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| **Princeton Plasma |                      |       |                 |
| Physics            |                      |       |                 |
| Laboratory**       |                      |       |                 |
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| **NSTX             |                      |       |                 |
| Experimental       |                      |       |                 |
| Proposal**         |                      |       |                 |
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| **Title:           |                      |       |                 |
| Parametric scaling |                      |       |                 |
| of H-mode          |                      |       |                 |
| plasmas**          |                      |       |                 |
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| **OP-XP-302**      | > **Revision: 0**    | >     |                 |
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| **PROPOSAL         |                      |       |                 |
| APPROVALS**        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Author: S.M.     |                      |       | > Date 1/28/03  |
| Kaye**             |                      |       |                 |
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| **ATI -- ET Group  |                      |       | > Date          |
| Leader: B.         |                      |       |                 |
| LeBlanc**          |                      |       |                 |
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| **RLM - Run        |                      |       | > Date          |
| Coordinator: R.    |                      |       |                 |
| Maingi for S. M.   |                      |       |                 |
| Kaye**             |                      |       |                 |
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| **Responsible      |                      |       |                 |
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| Research           |                      |       |                 |
| Operations**       |                      |       |                 |
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| [**Chit Review     |                      |       |                 |
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NSTX EXPERIMENTAL PROPOSAL

Title: Parametric Scaling of H-mode Plasmas No.: 302

# 1. Overview of planned experiment 

The goal of this experiment is to establish the parametric scalings of
H-mode plasmas in NSTX through systematic scans of steady-state
discharges. These studies are key to understanding the confinement
properties of low aspect ratio plasmas, and they are necessary for
connecting to the results at conventional aspect ratio. The experiments
will be carried out starting with a baseline LSN shot having I~p~=0.9
MA, B~T~=0.45 T, and one to two beam sources. The systematic scans will
include a current scan at fixed toroidal field, a toroidal field scan at
fixed plasma current, a field and current scan at fixed q (to understand
the beta and r^\*^scaling better), a density scan, and if there is time,
a power scan.

# 2. Theoretical/ empirical justification

Quasi-steady L-mode plasmas in NSTX exhibit parametric confinement
scalings that are similar to those at conventional aspect ratio,
although the power degradation is somewhat stronger. The global
confinement time in these plasmas scales as I~p~^0.76^ B~T~^0.15^
P~heat~^-0.76^, with no significant dependence on plasma density.
Results from systematic scans of these Inner Wall Limited L-mode plasmas
show different results, with less of a dependence on plasma current, and
a power dependence that seems to vary with plasma current. The
discharges from these systematic scans were more transient than those
used for the statistical study.

While H-mode plasmas were produced within a wide range of plasma
currents, toroidal fields and heating powers, the discharges exhibited a
great deal of variability in the dependence of confinement time on
current and field, most probably due to the variability of machine
conditions, and therefore these dependences could not be determined
quantitatively from data in the last operational period. The power
dependence of the H-mode plasmas on average is described by P^-0.50^
(see figure), which is a degradation that is weaker than that in the
conventional aspect ratio scalings, and may indicate that the H-mode
plasmas in NSTX are less limited by MHD than those in conventional
aspect ratio tokamaks or in the L-mode in NSTX. However, also as the
figure shows, the power degradation increases with plasma current and
may indicate the effects of MHD at the higher currents.

Parametric scans in steady-state H-mode plasmas will allow a
determination of the current, field and density scalings with controlled
and near constant machine conditions. This will also allow for a
comparison to the quasi-steady and transient L-mode plasmas to determine
how the confinement characteristics depend on the discharge dynamics.

The understanding of H-mode confinement even in an empirical sense will
help in designs of future ST devices. In addition, as is the case with
conventional aspect ratio scalings, the parametric descriptions provide
boundary conditions on an understanding of the local transport
properties. Finally, the empirical scalings based on engineering
parameters is a predecessor to the development of scalings based on
dimensionless physics variables.

# 3. Experimental run plan

> The experimental plan is laid out in the table below. The first scans
> are single parameter scans of current and power and density. A
> toroidal field scan and an I~p~, B~T~ scan at fixed I~p~/B~T~ (q~cyl~)
> will be performed later, when operation at B~T~0.45 T is permitted.
> The current and density scans will be performed using two beam sources
> to maximize the CHERS signal. The baseline condition at 0.9 MA will be
> developed, and the highest current condition comes next to start the
> current scan. The discharges need to be in quasi-steady state (little
> change in stored energy over at least a couple of confinement times,
> which is from 50 to 100 msec). Scans will be performed in LSN plasmas.
> This XP requires that there be no large MHD or impurity related
> perturbing events before or during the quasi-steady period. Efforts
> will be made to ensure that ELM behavior is similar, which may be
> difficult in the density scan. Attempts to maintain the ELM character
> will be made using gas puffing from the outer midplane or lower dome
> valves.

One or two shots at each condition will be necessary.

  -------------- -------------- -------------- -------------- --------------
  **Scan**       **I~p~ (MA)**  **B~T~ (T)**   **n~e­~ (10^19^ **NBI
                                               m^-3^)**       Sources**

  A (I~p~ at     0.9            0.45           \~ 4 to 5      A+B
  fixed B~T~)                                                 

                 max I~p~ (1.2  0.45                          
                 MA)                                          

                 0.75           0.45                          

                 0.6            0.45                          

  B (power)      0.9            0.45                          3 sources

                 0.9            0.45                          1 source

                 0.9            0.45                          1 source @ 90
                                                              kV

                 0.75           0.45                          3 sources

                 0.75           0.45                          1 source

                 0.75           0.45                          1 source @ 90
                                                              kV

                 Max I~p~       0.45                          3 sources

                 Max I~p~       0.45                          1 source

                 Max I~p~       0.45                          1 source @ 90
                                                              kV

  C (density)    0.9            0.45           \~3 (lower gas A+B
                                               feed)          

                 0.9            0.45           7 (higher gas  
                                               feed)          

  D (B~T~ at     0.9            0.35                          
  fixed I~p~)                                                 

                 0.9            0.6                           

  E (fixed q)    0.70           0.35                          

                 1.2            0.6                           
  -------------- -------------- -------------- -------------- --------------

# Total 26-30 shots for A-C. D & E will be expanded and performed when 0.6 T operation permitted.

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

> Machine conditions good enough for discharge reproducibility and
> quasi-steady conditions are required.

# 5. Planned analysis

EFIT will be required for determining the global confinement time
quickly. TRANSP will be required for determining more accurate
confinement times including the thermal confinement time.

# Planned publication of results.

> The H-mode results, along with L-mode results, will be published in a
> peer-reviewed journal, and will be presented at various conferences.
> The results will be contributed to the ITER confinement database for
> development of scalings with accurate aspect ratio dependences.

PHYSICS OPERATIONS REQUEST

Title: Parametric Scaling of H-mode Plasmas No.: 302

Machine conditions (specify ranges as appropriate)

> I~TF~ (kA): **36 - 53 (for A-C)** Flattop start/stop (s): **0.0 -
> 1.0**

I~P~ (MA): **0.6-1.2 MA** Flattop start/stop (s): **0.2 - 0.7**

Configuration: **Lower Single Null**

> Outer gap (m): **\~ 0.08**, Inner gap (m): **\~0.04**
>
> Elongation : **1.9**, Triangularity : **0.4**
>
> Z position (m): **0.00**
>
> Gas Species: **D**, Injector: **Inner wall**
>
> NBI - Species: **D**, Sources: **A/B/C**, Voltage (kV): **80, 80, 90**
> Duration (s): **0.4**

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

CHI: **Off**

*Either:* List previous shot numbers for setup: **109034**

*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

Title: Parametric Scaling of H-mode Plasmas No. 302

  ----------------------- ---------- ------------ --------------------------------
  **Diagnostic system**   **Need**   **Desire**   **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                                           

  Edge rotation                                   

  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.)                           

  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                              

  SOL reflectometer                               
  ----------------------- ---------- ------------ --------------------------------