Dust investigations at IPP:

Transcription

1 Dust investigations at IPP: Statistic relevant dust collection in AUG and LHD, F4E dust monitor and fast camera evaluation V.Rohde, M.Balden, N.Endstrasser, B.Reiter Max Planck Institut fur Plasmaphysik, Garching, Germany E. Fortuna-Zalesna, M. Rasinski Warsaw University of Technology, Poland F.Brochard, S.Bardin, J.L. Briancon H.Poincare University, Nancy, France N.Ashigawa NIFS, Japan

2 Dust collection by filtered vacuum technique analysis by WUT, Poland How to collect dust? Use a vacuum cleaner Most common technique Easy to apply No preparations needed Filters pores 0.02 microns Long experience Sampling probability? Dust versus debris Not ideal for analysis Agglomeration of particles Destroying of particles

3 Dust collection by filtered vacuum technique WUT, Warsaw Analysis by SEM, EDX Cutting by ion beam TEM analysis Tungsten flake Many different particles Interesting structure Detailed information Tungsten sphere Tungsten sphere Glass fibre How to extrapolate To ITER? Tungsten/carbon columnar structure

4 AUG Dust collector Collect dust during plasma operation Si wafer for easy analysis Simple design 5 collectors used in AUG LHD exposed, DIII-D build-in JET design phase for 2012 build-in

5 Wafer investigations: Measure all particles by area scanning (2*2 mm 2 ) Commercial Software particle identification EDX spectrum data storage part/weekend Dust analysis strategy automatic analysis / detailed investigations W-dominated flake 1 µm Detailed investigations Select typical particles High resolution SEM Analysis of inner morphology after focused ion beam cutting 50 µm

6 Dust collection in LHD first evaluation: particles 2 Holder prepared in Garching, sent to LHD Exposed in LHD from Holder back to Garching. Standard analysis applied on probe 4.5L LHD 400 part/mm 2 AUG 4000 part/mm 2 C spheres C flake Conglomerate C,O,Fe,Ni Al splash Steel agglomerate

7 CDF, PDF CDF, PDF Dust collection in LHD first evaluation: statistics Number of EDXspectra Number of particles further analysed 1 st run ( ) 2 nd run ( ) Sum Perc enta ge (%) 1. Others-class BN-class C-class Fe-class O-class Al-class Me-class Unclassified (rest) C-sphere (6.6) C spheres: dust injection experiments 9000 particle analyzed Classification by elements Major components C and Fe Distribution functions differ Fe-particle, 2nd run CDF particle size, ECD (µm) C-Sphere, 2nd run PDF*0.4 Fe conc.> 10% particle size, ECD (µm) Fe dust C dust CDF PDF*3 C-conc. <= 50% aspect ratio <= 1.18

8 Area Cover Fraction (10-5 s -1 ) Dust classification ASDEX Upgrade Campaign 2009 frequency (%) mm covered area (%) % of total area others Cu Fe 5 wafers mounted 4 campaigns evaluated 6 different dust classes defined 90 % of dust particles classified Flux (cm -2 s -1 ) Sampling Period a 2008b 2009 PSL Wafer no Wafer no. B-fks B-sph C-fks W-fks W-sph Classification 1: elements 2: shape Typical Flux: 10 part/cm -2 s -1 Origin of dust particles? Wsph Wfks C B Fe Cu N. Endstrasser et al. PMFC-13 & Phys. Scr. submitted

9 Dust collection in AUG dust classes: tungsten spheres Typical tungsten droplet diameter 1-5 microns Some material attached TEM lamella of some droplet internal grain structure solidification thin outer layer Tungsten droplet completely covered with coating coating during levitation in SOL plasma?? coating: boron-carbon

10 Dust collection in AUG dust classes: tungsten flakes Conglomerate W dominated Boron/Carbon/Tungsten 5-10 micron diameter W flake 0 52 Fragile structure will be destroyed during plasma contact vacuum sampling crosssection 1 µm 1 µm -38 Sponge like structure highly porous internal surface explosion risk? 500 nm

11 Dust collection in AUG production of dust particles Arc traces observed at inner baffle region Carbon tiles with tungsten coating and deposited layers on top Arcs splashes tungsten > tungsten droplet Depositions close to arc traces show similar morphology than W flakes Arcing at inner baffle region : source of W spheres and W flakes

12 Capacitative dust monitor F4E 2010 GRT 050 How to measure dust in-situ? use a ceramic capacitate gauge G.Counsell Rev. Sci. Instruments 77, (2006) Labor test at Open University Task: test in tokamak environment: ELMs, radiation, EM noise Main problem 40 m cable needed from sensor to electronics Gauge: capacity of 30 pf Cable : 3000 pf Second electrode and cable for compensation

13 Capacitative dust monitor sensor stability Original design: linear response on weight Artificial signal for cable movement Problem with long term stability Cable optimized Grounding EMV tests New electronics New housing Test under vacuum Stable within 5% Influence of lab temperature: 40 m cable in lab Temperatures CDM Lab cable

14 Capacitative dust monitor AUG build in Laboratory tests successful 2 CDM will be installed below AUG divertor AUG Restart Jan 2012 First results Mar 2012 dismounting Aug 2012

15 Capacitative dust monitor ITER conceptional design Location in divertor defined Material compatibility study Cable is part of sensor No ITER cable/connector definition up to now Detailed construction hindered

16 Real time dust measurements video analysis Analysis of standard video cameras S.H.Hong 2007 campaign Nucl. Fusion 50 (2010) Dust events localized Strong conditioning during campaign

17 Nombres de particules détectées Real time dust measurements long term behaviour # ECCD deposition width "Vraies" particules détectées durant les 5 dernières campagnes menées sur ASDEX Upgrade Autres conditions de décharge Tous types de disruption ELMs # H-Mode conditionning 250 H-mode pedetal structure USN-DN-LSN # # ITER Breakdown studies with flat-top Comparison of AUG small ELM regimes 100 # caméra indisponible Temps (en seconde) Fast camera evaluation by Nancy Group Particle tracking for more than 20 frames campaign (1500 shots evaluated) No conditioning observed Only 76 shots more than 40 dust events (5 %)

18 Real time dust measurement dust production by disruption Discharge with dust production # ka, 2.8e19 m 5 MW NBI, 3.4 MW ICRH Dust observed after disruption as in other devices mobilization of dust by disruption Particles observed Particles observed MHD activity Plasma density T=1.35s T=1.45s

19 Real time dust measurement dust production by unstable plasma Discharge with dust production # MA, 1.1e20 m 5 MW NBI, 1.3 MW ECRH Transition upper lower divertor Control coil oscillation due feed back plasma unstable dust production disruption : due to dust??? Particles observed MHD activity Plasma density

20 Summary and conclusion Dust collector: defined probe for analysis, automated evaluation Analysis : all particles scanned select typical ones detailed analysis of typical particeles typical particles define classes. Examples : C spheres in LHD W dust production by arcing in AUG Capacitate dust monitor: candidate for dust measurements in ITER runs stable for tokamak application AUG operation as final test Video analysis of fast cameras: particle tracing runs dust events in on 5% of discharges dust events mostly in unstable plasma phases