_04 to 1.25e20 m-2.
Sep 15 1999 02:11:58:623PM990915017Robert GranetzShot 17 -- Plasma. Good shot. Target density was 1.2-1.25e20 m-2. There was
a big impurity injection at 1.27 s which causes the plasma to
revert to L-mode momentarily.

Next shot: increase density to nl_04=1.4e20 m-2. RF is adjusting
tuning as the density is stepped up.
Sep 15 1999 02:29:31:390PM990915018Robert GranetzShot 18 -- Plasma. Good shot. Target density was 1.4e20 m-2. H-mode power
threshold was 1.4 MW.

Next shot: increase nl_04 to 1.5e20 m-2.
Sep 15 1999 02:47:15:840PM990915019Robert GranetzShot 19 -- Plasma. Good shot. Target density was 1.45e20 m-2. No H-modes.

Next shot: decrease nl_04 back to 1.4e20 m-2 to recover the EDA
H-mode.
Sep 15 1999 03:09:51:750PM990915020Robert GranetzShot 20 -- Plasma. Good shot. Target density was 1.4-1.45e20 m-2. E-port
antenna faulted at t=1.1 s. Got an EDA H-mode.

Next shot: repeat with no changes; re-tune RF.
Sep 15 1999 03:30:25:390PM990915021Robert GranetzShot 21 -- Plasma. Good shot. Similar to previous shot, including the
antenna fault.

Next shot: repeat, no PCS changes; re-tune RF.
Sep 15 1999 03:45:43:153PM990915022Robert GranetzShot 22 -- Plasma. Good shot. One RF antenna faulted early on.

Next shot: do an RF rampdown shot. Remove Bt blip.
Sep 15 1999 04:05:13:250PM990915023Robert GranetzShot 23 -- Plasma. Good shot. RF had good rampdown. Extreme hysteresis
on H-L back transition.

Next shot: flattop RF at 1.8-2 MW. Turn on Bt blip starting at
t=0.90 s.
Sep 15 1999 04:21:02:077PM990915024Robert GranetzShot 24 -- Plasma. Good shot. RF had a good flattop at 2 MW.

Next shot: lower the density to nl_04=0.7e20 m-2. Ramp the RF.
Sep 15 1999 04:38:45:750PM990915025Robert GranetzShot 25 -- Plasma. Good shot. RF ramped up to nearly 2 MW. Density was
nl_04=0.85e20 m-2, which is somewhat higher than we wanted.

Next shot: reduce density programming to nl_04=0.6e20 m-2. Add in
Bt blip starting at t=1.15 s.
Sep 15 1999 04:57:32:310PM990915026Robert GranetzShot 26 -- Plasma. Good shot. Density came down to nl_04=0.7e20 m-2. There
was actually a finite-duration ELM-free H-mode, followed by an EDA
H-mode. RF ramped up to 2.5 MW, but then one antenna faulted.
Edge and core x-ray emissivities were much higher on this shot than
on previous shots today.

Next shot: repeat, trying for no RF faults.
Sep 15 1999 05:30:07:827PM990915027Robert GranetzShot 27 -- Plasma. Good shot. Again there was an ELMfree period followed by
a brief L period and then an EDA. RF didn't do as well as earlier
today. Probably didn't get a good Te pedestal profile.

End of run.

Engineering Operator Comments
ShotTimeTypeStatusComment
109:03:25:937AMPlasmaOkshot#1 09:03/ no faults/plasma
209:27:49:873AMPlasmaOkno faults/plasma
309:45:39:077AMPlasmaOk(null)
410:03:55:640AMPlasmaOk(null)
510:20:39:123AMPlasmaOk(null)
610:40:12:483AMPlasmaOk(null)
710:57:46:250AMPlasmaOk(null)
811:14:50:733AMPlasmaOk(null)
911:32:47:827AMPlasmaOk(null)
1011:51:39:623AMPlasmaOk(null)
1112:13:08:357PMPlasmaOk(null)
1212:30:01:763PMPlasmaOk(null)
1312:47:29:920PMPlasmaOk(null)
1401:08:09:950PMPlasmaOk(null)
1501:26:09:670PMPlasmaOk(null)
1601:44:42:840PMPlasmaOk(null)
1702:01:40:717PMPlasmaOk(null)
1802:19:38:200PMPlasmaOk(null)
1902:39:10:890PMPlasmaOk(null)
2002:59:01:043PMPlasmaOk(null)
2103:15:54:967PMPlasmaOk(null)
2203:33:57:263PMPlasmaOk(null)
2303:51:36:153PMPlasmaOk(null)
2404:10:25:780PMPlasmaOk(null)
2504:28:09:530PMPlasmaOk(null)
2604:47:40:717PMPlasmaOk(null)
2705:04:42:827PMPlasmaOk(null)