Surface Wall Load due to Bremsstrahlung & Line Radiation

Transcription

1 Surface Wall Load due to Bremsstrahlung & Line Radiation Tetsuya Uchimoto APEX Study Meeting University of California Los Angeles November 2-4, 1998

2 Background & Objectives The operation of the liquid first wall may be strongly affected by the surface heat flux which is mainly caused by the Bremsstrahlung and line radiation and depends on the plasma operations and impurity ion penetration from liquid first wall. In order to provide the surface heat flux for the design of liquid blanket / first wall system, spectra of Bremsstrahlung and line radiation are estimated in the configuration of ARIES-RS, considering the impurity penetration from liquid first wall. In addition, the effect of high-z plasma operation on wall load is examined since high-z operation will increase the surface heat flux.

3 Description of Emission & Absorption Coefficients Emission and absorption coefficients κ () v, ε( v) of radiation were estimated using IONMIX code. g njk () bb κ v = nnjk n mjk α nm( v) k j n m> n gmjk n> n * bf [ n n exp( hv / k T )] α ( v) njk njk ( 1 exp( hv k T ))} ff ne n j+ 1, kα ( v) / 3 2hv g njk () bb ε v = n mjk αnm( v) 2 c k j n m gmjk n> n n * njk exp bf ( hv / k T ) α ( v) B B B n n ( hv k T )} ff ne n j+ 1, kα ( v) exp / B α bb bf ff ( v), α ( v), α ( v) : Cross sections for bound-bound, bound-free, free-free transitions Fraction of each ionization state was estimated assuming coronal equilibrium. Transport effects were not included in this analysis.

4 Description of Radiation Transfer Surface load was computed by solving the radiation transfer equation. Transfer equation : di ( v) = ε ( r, v) κ ( r, v) I ( v) dx a z r Z φ x y Z radiation β Specified intensity of radiation is I( φ, β ) = a asinφ sin β + exp ε ( r) rdr exp / 2 ( ) r a sin φ r sin β ( r a sin φ ) a asinφ sin β Radiation flux W (v) is a κ ( r ) r dr r κ ( r ) r dr κ ( r ) r dr ( ) ( ) / / 2 r a sin φ asinφ sin β r a sin φ 1/ 2 W ( v) = I( φ, β, v) cosϕ dω

5 Parameters Parameters in this analysis follows ARIES-RS design. The geometry of plasma was reduced to straight circular cylindrical with a radius of 2 m. The temperature and density profiles were parabolic, 2 ( 1 ( r / a) ), X T e ne X = X, 0 = R=2m Minor radius,a (m) 2.0 ( a = a κ =1.8) Temperature, < T > (kev) 14 Temperature profile peaking factor, T o / < T > 2 Edge temperature, T ea (kev) 0.1 Density, < n > ( m 3 ) 2.3 Density profile peaking factor, n o / < n > 2 Edge density, n ( m 3 ) 0.62 ( n ea / neo =0.2) ea Plasma main parameters

6 Comparison between ITER and ARIES-RS Radiated energy flux (MW Hz 1 m 2 ) H 64% He 10% Be 2% C 1% Ne 0.2% ARIES RS ITER Radiated energy flux (MW m 2 ) ARIES RS ITER Total ITER 0.11 MW/m2 ARIES 0.34 MW/m2 X ray and UV spectrum of the radiation losses from ITER and ARIES main plasma. Cumulative integral of X ray and UV spectrum of the radiation losses from main plasma.

7 Consideration of Liquid Wall and High Impurity Operation 1) Liquid Wall Fraction of Z due to the liquid wall impurity was assumed 1%, which corresponds to the operation temperature of 500 o C for Li and 600 o C for Flibe. 2) High Impurity Operation Parametric survey of Ne fraction was conducted to see the change of spectrum. Three cases (0.2%, 0.5%, 1%) were considered.

8 Effect of Li or Flibe wall on radiation losses Radiated energy flux (MW Hz 1 m 2 ) ARIES RS No Liquid Wall Li wall Flibe wall Radiated energy flux (MW m 2 ) ARIES RS Total No wall MW/m2 Li MW/m2 Flibe MW/m2 No Liquid Wall Li wall Flibe wall X ray and UV spectrum of the radiation losses from ARIES main plasma. Cumulative integral of X ray and UV spectrum of the radiation losses from main plasma.

9 High impurity operation (Li wall) 10 0 Radiated energy flux (MW Hz 1 m 2 ) ARIES RS Ne 0.2 % Ne 0.5 % Ne 1 % Radiated energy flux (MW m 2 ) ARIES RS Total 0.2 % MW/m2 0.5 % MW/m2 1.0 % MW/m2 Ne 0.2 % Ne 0.5 % Ne 1.0 % X ray and UV spectrum of the radiation losses from ARIES main plasma. Cumulative integral of X ray and UV spectrum of the radiation losses from main plasma.

10 Hi impurity operation (FLIBE wall) 10 0 Radiated energy flux (MW Hz 1 m 2 ) ARIES RS Ne 0.2 % Ne 0.5 % Ne 1 % Radiated energy flux (MW m 2 ) ARIES RS Total energy 0.2 % MW/m2 0.5 % MW/m2 1.0 % MW/m2 Ne 0.2 % Ne 0.5 % Ne 1.0 % X ray and UV spectrum of the radiation losses from ARIES main plasma. Cumulative integral of X ray and UV spectrum of the radiation losses from main plasma.

11 Power Deposition Rate (Li wall) Power Deposition Rate, W/cc 10 4 Ne 0.2 % Ne 0.5 % Ne 1.0 % Distance from surface (m)

12 Conclusions Bremsstrahlung and line spectra do not change considerably due to the impurity penetration from Li or Flibe walls as far as their Z-fractions are less than 1% Both Bremsstrahlung and line radiation will be increased by adding Ne. However, transport effects should be included in the calculation to obtain accurate wall load.