# Presentation: 908314

## Lithium Effects on Edge Neutral Density

- Patrick Ross

## Edge Neutral Density Diagnostic (ENDD) measures light emitted by the plasma edge

- Inboard

- Outboard

- The ENDD uses a 2-D ccd camera to measure Dβ emissions.  The emission profile is then Abel-inverted to provide a radial profile.

## XP 719, Day 1 Edge Neutral Dβ Emissions

- Day 1, most of the shots had a fairly long current flattop (250-750 ms).

- Edge Neutral emissions by radius.  Shot 12474 is the reference shot, after which the lithium deposition began.  Lithium in excess of 200 mg had a measurable effect on the plasma.

| Shot | lithium | total |
| --- | --- | --- |
| 123474 | 0 | 0 |
| 123479 | 40 | 270 |
| 123483 | 249 | 759 |
| 123489 | 260 | 1876 |

- Arbitrary Units

- Radius

## XP 719, Day 1 Edge Neutral Dβ Emissions

- Day 2 consisted of increased deposition between shots.  After depositions > 300 mg, the shots were short, with <100ms flattop.  The edge neutral emissions decreased with increasing lithium.

| Shot | lithium | total |
| --- | --- | --- |
| 123505 | 0 | 0 |
| 123508 | 239 | 676 |
| 123512 | 257 | 3699 |
| 123414 | 278 | 4237 |

- Day two deposited over 9 grams of lithium.  Later shots were not used because they did not run as long.

- XP 719, Day 1 Edge Neutral Dβ Emissions

- Radius

## Day 2- High Lithium Deposition shortened shots

| Shot | lithium | total |
| --- | --- | --- |
| 123505 | 0 | 0 |
| 123511 | 2283 | 3442 |
| 123514 | 278 | 4327 |
| 123419 | 516 | 6473 |

- During day 2 of XP 719, much more lithium was deposited.  After periods where >300 mg of lithium was deposited, the shots were either fizzles or significantly shortened.  In general, they exhibited the same behavior as shots with less lithium.

- Radius

## Lithium Edge Neutral Effects only last for a few shots

- The reference shots from day 1 to day 2 are very similar, even though more than 1.8 grams of Lithium was deposited into NSTX during Day 1 operation.  The lithium effects are seen in the final shot of Day 1 (shot 123489), but have completely disappeared by the reference shot of Day 2 (123505).

- Radius

## Edge Temperatures are not significantly different with Lithium while densities vary somewhat

- Although the central electron temperature is significantly higher after lithium deposition (~1.5x), the edge electron temperature does not appear to change significantly before and after lithium deposition.

- The edge electron density is slightly higher near the seperatrix before lithium deposition.  Beyond 150 cm, the electron densities are the same.

## Edge Neutral Density Affects Charge Exchange Losses

| Run  | Density | CXX | CXI | LIM | Total | % Input Power |
| --- | --- | --- | --- | --- | --- | --- |
| P04 | 1e10 | 41 | 44 | 300 | 385 | 9 |
| P06 | 1e11 | 221 | 36 | 285 | 542 | 13 |
| P08 | 1e12 | 627 | 20 | 247 | 894 | 21 |

- TRANSP Calcluations of Beam Power Losses due to Edge Neutral Density of shot 120442.  Density is cm-3 and lost power is in kW.

- BPCXX – External Charge Exchange Loss (Beam particles charge exchange outside Last Closed Flux Surface)
- BPCXI – Internal Charge Exchange Loss (Beam particles C-X inside LCFS)
- BPLIM – Fast Ions born on bad orbits, lost immediately to the wall

## Conclusions

- The lithium affects the edge neutral emissions, but the effects are short lived.  Within a few shots after the lithium deposition, the effects are gone and the plasma returns to the previous state
- Edge electron temperatures are not sigificantly affected by lithium
- Edge electron densities are decreased due to lithium by nearly 50% inside the seperatrix, but outside, the electron density is unchanged.
- TRANPS calculations show that decreased edge density may increase beam power deposited into the plasma.