Experimental evaluation of W 45+ recombination and W 44+ Ionization - PowerPoint PPT Presentation

14SEP2015 IAEA CM on W Deajeon, KAERI, Korea � Experimental evaluation of W 45+ recombination and W 44+ Ionization cross-sections T. Nakano Japan Atomic Energy Agency Acknowledgements Dr. N. Nakamura (Univ. of Electro-Communications) Dr. H. Ohashi (Toyama Univ.)

Tungsten: a candidate for PFCs in reactors � W plasma-facing component ! Merit : high melting point : high heat conductivity : low sputtering yield : low hydrogen (T) retention safety, economy � ⇒ ! Demerit : melting : cracking (Bulk W) : high Z (74) accumulation in plasma core ⇒ highly radiative ( n W / n e < 10 -5 ) ⇒ ⇒ W transport in plasmas For quantitative transport study, absolute W density is required. http://www.iter.org/mach/vacuumvessel �

Various W atomic data needed for W density measurement � W spatial / charge state distribution <= Ioniz/recomb. rates � Ioniz.Eq / Transport model � (Fractional abundance of W q+ ) � nW q+ � nW � nW (total W density) � Plasma � nW q+ � I q+ � (W q+ density) � Line identification Photon Emission Coefficient <= spectral data � <= excitation rate, A coef, Energy level � Collisional-radiatve model �

Availability of W atomic data Spectral data holdings at NIST* � 1 � Spectral data (wavelength, Acoef) : NIST is Worlds’ standard database But still far from ‘a complete set’ 20 � ⇒ Evaluated Atomic number � 40 � Mo � Collisional data ( Ioniz./recomb. Rates ): Derived data( Photon emission coef, 60 � Cooling rates ) : Present tokamak � ADAS high availability W � ⇒ Not evaluated 80 � ITER � *) NIST ASD version5. Charge � 40 � 60 � 80 � 20 � 1 � http://physics.nist.gov/ASD �

W fractional abundance under Ionization equilibrium still different amongst datasets � W Fractional Abundance � 1 46+ � Fractional Abandance 44+ � 45+ � 0.1 0.01 ADPACK 3) � FLYCHK code 1) � 0.001 1 Fractional Abandance 0.1 0.01 LANL code 2) � ADAS 4) � 0.001 10 3 � 10 4 � 10 3 � 10 4 � 3 4 10 10 T e ( eV ) � T e ( eV ) � T e ( eV ) Uncertainty of collisional data ( Ioniz./Recomb. rates ) needed ⇒ Evaluation 3)K. Asmussen, et al., Nucl. Fusion 38 (1998) 967-986. 1)http://nlte.nist.gov/FLY/ 4)T. Puetterich et al PPCF 50 (2008) 085016. � 2)http://aphysics2.lanl.gov/tempweb/lanl/ �

Issue 1: W density measurement � W spatial / charge state distribution <= Ioniz/recomb. rates � Ioniz.Eq / Transport model � 14% � (Fractional abundance of W 54+ ) � nW 54+ � nW � 7% � nW (total W density) � Factor of 2 deviation � Plasma � I 54+ � nW 54+ � Line identification Photon Emission Coefficient <= spectral data � <= excitation rate, A coef, Energy level � Collisional-radiatve model � *H.-K Chung et al., HEDP 9 (2013) 645. �

Issue 2: W cooling rate � -24 3 ) 10 Radative power rate ( W cm L w * ** � L w = ! q L W q+ F a ( q ) -25 10 shifted � -26 10 2 4 6 8 2 4 6 8 2 4 2 3 4 10 10 10 T e ( eV ) Shift of the cooling rates originates from ioniz. Eq calculation *T Puetterich et al Nucl. Fusion 50 (2010) 025012 � **T Nakano et al J. Nucl. Mater 415 (2010) S327 �

Issue 3: W density measurement � x10 -5 � 3 n W / n e from W 45+ line � +50% 20% lower 2 -50% -5 x10 1 0 x10 -5 � 0 1 2 3 -5 n W / n e from W 46+ line x10 Uncertainty of collisional data ( Ioniz./Recomb. rates ) needed *T. Nakano et al 41 st EPS conference (2014), submitted to J. Phys. B

Outline � ! Introduction ! Motivation ! Evaluation of W 44+ ionization / W 45+ recombination - Experiment in Tokyo EBIT device - Calculations for Excitation Auto-ionization and Dielectronic Recombination by FAC - Comparison ! Conclusions

Experimental setup � (W) � W source: W(CO) 6 � Format: 1340 x400 Pixel: 20 µ m Grating: 2400g/mm λ / Δλ = 1100 @ 5 nm Beam Energy : 2.5 – 3.3 keV Energy width : ~ 10 eV Beam Current: 20 – 50 mA * ) H. Ohashi et al, Rev. Sci. Instrum. 82 (2011) 083103

Constant excitation rate ratio of W 44+ and W 45+ useful for direct comparison btw Exp and Theory � Excitation Xsec � Excitation rate � Measurement � I W45+ (6.2 nm): 4s 2 S 1/2 - 4p 2 P 3/2 = 45 + (4s,4p) • n W 45 + (4s) • n e C e I W44+ (6.1 nm): 4s4s 1 S 0 - 4s4p 1 P 1 � Close excitation energy (199 ev and 204 eV) Ioniz. Equi. � ⇒ Similar energy dependence of C e S 44 + → 45 + S 44 + → 45 + (Ioniz.Xsec) � (Ioniz.rate) � ~ 0.43 � • -21 -8 LANL 1.5 1.5 10 10 α 45 + → 44 + α 45 + → 44 + (Recomb.rate) � (Recomb.Xsec) � FAC 3 / s ) 2 ) Ratio of Excitation rates 44+ W ORNL 44+ excitation X sec. eXcitation cross-section ( m Calculation � 44+ W 45+ Excitation rate ( cm W -22 -9 1.0 1.0 10 10 45+ W 45+ / W 44+ ~ 0.44 W -10 -23 0.5 0.5 10 10 45+ / W 44+ ~ 0.43 W 45+ / W -11 -24 0.0 0.0 10 10 1 2 3 4 10 10 10 10 2 3 4 5 10 10 10 10 W E e ( eV ) T e ( eV )

n W 45+ S 44+->45+ S = S direct (DI) + S excit.autoioniz. (EA) = � n W 44+ α 45+->44+ α = α radiative (RR)+ α die-electronic (DR) � -23 10 -24 10 DI -25 10 2 ) Xsec ( m -26 10 -27 10 -28 10 2400 2800 3200 3600 E e ( eV ) 6000 Term energy ( eV ) 4000 - e E e 45+ ) 10 4s Cu-like (W 3d 2000 10 4snl 3d direct ionization: DI 44+ ) 10 4s 2 Zn-like (W 3d 0

n W 45+ S 44+->45+ S = S direct (DI) + S excit.autoioniz. (EA) = � n W 44+ α 45+->44+ α = α radiative (RR)+ α die-electronic (DR) � Term energy ( eV ) 6000 3d excited 3p excited 3s excited 2 nl 3s4s 5 4s 2 nl auto-ionization: 3p 4000 ........ 9 4s 2 nl e ........ 3d ........ 2 4l radiation: 3s4s 5 4s 2 4l 5l 3p 10 4s 3d 2000 9 4s 2 4l 3d 4s nl excitation: 10 4s 2 44+ ) 3d Zn-like (W 0 Ionization � 3d 10 4s 2 = Excitation => 3d 9 4s 2 nl = Auto-ionization => 3d 10 4s 3d 10 4s 2 = Excitation => 3d 9 4s 2 nl = Radiative decay => 3d 10 4s 2 � Excitation & emission � Need branching ratio! �

n W 45+ S 44+->45+ S = S direct (DI) + S excit.autoioniz. (EA) = � n W 44+ α 45+->44+ α = α radiative (RR)+ α die-electronic (DR) � Term energy ( eV ) 6000 3d excited 3p excited 3s excited Total (W 44+ ) � 2 nl 3s4s 5 4s 2 nl auto-ionization: 3p 4000 ........ 9 4s 2 nl e ........ 3d ........ 2 4l radiation: 3s4s 5 4s 2 4l 5l 3p 10 4s 3d 2000 9 4s 2 4l 3d 4s nl Total (W 45+ ) � excitation: 10 4s 2 44+ ) 3d Zn-like (W 0 Cross sections (10 -24 m 2 ) � Excitation Auto-ionisation 3d excited(W 44+ ) � 3p excited(W 44+ ) � 3s excited(W 44+ ) � Electron energy (eV) �

n W 45+ S 44+->45+ S = S direct (DI) + S excit.autoioniz. (EA) = � n W 44+ α 45+->44+ α = α radiative (RR)+ α die-electronic (DR) � -23 20 10 44+ density ratio EA -24 16 10 DI -25 12 10 2 ) Xsec ( m -26 8 10 45+ / W -27 4 10 W -28 0 10 2400 2800 3200 3600 E e ( eV ) Term energy ( eV ) 6000 3d excited 3p excited 3s excited 2 nl 3s4s 5 4s 2 nl auto-ionization: 3p 4000 ........ 9 4s 2 nl e ........ 3d ........ 2 4l radiation: 3s4s 5 4s 2 4l 5l 45+ ) 3p 10 4s Cu-like (W 3d 2000 9 4s 2 4l 3d 4s nl excitation: 10 4s 2 44+ ) 3d Zn-like (W 0

n W 45+ S 44+->45+ S = S direct (DI) + S excit.autoioniz. (EA) = � n W 44+ α 45+->44+ α = α radiative (RR)+ α die-electronic (DR) � -23 20 10 44+ density ratio EA -24 16 10 DI -25 12 RR 10 2 ) Xsec ( m -26 8 10 45+ / W -27 4 10 W -28 0 10 2400 2800 3200 3600 E e ( eV ) 6000 Term energy ( eV ) 4000 - e E e 45+ ) 10 4s Cu-like (W 3d 2000 10 4snl 3d Radiative recombination: RR 44+ ) 10 4s 2 Zn-like (W 3d 0

n W 45+ S 44+->45+ S = S direct (DI) + S excit.autoioniz. (EA) = � n W 44+ α 45+->44+ α = α radiative (RR)+ α die-electronic (DR) � 3s4s 5 4s ........ 3p ........ 9 4s 9 4s 3s4s9l ........ 3d 3d ........ ........ ........ 4s 9l Term energy ( eV ) Term energy ( eV ) Term energy ( eV ) Term energy ( eV ) 6000 6000 6000 6000 ........ 3s4s5l ........ 4s 9l 4s 9l 5 4s 5l 3d excited 3p excited 3s excited 3d excited 3p excited 3s excited 3p 4s 6l 4s 6l 2 10 10 9 4s 5l 9 4s 5l 5 4s 2 3s4s 3d 3d 3d 3d 3p 2 nl 2 nl 46+ ) 2 nl 3s4s 3s4s 9 4s 9 4s 2 2 Ni-like (W 5 4s 5 4s 2 nl 2 nl 3s4s 5 4s 2 nl 3d 3d auto-ionization: A a e D C 3p 3p 4000 4000 4000 4000 3p 6l 6l ........ ........ ........ 9 4s 9 4s 9 4s 9 4s 2 nl 2 nl 2 nl 2 nl e e ........ ........ ........ 3d 3d 3d 3d 5l 5l A r E e ........ ........ 2 4l 2 4l radiation: A a E e A r A r 2 4l 3s4s 3s4s 4l 4l 3s4s 5 4s 5 4s 5 4s 2 4l 2 4l 2 4l 5l 5l 5l 5l 45+ ) 45+ ) 3p 3p 3p 10 4s 10 4s 10 4s 10 4s Cu-like (W Cu-like (W 3d 3d 3d 3d 2000 2000 2000 2000 9 4s 9 4s 9 4s 9 4s 2 4l 2 4l 2 4l 2 4l 45+ ) 3d 3d 3d 3d 4s nl 4s nl 4s nl Cu-like (W excitation: 10 4s 10 4s 10 4s 10 4s 2 2 2 2 44+ ) 44+ ) 44+ ) 3d 3d 3d 3d Zn-like (W Zn-like (W Zn-like (W 0 0 0 0 44+ ) Zn-like (W Nothing changes � 3d 10 4s = e capture => 3d 9 4s 2 nl = Auto-ionization => 3d 10 4s 3d 10 4s 2 = Excitation => 3d 9 4s 2 nl = Radiative decay => 3d 10 4s 2 � DR �

Comparison of W 45+ DR via 3d 9 4l 4l’ � 4 � DR Cross sections (10 -24 m 2 ) � E. Behar JQSRT 58 449 (1997) � Present � 2 � 0 � Electron energy (eV) �

Comparison of W 45+ DR via 3p 5 4l 4l’ � DR Cross sections (10 -23 m 2 ) � 3 � E. Behar JQSRT 58 449 (1997) � 2 � Present � 1 � 0 � Electron energy (eV) �