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| **Princeton Plasma |                      |       |                 |
| Physics            |                      |       |                 |
| Laboratory**       |                      |       |                 |
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| **NSTX             |                      |       |                 |
| Experimental       |                      |       |                 |
| Proposal**         |                      |       |                 |
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| **Title: CHI into  |                      |       |                 |
| an ohmic           |                      |       |                 |
| discharge**        |                      |       |                 |
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| **OP-XP-533**      | > **Revision:**      | >     |                 |
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| **PROPOSAL         |                      |       |                 |
| APPROVALS**        |                      |       |                 |
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| **Author: D.       |                      |       | > Date          |
| Mueller**          |                      |       |                 |
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| **ATI -- ET Group  |                      |       | > Date          |
| Leader: R. Raman** |                      |       |                 |
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| **RLM - Run        |                      |       | > Date          |
| Coordinator: J.    |                      |       |                 |
| Menard, S. Sabbagh |                      |       |                 |
| (Deputy)**         |                      |       |                 |
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| **Responsible      |                      |       |                 |
| Division:          |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations**       |                      |       |                 |
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| [**Chit Review     |                      |       |                 |
| Board**            |                      |       |                 |
| (designated by Run |                      |       |                 |
| Coordin            |                      |       |                 |
| ator)]{.underline} |                      |       |                 |
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| **MINOR            |                      |       |                 |
| MODIFICATIONS**    |                      |       |                 |
| (Approved by       |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations)        |                      |       |                 |
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NSTX EXPERIMENTAL PROPOSAL

CHI into an ohmic discharge OP-XP-533

# 1. Overview of planned experiment 

The aim of this experiment is to apply the CHI voltage after an ohmic
discharge has been established and to observe changes in plasma
parameters, especially the current, l~i~ or ~E~.

# 2. Theoretical/ empirical justification

Experiments on HIT-II have demonstrated that it is possible to increase
the observed plasma current by adding CHI to an already established OH
discharge and that this current persists after the CHI voltage is
reduced to zero. It is expected that the CHI current is added as a
surface current and that this may effect the energy confinement time as
well as provide current drive. Of course, other effects may occur such
as impurity generation or changes in the equilibrium that could affect
plasma control.

A condition for driving current inside closed flux surfaces by CHI is
that ~inj~ \> ~tok~ , where

> ~tok~ = ~0~ I~p~ / ~T~ and ~inj~ = ~0~ I~inj~ /~inj~

= ~0~J/B. Integrating **J** and **B** over a surface with current I
and flux gives = ~0~I/.

For the injector, the flux is taken to be the flux penetrating the
insulating gap.



~tok~ \~ 1 for Ip = 500 kA and B~T~ = 4.5 kG\
~inj~ \~ 4 for I~inj~ = 10 kA and ~inj~ \~ 0.03 Wb (from EFIT for shot
106447)

So this condition is easily satisfied.

# 3. Experimental run plan 

Establish ohmic targets (3 each):

500 kA, LSN, TF = 4.5 kG

500 kA, CS, TF =4.5 kG

500 kA, DN, TF = 4.5 kG

with \> 100 ms flattop and well-controlled shapes.

5 min. He GDC between shots.

Starting with the LSN plasma, apply the CHI voltage for 20 ms (time
between application of cap bank voltage voltage and firing the crowbar)
during the Ip flattop. Use a LDGIS branch 5 puff with fill of 1000 T
with gas timed to arrive at the time CHI voltage is applied..

A)  Begin with V~CHI~ = 400 V and increase V~CHI~ in \~200 V increments
    to 1500 V. (8 shots)

B)  Binary search from 0 to 2000 Torr for the \"best\" pressure for
    LDGIS branch 5 puff . (5 shots)

C)  Try another gas puff location (outer midplane and/or top) if time
    permits (3 shots)

D)  Use beam blips before and after CHI to compare current
    distributions. (4 shots)

E)  Delay firing of crowbar as appropriate to allow longer current
    penetration time at best condition (3 shots)

\"Best\" is that which gives most Ip, low l~i~ or improved ~E~ without a
large impurity influx or density increase.

Repeat A-E with the DN plasma

Repeat A-E with the CS plasma

Repeat LSN plasma at end to document changing wall conditions

# 4. Required machine, NBI, RF, CHI and diagnostic capabilities

See above ohmic target requirements. CHI must be ready; use 8 capacitors
in the CHI circuit and use the crowbar to terminate injector current.

Required diagnostics:

Magnetics, EFIT (timed to get bins immediately before and after injector
current pulse)

Filter scopes for C, H and O

Fast Camera with wide- angle view.

MPTS (at least some of the time)\
Dynamo Probe (desired, but not essential for first go-round)

> Divertor Langmuir probes (desired)
>
> Possible MSE with beam blips before and after injector current pulse

# 5. Planned analysis

EFIT,

# 6. Planned publication of results

PPPL report, APS talk, and or journal publication, depending upon
quality of results

PHYSICS OPERATIONS REQUEST

CHI into an ohmic discharge OP-XP-533

Machine conditions (specify ranges as appropriate)

> I~TF~ (kA): **53.5** Flattop start/stop (s): **-.01/1.0**

I~P~ (MA): **0.5** Flattop start/stop (s): **\~.15 / .5**

Configuration: **LSN**

> Outer gap (m): **0.1**, Inner gap (m): **0.1**
>
> Elongation : **2**, Triangularity : \~**0.4**
>
> Z position (m): **0.00**
>
> Gas Species: **D**, Injector: **Midplane / Inner wall / Lower Dome**
>
> NBI - Species: **D**, Sources: **A**, Voltage (kV): **90**, Duration
> (s): **.01-.02**

ICRF -- Power (MW): **\_\_\_\_**, Phasing: **Heating / CD**, Duration
(s): **\_\_\_\_\_**

CHI: **ON**

*Either:* List previous shot numbers for setup: **106447**

*Or:* Sketch the desired time profiles, including inner and outer gaps,
, , heating, fuelling, etc. as appropriate. Accurately label the sketch
with times and values.

DIAGNOSTIC CHECKLIST

CHI into an ohmic discharge OP-XP-533

+----------------------+----+-----+-----------------------------------+
| #### Diagnostic      | #  | ##  | #### Instructions                 |
|                      | ## | ##  |                                   |
|                      | #  | Des |                                   |
|                      | Ne | ire |                                   |
|                      | ed |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Bolometer --       |    |     |                                   |
| > tangential array   |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Bolometer array -  |    |     |                                   |
| > divertor           |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > CHERS              |    |     | > Beam Blips                      |
+----------------------+----+-----+-----------------------------------+
| > Divertor fast      |    |     |                                   |
| > camera             |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Dust detector      |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > EBW radiometers    |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Edge deposition    |    |     |                                   |
| > monitor            |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Edge pressure      |    |     |                                   |
| > gauges             |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Edge rotation      |    |     |                                   |
| > spectroscopy       |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Fast lost ion      |    |     |                                   |
| > probes - IFLIP     |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Fast lost ion      |    |     |                                   |
| > probes - SFLIP     |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Filtered 1D        |    |     |                                   |
| > cameras            |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Filterscopes       |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > FIReTIP            |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Gas puff imaging   |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Infrared cameras   |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Interferometer - 1 |    |     |                                   |
| > mm                 |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Langmuir probe     |    |     |                                   |
| > array              |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Magnetics -        |    |     |                                   |
| > Diamagnetism       |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Magnetics - Flux   |    |     |                                   |
| > loops              |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Magnetics - Locked |    |     |                                   |
| > modes              |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Magnetics - Pickup |    |     |                                   |
| > coils              |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Magnetics -        |    |     |                                   |
| > Rogowski coils     |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Magnetics - RWM    |    |     |                                   |
| > sensors            |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Mirnov coils --    |    |     |                                   |
| > high frequency     |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Mirnov coils --    |    |     |                                   |
| > poloidal array     |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Mirnov coils --    |    |     |                                   |
| > toroidal array     |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > MSE                |    |     | > Beam Blips                      |
+----------------------+----+-----+-----------------------------------+
| > Neutral particle   |    |     |                                   |
| > analyzer           |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Neutron            |    |     |                                   |
| > measurements       |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Plasma TV          |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Reciprocating      |    |     | > Dynamo Probe head               |
| > probe              |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Reflectometer --   |    |     |                                   |
| > core               |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Reflectometer -    |    |     |                                   |
| > SOL                |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > RF antenna camera  |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > RF antenna probe   |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > SPRED              |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Thomson scattering |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Ultrasoft X-ray    |    |     |                                   |
| > arrays             |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Visible            |    |     |                                   |
| > bremsstrahlung     |    |     |                                   |
| > det.               |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Visible            |    |     |                                   |
| > spectrometers      |    |     |                                   |
| > (VIPS)             |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > X-ray crystal      |    |     |                                   |
| > spectrometer - H   |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > X-ray crystal      |    |     |                                   |
| > spectrometer - V   |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > X-ray PIXCS (GEM)  |    |     |                                   |
| > camera             |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > X-ray pinhole      |    |     |                                   |
| > camera             |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > X-ray TG           |    |     |                                   |
| > spectrometer       |    |     |                                   |
+----------------------+----+-----+-----------------------------------+