+--------------------+----------------------+-------+-----------------+
| **Princeton Plasma |                      |       |                 |
| Physics            |                      |       |                 |
| Laboratory**       |                      |       |                 |
|                    |                      |       |                 |
| **NSTX             |                      |       |                 |
| Experimental       |                      |       |                 |
| Proposal**         |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| Title: **Current   |                      |       |                 |
| Profile            |                      |       |                 |
| Modifications and  |                      |       |                 |
| Fast Ion Loss from |                      |       |                 |
| BAAEs/EPMs**       |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **OP-XP-905**      | > Revision: **1**    | >     |                 |
|                    |                      |  Effe |                 |
|                    |                      | ctive |                 |
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+--------------------+----------------------+-------+-----------------+
| **PROPOSAL         |                      |       |                 |
| APPROVALS**        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Responsible      |                      |       | > Date 4/1/09   |
| Author: D.         |                      |       |                 |
| Darrow**           |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **ATI -- ET Group  |                      |       | > Date          |
| Leader: G.         |                      |       |                 |
| Taylor**           |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **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: **Current Profile Modifications and Fast Ion  No. **OP-XP-905**
  Loss from BAAEs/EPMs**                               

  AUTHORS: **D. Darrow, N. Crocker, E. Fredrickson, N. DATE: **4/1/2009**
  Gorelenkov, W. Heidbrink, S. Kubota, K. C. Lee, M.   
  Podestá, K. Tritz, H. Yuh**                          
  ---------------------------------------------------- ------------------

# 1. Overview of planned experiment 

Alfvénic modes driven by beam ions in NSTX are known to redistribute and
expel fast ions and are thought to alter the current profile. The goal
of this experiment is to visit plasma conditions in NSTX where bursts of
beta-induced Alvfén acoustic eigenmodes (BAAEs) or energetic particle
modes (EPMs) have previously occurred, measure the mode radial
structure, and make detailed measurements of the changes in the current
profile produced by these bursts, along with any redistribution and loss
of fast ions resulting from the bursts. In addition, eternal braking
fields will be applied to slow the toroidal rotation of the plasma in
order to obtain more details of the mode radial structure and frequency
vs minor radius to allow more detailed comparison with NOVA predictions
of BAAE eigenfunctions. Comparison with calculated BAAE eigenfunctions
will improve understanding of the exact nature of these bursting modes
in NSTX and whether they are strictly ideal MHD modes (BAAEs) or whether
they are EPMs which can only exist when the fast ions are present.

# 2. Theoretical/ empirical justification

Previous measurements of EPM/BAAE bursts have shown drops in the neutron
rate of \~10% with clearly observable beam ion losses at the edge of the
plasma. \[D. Darrow, *et al. Nucl. Fusion* **48** (2008) 084004.\] There
is anecdotal evidence \[H. Yuh, private communication 2009, S. Gerhardt,
private communication, 2009\] that bursting MHD modes, especially during
intervals of reversed shear during the plasma current ramp up (when
EPM/BAAE bursts are often observed), have caused significant changes in
the MSE pitch angle profile in NSTX plasmas. These observations warrant
a more systematic investigation.

# 3. Experimental run plan

A. Start the experiment by reloading the machine settings for shot
127393 (900 kA, 0.44 T, 3 beam sources at 90 kV). This is a discharge
which had 5 bursts during the current flattop, between 610 and 710 ms.
The bursts were \~15-20 ms apart, not far enough separated to obtain MSE
data before and after each one.

B. Confirm presence of EPM/BAAE bursts in the discharge. If bursts are
absent, reduce plasma current in steps of 100 kA until bursts are
observed again.

C. (Permit a maximum of 2 hours for this step.) Try to diminish the fast
ion drive for the bursts by incrementally increasing the gas puff rate
in order to increase the plasma density shot by shot, in steps of
\~1x10^19^m^-3^ in order to increase the separation in time between the
bursts. An MHD-free interval of at least 50 ms is sought before and
after a single burst in order to acquire MSE data with a reasonable
signal-to-noise ratio. Try up to 5 steps in gas puff rate. If that is
successful, then the new gas puff rate will define the baseline
condition.

D. (Permit a maximum of 2 hours for this step.) If the desired 50 ms
interval for MSE is not attainable, then increase the plasma current in
100 kA steps as an alternative method to lengthen the interval between
bursts. If the higher current results in bursts with the desired
quiescent interval between, then use this as the baseline condition for
the XP. If higher current eliminates bursts entirely, then step back
downward in current in smaller steps. If this proves unsuccessful, then
the experiment will revert to the original plasma condition as the
baseline discharge and attention will be focused on measuring the
accumulated effect on the current profile of several bursts in
succession. In this event, a quiescent interval of at least 50 ms on
both ends of the set of bursts is sought, which will allow
characterization of the effect of the set of bursts on the current
profile.

E. Repeat the baseline discharge 5-10 times to obtain at least 30 burst
events. Confirm that good quality data has been acquired with MSE,
Mirnov coils, USXR arrays, CHERS, reflectometers (if possible), neutron
detectors, FIDA, sFLIP, SSNPA, NPA, FIReTIP and the high-k scattering
system. If the initial discharges in this sequence produce a reasonable
signal level on the E\|\|B NPA, then conduct a vertical scan with that
diagnostic on successive shots in order to gather additional information
on the effect of the bursts on the radial profile of the beam ions.

F. (Reserve at least 2 hours for this step.) Once the desired number of
burst events have been obtained and good data has been acquired on the
requisite diagnostics, repeat the discharges and add n=3 braking.
Increase the current in the braking coils until the central rotation
frequency is less than 5 kHz. Obtain 5-10 well-documented discharges
under this condition, paying careful attention to the quality of the SXR
camera data for fitting of the mode radial structures.

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

# A prerequisite for the running of this XP is that long pulse discharges have been reliably obtained previously within the same campaign.

# 5. Planned analysis

A. TRANSP runs for each shot.

B. LRDFITs for each shot

C. Detailed analysis of MSE profiles, comparing before and after the set
of bursts in order to define the degree to which current density changes
from before to after the bursts as a function of minor radius in the
discharge.

D. Assessment from NPA, SSNPA, and FIDA data of the amount of beam ion
redistribution within each burst and over the set as a whole.

E. Determination of the beam ion loss fraction from the neutron rate,
and the lost beam ion pitch angle distribution from sFLIP.

F. Analysis of the Mirnov coil data for mode frequency, amplitude, and n
number composition in each burst.

G. Fitting of mode amplitude radial profiles to the SXR array, FIReTIP,
and reflectometer data.

H. Calculation of ideal BAAE eigenfunctions and frequencies for some
typical bursts with NOVA, and comparison with the measured profiles and
frequencies.

I. Look for changes in toroidal rotation profiles after bursts to
evaluate radial transport of fast ions.

# 6. Planned publication of results

Results will be published in PPCF or Nuclear Fusion, within 1 year of
the experiment.

PHYSICS OPERATIONS REQUEST

  ---------------------------------------------------- ------------------
  TITLE: **Current Profile Modifications and Fast Ion  No. **OP-XP-905**
  Loss from BAAEs/EPMs**                               

  AUTHORS: **D. Darrow, N. Crocker, E. Fredrickson, N. DATE: **4/1/2009**
  Gorelenkov, W. Heidbrink, S. Kubota, K. C. Lee, M.   
  Podestá, K. Tritz, H. Yuh**                          
  ---------------------------------------------------- ------------------

*(use additional sheets and attach waveform diagrams if necessary)*

+-----------------------------------------------------------------------+
| **Describe briefly the most important plasma conditions required for  |
| the experiment:**                                                     |
|                                                                       |
| The most important condition for this XP is the occurrence of the     |
| EPM/BAAE bursts                                                       |
+-----------------------------------------------------------------------+
| **Previous shot(s) which can be repeated: 127393**                    |
|                                                                       |
| **Previous shot(s) which can be modified: 127393**                    |
+-----------------------------------------------------------------------+
| **Machine conditions** *(specify ranges as appropriate, strike out    |
| inapplicable cases)*                                                  |
|                                                                       |
| I~TF~ (kA): 53 Flattop start/stop (s): -0.02 / 1.35                   |
|                                                                       |
| I~P~ (MA): 0.9 Flattop start/stop (s): 0.21 / 0.87                    |
|                                                                       |
| Configuration: **LSN**                                                |
|                                                                       |
| Equilibrium Control: **Isoflux** (rtEFIT)                             |
|                                                                       |
| Outer gap (m): Inner gap (m): Z position (m):                         |
|                                                                       |
| Elongation : Upper/lower triangularity :                              |
|                                                                       |
| Gas Species: Injector(s):                                             |
|                                                                       |
| **NBI** Species: **D** Voltage (kV) **A:** 90 **B:** 90 **C:** 90     |
| Duration (s):                                                         |
|                                                                       |
| **ICRF** Power (MW): none Phase between straps (°): Duration (s):     |
|                                                                       |
| **CHI**: **Off** Bank capacitance (mF):                               |
|                                                                       |
| **LITERs: On** Total deposition rate (mg/min): **TBD**                |
|                                                                       |
| **EFC coils: On** Configuration: **Odd** (n=3) *(attach detailed      |
| sheet*                                                                |
+-----------------------------------------------------------------------+

DIAGNOSTIC CHECKLIST

  ----------------------------------------------------- -----------------
  TITLE: **Current Profile Modifications and Fast Ion   No. **OP-XP-905**
  Loss from BAAEs/EPMs**                                

  AUTHORS: **D. Darrow, et al.**                        DATE: 4/1/2009
  ----------------------------------------------------- -----------------

*Note special diagnostic requirements in Sec. 4*

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

  Bolometer -- divertor                                      

  CHERS -- toroidal                             **X**        

  CHERS -- poloidal                                          **X**

  Divertor fast camera                                       

  Dust detector                                              

  EBW radiometers                                            

  Edge deposition monitors                                   

  Edge neutral density diag.                                 

  Edge pressure gauges                                       

  Edge rotation diagnostic                                   **X**

  Fast ion D_alpha - FIDA                       **X**        

  Fast lost ion probes - IFLIP                               **X**

  Fast lost ion probes - SFLIP                  **X**        

  Filterscopes                                               

  FIReTIP                                       **X**        

  Gas puff imaging                                           

  H camera - 1D                                              

  High-k scattering                                          

  Infrared cameras                                           

  Interferometer - 1 mm                         **X**        

  Langmuir probes -- divertor                                

  Langmuir probes -- BEaP                                    

  Langmuir probes -- RF ant.                                 

  Magnetics -- Diamagnetism                                  

  Magnetics -- Flux loops                       **√**        

  Magnetics -- Locked modes                                  

  Magnetics -- Pickup coils                     **√**        

  Magnetics -- Rogowski coils                   **√**        

  Magnetics -- Halo currents                                 

  Magnetics -- RWM sensors                      **X**        

  Mirnov coils -- high f.                       **X**        

  Mirnov coils -- poloidal array                **X**        

  Mirnov coils -- toroidal array                **x**        

  Mirnov coils -- 3-axis proto.                              
  -----------------------------------------------------------------------

*Note special d*iagnostic requirements in Sec. 4

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

  MSE                                           **X**        

  NPA -- E\|\|B scanning                        **X**        

  NPA -- solid state                            **X**        

  Neutron measurements                          **X**        

  Plasma TV                                                  

  Reciprocating probe                                        

  Reflectometer -- 65GHz                        **X**        

  Reflectometer -- correlation                               

  Reflectometer -- FM/CW                                     

  Reflectometer -- fixed f                                   

  Reflectometer -- SOL                                       

  RF edge probes                                             

  Spectrometer -- SPRED                                      

  Spectrometer -- VIPS                                       

  SWIFT -- 2D flow                                           

  Thomson scattering                            **X**        

  Ultrasoft X-ray arrays                        **X**        

  Ultrasoft X-rays -- bicolor                                

  Ultrasoft X-rays -- TG spectr.                             

  Visible bremsstrahlung det.                                

  X-ray crystal spectrom. - H                                

  X-ray crystal spectrom. - V                                

  X-ray fast pinhole camera                                  

  X-ray spectrometer - XEUS                                  
  --------------------------------------------- ------------ ------------