Impurity transport analysis & preparation of W injection experiments on KSTAR

Transcription

1 Impurity transport analysis & preparation of W injection experiments on KSTAR J. H. Hong, H. Y. Lee, S. H. Lee, S. Jang, J. Jang, T. Jeon, H. Lee, and W. Choe ( ) S. G. Lee, C. R. Seon, J. Kim, ( ) 마스터부제목스타일편집 I. N. Bogatu ( ) S. Henderson and M. O Mullane ( ) D. Pacella ( )

2 Outline 1. Introduction - Current issues on W in tokamak plasmas 2. Current analysis tools for impurity transport study on KSTAR - ADAS-SANCO impurity code analysis - Diagnostics: SXR and VUV 3. Preparation of W experiments - Development of W injection system - Upgrading diagnostics : SXR and VUV - Estimation of Ar & W emission power on KSTAR for designing SXR filters 4. Summary

3 Impurities in fusion plasmas Origin of Impurities - Plasma-wall interaction: C, Fe, Be, W, - Fusion reaction: He (alpha particle) - Deliberately introduced: Ne, Ar, Si Effects in tokamak - Diluting fuel ions and reducing heating efficiency & plasma reactivity - Enhancing radiation power losses especially in the core by central accumulation - Can be used for diagnostic purpose and shielding of the wall from excessive load Ideal impurity profile - Mantle in the Edge - Low in the Core ne (r) nimp (r) It is important to understand transport of impurities in order to prevent central accumulation and its negative consequences r/a

4 Current issues on W in tokamak plasmas Influence of W divertor on the access to the H-mode Effect of W divertor on pedestal parameters and plasma confinement Predicted impacts of wall and divertor material on pedestal structure High radiation loss from W core accumulation R. Neu, ADAS Workshop, 2007, Ringberg ITPA: Transport of high Z impurities (including W) in the core plasma and possibilities for its control W injection experiments on KSTAR (superconducting machine)

5 Current analysis tools for impurity transport study on KSTAR - Focused on Ar injection experiments Transport codes (ADAS-SANCO) Diagnostics (SXR & VUV)

6 Impurity transport analysis SANCO (collaboration with JET) 1D radial continuity equation - Radial particle flux Diffusion coefficient : impurity ion density : particle flux via magnetic surface : source and sink (ionization & recombination from ADAS) Convection coefficient Experimental data Fitting Impurity transport modelling KSTAR diagnostics - Soft X-ray array - VUV spectrometer - X-ray imaging crystal spectrometer, etc D, V determination - Impurity transport code SANCO - Fitting analysis code UTC

7 Soft X-ray arrays with Ar Ross filter KSTAR D-port X-ray Ross Filter (XRF) NaCl and CaF 2 Band pass filter within the narrow region between their L III or K absorption edges 16 ch (32) HU HD 16 ch (32) kev Ar 13+, Ar 14+, Ar 15+, mainly Ar 16+, Ar 17+

8 Model for Ar emission in soft X-ray range (1) Calculation of local Ar radiation power (r,t) Power coeffs of Line Transition Power coeffs of RecomBination (2) Response function of Ross filter (3) LoS calculation and line integration

9 ITER VUV spectrometer prototype Collaboration with ITER KO-DA (C.R. Seon) Current (15-60 nm, ~13-40 ms) (1) Measurable major line transitions VUV spectrometer on the optical table 1 ch, survey Vacuum extension He I nm He II nm O V : 15.61, 19.28, nm O VI : 17.30, nm C III : nm C IV : 24.49, 38.41, nm C V : 22.72, nm Fe XV : nm Fe XVI : 33.54, nm Ar XIV nm Ar XV nm Ar XVI nm (2) Modeling of Ar line transitions - All atomic coefficients are from ADAS

10 Preparation of W experiments - Development of W injector system - Upgrading current diagnostics (VUV & SXR) - Estimation of W & Ar emission power on KSTAR for designing filters of new SXR system

11 Candidates for the W particle injector Laser blow-off system (C-Mod) - Well controlled temporal form of the source function - Adjustable injecting amount of particles - Difficulties : high cost (laser system), short preparation time Pellet injection (LHD) - Can deposit impurities deep inside the confined plasma - Difficulties : designing of pellet, short preparation time Particle dropper (NSTX) - Simple design, easy to inject W dusts into plasmas - Difficulties : A lack of install locations (need to modify passive stabilizer and upper port of KSTAR) Using H-port halls on PS? It is required to try a simple injector system under the current condition for first W injection experiments on KSTAR.

12 Design of Tungsten Injection System Design goals 1) Flight-distance of particles > 10 cm Injection system will be mounted on the manipulator The manipulator is inserted into the vacuum vessel around 10 cm away from the LCFS. 2) Compact size Gun: diameter ~ 8 mm, length ~ 50 mm Piezo-electric motor (R40NM, Piezo technology ) 10 cm 3) Tolerance for strong B-field & high vacuum environments STS316 Piezo-electric motor (R40NM, Piezo technology ) 4) Reloadable system in preparation 5) Capability to inject a small amount of metal particles

13 Experimental Set-up Target plate position: l =100 mm Central axis (y,z)=(0,0) on the target plate A piezoelectric motor moves the trigger. Pictures of deposited particles on the target plate are taken by a DSLR camera (CANON EOS 500D).

14 Example of Performance Test (y,z)=(0,0): central axis evaluated from edges of injection gun (Injection gun s diameter ~ 8 mm) 0.2 mm diameter of Cu, l = 100 mm Deposited locations Averaged drop Cu particles on the target plate Edges 10 mm To evaluate deposited locations 2-D distribution image z To estimate 2-D distribution y

15 Particle size (W 0.2, 0.1 & 0.06 mm) Target plate: 10 cm away from the injection gun Launched W particles 0.2, 0.1 & 0.06 mm, (10 mg x 5 times = 50 mg) Amount of particles reached to the target plate Less than 2 mg (< 5%) Distribution of l = 10 cm 1) Averaged vertical drop at the target plate mm: Δz = mm mm: Δz = mm mm: Δz = mm 2) Average initial velocity (v 0 ): ignoring air resistance - v 0 ~ 2.3 m/s (like sputtering from wall) z 1 2 gt 2 l v 0 t In the case of W, particle size does not affect change of averaged drop

16 Distribution of W on the target plate I (a) (b) (c) 0.06 Deposited locations of launched W particle on the target plate (a) 0.2 mm, (b) 0.1 mm, and (c) 0.06 mm

17 Distribution of W on the target plate II (a) (b) (c) 0.06 Distribution of launched W particle on the target plate (a) 0.2 mm, (b) 0.1 mm, and (c) 0.06 mm

18 W dust dropper system from NSTX Collaboration with PPPL (NSTX team) Dust selector Compact version Clementson et al. Rev. Sci. Instrum. 81, 10E Vibrator Using KSTAR H-port? (supposed to be used for SXR)

19 VUV imaging spectrometer This summer(5-20 nm, ms) 28 ch, imaging Collaboration with ITER KO-DA (C.R. Seon) Preparation in laboratory Active pixels: 1024 x 256 Pixel size (W x H): 26 x 26 μm Image area: 40 mm x 12mm of MCP adopted to CCD of nm He II from Hollow Cathode Lamp ~5.5 mm Slit Imaged to CCD Slit Pattern Spacing ~ 2mm 5~7 nm quasi-continuum nuum peaks of W are expected 24.6 nm 23.4 nm Clementson et al. Rev. Sci. Instrum. 81, 10E

20 Soft X-ray array system Current This summer 2 arrays, 64ch 4 arrays, 256 ch 1 array, 48 ch VU2 edge 16 ch (32) HU HD 16 ch (32) VD2 HU HD Be filters (10, 50 um) Ar Ross filters ( kev Ar 16+, Ar 17+ ) Bolometer (No filter) 4 arrays, 256 chs 2D Tomography Poloidal asym. study < 2 cm, 2 μs 3 filters multi energy, neural network < 1.3 cm, 2 μs 2D fast MHD & transport study

21 Estimation of W & Ar emission power For designing new multi-array SXR filter to measure W & Ar emission, ADAS-SANCO simulation has been done Input EFIT D, V (Trial value) Background (T e, n e ) Impurity Influx T e, n e n z (r, t) SANCO Calculates - n z (r, t) for every charge states z of W & Ar ADAS Calculates line emission for every line transition Line integration along LOS Final power spectrum of W & Ar

22 Input profiles for ADAS-SANCO (1) T e & n e profiles of typical KSTAR L-mode and H-mode - Evaluated by ECE, TS, interferometer L-mode H-mode L-mode H-mode n e [ m -3 ] T e [kev] r/a (2) Influx : flow meter signal for both W & Ar r/a (3) EFIT Recycling rate Ar = 0.6 W = s By S. Sabbagh

23 Input profiles for ADAS-SANCO - D & V for L mode (experimentally obtained from KSTAR #7574 Ar) Diffusion (m 2 /s) Convection (m/s) r/a - D & V for H mode (from ASDEX-U results) r/a T. Putterich, 2005, Investigations on Spectroscopic Diagnostic of High-Z Elements in Fusion Plasmas, PhD Thesis University Augsburg

24 W & Ar emission spectrum under KSTAR condition L-mode case H-mode case W cm- W/cm 2 ev 3-1 ev W quasi-continuum nuum (VUV) W peaks Ar peaks (Ross filter) W W/cm cm- 2 ev 3 ev W peaks Ar peaks (Ross filter) X-ray energy (kev) X-ray energy (kev) Continuum radiation was calculated by where Z eff ~ 2.5 with C dominant situation S. von Goeler et al., Nucl. Fusion 15, 301 (1975)

25 Expected studies 1. Z-dependence study of impurity transport JET result - Simultaneous injection of Ar & W for the 2014 campaign Closed symbol: [Dmeas, Vmeas] Open symbol: [Dmeas, Vneo] ne /<ne> 0 Giroud C. et al 13 th ITPA Confinement Database & Modelling Topical Group, Naka, Japan H Nordman et al, 2011 Plasma Phys. Control. Fusion - Various turbulent-based transport theories have been trying to estimate impurity transport with varying Z. Nevertheless, there is no theory explaining experimental results well. - It is required to have more experimental data to develop and revise impurity transport models.

26 Expected studies 2. Control impurity transport by applying auxiliary power 4.5 x No ECH Total Ar Ar +16 Ar x On-axis ECH Total Ar Ar +16 Ar #/m #/m r/a Controllability of Ar impurity was confirmed by ECH on KSTAR. - Applying ICRH, ECCD as well. - Effects on not only Ar but also W. 3. Effects of RMP on impurity transport - Find out the relationship and mechanism between magnetic perturbation and impurity transport from edge (ELM) to core (impurity accumulation). - Applying MP after injection and before injection. r/a

27 Expected studies 4. Impurity formation of poloidal asymmetry H-mode ICRH L-mode C-Mod Mo injection C-Mod, Mo injection M Reinke, et al., E1/E2 Task force meeting Full 2-D tomography reconstruction will be available with vertical arrays Finding poloidal asymmetry of high-z impurities such as W Comparing between Ar & W cases - For various plasma modes and conditions

28 Summary Impurity transport analysis tools on KSTAR - ADAS-SANCO impurity transport code - Soft X-ray array system and VUV spectrometer system - It has well worked for KSTAR Ar injection experiments since W injection experiment is under preparation on KSTAR - Injecting system : W injector gun, W dust dropper (Collaboration with NSTX) - Imaging VUV spectrometer having W quasi-continuum peaks is installed on KSTAR F-port. - Additional SXR arrays will be installed on KSTAR D-port with Be filters for W and Ar measurement. - ADAS database set is also ready for simulating W emissions in fusion plasmas.