+--------------------+----------------------+-------+-----------------+
| **Princeton Plasma |                      |       |                 |
| Physics            |                      |       |                 |
| Laboratory**       |                      |       |                 |
|                    |                      |       |                 |
| **NSTX             |                      |       |                 |
| Experimental       |                      |       |                 |
| Proposal**         |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Title:           |                      |       |                 |
| Characterize NBI   |                      |       |                 |
| driven current     |                      |       |                 |
| evolution**        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **OP-XP-518**      | > **Revision:**      | >     |                 |
|                    |                      |  Effe |                 |
|                    |                      | ctive |                 |
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|                    |                      | OP-AD |                 |
|                    |                      | -97)* |                 |
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|                    |                      | Expir |                 |
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|                    |                      | Date: |                 |
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|                    |                      | > u   |                 |
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+--------------------+----------------------+-------+-----------------+
| **PROPOSAL         |                      |       |                 |
| APPROVALS**        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Author:**        |                      |       | > Date          |
+--------------------+----------------------+-------+-----------------+
| **ATI -- ET Group  |                      |       | > Date          |
| Leader:**          |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **RLM - Run        |                      |       | > Date          |
| Coordinator: J.    |                      |       |                 |
| Menard, S. Sabbagh |                      |       |                 |
| (Deputy)**         |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Responsible      |                      |       |                 |
| Division:          |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations**       |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| [**Chit Review     |                      |       |                 |
| Board**            |                      |       |                 |
| (designated by Run |                      |       |                 |
| Coordin            |                      |       |                 |
| ator)]{.underline} |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **MINOR            |                      |       |                 |
| MODIFICATIONS**    |                      |       |                 |
| (Approved by       |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations)        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
|                    |                      |       |                 |
+--------------------+----------------------+-------+-----------------+

NSTX EXPERIMENTAL PROPOSAL

Characterize NBI driven current evolution *Assess the effects of
supra-Alfvénic fast ion driven instabilities on driven current in the
plasma core* OP-XP-518

# 1. Overview of planned experiment 

Experiments will be carried out where the neutral beam driven current is
maximized, such as in moderate density, high electron temperature
plasmas. The goal of this year's experiments is primarily to identify a
target plasma fit for more extensive experiments. In previous
experiments it was found that Toroidal Alfvén eigenmodes (TAE) and
energetic particle modes (EPM) were stable below a fairly sharp
threshold in beam voltage. This may reflect a dependence on power,
fast-ion velocity, or a more subtle change in the fast ion distribution.
By scanning the beam voltage from above to below this threshold, the
current profile evolution can be compared in otherwise very similar
discharges, correlated with the presence and absence of these modes. The
Motional Stark Effect (MSE) diagnostic will be used to measure current
profile evolution. Mirnov coils, soft x-ray cameras, heterodyne
reflectometers, and far infrared tangential interferometers will be used
to characterize the mode activity. The scanning and solid-state neutral
particle analyzer (NPA) diagnostics will be used to monitor fast ion
transport, assisted by the fast-lost-ion probes (FLIP) and neutron
diagnostics. Analysis will be carried out using TRANSP, which calculates
the fast ion distribution and beam driven currents, and EFIT, which to
ensures MHD equilibrium consistency with measured plasma density,
temperature, rotation and current profiles.

It is fortuitous for this experiment that the beam driven current
fraction depends only weakly on the beam voltage so that the experiments
may be done where the effects of MHD on the beam driven current and the
bootstrap contribution to the current are minimized. Further, the shots
should be at moderate beta and toroidal rotation, minimizing
complexities resulting from mapping of the ion and electron kinetic data
to flux surfaces. These lowest voltage shots should provide the cleanest
experimental data for benchmarking the TRANSP beam driven current
calculation.

The results will be used to benchmark the Alfvén eigenmode mode theory
of mode structure and evolution that can affect on the fast ion
distribution and the core plasma current densities in NSTX as well as
future burning plasmas such as ITER.

# 2. Theoretical/ empirical justification

Supra-Alfvénic fast ion driven instabilities and fast ion loss and
dispersion may play a strong role in the determination of NB heating and
current drive efficiencies in NSTX. These processes may affect the
sustainable current density profiles in high-performance NBI-heated NSTX
plasmas and the long-pulse \"hybrid\" plasmas projected in ITER.
Enhanced losses of fast ions have been observed in the presence of a
broad range of fast ion driven MHD activity on NSTX. This research will
therefore aim to develop a basis for predictive understanding to advance
long-pulse high performance plasma research on NSTX, and to strengthen
the scientific basis for the ITER hybrid mode operation.

# 3. Experimental run plan

The approach is based on '04 low neutral beam voltage shots where low
frequency MHD was weak or non-existent. An example is shot 113114 with a
single 60 kV beam from 0.05s. Current drive is more efficient at low
voltage, which will help in the analysis. However, even in this example
the bootstrap current is calculated to be roughly twice the beam driven
current, with the total beam and bootstrap current of 150 kA compared to
the total current of 800 kA. The actual target plasma will be a long
pulse shot from this year.

The run plan will be to start the day with source A conditioned to 90 kV
for the MSE diagnostic. It will be used to provide pulses during the
discharges for the measurement of the q profile. The remaining sources
(B &C) will begin at 65 kV. If fast ion instabilities are present, the
density or beam voltage will be lowered, if possible, to reduce ratio of
fast ion velocity to Alfvén velocity. If fast ion instabilities are
absent at 65 kV, raise density or beam voltage to find additional
conditions with and without fast ion instabilities. If a set of
conditions with similar plasma parameters is found where fast ion
instabilities can be controlled, the current profile evolution will be
documented with MSE by varying the source A on time.

The NPA will be used for a mini-documentation of the fast ion profile in
target plasmas of interest Following this, the beams (B&C) will be
conditioned back up to 85 kV and a set of data will be collected with
strong fast ion MHD.

1.  Start day with source A conditioned to 90 kV, B & C at 65 kV.

    a.  Reproduce long pulse shot 117541, but with only sources B&C at
        65 kV

2.  If TAE/EPM activity, then try single source shots with only B or C,
    else goto 7.

3.  If TAE/EPM activity persists, raise field to 5+ kG, else goto 7.

4.  If TAE/EPM activity persists, drop beam voltage to 60 kV, repeat
    steps 1-3, else goto 7.

5.  If TAE/EPM activity persists, try density scans up or down, else
    goto 7.

6.  if TAE/EPM activity persists, increase and decrease current 650 kA
    and 850 kA, else goto 7.

7.  Document current profile evolution with MSE, fast ion transport with
    NPA.

    a.  Scan source A ontime in 50 ms intervals from 200 ms. Scan NPA
        tangency radius.

8.  Document current profile evolution, fast ion transport with TAE/EPM
    in best comparison shot.

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

Describe any prerequisite conditions, development, XPs or XMPs needed.\
Attach completed Physics Operations Request and Diagnostic Checklist

> Toroidal field of 5 kG or 5.5 kG should be available. MSE should be
> reliably available.

# 5. Planned analysis

What analysis of the data will be required: EFIT, TRANSP, etc.

Extensive TRANSP analysis to calculate fast ion distribution. Benchmark
TRANSP resistive current diffusion modeling against MSE data. As much
useful data as possible will be used to benchmark M3D-k and NOVA
simulations.

# 6. Planned publication of results

What will be the final disposition of the results; where will results be
published and when?

> Target would be Physics of Plasmas Journal article.

PHYSICS OPERATIONS REQUEST

Characterize NBI driven current evolution OP-XP-518

Machine conditions (specify ranges as appropriate)

> I~TF~ (kA): **34-52** Flattop start/stop (s): **0.0/1.0**

I~P~ (MA): **0.750** Flattop start/stop (s): **0.2/0.9**

Configuration: **117541**

> Outer gap (m): **\_\_\_\_\_**, Inner gap (m): **\_\_\_\_\_**
>
> Elongation : **\_\_\_\_\_**, Triangularity : **\_\_\_\_\_**
>
> Z position (m): **0.00**
>
> Gas Species: **D / He**, Injector: **Midplane / Inner wall / Lower
> Dome**
>
> NBI - Species: **D**, Sources: **A/B/C**, Voltage (kV): **90/65/65**,
> Duration (s): **0.90**

ICRF -- Power (MW): **0**, Phasing: **Heating / CD**, Duration (s):
**\_\_\_\_\_**

CHI: **On / Off**

*Either:* List previous shot numbers for setup: **117541**

*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

Characterize NBI driven current evolution OP-XP-518

+----------------------+----+-----+-----------------------------------+
| #### Diagnostic      | #  | ##  | #### Instructions                 |
|                      | ## | ##  |                                   |
|                      | #  | Des |                                   |
|                      | Ne | ire |                                   |
|                      | ed |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Bolometer --       |    |     |                                   |
| > tangential array   |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Bolometer array -  |    |     |                                   |
| > divertor           |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > CHERS              |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > 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                |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Neutral particle   |    |     |                                   |
| > analyzer           |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Neutron            |    |     |                                   |
| > measurements       |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Plasma TV          |    |     |                                   |
+----------------------+----+-----+-----------------------------------+
| > Reciprocating      |    |     |                                   |
| > 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       |    |     |                                   |
+----------------------+----+-----+-----------------------------------+