ILE Osaka Concept of KOYO-F and Formation of Aerosols and Micro Particles T. Norimatsu Presented at TITAN workshop on MFE/IFE Common Research UCSD, Feb , 2009

ILE Osaka Common task on TITAN To construct system integration model on tritium and thermo fluid system Identify key issues & design priorities Identify baseline design(s) - FFHR, ARIES - KOYO Assess concept attractiveness & feasibility Perform analysis of key issues Goal Now….

ILE Osaka Outline Introduction of KOYO-F and the critical issues Researches on chamber clearance –Code development (by H. Furukawa, ILT) Experimental check 1 (by T. Norimatsu) Experimental simulation with laser ablation (to be presented by K. A. Tanaka) –Experimental simulation on hydrodynamic instabilities on ablation by alpha particles (by Y. Shimada, ILT)

ILE Osaka Conceptual laser fusion reactor KOYO-F based on fast ignition Electrical output power 1200 MW Target gain 167 Fusion yield 200MJ/shot Laser 1.2 MJ x 16Hz,12% 4 modular reactors with 32 compression beams and 1 ignition beam System efficiency 40%

ILE Osaka Reactor with cascade flow of liquid LiPb Coolant Li 17 Pb 83 Chamber/Blanket wall Ferrite / SiC/SiC Fusion yield 200 MJ x 4 Hz Thermal output 916 MW Chamber size (inner/outer/high) 3m / 5m/14m  pulse load 0.3 MJ/m 2  peak load 2 x W/m 2 Average thermal load 1.2 MW/m 2 Neutron load 5.6 MW/m 2 Solid angle of beam ports < 5% TBR 1.3

ILE Osaka KOYO-F with 32 beams for compression and one heating beam Vertically off-set irradiation Cascade surface flow with mixing channel SiC panels coated with wetable metal Tilted first panel to make no stagnation point of ablated vapor Compact rotary shutters with 3 synchronized disks Chamber

ILE Osaka The surface flow is mixed with inner cold flow step by step to reduce the surface temperature Chamber If the surface flow is a laminar flow, vapor pressure is too high to reach designated pressure of 5-10 Pa.

ILE Osaka Thermal flow of KOYO-F Chamber  t=0.5 o C/shot  t=1.3 o C/shot Thermal shock in closed blanket  p=0.1MPa

ILE Osaka Critical issues in chamber 1 (from J-US WS on reactor 2007) Probability for direct exposure of the same place <1/10 3 – 1/10 4 –If we assume maintenance period of 2 years and acceptable erosion of 3-mm-thick, the probability for direct exposure of the same place with  particles must be less than 1/10 4. –Improve flow control, material selection, chamber radius Protection of beam ports –Our first plan was to keep the surface temperature less than surrounding area to enhance the condensation. But this would not work because of the small temperature dependence of condensation. –Porous metal saturated with liquid LiPb –Magnetic field Dry surfaceLiquid LiPb Dr Kunugi demonstrated a stable flow >3 mm using water Dr. Kajimura showed protection of the beam port by a 1T magnetic field.

ILE Osaka Critical issues in chamber 2 (from J-US WS on reactor 2007) Chamber clearance –Formation of aerosols –Large ( ~10  m) particles due to RT instabilities and related secondary particles Tritium diffusion through the heat cycle –To be solved during TITAN

ILE Osaka Outline Introduction of KOYO-F and the critical issues Researches on chamber clearance –Code development (by H. Furukawa, ILT) Experimental check 1 (by T. Norimatsu, ILE) Experimental simulation with laser ablation (to be presented by K. A. Tanaka, Osaka U.) –Experimental simulation on hydrodynamic instabilities on ablation by alpha particles (by Y. Shimada, ILT)

ILE Osaka We estimated the ablation process using ACORE. Stopping power in ionized vapor was calculated. Ionization rate of Pb Ziegler’s model Present model

ILE Osaka ACONPL (Ablation and CONdensation of a PLume) p 11

ILE Osaka Treatment of Phase Transition in ACONPL p 12 ○ Equation of Motion of Ablation Surface ( The boundary of liquid and neutral gas or plasma ) L v : Latent Heat of Vaporization T v : Temperature of Ablation Surface ○ Equation of Energy in Liquid T vap : Vaporization Temperature If U l >U l crt, Peeling will occur. Q p : Heat quantity due to charged particles Q x : Heat quantity due to absorption of X-ray

ILE Osaka Treatment of Hydro Dynamics in ACONPL ○ 1 Fluid and 2 Temperature Model, Lagrange Scheme P nv : numerical viscosity Vaporization Temperature ( Condensation Temperature ) q : Latent heat of Vaporization （ Kelvin) 4-th term of right hand side is temperature increment due to phase transition from gas to liquid (clusterization).

ILE Osaka p 16 q : Latent Heat of Vaporization （ Kelvin) ◯ Two-Phase Mixture Effects Temperature of Clusters Condensation Rate Rate of Nucleation Cluster Growth Super Cooling Parameter Reference B. S. Luk’yanchuk, S. I. Anisimov et. al., SPIE 3618 (1999) Condensation of a Plume ◯ Condensation Temperature

ILE Osaka To check the code, 10  m thick Pb membrane was heated and aerosols were captured on a witness plate.

ILE Osaka There is geometrical effect on the diameter of particles. Geometrical effect The minimum diameter gives aerosol diameter. Model for large particles

ILE Osaka Diameter of particles agreed with simulation result. Particles on continuous membrane The continuous membrane was formed with leading, super-cooled plume.

ILE Osaka Density, Temperature and velocity profile of ablated material.

ILE Osaka Density, Temperature and velocity profile of ablated material Time = 2000 ns Number Density T e v (m/s) x (cm)

ILE Osaka Number density at the next target injection is estimated to be 10 7 /cm 3. If interaction with opposite plume, clusters in this region will disappear after collisions with the opposite wall. Clusters in this region expand to chamber volume before next target injection. The resulting n c at the next target injection is; 50  m 8 X 10 6 /cm 3

ILE Osaka Influence of aerosols on target injection can be ignored. Chamber centerWall N c =10 7 cm 3 3m Total mass of aerosols in the column 1.06 x g Target mass Aerosol mass = 2 x (0.4  m in the thickness of deposition layer) We can ignore the influence on target trajectory.

ILE Osaka Future work Influence of ions as “seeds” for clusters In this simulation, clusters move with fluid. –PIC code Interaction with opposite plume –Stagnation at the center –Condensation on the opposite wall

ILE Osaka Outline Introduction of KOYO-F and the critical issues Researches on chamber clearance –Code development (by H. Furukawa, ILT) Experimental check 1 (by T. Norimatsu) Experimental simulation with laser ablation (to be presented by K. A. Tanaka) –Experimental simulation on hydrodynamic instabilities on ablation by alpha particles (by Y. Shimada, ILT)

ILE Osaka To understand the ablation phenomena by alpha particles, we used laser backlighting. To know the influence of internal hot zone due to Bragg’s peak, we used back-light heating of Pb membrane. Electric discharge was used to check simulation code for aerosol formation. Particle loadsEnergy deposition Volumetric heating Bragg’s peak

ILE Osaka Experimental setup. Laser-scattering measurement was used to observe flying situation of metal Punch out laser 50 mm Probe laser 2×10 -4 torr Nd:YAG laser Intensity: 0.5 – 1 GW/cm 2 Spot size :  m φ Pulse duration : 15 ns Cylindrical lens CCD camera Scattered lights Target (glass plate with coated tin or lead) 27 Line focus 9  s 12  s 15  s Laser Glass plate Dot target Diameter ：  500  m (smaller than laser spot size)

ILE Osaka Spouted gas and small particles, and large particles were detected at 10-mm away from glass plate 10 mm 2  s 4  s 6  s 8  s 10  s 12  s 500  m 6s6s 800  m 9s9s 12  s Averaged density 2×10 18 (cm -3 )  s Diameter ~10 μm Gases Gases small particles Large particles

ILE Osaka RT instability and break up would make larger( 3  m), slow ( m/s) particles. Dot target Laser High speed gases RT Instability Gas, clusters Small particles Large particles High density columns Glass plate Depend on thickness of target etc. λ few joules energy It may cause secondary ablation of panel 29 big particles 3km/s 0.5km/s

ILE Osaka Stagnation at the center needs more analysis Laser back lightingElectric discharge cos  cos n  Volumetric heating Planer heating Tilted first panel concept may reduce the stagnation to 1/5 of cylinder case. Recently we started simulation on collisions of plumes. Preliminary result indicates condensation and formation of droplets are not critical because the kinetic energy of leading plume is much higher than latent heat of condensation. 80% 20% (At end of after glow)

ILE Osaka Summary Aerosols and particles –In KOYO-F, the diameter of aerosols 100 – 200 nm –No influence on target trajectory and performance if we ignore the interaction with opposite plume. Hydrodynamic process must be considered to discuss formation of particles. Remaining issue: Secondary particles More detailed estimation of stagnation at the chamber center 31

ILE Osaka Cooled Yb:YAG ceramic laser will be used for both compression and ignition beams. Lasers 60kJ x 8 beams Fiber Oscillator Pre-Amplifier (~ kJ, NIR) Main-Amplifier (~ MJ, NIR) 3rd Harmonics 2nd Harmonics Pulse Compressor compression Laser (1.1MJ, blue, ns) Heating Laser (0.1MJ, NIR, ps) OPCPA Pulse Stretcher Mode-lock Oscillator Compression laser 1.1 MJ, 12% Heating laser 0.1 MJ, 5%

ILE Osaka Target for KOYO-F Tritium burn ratio 23%