RE hunting (30. - 31. 1. 2019)

#RE hunting regime

##Aim of experiments

find the right setup of the diagnostics - strip detector (radial position)
tests of new scintillation detectors (Vláďa Linhart) - 2 same NaI(Tl) detectors
find good regime for RE generation - basically to improve performance of plasma with help of vertical stabilisation, plasma is always terminated by hitting the first wall

##Experimental setup

RE related diagnostics:

strip detector
2 x NaI(Tl) - for details contact V. Linhart
Medipix detector for details contact V. Linhart
plastics scintillation detector - HW: \(0.9 \ \mathrm{kV}\) - for details contact H. Čepila
standart NaI(Tl) - HW: \(550 \ \mathrm{kV}\)
standart YAP - HW: \(1 \ \mathrm{kV}\)

Other useful diagnostics:

standart Golem diagnostics, which were available

\(\rightarrow\) bolometers, fast camera etc.

Photos and scheme:

Scheme of used diagnostics during the session.

Photo of experimental setup at the beginning of session.

Photo of experimental setup after shot #29314. Data from YAP was collected by Vláďa Linhart.

Original photo 1,Original photo 2

##Logbook

###First day

Session starts with the shot #29298. Baking and glow discharge were done before session.

####29298:

first shot of session
standart test

####29304:

plastics scintillation detector turn on (HW: \(0.9 \ \mathrm{kV}\))

####29313:

new position of strip detector: \(4.735 \ \mathrm{cm}\)

####29314:

data from YAP detector started to be collected by V. Linhart \(\rightarrow\) comparison with 2 new NaI(Tl) detectors

####29315:

new position of strip detector: \(6.270 \ \mathrm{cm}\)

####29316:

new position of strip detector: \(5.390 \ \mathrm{cm}\)

####29318:

one of probes was placed deeper into port

####29320:

new orientation of head of the strip detector, turn left (=or.: left), before oriented up (=or.: up)

####29321:

change direction of electric field (ONLY) (=DEF: ACW) \(\rightarrow\) looks like unfavourable setting for successful Golem discharge

####29322:

DEF: ACW, DMF: ACW \(\rightarrow\) successful discharge

NOTE I:

discharges are terminated after touching the wall, plasma current starts drop and high loop voltage is induced, but after this event plasma current start to drop exponentially with relatively high time constant see
the moment, when plasma touches wall is clearly visible on Visible or \(H_{\alpha}\) radiation

NOTE II:

we don’t know precise location of the detector head of strip detector
during some shots we heard weird sound, probably the termination of plasma was caused by interaction with strip detector, strip detector was than operated closer to vacuum vessel (in the shadow of limiter?)
exact location will be determined after removing of detector from vessel

####29323:

strip detector or.: left

####29324:

strip detector was placed on position inside the port (probably)
first good shot of the day (\(t_d = 12.1 \ \mathrm{ms}\)) \(\rightarrow\) WHY? Better condition of vessel or it is caused by removing of detector?

####29325:

new position of strip detector \(6.470 \ \mathrm{cm}\), or.: up

####29327:

new position of strip detector \(7.13 \ \mathrm{cm}\), or.: up

####29328:

new position of strip detector \(7.635 \ \mathrm{cm}\)

####29329:

new position of strip detector \(8.08 \ \mathrm{cm}\)

####29330:

new position of strip detector \(8.59 \ \mathrm{cm}\)

####29331:

new position of strip detector \(8.956 \ \mathrm{cm}\)
the longest shot of the day (\(t_d = 13.7 \ \mathrm{ms}\)) (see)

####29332:

new position of strip detector \(9.4 \ \mathrm{cm}\)
last shot of the first day

NOTE III.:

it seems to us that only hope for peaceful termination of the discharges is vertical stabilisation \(\rightarrow\) first tests will be done tomorrow
tomorrow will be start without wall conditioning
Suggestions for data analysis: compute plasma position (cross check between plasma position determined from magnetic diagnostics and from bolometers, possible comparison with fast camera images), analyse termination of discharge

###Second day

Session starts with the shot #29333. Same setting as after the last yesterday shot. No wall conditioning before the session.

####29334:

same shot as yesterday, but wit CW field -> \(U_{CD} = 450 \ \mathrm{V}\), \(U_{BT} = 1300 \ \mathrm{V}\), \(t_{CD} = 0 \ \mathrm{ms}\)
we will repeated this shot, until performance of the plasma will be same as yesterday
settings of strip detector: 9.4 cm, upwards oriented

####29341:

orientation of field changed -> ACW
performance of plasma still poor comparing to yesterday

####29343:

after this shot baking up to \(200 \ ^{\circ}C\) and glow discharge

####Baking and glow discharge

####29344:

first after baking and glow discharge -> 11.1 ms
it looks like that wall conditioning works . . . (or hot first wall?)

####Lunch break

####29347:

first after lunch break
poor plasma performance

####29352:

longer than 10 ms

####29353:

new position of strip detector: 9.1 cm

####29356:

new position of strip detector: 8.9 cm
Plastic scintillation detector: “signal divider = black box” changed with hope for reasonable signals

####29359:

Vertical stabilisation: ON

Note IV.:

For waveform of vertical stabilisation see output from oscilloscope NI TURBO RT channel 15 (see)
For details about vertical stabilisation contact J. Kocman
In our case plasma is drifting upwards and we use DMF: ACW and DEF: ACW \(\rightarrow\) voltage has to be negative in this case
We have problems with setting of proper waveform for stabilisation. Usual mistakes: wrong name, file has to contain TABs instead of spaces, wrong time in file, in name of file can´t be used dot
if the waveform is not correct, the shot is made with last waveform which works

####29363:

New orientation of strip detector: \(45 \ \mathrm{^\circ }\) right

####29367:

New orientation of strip detector: \(90 \ \mathrm{^\circ }\) right

####29367:

New orientation of strip detector: \(135 \ \mathrm{^\circ }\) down right

####29371:

plastic scintillation detector in greater distance

Note for vertical stabilisation:

ftp://192.168.2.201 for check the waveform

####29372:

new orientation of strip detector: down

####29373:

plastic scintillation detector in the corridor and shielded by brick from led to see what happened

####29374:

new orientation of strip detector: \(45 \ \mathrm{^{\circ}}\) left

####29379:

new orientation of strip detector: \(90 \ \mathrm{^{\circ}}\) left

####29380:

power bank, which was charging strip detector, was discharged

####29381:

strip detector is powered by notebook

####29382:

new orientation of strip detector: \(135 \ \mathrm{^{\circ}}\) left down

####29384:

pos. of strip detector: \(8.7 \ \mathrm{cm}\)
or. of strip detector: up

####29386:

or. of strip detector: down

####29388:

pos. of strip detector: \(8.9 \ \mathrm{cm}\)
or. of strip detector: up

####29389:

pos. of strip detector: \(8.97 \ \mathrm{cm}\)
or. of strip detector: up

####29390:

pos. of strip detector: \(9.06 \ \mathrm{cm}\)
or. of strip detector: up

####29391:

or. of strip detector: \(45^{\circ}\) right

####29393:

or. of strip detector: \(90^{\circ}\) right

####29395:

or. of strip detector: \(45^{\circ}\) left

####29397:

or. of strip detector: up

####29398:

best discharge of the campaign - duration of the shot \(18.9 \ \mathrm{ms}\) (see #29398)
Vertical stabilisation: ON