# Presentation: 330438

## Overview of TFTR Li experiments

- Dennis K. Mansfield
- reported by Leonid E. Zakharov at
- ALPS/APEX meeting
- SNL Albuquerque NM
- Nov.13-17, 2000

## Outline

- Lithium pellets and TFTR physics.
- DOLLOP
- Limiter H-mode.

## Li pellets introduced Li into the limiter.

**NBI**

**0**

**2**

**4**

**6**

**8**

**Line Average Density **

**0.0**

**0.2**

**0.4**

**0.6**

**0.8**

**1.0**

** ****Li PELLETS**

**Time (sec)**

** ****B**

**t**

** ****= 5.0- 6.0 T **

** ****I**

**p**

** ****= 2.0- 2.7 MA**

** **

**No Li in **

**Plasma  **

**During **

**NBI**

**Experimental Technique: Lithium Introduced    **

**onto Limiter by Injection of Pellets**

**10**

**14**

** **

**cm**

**-3**

- This improved fusion performance during NB injection.
- Improvement took several forms.

## 

**Neutral Beam Power (MW)**

**0.4**

**0.3**

**0.2**

**0.1**

**0.0**

**0**

**10**

**20**

**30**

**40**

** **

**•  **

**D-T Discharges, R**

**p**

** ****= 2.52 m, I**

**p**

** ****> 2.0 MA**

**ITER - 89P**

**Confinement Time - **

****

**E**

** **

- Li conditioning of the limiter improved energy confinement over
- 1. ITER-89 P
- 2. TFTR        supershots
- 3. TFTR tritium isotope/enhancedsupershots.
- More Li ->
- More improvement.

## Li conditioning improved overall DT fusion power.

**Q = 0.27**

**Neutral Beam Power (MW)**

**0**

**10**

**20**

**30**

**40**

**0**

**5**

**10**

** **

**•  **

**D-T Discharges, R**

**p**

** ****= 2.52 m, I**

**p**

** ****> 2.0 MA**

**MW**

- TFTR record fusion power shot was designed using precise Li conditioning.
- Use of less Li at higher power was because of MHD high-beta disruption limits in TFTR.

**D, no Li**

**DT,**

** ****4 Pellets**

** **

**Neutral Beam Power (MW)**

****

**E**

** ****(s)**

**0.3**

**0.7**

**0.3**

**0.5**

**5**

**10**

**15**

**20**

**0.1**

**Time (s)**

**Confinement Time - **

****

**E**

** **

****

**E   **

**&  NBI Power**

**"Painted" **

** ****Supershots**

**MW**

**0**

**20**

**0.4**

**0.1**

**0.2**

**0.0**

## “Heavy” Li conditioning led to reversal of typical energy confinement drop with  heating power. 

**D, no Li**

**DT,**

** ****4 Pellets**

** **

**Neutral Beam Power (MW)**

****

**E**

** ****(s)**

**0.3**

**0.7**

**0.3**

**0.5**

**5**

**10**

**15**

**20**

**0.1**

**Time (s)**

**Confinement Time - **

****

**E**

** **

****

**E   **

**&  NBI Power**

**"Painted" **

** ****Supershots**

**MW**

**0**

**20**

**0.4**

**0.1**

**0.2**

**0.0**

- “Heavy” Li conditioning led to reversal of typical energy confinement drop with  heating power.
- Instead, with enough Li, energy confinement rose with NB power.
- This suggests formation of a transport barrier.

## All 3 factors of the fusion triple product were enhanced by Li conditioning (involving only few milligrams of Li)

** ****Ion Temperature - T**

**i**

**(0)**

**n**

**e**

** ****(0) **

****

**E**

** ****T**

**i**

**(0)**

*****

**sec**

**keV**

**50**

**40**

**30**

**20**

**10**

**0**

**0.4**

**0.3**

**0.2**

**0.1**

**0.0**

**10**

**21**

** ****m**

**-3**

**s keV**

**T-only **

**with Li**

**D-only **

**no Li**

**17 MW NBI**

**Time (Sec)**

**Time (Sec)**

## For at least 0.2 sec Li conditioning prevented a rise in the edge density even at High NB power.

**Confinement Time **

**H-Alpha  Emission**

**CII Emission**

**Edge line density **

**10**

**15**

**cm**

**-2**

**0.4**

**0.3**

**0.2**

**0.1**

**0.0**

**1.0**

**0.0**

**1.0**

**0.0**

**2.0**

**0.8**

**1.0**

**1.2**

**1.4**

**1.6**

**1.8**

**Sec**

**A. U. **

** ****A. U.**

**T-only  **

**with Li**

**D-only **

**no Li**

**17 MW NBI**

**Time (Sec)**

**Time (Sec)**

** ****Slope = 0**

**0.0**

**0.7**

**0.0**

**0.7**

- (This result led to the DOLLOP idea)

## Transport barrier in the core was obvious with Li conditioning.

**50**

**40**

**30**

**20**

**10**

**keV**

**Ion Temperature**

**Major Radius**

** ****(m)**

**2.50 **

**3.00 **

**0**

**7**

**6**

**5**

**4**

**3**

**2**

**1**

**10**

**19**

** ****m**

**-3**

**Electron Density**

**Magnetic **

** ****Axis**

**0**

**0**

**2**

**4**

**6**

**8**

**10**

**5**

** ****m s**

**-1**

**Toroidal Velocity**

**1**

**2**

**3**

**4**

**5**

**6**

**10**

**5**

** ****Pascals**

** ****Pressure & q (R)**

**1**

**2**

**3**

**4**

**0**

**DT Supershot 4 Pellets + Painting**

**•**

- Lower edge density “decouples” the core rotation from the walls and resulted in higher toroidal velocity.
- #83545 did not disrupt being close to MHD limits.

## This shot 83545 

**keV**

**MHD**

**16**

**.3**

** ****MW NBI**

**(a)**

**(b)**

**      ****MHD **

**Instabilities**

**2.50**

**3.00**

**R (m)**

**(b)**

**(a)**

**0.0**

**10**

**18**

** ****s**

**-1**

**MW**

**0**

**15**

**T**

**e**

** ****(keV)**

**Begin **

**Ramp **

**Down**

**End **

**Beams**

**Li + Tritium ---   Large Rise in Te **

**       ****After Neutral Beams**

**DT Supershot 4 Pellets + Painting**

**•**

**DT**

**DD**

- This shot 83545
- maintained transport barrier after termination of NB
- (and influx of cold electrons).
- Dramatic rise and peaking in electron temperature was
- discovered.
- About 15% of it was due to alpha heating.
- (not yet published).

## “Steady state” enhanced electron temperature was kept for several energy confinement times at reduced NB power.

**4.0**

**5.0**

**6.0**

**Time (Sec)**

**Electron Density**

**Electron Temperature**

**Neutrons**

**Beam Power**

**4.0**

**5.0**

**6.0**

**10**

**13**

** ****cm**

**-3**

**keV**

**10**

**18**

** ****Sec**

**-1**

**MW**

**0**

**7**

**1**

**0**

**5**

**6**

**7**

**8**

**9**

**10**

**11**

**12**

**13**

**0**

**2**

**4**

**6**

**8**

**10**

**12**

**14**

**16**

**Ramp Down**

**Ramp Down**

**Ramp Down**

**Ramp Down**

**DT **

**DD**

- 89402,403,387,385

**A Brief Step-Down Experiment : **

** ****Li + Tritium vs Li + Deuterium**

- “Steady state” enhanced electron temperature was kept for several energy confinement times at reduced NB power.
- Retro-heating was seen again after NB phase.

**Laser  **

**  ****on**

**YAG LASER**

**Total Electrons (10**

**21**

**) **

**0**

**2**

**4**

**6**

**3.5**

**5.5**

**Neutron Rate (10**

**16**

**s**

**-1**

**)**

**Time (s)**

**0**

**1.0**

**0**

**2.5**

**NBI**

**Molten **

**Lithium**

**Li Aerosol: **

**Controlled  **

**by Laser **

**DOLLOP: Li Aerosol Controls Influxes and Increases **

**Performance - Nonperturbing and Controllable**

**No DOLLOP**

**4.5**

**18 MW **

**  ****NBI**

## Three TFTR records were achieved (with NO optimization of DOLLOP)

**0**

**1**

**2**

**3**

**4**

**Z**

**eff**

**Sawtooth**

**10**

**16**

** ****s**

**-1**

**NO Li**

**104017/104039**

**DOLLOP Has Led to Enhanced and Sustained **

**    ****Performance with No Harmful Effects**

**Time (s)**

**4.0**

**4.5**

**0**

** ****NBI Power **

**10**

**20**

**MW**

**4.0**

**4.5**

**0**

**3.5**

**With DOLLOP **

**+ 2 Pellets**

**Z = 1.3**

**LASER ON**

- Highest DD energy confinement (no rollover);
- Highest Q DD;
- Lowest Zeff.

## Li flux to the plasma edge resulted in LOWER Zeff both at the edge and in the plasma core.

**2.7**

**2.9**

**3.1**

**3.3**

**0**

**1**

**2**

**3**

**4**

**5**

**6**

**7**

** ****83362**

**No Li**

**  ****104039**

**With DOLLOP **

**    ****Laser on**

** **

**Major Radius (m)**

**Z**

**eff**

**magnetic axis**

**Zeff Profiles With and Without Li  **

**Zeff data determined spectroscopically and displayed **

**at t = 4.4 sec for discharges with identical externally- **

**controlled parameters.  **

**( R = 2.52 m, I**

**p**

** ****= 2.3 MA, B**

**t**

** ****= 5.6 T, P**

**b**

** ****= 18 MW).**

**•**

**2.3**

## 

**Start **

**Elms**

**  ****Start  **

**H-Mode**

**Confinement Time -  **

****

**E **

**0.0**

**0.5**

**1.0**

**0.0**

**0.1**

**0.2**

**0.3**

**3.0**

**3.5**

**4.0**

**NBI**

- Lithium injection benefited both TFTR supershots and limiter H-mode.
- Elms were delayed.