# Presentation: 326692

**Real-time Control****(****and development of control systems****)****at ASDEX Upgrade **
**George Sips**
*Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, D-85748, **Garching,**Germany**.*

## Covers many physics areas, and various different diagnostic input data in real time.

**Areas for plasma control (development) at ASDEX Upgrade**

- Control of plasma performance: (density profile, regime identification).
- Control of MHD instabilities: (NTM ́s, sawteeth, ELM ́s, ELM type).
- Control of q-profile, with on-line q(r) identification.
- Other control schemes including plasma protection.

## Actuators at ASDEX Upgrade

## Off axis heating: Peaking of density profile, but MHD unstable (NTM’s).

- Use of central ICRH or ECRH: Can control the density peaking.

**Control of density p****rofile**

- AIM: Density profile control, also including the heating power as actuator

## Control of High Z impurities in the core

- Improved H-mode: NBI: 5 MW (2.5 MW off axis), ECRH, no sawteeth.
- With ECRH: Density peaking reduced, no accumulation of Tungsten.

## Regime identification

- If you would like to know if the discharge is in L-mode or H-mode.
- Important for other control schemes: Density feedback, plasma protection, divertor.
- Use of power threshold scaling law is not sufficient at all.

- H-mode or L-mode

## Regime identification

**Regime identification**

- Construct training data set > 3000 observations (by hand).
- Identify:
- H-mode or L-mode.
- Improved H-mode or not.
- Store for each data point 0-D diagnostic data.
- Automated search using discriminant analysis on best variables to use and optimimum number of variables.

- H-mode or L-mode dataset.

## Regime identification

- H-mode or L-mode.
- Variables used for identification
- Ploss,q95,p,Ip,Vloop

- Similar good results for Improved H-mode or Not

- Probability x100%

## 3/2 NTM stabilisation

- More ECRH power, new mirror system for launch angle control.
- NTM detection algorithm using real time Te(r) data

## Sawteeth control with ECCD

- Sawteeth stabilisation (A. Mück):
- Counter ECCD, inside q=1 surface.
- Co ECCD, just outside q=1 surface.
- ECCD deposition tuned with B-field.

- New gyrotrons and mirror systemfor 2003/2004

- Co-ECCD

## Control of ELM behaviour: plasma shape

- q95  = 3.6, sep.= 0.43, N=3.5

- q95  = 3.7, sep.= 0.44, N=3.2

- q95  = 4.4, sep.= 0.34, N=2.2

- q95  = 3.3, sep.= 0.17, N=3.0

**Control of ELM behaviour: plasma shape**

## q95 > 3.5, pure Type II ELM ́s possible.

- q95 > 3.5, pure Type II ELM ́s possible.
- 0.85 < ne/nGW < 0.95.
- Close to double null shape.

- Type II

**Control of ELM type: Type II ELM ́s access conditions**

## Controlled external ELM triggering

**Controlled external ELM triggering**

- Small pellets at 20 Hz are used to trigger ELM ́s (P. Lang)

##    2 NBI sources (#6, #7) at NI-2 are off-axis, 

-    2 NBI sources (#6, #7) at NI-2 are off-axis,
-       tangential injection at 93kV, Deuterium
-    Higher current drive efficiency
-    With other NB sources: Control of power/particle deposition

-    NBI system at ASDEX Upgrade :

**Motivation for current profile control at ASDEX Upgrade**

## Current profile control at ASDEX Upgrade

**Current profile control at ASDEX Upgrade**

## ASTRA Simulations of 4 different NBI sources

**ASTRA Simulations of 4 different NBI sources**

## Astra Simulation vs Experiment at 400 kA

- MSE signal : exp .VS. ASTRA

**Astra Simulation vs Experiment at 400 kA**

- Different NBI sources:

## ASTRA Simulations of modulated NBI sources

-   Neutral beam power modulated for optimum response on current   diffusion time scale

- ASDEX Upgrade

- ASDEX Upgrade

**ASTRA Simulations of modulated NBI sources**

- These simulations are used to identify the system response function

## System identification and validation with step response

- Source8 - j(0.225)

**best**
**result**

**worst**
**result**

**System identification and validation with step response**

## Otrher control schemes

- Control of several neutral particle flux densities via D gas injection.
- Choice of several different line densities control via D gas injection. (including edge density and possibility to switch during the pulse).
- Control of these line densites with pellet injection.
- Control of Tdiv (thermoelectric currents), or control of Pdiv via impurity gas injection.
- Control of isotope mix H/(H+D).
- Reduction of Halo currents.
- Pulse repair from Deep Detachment.

## Control of H/(H+D) mixure and line average density

## Killer pellet activated with Neural net, trained to predict time to disruption.

- O:  Without Killer pellet.
- :  With mode-lock detector.
- X:  With Killer pellet.

- Killer pellet activated with Neural net, trained to predict time to disruption.
- But network ages rapidly, to give < 80% reliability.

**Reduction of Halo current during disruptions**

## Deep detachment repair vs. Termination with killer pellet

**Deep detachment repair vs. Termination with killer pellet**

- Repair,
- But experiment
- compromised ?

- Termination,
- Experiment finished
- Machine safe.

## Design of new digital control system (ready 2003)

- Termination,
- Experiment finished
- Machine safe.

- Present system (own design):		Transputer network, 	~ 2 - 5 ms
- New system (commercial):		Shared memory netw.	~ 1 ms

## Conclusions

- Major new real time control schemes are being developed for ASDEX Upgrade: Density profile control, Regime identification, NTM and sawtooth stabilisation, ELM control and current profile control.
- Together with existing control scheme and real time diagnostic measurements  form a consistent set of control tools.
- New real time control hardware is being installed and should be ready for commissioning in 2003