+--------------------+----------------------+-------+-----------------+
| **Princeton Plasma |                      |       |                 |
| Physics            |                      |       |                 |
| Laboratory**       |                      |       |                 |
|                    |                      |       |                 |
| **NSTX             |                      |       |                 |
| Experimental       |                      |       |                 |
| Proposal**         |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| Injection of       |                      |       |                 |
| Lithium Aerosol    |                      |       |                 |
| into NSTX SOL      |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **OP-XP-913**      | > Revision: **0**    | >     |                 |
|                    |                      |  Effe |                 |
|                    |                      | ctive |                 |
|                    |                      | >     |                 |
|                    |                      | Date: |                 |
|                    |                      | >     |                 |
|                    |                      | **2/5 |                 |
|                    |                      | /09** |                 |
|                    |                      | >     |                 |
|                    |                      | >     |                 |
|                    |                      | *(App |                 |
|                    |                      | roval |                 |
|                    |                      | >     |                 |
|                    |                      |  date |                 |
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|                    |                      | nless |                 |
|                    |                      | >     |                 |
|                    |                      |  othe |                 |
|                    |                      | rwise |                 |
|                    |                      | > st  |                 |
|                    |                      | ipula |                 |
|                    |                      | ted)* |                 |
|                    |                      | >     |                 |
|                    |                      | >     |                 |
|                    |                      | Expir |                 |
|                    |                      | ation |                 |
|                    |                      | >     |                 |
|                    |                      | Date: |                 |
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|                    |                      | > *(2 |                 |
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|                    |                      |  yrs. |                 |
|                    |                      | > u   |                 |
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|                    |                      | rwise |                 |
|                    |                      | > st  |                 |
|                    |                      | ipula |                 |
|                    |                      | ted)* |                 |
+--------------------+----------------------+-------+-----------------+
| **PROPOSAL         |                      |       |                 |
| APPROVALS**        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Responsible      |                      |       | > Date 2/5/09   |
| Author: D. K.      |                      |       |                 |
| Mansfield**        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **ATI -- ET Group  |                      |       | > Date          |
| Leader:**          |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **RLM - Run        |                      |       | > Date          |
| Coordinator: R.    |                      |       |                 |
| Raman**            |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Responsible      |                      |       |                 |
| Division:          |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations**       |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| [**Chit Review     |                      |       |                 |
| Board**            |                      |       |                 |
| (designated by Run |                      |       |                 |
| Coordin            |                      |       |                 |
| ator)]{.underline} |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **MINOR            |                      |       |                 |
| MODIFICATIONS**    |                      |       |                 |
| (Approved by       |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations)        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
|                    |                      |       |                 |
+--------------------+----------------------+-------+-----------------+

NSTX EXPERIMENTAL PROPOSAL

  ---------------------------------------------------- ------------------
  TITLE: Injection of Lithium Powder in NSTX           No. **OP-XP-913**

  AUTHORS: **D. K. Mansfield, A.L. Roquemore, R.       DATE: **2/5/09**
  Maingi, H. Kugel**                                   
  ---------------------------------------------------- ------------------

# 1. Overview of planned experiment 

*Briefly* describe the scientific goals of the experiment.

This work will allow an assessment to be made of the efficacy of Li
powder for the purposes of improving plasma performance and/or reducing
plasma density. This is a follow-up experiment to OP-XP-828 which was
partially completed in July 2008.

# 2. Theoretical/ empirical justification

*Brief* justification of activity, including supporting calculations as
appropriate. Describe *briefly* any previous or related experiments.

There are at least 4 reasons to attempt the injection of lithium aerosol
into NSTX. They are in order of importance:

\(1\) Recent experiments involving the shuttered LITER system on NSTX
have demonstrated the effectiveness of "just in time" Li coatings for
improving plasma performance. Moreover, while the LITER experiments have
demonstrated a sustainable reduction in density, a secular density rise
can still be seen in the data. Based on the TFTR experience with
injected lithium aerosols, there is reasonable cause to speculate that
the introduction of Li powder (a dry aerosol) into the SOL of an NSTX
H-Mode plasma might lead to improvements in plasma performance which
were similar to those demonstrated during the LITER experiments while
simultaneously causing a further reduction in the plasma density. If
such improvement in performance can be demonstrated, it will allow NSTX
to have a more flexible Li conditioning capability than is presently
available. Such a system could then be incorporated into an advance
performance scenario most likely involving a high elongation, high
triangularity discharge that at least begins to *approach* a double null
configuration. In this type of discharge, there may be some advantage to
introducing lithium into the upper divertor in addition to the lower
divertor. Base on our experience with injecting lithium powder using the
LPI, it can be anticipated that a substantial fraction of the injected
lithium will be transported along open filed lines terminating in the
upper divertor.

\(2\) If a *steady* flow of lithium powder can be evaporated in the edge
of a stable discharge with an outer strike point located where the LLD
will be when it is installed, then it is *conceivable* that such a flow
of particles could be used to re-supply the LLD in real time because
some fraction of the injected lithium will follow open field lines that
terminate in the vicinity of the LLD - thus obviating the need to
resupply by using LITER.

\(3\) If some unspecified temporal profile of injected lithium particle
flux could be used to perturb the plasma edge /SOL such that small
grassy or random ELMS where to appear in response, then such ELMS could
*conceivably* purge the core of accumulated impurities brought on by
lithium conditioning with LITER.

\(4\) Because the dropper system should work with any reasonably behaved
collection of particles. It could be used to inject small amounts (\<\<
1 mg/sec) of dust into the NSTX SOL in a controlled manner. Such a
system has the advantage of introducing dust of known size, morphology,
composition location and velocity. The types of dust injected can be
also be rather exotic and could be used to address some basic physics
issues concerning dust in fusion devices. For example S. Krasheninnikov
has suggested injecting small amounts of binary particles (i.e. a single
sphere comprising two half spheres of different materials) so as to
study the physics of differential ablation. A fair approximation to this
might be, for instance, diamond powder that has be sprayed on one side
only with (lets say) aluminum.

During XP-828, several interesting and salutary phenomena were observed
when aerosol injection took place before the L-H transition. These
phenomena include the reduction of OH consumption, the transient
appearance of extremely flat density and Te profiles with steep edge
gradients, the suppression of impurity influx into the plasma core and
the transient suppression of ELMs. These phenomena were, however, only
seen during one discharge (130389) and that discharge had two
non-standard features: (1) it was driven into the H-mode with early beam
overdrive and (2) it did not receive a center stack gas puff. Further,
XP-828 employed He glow and was run near the end of the 2008
experimental campaign when there was a large amount of residual
evaporated Li from the LITER use prior to XP-828. Assigning any of the
salutary features described above solely to aerosol injection is,
therefore, problematic. The aim of XP-913, therefore, is to document the
effects of lithium powder injection while addressing as many of the
points discussed above (theoretical / empirical justification) as
practical. The primary objective of this experiment, however, will be to
the determine whether or not the salutary effects observed briefly
during XP-828 are, in fact, reproducible and solely a consequence of Li
aerosol injection rather than a consequence of the large amount of
residual evaporated lithium from LITER use prior to XP-828. To that end
we propose using the standard NSTX fiducial discharge (for example
129012 or 130389) with the following difference: a brief period of NBI
overdrive will be employed for entry into the H-mode. As we progress
during the experiment, the center stack gas puff will be eliminated to
the greatest degree possible.

# 3. Experimental run plan

Describe experiment in detail, including decision points and processes.

The experiment will be divided into two sections -- the first section
comprising ∼23 discharges and the second section comprising ∼13
discharges (total:1.5 days). In all cases, He glow will be used as
needed.

During the first section of the experiment an attempt will be made to
reproduce and expand the performance of 130389. After establishing a
standard NSTX No-Li fiducial shot (129012), a slightly different shot
will be used as an XP-913 baseline discharge. This shot (130388) will
have a CS gas puff and will be driven into the H-mode with NBI
overdrive. After establishing this No-Li shot, 1 - 3 attempts will be
made run the same shot without the CS gas puff. If successful, this
No-CS-gas shot will serve as the fiducial for the remainder of the XP
and can be compared directly to 130389 -- the "best" shot from XP-828.

The first use of aerosol injection will begin at this point. The first
discharge will employ a CS gas puff (130388) and uniform flux (Fig 5) of
Li aerosol at 10 mg/s. Injection will begin well before the L-H
transition, essentially at t ∼ 0 (although the plasma will not expand
enough to "encounter" the vertical stream of Li particles until ∼ 25
ms). The flux of Li particles will then be increased systematically over
the next three discharges from 10 mg/s to 20mg/s to 35mg/s to 50 mg/s.
If successful, identical discharges will then be attempted without a CS
gas puff at the highest successful Li flux. In addition to trying to
reproduce the "best" shot from XP-828, the purpose of this part of the
XP is to establish whether or not Li aerosol injection can facilitate
successful operations without use of CS gas injection (i.e. can LFS Li
aerosol fuelling be used to replace LFS gas puffing in the absence of CS
gas fuelling?).

**[Decision Point]{.underline}:** **At this point a decision will be
made as to whether or not a CS gas puff will be routinely employed.**

**[Decision Point]{.underline}: Having demonstrated the reproducibility
of 130389 - or not having done so - a choice of which conditioning
tactic and/or which aerosol flux temporal profile to employ will be
made.**

A systematic attempt will next be made to improve plasma performance by
injecting Li aerosol with temporal flux profiles different from those
used to this point in the experiment. The choice of temporal profile
will be dictated by which aspect of performance seems to be mostly
likely to be affected based on the data taken to this point in the
experiment. As an example, if it appears that the extremely flat and
"square" spatial profiles observed during XP-828 are reproducible, then
a scan of the baseline discharge described above will be taken with
increasing amounts of Li introduced with using profile B shown in Fig 6.
If on the other hand it appears that the reduction of OH consumption
observed during XP-828 is reproducible, then a scan might be taken using
aerosol profile C shown in Fig 6. Another contingency would be to
attempt to exploit a Li conditioning discharge before the shot of
interest to investigate whether or not Li can be deposited
preferentially on the CS by injecting a large amount ( \>25 mg) of Li
aerosol into a discharge -- either Ohmic or low-power NBI heated - that
is limited by the CS. The residual effects of the Li deposited in this
manner would then be exploited on the following high-power discharge. If
this tactic were successful it would demonstrate that the CS is playing
a larger role in recycling than had previously been suspected.

**Table 1 Shot list for the 1st section of the XP-913 (with 130388 -
89)**

+--------------+-------------+-------------+-------------+-------------+
| **XP913**    | **Dropper** | **Aerosol** | **Total     | **HeGDC     |
|              |             |             | Lithium     | (min)**     |
| **(130389)** | **mg/s      | *           | (mg)**      |             |
|              | (Max)**     | *Temporal** |             |             |
| **Shot No.** |             |             |             |             |
|              |             | **Profile** |             |             |
+--------------+-------------+-------------+-------------+-------------+
| Ref 129019   | 0           | N/A         | 0           | 6           |
+--------------+-------------+-------------+-------------+-------------+
| Ref 130388   | 0           | N/A         | 0           | 6           |
+--------------+-------------+-------------+-------------+-------------+
| Ref 130388   | 0           | N/A         | 0           | 6           |
+--------------+-------------+-------------+-------------+-------------+
| Ref 130389   | 0           | N/A         | 0           | 6           |
+--------------+-------------+-------------+-------------+-------------+
| Ref 130389   | 0           | N/A         | 0           | 6           |
+--------------+-------------+-------------+-------------+-------------+
| Ref 130389   | 0           | N/A         | 0           | 6           |
+--------------+-------------+-------------+-------------+-------------+
| xxxxxxxxxxxx | xxxxxxxxxx  | xxxxxxxxxxx | xxxxxxxxxx  | xxxxxxxxxxx |
+--------------+-------------+-------------+-------------+-------------+
| 1            | 10          | A           | 10          | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 2            | 20          | A           | 30          | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 3            | 35          | A           | 65          | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 4            | 50          | A           | 115         | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 5            | 10-50 TBD   | A           | 165 (max)   | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 6            | 10-50 TBD   | A           | 215 (max)   | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 7            | 10-50 TBD   | A           | 265 (max)   | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 8            | 10-50 TBD   | A           | 311 (max)   | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| xxxxxxxxxxxx | xxxxxxxxxx  | xxxxxxxxxxx | xxxxxxxxxx  | xxxxxxxxxxx |
+--------------+-------------+-------------+-------------+-------------+
| 9            | TBD         | TBD         | TBD         | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 10           | TBD         | TBD         | TBD         | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 11           | TBD         | TBD         | TBD         | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 12           | TBD         | TBD         | TBD         | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 13           | 10          | TBD         | TBD         | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 14           | 12          | TBD         | TBD         | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+
| 15           | 14          | TBD         | TBD         | 6 or TBD    |
+--------------+-------------+-------------+-------------+-------------+

During the second section of the experiment, aerosol injection will be
undertaken into discharges that are (1) known to exhibit robust ELMing
behavior and (2) are relevant to LLD operation because they have an
outer strike point near the future location of the LLD. The aim of this
part of the experiment is to compare the efficacy of aerosol injection
into discharges (129019) that are well-documented as having benefitted
(higher confinement and ELM elimination) from large amounts (up to 8 gm)
of Li deposited by LITER.

**Decision Point: To use a hydrogen glow or not so as to re-introduce
ELMs or to simply proceed with aerosol injection.**

At this point in the experiment there will be an amount of
previously-deposited lithium (i.e. from the first part of the
experiment) that is at the low end of the amount that was required to
thoroughly eliminate ELMs and thus cause a large increase in energy
confinement (and radiated power). Hence this type of discharge may or
may not be ELMing when it is "called up". If it is ELMing, the
experiment will proceed with aerosol injection to determine the effects
of aerosol injection. If it is not ELMing hydrogen glow will be
undertaken in an attempt to vitiate the effects of previously deposited
lithium and thereby re-introduce ELMs.

When ELMing behavior has been established and documented, a systematic
introduction of Li aerosol will begin and the effects of such injection
on ELMs will be studied. Extremely aggressive flux levels will be
employed in this part of the XP because (1) we know that ∼ 1000 mg of Li
is needed to eliminate ELMs and we must get there in a reasonable number
of shots to make a sensible comparison. If the plasma can survive such
high levels of Li aerosol (at ∼ 50 mg/s more Li atoms will be injected
into the NSTX vacuum vessel than deuterium atoms needed to sustain the
discharge) then the excess Li must end up *somewhere* and could possibly
end up near the strike point - approximately where LLD will be located.
Hence if it can be demonstrated that this level of Li aerosol can be
tolerated, then a method of partially resupplying the LLD using aerosol
injection might be developed in the future. The last few discharges of
this experiment are directed toward that (admittedly remote) possibility
and will likely end in a disruption.

**Table 2 Shot list for 2nd section of XP-913 (with 129019)**

+-------------+-------------+-------------+-------------+-------------+
| **XP828**   | **Dropper** | *           | **Total     | **HeGDC     |
|             |             | *Temporal** | Lithium     | (min)**     |
| *           | **mg/s      |             | (mg)**      |             |
| *(129019)** | (Max)**     | **Profile** |             |             |
|             |             |             |             |             |
| **Shot      |             |             |             |             |
| No.**       |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
| Ref 129019  | 0           | N/A         | 0           | 6           |
+-------------+-------------+-------------+-------------+-------------+
| xxxxxxxxxx  | xxxxxxxxxx  | xxxxxxxxxxx | xxxxxxxxxx  | xxxxxxxxxxx |
+-------------+-------------+-------------+-------------+-------------+
| Ref 129019  | 0           | N/A         | 0           | 6           |
+-------------+-------------+-------------+-------------+-------------+
| Ref 129019  | 0           | N/A         | 0           | 6           |
+-------------+-------------+-------------+-------------+-------------+
| 1           | 10          | A           | 10          | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+
| 2           | 20          | A           | 30          | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+
| 3           | 30          | A           | 60          | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+
| 4           | 40          | A           | 100         | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+
| 5           | 50          | A           | 150         | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+
| 6           | 60          | A           | 210         | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+
| 7           | 70          | A           | 280         | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+
| 8           | 90          | A           | 370         | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+
| 9           | 100         | A           | 470         | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+
| 10          | 120         | A           | 590         | 6 or TBD    |
+-------------+-------------+-------------+-------------+-------------+

# 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.

# 5. Planned analysis

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

EFIT, TRANSP as appropriate

# 6. Planned publication of results

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

APS at a minimum.

PHYSICS OPERATIONS REQUEST

  ---------------------------------------------------- ------------------
  TITLE: Injection of Lithium Powder in NSTX           No. **OP-XP-913**

  AUTHORS: **D. K. Mansfield, A.L. Roquemore, R.       DATE: **2/5/09**
  Maingi, H. Kugel**                                   
  ---------------------------------------------------- ------------------

Machine conditions (130389 and 129012)

I~TF~ (kA):-53 Flattop start/stop (s): -0.01/1.1

I~P~ (MA):0.8 Flattop start/stop (s): 0.2/1.0

Configuration: **LSN**

Outer gap (m): Inner gap (m):

Elongation κ: Upper/lower triangularity δ:

Z position (m):

Gas Species: **D** Injector(s): CS mid, OM#2

**NBI** Species: **D** Sources: All Voltage (kV): 90 Duration (s): 0.8

**ICRF** Power (MW): 0 Phasing: Duration (s):

**CHI**: **Off** Bank capacitance (mF):

**LITER: Off**

*Either:* List previous shot numbers for setup: 129019 and 129059

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

DIAGNOSTIC CHECKLIST

  ------------------------------------------------------ ----------------
  TITLE: Injection of Lithium Powder in NSTX             No.
                                                         **OP-XP-913**

  AUTHORS: **D. K. Mansfield, A.L. Roquemore, R. Maingi, DATE: 2/5/09
  H. Kugel**                                             
  ------------------------------------------------------ ----------------

*Note special diagnostic requirements in Sec. 4*

  -----------------------------------------------------------------------
  **Diagnostic**                                **Need**     **Want**
  --------------------------------------------- ------------ ------------
  Bolometer -- tangential array                 **x**        

  Bolometer -- divertor                                      

  CHERS -- toroidal                             **x**        

  CHERS -- poloidal                             **x**        

  Divertor fast camera                          **x**        

  Dust detector                                              **x**

  EBW radiometers                                            

  Edge deposition monitors                      **x**        

  Edge neutral density diag.                                 **x**

  Edge pressure gauges                          **x**        

  Edge rotation diagnostic                                   

  Fast ion D_alpha - FIDA                                    

  Fast lost ion probes - IFLIP                               

  Fast lost ion probes - SFLIP                               

  Filterscopes                                  **x**        

  FIReTIP                                       **x**        

  Gas puff imaging                                           **x**

  Hα camera - 1D                                **x**        

  High-k scattering                                          

  Infrared cameras                              **x**        

  Interferometer - 1 mm                                      

  Langmuir probes -- divertor                                **x**

  Langmuir probes -- BEaP                                    

  Langmuir probes -- RF ant.                                 

  Magnetics -- Diamagnetism                     **x**        

  Magnetics -- Flux loops                       **√**        

  Magnetics -- Locked modes                     **x**        

  Magnetics -- Pickup coils                     **√**        

  Magnetics -- Rogowski coils                   **√**        

  Magnetics -- Halo currents                                 

  Magnetics -- RWM sensors                                   

  Mirnov coils -- high f.                       **x**        

  Mirnov coils -- poloidal array                **x**        

  Mirnov coils -- toroidal array                **x**        

  Mirnov coils -- 3-axis proto.                              **x**
  -----------------------------------------------------------------------

Note special diagnostic requirements in Sec. 4

  --------------------------------------------- ------------ ------------
  **Diagnostic**                                **Need**     **Want**

  MSE                                                        **x**

  NPA -- ExB scanning                                        

  NPA -- solid state                                         

  Neutron measurements                          **x**        

  Plasma TV                                     **x**        

  Reciprocating probe                           **x**        

  Reflectometer -- 65GHz                        **x**        

  Reflectometer -- correlation                  **x**        

  Reflectometer -- FM/CW                        **x**        

  Reflectometer -- fixed f                      **x**        

  Reflectometer -- SOL                          **x**        

  RF edge probes                                **x**        

  Spectrometer -- SPRED                         **x**        

  Spectrometer -- VIPS                          **x**        

  SWIFT -- 2D flow                                           **x**

  Thomson scattering                            **x**        

  Ultrasoft X-ray arrays                        **x**        

  Ultrasoft X-rays -- bicolor                                **x**

  Ultrasoft X-rays -- TG spectr.                             **x**

  Visible bremsstrahlung det.                   **x**        

  X-ray crystal spectrom. - H                   **x**        

  X-ray crystal spectrom. - V                   **x**        

  X-ray fast pinhole camera                                  **x**

  X-ray spectrometer - XEUS                                  **x**
  --------------------------------------------- ------------ ------------