Preparation for Plasma Boundary Research on NCSX
-
Upload
kasimir-buckley -
Category
Documents
-
view
26 -
download
1
description
Transcript of Preparation for Plasma Boundary Research on NCSX
07-06.2004.pkm 1NCSX
Preparation for Plasma Boundary Research on NCSX
presented for the NCSX Plasma Boundary Group
by
Peter MioduszewskiORNL
NCSX PAC-7 MeetingJuly 13-14, 2004
07-06.2004.pkm 2NCSX
Mission of the Plasma Boundary Program
1.1. Develop power- and particle exhaust methods compatible with high Develop power- and particle exhaust methods compatible with high beta, high confinement operation of NCSX beta, high confinement operation of NCSX
2.2. Generate the knowledge base for plasma boundary operation in Generate the knowledge base for plasma boundary operation in compact stellaratorscompact stellarators
Confinement and High Beta:• 6 MW,• divertor• power handling • neutrals control• impurity control
Long-pulse pumpeddivertor operation:• 6 MW• divertor pumping• 6 MW; several secs• 20 Pa m3/s exhaust• active density control
VIVIVIII
Auxiliary Heating:• 3 MW NBI, • PFC liner• 350ºC bake• edge parameters• power/particle control
Initial Experiments:• 1.5 MW NBI, • partial PFCs
• plasma-wall contact• boundary structure
FY 2008 - 2010
Evolution of the boundary program:
> FY 2010
07-06.2004.pkm 3NCSX
Boundary Schedule and Tasks
FY 2005 - 2008: Research Preparation Start
Boundary Modeling
- magnetic topology FY 2005 (ongoing)
- plasma: 3-D FY 2005 (mid ‘05)
- neutrals transport: 3-D FY 2006 (2D ongoing)
Diagnostics
- choice of diagnostics FY 2005 (done)
- views and port allocation FY 2005 and FY 2007
FY 2008-2010: Experimental Program
- investigation of plasma-wall contacts FY 2008 ff.
- boundary configurations FY 2008
- particle/impurity control (coatings) FY 2009
- edge parameters FY 2009
- power handling FY 2009
07-06.2004.pkm 4NCSX
Status and Preparation of Boundary Modeling
Magnetic field topology:
1. VMEC-MFBE*-Gourdon codes (A. Grossman, A. Koniges)2. PIES-Drevlac-Integrator (T. Kaiser)--> generated Poincaré plots of edge fields and footprints on wall
status: both approaches work and are presently being benchmarked against each otherneeds: foot prints on wall panels and peaking factors of power fluxes
Neutrals:
we have carried out investigations of neutrals penetration in the “bean” cross-section (for PVR); DEGAS 2-D axisymm.; 3-D for HSX
Fast particles:
have separatrix exits; need to couple with a field-line code for wall intercepts
*E. Strumberger
07-06.2004.pkm 5NCSX
Status and Preparation of Boundary Modeling cont’d
3-D plasma boundary codes:
1. Started collaboration (LLNL) with Greifswald group on the development of the BoRiS code (no funding at this time)
2. The EMC3-EIRENE code (Feng, Sardei) solves self-consistently plasma, neutrals, and impurity behaviour.
It has correctly predicted major parameters of W7-AS, it can treat 3-D structures, islands, stochastic areas.
It has been tested on W7-AS, W7-X, LHD, and TEXTOR DED.
Bottom line: F. Sardei says it is fully parallelized and it works. Wendelstein group will be happy to train a post-doc… We need to get on board as soon as we have the resources (no later than mid ‘05) !
07-06.2004.pkm 6NCSX
Boundary Diagnostics Preparation
Flared ports
Phase III: Initial Experiments
plasma-wall interactions visible cameras
impurity identification visible spectrometer
H and carbon line emission visible filterscopes
PFC temperatures compact IR camera
SOL ne and Te movable Langmuir probe
edge neutral pressure fast pressure gauges
Phase IV: Auxiliary Heating (additional)
energetic particles fast ion loss probe
The most likely location for a divertor has excellent diagnostics access.
adequate set of initial diagnostics has been identified; views are being defined
07-06.2004.pkm 7NCSX
Investigation of Plasma-Wall Contact (Phase III)
Interaction locations:1. divertor: helical ridges2. NBI-wall shine-through3. fast particle intercepts
In conjunction with modeling these measurements will provide the input for the divertor design.
Preparatory work:modeling of intercepts with first wall and peaking factors of power fluxes
1.5 MW, Partial PFC GDC
Diagnostics:fast visible cameravisible spectrometervisible filterscopescompact IR cameramovable Langmuir probefast pressure gauges
07-06.2004.pkm 8NCSX
Plasma-Wall Contact Modeling : Foot-Prints Used For Divertor and Baffle Design
A. KonigesA. Koniges
toroidaltoroidal
poloidalpoloidal
outeroutermidplanemidplane
07-06.2004.pkm 9NCSX
So far, we are learning from the W7-AS and W7-X experience, focused on the island divertor concept:
the divertor intercepts islands, formed by field-lines with very small pitch
angles (10-3) which scale with 1/Lc, leading to very specific effects:
cross-field transport may dominate (control coils) 2-point divertor model does not apply observed momentum loss along the field line of factors 4 - 5, in contrast
to the usual factor of 2 (detachment!)
ndownstream ≤ nupstream
In NCSX the field-lines wind around the main plasma. The pitch
angles (and divertor config.) are more tokamak-like (0.1).
Long connection lengths are favorable for achieving parallel temperature gradients only with sufficiently large pitch angle.
Structure of the Plasma Boundary: NCSX vs.W7-AS
07-06.2004.pkm 10NCSX
Structure of the Plasma Boundary cont’d
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8
fort._0deg_9_in_kg 1:12:27 PM 6/25/04
Z9-1cm
R9-1cm
0
1
2
3
4
5
6
7
8
9
13
14
12
11
1015
16
1718
19
20
21
22
23
24
26
27
21
field-lineswind around main plasma
pitch angle islarge (10-1)
NCSXconnection lengths are similar
divertor plates
island
W7-AS
field-line pitchangle is very small (10-3)
(getting smaller with increasing connection length)
07-06.2004.pkm 11NCSX
Auxiliary Heating Experiments (Phase IV)
Diagnostics:fast visible cameravisible spectrometervisible filterscopescompact IR cameramovable Langmuir probefast pressure gauges
fast ion loss probe
3 MW NBIPFC liner350 ºC baking
Along with 3 MW of NBI, there will be new capabilities for particle and impurity control:
• graphite PFC liner, • baking at 350ºC,• wall coatings
During this phase we will investigate:
• more details of the plasma-wall contact areas
• power fluxes and wall temperatures
• temperatures and densities of the boundary plasma
• neutral pressure and particle fluxes during the discharge
• the control of neutrals with wall coatings
• impurity sources as a function of wall conditions
• energetic particles interactions with wall locations
• predictive and interpretive modeling
07-06.2004.pkm 12NCSX
Summary
Preparations for the plasma boundary program are underway.
Highest priority so far has been modeling of the magnetic boundary topology and defining the boundary diagnostics set.
The most important tasks for FY 2005 are:
develop and finalize the diagnostics views
continued modeling of the magnetic topology (benchmarking)
calculation of foot prints and peaking factors on the wall
conceptual design of the partial PFCs
Other priority tasks are:
plasma and neutrals modeling (EMC3-EIRENE)
energetic particle modeling (wall intercepts)