# Presentation: 708624

## Mid-Run Assessment - ISD

- S. Kaye, D. Gates
- 10 May 2006

## ISD Priorities: Co-Injection

| Menard:  | Long pulse development at low density using EF correction coil | 2 |   | 1 | 1 | 2 |
| --- | --- | --- | --- | --- | --- | --- |
| Maingi:  | Extension of enhanced H-mode through current profile and shape control | 1 |   | 1 | 0.5 | 1 |
| Gates: | Long pulse double null development with rtEFIT | 2 | 1 | 1 | 1 | 3 |
| Kaye: | Dependence of ELM severity and confinement on boundary shape | 1 |   | 1 | 1 | 1 |
| Kessel:  | Systematic Variation of the Front-End of Long Pulse Discharges | 1 |   | 1 | 1 | 1 |
| Kessel: | Non-Solenoidal Ip Rampup | 5 |   | 1.5 | 1 | 2 |
| Soukhanovskii:  | Divertor detachment in highly shaped long pulse LSN plasmas | 0.5 |   | 2 |   | 0.5 |
| Soukhanovskii: | Gas fueling efficiency and H-mode access with various gas jet injectors  | 0.5 |   | 2 |   | 0.5 |
| Leuer: | NSTX MIMO control collaboration | 1 |   | 2 | 0.5 | 1 |
| 9 | Total: | 14 |  |  | 6 | 11 |

- Requested

- Contingency

- Priority

- Assigned

- Needed

## Progress on XP603 (2 x 0.5 run days) - Gates

- Attempted to achieve early H-mode by:
- Divert earlier - failed PF1A problem
- Larger Ip flat-spot, les dIp/dt - failed
- Adjust early gas - failed
- Requires higher  early with PF3U/L (a few more shots)
- Raised elongation to  = 2.45 (maintained 119991)
- Led to record 1MA pulse length (at the time)
- After remaining adjustments made push wall conditions to improve confinement
- He discharges, Li, B, - no bakeout
- Need field and current scan broaden operating space (see Fig.)

- Plot showing improvement in pulse averaged  and pulse length with shaping over narrow range
- (for 2006)

## XP526:  Scans – Effect on Confinement & ELMs (Kaye)

- Initial attempt (1 day) unsuccessful
- Facility, plasma issues
- Spent several hours on 5/2 to develop target
- Successful
- Will attempt low--scan first, then high- -scan, then mid- -scan

- Shot 120423

## XP602 run plan status (Menard)

**Day 1 – 30 shots ******** need to finish phase scan**
- Re-obtain long-pulse discharge at 4-4.5kG and IP = 0.8MA   **done**
**Implemented rt-EFIT control of LSN long-pulse shots – took 1⁄2 day**
- Scan ramp-up density to determine MHD locking threshold  **started**
- Scan EFC amp & phase during locking  **scanned amp, not phase**
**Day 2 – 30 shots ******** only have 2 shots at lower ne**
- If EFC enables lower ne operation, reduce ne again (12 shots)
**From May 5 data, lower n****e**** delayed early H-mode, shot dev. required**
- Increase IP to 0.9, 1.0, 1.2MA			         (18 shots)
**Developed a 700kA target via XP614 – obtained info about optimal P****NBI**
**Day 3 (1/2 day) – 15 shots ******** Unlikely to get here this year**
- Obtain density flat-top in longest-pulse obtained with EFC at 0.8MA
- Scan Li deposition to achieve desired pumping for ne control  (10 shots)
- Increase fueling for constant line-average density = 3e19 m-3    (5 shots)

## XP602: Long-pulse development at reduced ne using EFC

-  Developed shot with 30% lower density early
-  q-min higher initially even w/ lower heating
-  EFC used during early phase of shot

## XP602: Long-pulse development at reduced ne using EFC

-  Applying early EFC can increase early plasma rotation
-  Other shots (120336) show smaller increase

**Predictive OHxTF EFC on by t=150ms**

**EFC off**

## Run plan wish-list

- Start and finish EFC phase scan
- 8 shots
- Run @ lower ne  multiple He-cond shots needed?
**H-mode threshold** strongly affected at lowest ne values
- 8-15 shots
- Increase IP to 1, 1.2MA
- Tested at 700 and 800kA so far
- 5-10 shots

## XP627 Non-Solenoidal Ip Rampup (Kessel)

- Part A:  HHFW (1/2 day)
- Use k|| = 14 m-1 heating, run at Ip = 250 kA, utilize trip avoidance (power reduction before voltage reaches trip limit)
- Use k|| = 10 m-1 heating, co-CD, and cntr-CD, run Ip = 250 kA
- Using best phasing result attempt OH clamp
- _For additional run time_ attempt lower Ip values (200, 150 kA) for both 14 and 10 m-1
- Part B: NBI (1/2 day)
- At Ip = 600 kA, inject A @ 70 keV, inject B @ 70 keV, and inject A+B @ 70 keV
- Repeat at Ip = 500 kA
- Repeat at Ip = 400 kA
- Repeat at Ip = 300 kA
- _For additional run time_ try source C @ 70 keV, and sources A and B @ higher energy

**Examine the replacement of inductive current by non-inductive current in the form of CD and bootstrap current from HHFW and NBI, to determine the efficiency of these sources to rampup the plasma current**

## Summary of XP627 Part A: HHFW 

- Part A of this XP were run for 1/2 day to examine the effectiveness of HHFW to replace inductive current and provide non-solenoidal plasma current rampup.
- The experiments used low plasma currents 250-350 kA, isoflux/rtEFIT control of the outer gap for antenna coupling, HHFW powers ranging from 1.2-1.7 MW, and HHFW heating phasing at 14 m-1.
- Initially there were difficulties getting the plasma control system to function at low Ip, but these were corrected, and reliable discharges were produced, but resulted in the loss of 1/4 day.
- The HHFW system was choppy at first due to gap control oscillations and non-optimal matching, however, this improved significantly as the matching was tuned.
- The plasma did enter H-mode in several discharges, however, it did not stay in H-mode, which appears to be correlated to the HHFW power dropping out.
- The HHFW power required to enter the H-mode is lower than previously observed at these Ip values by about 1.5-2 times, and more work is required to understand the HHFW power and H-mode sustainment.

## More Run Time for XP627 Part A: HHFW

- Lost 1/4 day did not allow the time necessary to get good matching with the antenna, this must be improved to provide longer steady HHFW power input
- Expand power scan and power trajectory (step up in power) of HHFW to identify reliable entry into H-mode and sustainment of H-mode, including gap adjustments after plasma is in H-mode
- Extend pulse lengths (to 700 ms) to get HHFW conditioning over long periods (HHFW on at 100 ms and off at 650 ms)
- Keep plasma current LOW to (250 kA) to make HHFW heating effects strong, unless control issues force Ip to higher values
- Try intermediate phasing at <k||> = 10 m-1 to see CD and heating effects
- Have good starting discharge for this work, 120297, with reasonable HHFW antenna matching

## Summary of XP627 Part B: NBI

- Part B of this XP was run for 1⁄2 day, examining NBI into low Ip plasmas to establish database for non-solenoidal plasma current rampup.
- The plasma stored energies under a single NB source reached 120 kJ at 600 kA, 70-90 kJ at 500 kA, and 60 kJ at 400 kA.
- With 2 NB sources the plasma stored energy reaches 120 kJ at 600 kA, 120 kJ at 500 kA, and 80-90 kJ at 400 kA.
- With 3 NB sources at 500 kA, the stored energy was 120 kJ, indicating that source C is not well confined at these low Ip values.
- The li values were 0.75-0.9 at 600 kA, 0.7-0.85 at 500 kA, and 0.85 at 400 kA.
- The lowest surface voltage was 0.1 V, although more typically across these discharges about 0.2 V.
- The density regularly exceeded the Greenwald density by about 50% due to the low plasma currents and strong NB fueling.
- Analysis of the NB characteristics with TRANSP will help to understand the trade-offs of NB confinement vs Ip, bootstrap and NBCD, and single and double source effects.
- The diminishing returns of NBI for non-solenoidal current rampup are becoming evident at 400 kA, although the easy transitions to H-mode are encouraging.

## More Run Time for XP627 Part B: NBI

- Add source C @ 70 keV to the 2 NB source cases at all currents
- Examine Ip = 300 kA to find the “cliff” for NB confinement, where it is no longer effective.  So far the trend is smooth.
- Begin NB injection into plasmas at low Ip with HHFW heating (Ip = 500-250 kA) to examine the parasitic absorption effects when Ip is low and the NB is poorly confined.  This serves as the transition from the HHFW-only rampup phase to the HHFW+NBI phase

## Counter-Injection Campaign Priorities

| Kaye: | Overview and issues, Thermal confinement trends | 1 |   | 1 | 1 | 1.5 |
| --- | --- | --- | --- | --- | --- | --- |
| Akers: | Ideas from across the ocean | 0 |   |   |   |   |
| Bush:  | H-mode power threshold |   |   | 1 | 0.5 | 1 |
| Menard:  | J-profile modifications during ctr with early H-mode startup | 2 |   | 1 | 1 | 2 |
| Lee:  | Assessment of the magnitude and direction of ELMs with FIRETIP | 1 |   |   |   |   |
| Darrow:  | Ctr-inj beam blips | 0.5 |   |   | 0.5 | 1 |
| West:  | Search for the QH-mode with ctr-inj and low target density | 1 |   | 1 | 1 | 1 |
| Bernabei:  | HHFW operation with reversed fields | 2 |   | 1 |   | 2 |
| Soukhanovskii
 | Edge and boundary characterization in reversed Bt Bp plasmas | 0.5 |   | 2 |   | 0.5 |
| Stutman:  | Development of ctr-inj L-modes  | 1 |   | 2 |   | 1 |
| Petty: | Displacement of neutral beam ions by MHD instabilities | 2 |   | 2 |   |   |
| 11 |  | 8 |  |  | 4 | 9 |

- Requested

- Contingency

- Priority

- Assigned

- Needed