+--------------------+----------------------+-------+-----------------+
| **Princeton Plasma |                      |       |                 |
| Physics            |                      |       |                 |
| Laboratory**       |                      |       |                 |
|                    |                      |       |                 |
| **NSTX             |                      |       |                 |
| Experimental       |                      |       |                 |
| Proposal**         |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Title:**         |                      |       |                 |
| **Comparison of    |                      |       |                 |
| Small ELM regimes  |                      |       |                 |
| on C-Mod, MAST,    |                      |       |                 |
| and NSTX**         |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **OP-XP-621**      | > **Revision:**      | >     |                 |
|                    |                      |  Effe |                 |
|                    |                      | ctive |                 |
|                    |                      | >     |                 |
|                    |                      | Date: |                 |
|                    |                      | > 03/ |                 |
|                    |                      | 08/06 |                 |
|                    |                      | >     |                 |
|                    |                      | > *   |                 |
|                    |                      | (Ref. |                 |
|                    |                      | >     |                 |
|                    |                      | OP-AD |                 |
|                    |                      | -97)* |                 |
|                    |                      | >     |                 |
|                    |                      | >     |                 |
|                    |                      | Expir |                 |
|                    |                      | ation |                 |
|                    |                      | >     |                 |
|                    |                      | Date: |                 |
|                    |                      | >     |                 |
|                    |                      | > *(2 |                 |
|                    |                      | >     |                 |
|                    |                      |  yrs. |                 |
|                    |                      | > u   |                 |
|                    |                      | nless |                 |
|                    |                      | >     |                 |
|                    |                      |  othe |                 |
|                    |                      | rwise |                 |
|                    |                      | > st  |                 |
|                    |                      | ipula |                 |
|                    |                      | ted)* |                 |
+--------------------+----------------------+-------+-----------------+
| **PROPOSAL         |                      |       |                 |
| APPROVALS**        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Author: A.       |                      |       | > Date          |
| Hubbard (MIT), R.  |                      |       |                 |
| Maingi, H. Meyer   |                      |       |                 |
| (UKAEA)**          |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **ATI -- ET Group  |                      |       | > Date          |
| Leader: R.         |                      |       |                 |
| Maingi**           |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **RLM - Run        |                      |       | > Date          |
| Coordinator: R.    |                      |       |                 |
| Raman (S.          |                      |       |                 |
| Sabbagh)**         |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **Responsible      |                      |       |                 |
| Division:          |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations**       |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| [**Chit Review     |                      |       |                 |
| Board**            |                      |       |                 |
| (designated by Run |                      |       |                 |
| Coordin            |                      |       |                 |
| ator)]{.underline} |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
| **MINOR            |                      |       |                 |
| MODIFICATIONS**    |                      |       |                 |
| (Approved by       |                      |       |                 |
| Experimental       |                      |       |                 |
| Research           |                      |       |                 |
| Operations)        |                      |       |                 |
+--------------------+----------------------+-------+-----------------+
|                    |                      |       |                 |
+--------------------+----------------------+-------+-----------------+

NSTX EXPERIMENTAL PROPOSAL

Error: Reference source not found OP-XP-621

# 1. Overview of planned experiment 

> The primary aim is to match, to the extent possible, the shape (except
> R/a) and key dimensionless parameters of small ELM regimes on Alcator
> C-Mod, MAST and NSTX. The Enhanced D H-mode and higher power ELMy
> H-mode in C-MOD will be compared with the Type V ELMy H-mode and mixed
> Type I/V ELMy H-modes in NSTX and MAST. We will compare access
> conditions and fluctuation properties of these ELM regimes in each
> device, to improve our understanding of the relationships between
> these regimes, including the possible role of aspect ratio.

# 2. Theoretical/ empirical justification

> ![](media/image1.png){width="4.519291338582677in"
> height="5.529133858267716in"}While the "Type I" ELMy H-mode regime is
> currently the baseline scenario for ITER, it is recognized that
> operation with large ELMs has serious disadvantages; extrapolation
> from present experiments indicates divertor erosion will be a serious
> issue. Development of regimes with high confinement but with smaller
> or no ELMs is thus a high priority on all tokamaks. A variety of small
> ELM regimes on various devices have been reported such as grassy ELMs
> (JT-60U, JET), type-II ELMs (JET, AUG, DIII-D, C-Mod), HRS-mode
> (JFT-2M, C-MOD), EDA (C-MOD), and type-V ELMs (NSTX) mostly at high
> collisionality ~e,ped~^\*^ \> 0.5. The physics leading to these
> different regimes and, hence, the scalability towards ITER is not
> fully understood.
>
> A recent ITPA-sponsored dimensionless comparison between C-MOD and the
> higher aspect ratio JFT-2M (PEP-12) showed much commonality between
> EDA H-mode and the HRS-mode. It is of interest to find out whether the
> new "type-V" ELM regime in NSTX, and possibly also observed in MAST,
> has the same physical mechanism as HRS/EDA or type-II; some properties
> appear similar, although the details seem to be different. A similar
> comparison between C-MOD, NSTX and MAST would help to understand the
> differences and commonalities of these regimes, and improve the
> reliability of extrapolations to ITER. They should also help establish
> such operation more routinely on MAST. The difference in field line
> pitch between small and large aspect ratio would highlight the role of
> *q*~95~ for the instabilities. This experiment (PEP-16) was proposed
> as a high priority activity by the Pedestal ITPA group at its meeting
> in Lisbon (Nov 2004), and accepted by the representatives of MAST,
> NSTX and C-Mod at the IAE Program Leaders' meeting in Culham, Dec
> 2004. A similar proposal has been submitted to MAST.
>
> A common cross-sectional shape has been identified within the 3
> machines: a lower-single null with elongation \~ 1.7 and triangularity
> \~ 0.45, as shown in Figure 1. Here the C-Mod shape is scaled to match
> the MAST shape, which is \~ 10% smaller than the NSTX shape. The
> target dimensional and dimensionless parameters for each machine are
> shown in Table I.
>
> ![](media/image2.pct){width="6.50984251968504in"
> height="4.236614173228347in"}

# 3. Experimental run plan (1 day in two 1/2 day increments)

> We will focus on shape matching with C-Mod H-modes while achieving the
> target dimensionless parameters in Table I. The shape match is key
> since edge fluctuation characteristics are known to be highly
> sensitive to shape. It will not be possible to match aspect ratio,
> which is higher on C-Mod; the experiment will thus help to clarify the
> role of r/a on small ELM behaviour and the associated pedestal
> characteristics. Pedestal parameters will be measured and
> dimensionless parameters (\*, \* and) computed.
>
> Because of the different r/a, it will not be possible to
> simultaneously match q~95~ and \*, \* and at the pedestal. The target
> ranges for these quantities are: ~ped~=0.6%-0.7% flux-surface averaged
> (1.3% at outer midplane in C-MOD, 2% in NSTX and MAST),
> \*~ped~=0.004-0.007 flux-surface averaged (0.008-0.014 outer
> midplane), and \*~e,ped~=0.5-3 at the outer midplane. The C-Mod/JFT2M
> comparison revealed very similar access conditions for EDA/HRS and for
> small ELMs in terms of operation spaces in q~95~ vs \*~ped~. We
> therefore anticipate that the second phase experiments will match
> these two parameters, and will separately attempt to match \* ~ped~
> and ~ped~through variation of the density and heating power.
>
> We propose to execute the run plan in two 1/2 experiments, with the
> break somewhere between the end of step 1 and step 2, depending on
> machine availability. This will allow us to compare the pedestal
> characteristics and finalize the target ranges in the second 1/2 day.

1.  Reproduce target shape with rtEFIT at higher I~p~ and B~t~ than in
    the old target discharge #111382. (5-10 discharges)

2.  Vary the ~ped~ value by doing an NBI scan from 1 to 3 NBI sources;
    we expect 1-2 sources will yield the target ~ped~ value. NBI
    modulation may be used here. (3-5 discharges)

3.  Match \* ~ped~ and ~ped~ by simultaneously controlling the density
    ramp in NSTX, either by controlling the gas fueling and/or by using
    Lithium, since ~ped~ depends on density but \* ~ped~ does not; NBI
    may need to be varied here as well. Adjust B~t~ to 0.5 T, 0.45 T if
    needed to change ratio of \* ~ped~ to and ~ped~. (5-10 discharges)

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

This XP requires an operational NBI system, as well as the capability of
performing a detailed ~r~^sep^ scan with rtEFIT. We desire HeGDC between
shots of \~ 6.5-7.5 minutes for a 12.5 minute repetition rate.

# 5. Planned analysis

> Accurate EFIT reconstructions suitable for mapping pedestal
> diagnostics will be required. The pedestal profiles will be fitted
> with the widely accepted tanh function for comparison between
> machines. Edge stability calculations will be done with a number of
> codes, including PEST, DCON, and ELITE, and possibly MARS.

# 6. Planned publication of results

Results will first be presented and discussed at the next Pedestal ITPA
meeting, and will then be published and/or presented at appropriate
conferences. After this, data will be submitted to the ITPA pedestal
profile database. Detailed analysis will be submitted to a refereed
journal.

PHYSICS OPERATIONS REQUEST

Error: Reference source not found OP-XP-621

Machine conditions (specify ranges as appropriate)

> I~TF~ (kA): **52-64** Flattop start/stop (s):
> **\_\_\_\_\_/\_\_\_\_\_**

I~P~ (MA): **0.8-1.0** Flattop start/stop (s): **0.15/1.5 (max)**

Configuration: **Lower Single Null**

> Outer gap (m): **5-15cm** Inner gap (m): **5-10cm**
>
> Elongation : **1.7** Triangularity : **0.45**
>
> Z position (m): **0.00**
>
> Gas Species: **D**, Injector: **Inner wall Midplane**
>
> NBI - Species: **D**, Sources: **A/B/C**, Voltage (kV): **90**,
> Duration (s): **\<1.5 sec**

ICRF -- Power (MW): **\_\_\_\_**, Phasing: **     **, Duration (s):
**\_\_\_\_\_**

CHI: **Off**

*Either:* List previous shot numbers for setup: **#111382 or more recent
version**

*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

Error: Reference source not found OP-XP-621

+-------------------------------+-----+----+--------------------------+
| #### Diagnostic               | ### | #  | #### Instructions        |
|                               | # N | ## |                          |
|                               | eed | #  |                          |
|                               |     | De |                          |
|                               |     | si |                          |
|                               |     | re |                          |
+-------------------------------+-----+----+--------------------------+
| > Bolometer - tangential      |     |    |                          |
| > array                       |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Bolometer array - divertor  |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > CHERS                       |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Divertor fast cameras       |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > 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            |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > High-k scattering           |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Infrared cameras            |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Interferometer -- 1 mm      |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Langmuir probes - PFC tiles |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Langmuir probes - RF        |     |    |                          |
| > antenna                     |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > 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 Rate (2 fission, 4  |     |    |                          |
| > scint)                      |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Neutron collimator          |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Plasma TV                   |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Reciprocating probe         |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Reflectometer - FM/CW       |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Reflectometer - fixed       |     |    |                          |
| > frequency homodyne          |     |    |                          |
| > quadrature                  |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Reflectometer - homodyne    |     |    |                          |
| > correlation                 |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Reflectometer - HHFW/SOL    |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > RF antenna camera           |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > RF antenna probe            |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Solid State NPA             |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > SPRED                       |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Thomson scattering - 20     |     |    |                          |
| > channel                     |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Thomson scattering - 30     |     |    |                          |
| > channel                     |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Ultrasoft X-ray arrays      |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > Ultrasoft X-ray arrays - 2  |     |    |                          |
| > color                       |     |    |                          |
+-------------------------------+-----+----+--------------------------+
| > 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        |     |    |                          |
+-------------------------------+-----+----+--------------------------+