+--------------------+----------------------+-------+-----------------+
| **Princeton Plasma |                      |       |                 |
| Physics            |                      |       |                 |
| Laboratory**       |                      |       |                 |
|                    |                      |       |                 |
| **NSTX             |                      |       |                 |
| Experimental       |                      |       |                 |
| Proposal**         |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Title:           |                      |       |                 |
| Characterization   |                      |       |                 |
| of turbulence in   |                      |       |                 |
| the NSTX           |                      |       |                 |
| boundary**         |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **OP-XP-523**      | > **Revision: 2**    | >     |                 |
|                    |                      |  Effe |                 |
|                    |                      | ctive |                 |
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|                    |                      | Date: |                 |
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|                    |                      | 04/01 |                 |
|                    |                      | /2005 |                 |
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|                    |                      | (Ref. |                 |
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|                    |                      | ipula |                 |
|                    |                      | ted)* |                 |
+--------------------+----------------------+-------+-----------------+
| **PROPOSAL         |                      |       |                 |
| APPROVALS**        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Author: J.       |                      |       | > Date          |
| Boedo, H. Kugel,   |                      |       | > 04/01/2005    |
| S. Zweben, R.      |                      |       |                 |
| Maingi, R. Kaita** |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **ATI - Task Force |                      |       | > Date          |
| Leader: R. Kaita,  |                      |       | > 04/01/2005    |
| deputy --- J.      |                      |       |                 |
| Boedo ET5 Boundary |                      |       |                 |
| Physics Group**    |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **RLM - Run        |                      |       | > Date          |
| Coordinator: S.    |                      |       | > 04/01/2005    |
| Kaye**             |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Responsible      |                      |       |                 |
| Division:          |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations**       |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| [**Chit Review     |                      |       |                 |
| Board**            |                      |       |                 |
| (designated by Run |                      |       |                 |
| Coordin            |                      |       |                 |
| ator)]{.underline} |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **MINOR            |                      |       |                 |
| MODIFICATIONS**    |                      |       |                 |
| (Approved by       |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations)        |                      |       |                 |
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|                    |                      |       |                 |
+--------------------+----------------------+-------+-----------------+

**NSTX EXPERIMENTAL PROPOSAL**

**TITLE:** **Characterization of turbulence in the NSTX boundary**
**NUMBER:** 523 Rev 1

**AUTHORS: J. Boedo, H. Kugel, S. Zweben, R. Maingi, R. Kaita**
**DATE:** 04/01/2005

# Overview of the Planned Experiments

> A basic characterization of the properties of turbulence in the NSTX
> edge is required to develop an elementary knowledge of the cross-field
> transport, benchmark NSTX against other devices and eventually,
> advance basic understanding by comparing measurements to BOUT
> predictions. Further experiments will eventually allow a systematic
> survey of the dependence of turbulence on heating power, shape, and
> density. We will start with L-mode since the signal/noise ratio is
> higher. The GPI camera and the edge reciprocating probe were
> repositioned during the last vacuum opening and are now set for a
> 30-35° pitch angle. Consequently, the experiments should be performed
> at \~800-900 kA plasma current and a \~4.5 kG toroidal field,
> conditions that also have been shown to have long duration H-modes.
>
> A density scan will be first priority since the edge turbulence is
> predicted to depend crucially on a combination of Ballooning/Resistive
> X-point interplay as can be seen in Fig. 1. The simulations indicate
> that as the density is increased (at constant pressure), the
> turbulence peaks more strongly on the LFS midplane and its intensity
> increase. Although NSTX does not have poloidally resolved turbulence
> diagnostics yet, the changes in turbulence intensity should be clearly
> observable. Further data will be obtained in H-mode, where the
> predictions hold, although at lower intensity levels due to the
> stabilization of turbulence by velocity shear. The key diagnostics for
> this XP will be:

-   Fast Probe for edge fluctuations and profiles

-   Reflectometers

-   GPI edge camera for edge fluctuations

-   H/D cameras and diodes particle inventory/transport analysis

-   Divertor Langmuir probes for divertor electron density, temperature,
    and particle flux

> The basic L-mode experiments should be performed with fairly low NBI
> power or strong gas puff to keep the plasma in L-mode. For true LSN,
> (800 kA, 0.45 T) the L-H transition power threshold should be \~650 kW
> unless LFS fueling is used. The plasma should be run so that \~4
> density values ranging from 1.5 to \~4.5 10^13^ cm^-3^ (high density
> values may be too high for low power conditions) can be achieved.
> Particular attention will be paid to detecting MARFEs and the effects
> of plasma detachment. The diagnostics can take data at various times
> during the discharge to have the desired density.
>
> The power levels will be obtained by using derated NBI sources if
> needed, instead of modulated, to avoid separatrix oscillations. The
> higher power discharges can be kept in L-mode if desired by strong
> outboard gas fueling:

-   Run with higher power sources (de-rated \~ 60 kV if needed) or 750
    kW per source and add sources for total power levels of 750, 1500
    and 2250 kW.

> The experiments can start with the lowest power set (\~750 kW) and
> fuel the plasma on the LFS so that it is kept in L-mode and the lowest
> desired density is achieved. The density increase in NSTX will
> naturally provide higher densities. The gas puff can be increased to
> achieve higher densities if needed.
>
> After the first density scan, the power should be increased to the
> next step and if possible, kept in L-mode by gas puffing and the
> density scan repeated. A third power point at (\~2250 kW) will follow,
> obtaining H-mode, and a density scan will be performed. If short for
> time, sacrifice the mid power series.
>
> The second data set concentrates on comparing the LSN configuration to
> a double null diverted (DND) plasma at two NBI power levels conducing
> to L and H-mode. The physics basis for this comparison is the addition
> of a second X-point and the corresponding resistive mode. The
> expectation is that a second X-point not only would increase the
> source but also pin down the existing mode and thus the fluctuation
> levels should increase on the LFS

# 2. Theoretical justification

A density scan will be first priority since the edge turbulence is
predicted to depend crucially on a combination of Ballooning/Resistive
X-point interplay as can be seen in Fig. 1. The simulations indicate
that as the density is increased (at constant pressure), the turbulence
peaks more strongly on the LFS midplane and its intensity increase.
Although NSTX does not have poloidally resolved turbulence diagnostics
yet, the changes in turbulence intensity should be clearly observable.

![](media/image1.png){width="4.552083333333333in"
height="3.7055555555555557in"}

> *Figure 1. BOUT-predicted poloidal/radial variation of normalized
> density fluctuations with Greenwald factor (DIII-D simulation).*
>
> The second data set concentrates on comparing the LSN configuration to
> a double null diverted (DND) plasma at two NBI power levels conducing
> to L and H-mode. The physics basis for this comparison is the addition
> of a second X-point and the corresponding resistive mode. The
> expectation is that a second X-point not only would increase the
> source but also pin down the existing mode and thus the fluctuation
> levels should increase on the LFS. Another BOUT prediction is that the
> ExB velocity shear levels will change substantially when the
> configuration is shifted from LSN to DN. An example of changes induced
> by modifying the grad-B direction (or the location of the X-point) is
> shown in Fig. 2, where the turbulent radial particle flux varies by
> factors of \~2 inside the LCFS.

![](media/image2.png){width="3.3493055555555555in"
height="3.002083333333333in"}

*Figure 2. BOUT-predicted variation of the surfaced-averaged particle
flux with change in the direction of the Grad-B drift. Factors of \~2 at
the LCFS.*

# 3. Experimental Run Plan

> The main mode of operation is in lower single null divertor geometry,
> and later in DN for comparison. Operations are design to be a
> compromise between having enough flux-swing to maintain a 200-300 msec
> current flat-top and running in H-mode with I~p~\~ 800 kA and B~t~ =
> 4.5 kG reference shot is 112508 or a more recent 112819. Note that ELM
> free H-modes are to be avoided because they are transient in nature.
> H-modes with continuous ELM's are acceptable, especially if shots with
> and without transitions can be taken for comparison. A shots such as
> 112819, 112823, etc or 110194, 111543, 111902 and 112508 are a good
> reference.
>
> ![](media/image3.pct){width="4.160416666666666in"
> height="3.2868055555555555in"}
>
> *Figure 3. Configuration for reference shot 110194 (other references
> 111543 and 111902).*
>
> ![](media/image4.pct){width="5.5465277777777775in"
> height="4.545138888888889in"}
>
> *Figure 4. Timeline for reference shots 110194, 111543 and 111902.
> Proposed discharges have lower power levels. H-mode transition will be
> avoided by LFS gas puff. The probe will plunge at various times during
> the discharge to sample different densities.*
>
> Planning is for \~24 shots per day and He glow between discharges to
> maintain some density control. All shots are with deuterium prefill
> with deuterium beams. Helium GPI will be used in conjunction with the
> Edge TV system on every shot unless the gas puffing is found to be too
> perturbative. Typically each ***series*** requires at least one setup
> shot to verify the geometry for the scanning probe, no significant
> shape changes are expected by modifying the density unless
> instabilities are excited.
>
> **Detailed Experimental Run Plan (1 day)**
>
> Priorities are: SNL with L-mode and density scan, then LSN with
> H-mode, later DN with density scan. ***Optional:*** We will hunt for
> L-H transitions if time allows.
>
> We start with SNL and L-mode with \~750 kW (de-rated beams if needed
> at 60 kV). Gas puff in the low field side to maintain discharge in
> L-mode. He glow will be required between discharges to keep the
> density under control but we will decide on the fly what the glow
> length should be to keep the discharge in L-mode (perhaps down to
> \~5-7 min). The density series will be stared at a medium value (\~2.5
> or 3.5 e 13) to avoid locked modes or density limit events related to
> too low or too high densities. Once we establish a good discharge, we
> sample it at two times with different densities. If all goes well, we
> increase the density until we reach the Greenwald limit. If the first
> series goes well, we move to \~150 kW. If we have problems we jump to
> 2.25 MW. Once finished the LSN, we move to DN (reference shot 112523)
> and repeat the L-mode density scan, moving on to H-mode later.

##### 

1.  Conditioning:

> Perform 5 minutes of He GDC.

2.  L-mode, LSN low power (\~750 kW) ne scan (1 good setup shot+ 4 good
    shots)

> Establish discharges with I~p~\~ 800 kA with a 200-300 msec flat top,
> B~t~ = 4.5 kG. Scan sensity \<n~e~L\> = 2 10^15^ cm^-2^, 4 10^15^
> cm^-2^, and 5 10^12^ cm^-3^, make sure to check for signs of plasma
> detachment. Use #112508 (a LSN with NBI but power will be different
> here) as a reference discharge. Lowest density is to be determined by
> locked mode limit, i.e. execute discharges with density high enough to
> avoid locked modes, nominally with n~e~\> = 2.5 10^13^ cm^-3^. Attempt
> to keep l~p~ as constant as possible during the flat top. If discharge
> goes into H-mode, puff vigorously in the LFS. If discharge still
> resists, reduce He glow to \~5 min.

3.  L-mode, LSN Threshold power (\~1500 kW) ne scan (1 good setup shot+
    4 good shots)

> Stack another NBI source into plasma (de-rated if needed) with above
> conditions (using shot #112823 as a reference discharge) so that the
> injected power is varied from 300 to 600 kW. Shots may have helium
> puffs for the edge camera. Avoid operations near disruption limit to
> prevent damage to edge probe. D~~ cameras will be used to judge if
> there are transitions to H-mode. If discharge goes into H-mode, puff
> vigorously in the LFS. If discharge still resists, reduce He glow to
> \~5 min. If discharge resists L-mode, move on to next step.

4.  H-mode LSN (2.250 MW) ne scan (1 good setup shot+ 4+ 6 good shots)

> Repeat ne scan in H-mode (4 shots)
>
> ***(optional)*** Study L-H transition physics. Find transition time
> and place GPI and scanning probe on it. Fist 3 shots with GPI, then
> add the probe. (6 good shots)

5.  LSN to DN L and H mode

> DN Configuration power and ne scan: (1 setup shot + 8 good shots)
>
> Convert to DND configuration (reference 112523) with same operating
> conditions, injecting with NBI sources as detailed below. To the
> extent possible, keep , , q, l~i~ as similar as possible to the LSN
> case. Scan density \<n~e~L\> = 2 10^15^ cm^-2^, 4 10^15^ cm^-2^, and 5
> 10^12^ cm^-3^, make sure to check for signs of plasma detachment.
>
> L-mode 750 kW (4 shots)
>
> H-mode 1.5 or 2.250 MW (4 shots)

6.  DN H-mode 1.5 or 2.25 MW LCFS scan (4 shots)

####### TOTAL XP GOOD SHOTS: 28

####### TOTAL XP GOOD SHOTS w OPTIONAL: 34

1.  No RF is required.

2.  NBI is required throughout

3.  The following diagnostics are required: scanning probe,
    interferometer, magnetics, filterscopes, mid-plane bolometers,
    plasma TV, and VB emission, Thomson Scattering, divertor/wall
    probes, divertor bolometer, thermal helium injector/edge camera
    sytem, IRTV cameras.

# 5 Planned Analysis

-   Characterize turbulence levels of density and potential in NSTX

-   Calculate cross-field turbulent transport from turbulence levels

-   Separate broadband and intermittent fluctuations

-   Characterize intermittent fluctuations vs radius

-   Scale all of the above with density and confinement (L or H mode)

-   Provide enough data for UEDGE and BOUT

-   UEDGE run needed

-   BOUT run needed

-   Compare data with BOUT results

-   Calculate radial particle and heat transport (perpendicular and
    parallel flows)

-   D~~ emission from lower divertor will be used to calculate particle
    balance

-   Electrostatic cross-field transport measurements will be obtained.
    Scaling of rms levels and intermittency levels with density will be
    calculated. Basic properties of intermittency will be deduced.

# 6. Planned publication of results

1.  Initial results will be included in the upcoming meeting abstracts
    such as APS and PSI.

2.  Final results will be published in PoP in late 2004, early 2005.

PHYSICS OPERATIONS REQUEST

Error: Reference source not found Error: Reference source not found

Machine conditions (specify ranges as appropriate)

> I~TF~ (kA): **4.5 kG** Flattop start/stop (s): **throughout**

I~P~ (MA): **0.9** Flattop start/stop (s): **0.15/0.5**

Configuration: **Inner Wall / Lower Single Null / Upper SN / Double
Null**

> Outer gap (m): **\~0.05 (see ref)**, Inner gap (m): \~0.06 (see ref.)
>
> Elongation : **\_\_\_\_\_**, Triangularity : **\_\_\_\_\_**
>
> Z position (m): **0.00**
>
> Gas Species: X**D / He**, Injector: X **Midplane / Inner wall / Lower
> Dome**
>
> NBI - Species: **D**, Sources: **A/B/C**, Voltage (kV): **60**,
> Duration (s): **0.5**

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

CHI: **Off**

*Either:* List previous shot numbers for setup: **112508 LSN except for
NBI. 112523 for DN except for NBI. Note, Strike points sweep intended
and should be programmed.**

## ![](media/image5.pct){width="4.925in" height="4.0625in"}

![](media/image6.pct){width="5.383333333333334in"
height="4.440972222222222in"}

## ![](media/image7.pct){width="5.672916666666667in" height="4.198611111111111in"}

## ![](media/image7.pct){width="5.672916666666667in" height="4.198611111111111in"} 

## DIAGNOSTIC CHECKLIST

**Characterization of the Boundary Layer and Power Flow to the Divertor
No. 217**

  ----------------------- ---------- ------------- --------------------------------
  **Diagnostic system**   **Need**   **Desired**   **Requirements** (timing, view,
                                                   etc.)

  Magnetics                                        

  Fast visible camera                              

  VIPS-1                                           

  VIPS-2                                           

  SPRED                                            

  GRITS                                            

  Visible filterscopes                             

  VB detector                                      

  Midplane bolometer                               

  Diamagnetic flux                                 

  Density interferometer                           
  (1mm)                                            

  FIReTIP                                          
  interf\'r/polarimeter                            

  Thomson scattering                               

  CHERS                                            

  NPA                                              

  X-ray crystal                                    
  spectrometer                                     

  X-ray PHA                                        

  EBW radiometer                                   

  Mirnov arrays                                    

  Locked-mode detectors                            

  USXR arrays                                      

  2-D x-ray detector                               
  (GEM)                                            

  X-ray tangential camera                          

  Reflectometer (4 ch.)                            Scanning mode

  Neutron detectors                                

  Neutron fluctuations                             

  Fast ion loss probe                              

  Reciprocating edge                               
  probe                                            

  Tile Langmuir probes                             

  Edge fluctuation                                 
  imaging                                          

  H-alpha cameras (1-D)                            

  Divertor camera (2-D)                            

  Divertor bolometer (4                            
  ch.)                                             

  IR cameras (2)                                   

  Tile thermocouples                               

  ERD                                              

  ORNL Reflectometer                               

  UCLA Reflectometer                               
  Kubota                                           
  ----------------------- ---------- ------------- --------------------------------