# Presentation: 016103

## Fast ion transport by interaction of multiple modes

- E D Fredrickson, N N Gorelenkov, G Fu

## Motivation for this XP:

- Fast-ion modes move fast ions in phase-space;
- Even when ions aren't lost
- Even when no affect on neutron rate is seen.
- Redistribution can affect stability of other modes.
- CAE/GAE/TAE/EPM can all interact
- CAE may not directly have strong affect fast ion transport, but could trigger EPMs.
- Re-distribution in phase-space will:
- Affect beam driven current magnitude or profile.
- Also affects fast ion heating profile
- Concentrated losses could damage PFCs
- It would be desirable to have predictive capability of fast ion transport.

## Phase space interactions of multiple modes may enhance fast ion losses 

- Phase-space islands grow as mode amplitude increases.
- Overlap triggers "avalanche" where multiple modes are destabilized.
- Relevant to small * regime

- Additional data needed:
- Higher resolution documentation of modes' structure, amplitudes
- NPA/FLIP measurements of affect on fast ion transport.
- Power-scaling of onset, MSE-constrained q-profile

## TAE bursts suggest "Avalanche" physics

*TAE bursts suggest "Avalanche" physics*

- No correlation of repetitive small bursts; increased amplitude  leads to strong multiple mode burst

- Weak chirping/bursting simulated with M3D-K (Fu)
- Strong bursts consistent with model of "island" overlap in fast ion phase space
- TAE have multiple resonances, more complex physics

- Berk, et al., PoP **2** 3007

## Goals for this XP:

*Goals for this **XP**:*

- Higher resolution documentation of modes' structure, amplitudes
- Goal is to estimate EP phase-space island sizes, develop capability to predict amplitude at which avalanche is triggered
- NPA/FLIP measurements of affect on fast ion transport.
- Particularly the fast NPA data to look for transport on TAE burst timescales
- Power-scaling of onset
- Start from quiescent regime, increase fast ion beta until TAE onset, then until TAE avalanches
- MSE-constrained q-profile (best documented avalanche cases pre-date MSE)

## *AE-quiescent regime developed in '06

**AE-quiescent regime developed in '06*

- Additional information required:
- Document q-profile evolution in quiescent phase.
- Benchmark Vertical NPA scan; transition to *AE regime.
- Increase fast ion beta by reducing density, increasing beam power to trigger TAE avalanches - clearly identify thresholds for excitation of fast ion modes.

- Starting point for documenting affect of fast-ion MHD on current drive
- Valuable to understand thresholds for *AE onset .

## Draft run plan - day 1

*Draft run plan - day 1*

- Phase 1, reproduce quiescent regime, try to increase beam power:	10
- Reproduce quiescent plasma as in 121210, with source C at ≈ 60 kV	1
- Increase toroidal field current to ≈ 53 kA, change current waveform (120124)	1
- If not quiescent, increase density to lower beam beta	2
- Substitute source A from 0.1s to 0.16s and add/substitute after 0.32s	1
- Add source B at ≈ 60 kV, 	1
- If not quiescent, increase density to lower beam beta	2
- If quiescent, increase source B or C voltage in 5 kV steps until TAE/CAE appear	2
- Step 2, Document highest power quiescent plasma	10-20
- NPA scan with source A on at 0.32s	6
- Document impact of EPM onset on fast ion redistribution
- Step source A at 90 kV back in time from 0.32s in 0.02 s intervals to 0.22s	5
- Step source A forward from 0.16s to 0.2s in 0.02s intervals	2
- Acquire reflectometer/sxi data on modes present with source A

## Draft run plan - second run day

*Draft run plan - second run day*

- Requirements:
- L-mode ne(0) ≈ 3.5x1013/cm3 on axis for reflectometer coverage.
- Best TAE avalanches were with A&B at 65 kV, try with B&C at 65 kV.
- Source A at 90 kV tends to excite EPMs
- Argon doping for SXI, HSXI?
- Step 1: Increase fast ion beta until TAE avalanches start (B&C at 65 kV?)
- Start with best quiescent case from Part A, ne(0) ≈ 3.5x1013/cm3	3
- Increase beam voltage in 5 kV increments to avalanche onset	4
- Document TAE (reflectometer/sxi), when they show up 	4
- Step 2: Document avalanches
- Document q evolution during avalanches	5
- n=3 braking to minimize rotational shear, if time
- NPA scan if there is time
- Evaluate data acquired to this point, return to conditions where documentation is uncertain.  Verify that good reflectometer and MSE data was acquired.