# Presentation: 223685

## Integration and Plasma Control

- M.G. Bell, D.A. Gates
- 5-Year Plan Review
- December 12–13, 2002

## IPPA & FESAC Have Established Ambitious Goals for NSTX

- IPPA goal 3.2.1.6:
- “integrate high confinement and high beta”
- FESAC 5-year Objective #2.1
- “...assessing high-beta stability, confinement, self-consistent high-bootstrap operation, and acceptable divertor heat flux, for pulse lengths much greater than energy confinement times”
- Each component represents a challenge in itself
- Integration requires accommodating competing discharge requirements
- Achieving compatibility of conditions for long pulse will be particularly challenging

## Considerable Progress Achieved Towards Goal of High  and E

- During 2002, NSTX achieved in a discharge
-  N ≈ 6%·m·T/MA
-  E ≈ 50ms, H89P ~ 2.5
-  duration ~400ms, ~ 8E

## Advanced Plasma Control Necessary for Achieving “Integration Goals”

- Equilibrium
- Ip, Rp, Zp, , , stabilizer gaps
- Heating and current drive
- PNBI, RNBI, PHHFW, **k**||, [J(r)], [EBW coupling]
- Fueling and density control
- gas [supersonic], pellets, [CTs], [edge pumping]
- Instabilities
- Vertical, , error fields, RWM, NTM
- Edge power and particle fluxes
- Divertor strike point sweeping, edge density, divertor density, divertor radiation, [lithium module]

## Elements of Control

- Diagnostics
- Configuration, profiles (p, v, J), instabilities, fluxes
- Real-time processing
- Equilibrium, stability limits, mode structure, driven current
- Actuators
- Coils & power supplies, NBI, HHFW, [EBW], CHI, fueling, pumping
- Telemetry
- Fast, flexible, expandable data communication
- Will require upgrade of power supply data link

## Control System Hardware

**Control System Hardware**

- High Speed low-latency data acquisition FPDP + Fiberchannel
- 50MB/s sustained data rate
- “Skybolt 2” computer (8  333MHz G4  20GFlop)
- Expandable up to 64 processors in one chassis
- Up to 768 channels of data

**Control**
**Room**

**NSTX**
**Test Cell**

- • Clock

**VME****crates**

**Junction**
**Area**

**Storage**

- USP-1

- (Workstation)

**Digital link to**
**Power Supplies**

**Skybolt 2**

**Analog inputs**

**Fiberchannel****Links**

**FIMM**

**VME bus to****gas injectors**

**Ethernet****Link**

**Operator**
**Terminals**

## 2003 – 2004: Control of Plasma Shaping and Heating Power

*Status**	*Plasma shape with programmed currents
-   ≈ 2.5 transiently; highest  with  ≈ 2.0,  ≈ 0.8
- higher  would facilitate high  at high fbs
- first control with rt-EFIT at end of ‘02 run
*2003*	1) Develop routine feedback control for     shape (, , gaps) with rt-EFIT analysis2) Investigate prospects for higher 
*2004*	1) Upgrade control for  higher – faster power supply link2) Feedback control of NB power (PWM)    to control 

## 2005 – 2008: Inclusion of Profile Data in Real-Time Equilibrium Analysis

*Status*	rt-EFIT has operated with only magnetic data
- inclusion of profile data will substantially improve analysis
*2005*	1) Include MPTS data for pe (*c.f.* offline EFIT)  –  expand real-time diagnostic data acquisition
- 	2) Initiate real-time assessment of stability limit
- – may be based on li, Fp in first instance
*2006*	Include MSE-CIF polarimetry data
*2007*	Include MSE-LIF |**B**| data
*2008*	Develop real-time stability assessment

## 2003 – 2005: Control for Resistive Wall Modes

*Status*	RWM growth inferred from development of kink-like perturbations for  above no-wall limit and rapid slowing of plasma rotation
*2003*	Detailed measurements of RWM structure with newly installed set of Br, Bp pickup coils
*2004*	Installation of RWM control coils (BR) and power supplies
- null “average” BR perturbation with preprogrammed currents
*2005*	Implement feedback control to counteract mode drag and maintain plasma rotation

## 2003 – 2004: Control for Coaxial Helicity Injection

*Status*	400kA toroidal current in 300ms discharge
- Preprogrammed currents - no feedback control
- Absorber arcs terminated most discharges
- New absorber insulator and nulling coils in 2002 opening
*2003**	* 1) Assess new absorber insulator and need for      local field control in absorber 2) Assess HIT-II “forced reconnection” scheme      and add programmed inductive drive
*2004*	1) Absorber field control, if needed2) Feedback control of CHI plasma to
- promote reconnection
- diagnose profiles and MHD activity

## 2004 – 2008: Control ofNeoclassical Tearing Modes

*Status*	 – NTMs identified at high P with qmin < 3/2
*But* not seen in recent high P plasmas with higher qmin
- – Expect control through localized current drive
*2004*	Assess conditions for and impact of NTMs
- Develop NTM detection & localization methods
*2005*	Develop control of localized HHFW-CD
*2006*	Combine real-time detection and localized HHFW-CD to control NTMs
*2008*	EBW-CD for NTM control

## 2003 – 2008: Integrating Techniques for Particle & Power Flux Management

*Status*	- Continuous density rise during H-mode
- 	- Divertor heat fluxes probably acceptable for 2s    but marginal for 5s pulses at full power
*2003**	*Control of improved HFS gas injector
*2004*	Control supersonic gas injector
- 	Assess density control with Li pellet coating
*2005*	Install & control deuterium pellet injector
*2006-7*	Assess and integrate cryo-pump
-  	Strike-point control for power flux mitigation
*2008*	Density control with lithium wall module

## 2005 – 2008: Integrating Techniques for Solenoid-Free Startup & Sustainment

*Status*	Indications of HHFW-CD, ~100kA @ 1 – 2 MW
*2005**	*Integration and control of HHFW-CD with CHI  initiation
*2006*	Reduce role of induction for current sustainment
*2007*	Integration and control of EBW-CD with CHI initiation
*2008*	Demonstration of fully non-inductive startup & sustainment with increasing pulse length

## Integration & Control Builds on Progress in Facility, Diagnostics & Topical Research

**Integration & Control Builds on Progress in Facility, Diagnostics & Topical Research**

- rt-EFIT

-  RWM
- coils

- RWM
- assess

- RWM
- control

- +pressure

- +MSE

- +|B|

- Stability
- calc’n

- HHFW-CD
- assess

- EBW-CD
- control

- EBW-CD
- assess

- High-
- control

- High-
- assess

- Stabilizer
- reconfig.

- HHFW-CD
- control

- Heating
- control

- NTM
- control

- NTM
- assess

## Integration & Control Timeline (2)

**Integration & Control Timeline (2)**

- CHI abs.
- assess

- CHI abs.
- control

- CHI+OH
- control

- CHI+OH
- assess

- CHI+HHFW
- control

- CHI+EBW
- control

- EBW-CD
- assess

- HFS gas
- control

- Pellet
- fueling

- Li pellet
- coating

- Li-wallmodule

- Supersonic
- gas fueling

- Power flux
- assess

- Power flux
- control

- Cryo-pump

- CHI+HHFW
- assess