ARIES-IFE

1. ARIES-IFE ARIES Project Meeting Georgia Institute of Technology, Atlanta, Georgia September 3-4, 2003 Summary of Issues, Results, Findings and R&D Guidance Farrokh Najmabadi and A. René Raffray University of California, San Diego

2. ARIES Integrated IFE Chamber Analysis and Assessment Research Goals: • Analyze & assess integrated and self-consistent IFE chamber concepts • Understand trade-offs and identify design windowsfor promising concepts. The research was not aimed at developing a point design. • Approach: • • Six classes of target were identified. Advanced target designs from NRL (laser-driven direct drive) and LLNL (heavy-ion-driven indirect-drive) were used as references. • • To make progress, we divided the activity based on three classes of chambers: • - Dry wall chambers; • - Solid wall chambers protected with a “sacrificial zone” (e.g. liquid films); • - Thick liquid walls. • • We researched these classes of chambers in series with the entire team focusing on each concept. • • ARIES core team + contribution from a number of other players in the field.

3. Example Results from ARIES-IFE Effort on Solid Wall Chambers • Evolution of parametric design window for carbon armor in a 6.5 m radius chamber for the 154 MJ direct drive target- Armor survival (including time of flight effect) - Laser breakdown constraint- Target survival

4. 800 mtorr 500 mtorr 200 mtorr 100 mtorr 20 mtorr Example Results from ARIES-IFE Effort on Thin Liquid Wall Chambers • Vapor and aerosol mass histories for a 6.5 m chamber with a flibe wetted wall exposed to the photon threat spectrum of the 400 MJ indirect-drive target- Potentially major effect on choice of mode of transport and focusing of heavy ion driver based on pre-shot chamber gas density - Neutralized ballistic transport: <1 mtorr - Channel transport: <1 torr. - Self-pinched transport: < 100 mtorr.- Need better understanding of aerosol behavior including coagulation at wall

5. ARIES-IFE Effort on Thick Liquid Wall Chambers Major Processes and Areas of Study • Indirect-drive target - material choice - constraints on chamber conditions • Heavy-ion beam - study of transport modes - requirements on chamber conditions • Liquid wall ablation mechanisms - evaporation, explosive boiling - spalling • Chamber dynamics - aerosol formation and behavior - condensation and chamber clearing • Liquid jet reformation and droplet formation • Shielding of driver components - final focus magnet • Choice of chamber structural materials

6. Indirect Drive Target • Key Issues - material choice - constraints on chamber conditions • Results and Findings - single use better than recycling - window of material choice exists - in-chamber tracking not needed for gas densities < ~ 1g/cm3 in a 3 m chamber • R&D Guidance - final selection requires overall system study • Documentation - partly in wetted wall paper - material choice to be included in overall thick liquid wall paper

7. Heavy-Ion Beam Driver • Key Issues - mode of transport - constraints on chamber conditions • Results and Findings - neutralized-ballistic transport is main approach but tight constraint on vacuum (1 mtorr) - pinch transport are higher risk, higher payoff alternatives (channel: 100 mtorr, self-pinch: 1 torr) but need to improve transport efficiency - not much flexibility in relaxing requirements on chamber conditions • R&D Guidance - need focused modeling & experimental studies of assisted-pinch and self-pinch transport for further evaluation and improvement • Documentation - assisted pinch transport paper already prepared? - possible self-pinched paper to be added? - material choice to be included in overall thick liquid wall paper

8. Liquid Wall Ablation Mechanisms • Key Issues - evaporation and explosive boiling - shock-wave induced spalling • Results and Findings - >~100 mm of ablated thickness due to explosive boiling in flibe at 0.5 m from center --> leads to large impulse and shock wave - will shock wave be dampened as it traverses the thick liquid jet? - for free liquid jet, fracture occurs at the back of the jet following rarefaction wave formation - will spalled material be cleared as pocket reforms or will it reach region outside the pocket and possibly affect driver transmission? - vapor cloud from photon energy deposition will absorb most of the debris ion energy reducing the total amount of evaporated liquid • R&D Guidance - need combination of experimental and modeling studies to better understand and evaluate mechanisms under IFE like conditions - experiments in facilities reproducing IFE photon energy deposition and time scale such as in a laser facility • Documentation - full journal paper being prepared - also briefly summarized in town meeting paper

9. Chamber Dynamics • Key Issues - aerosol formation and behavior - condensation and chamber clearing • Results and Findings - need to prevent debris accumulation in beam access region - need condensation surfaces for droplets ablated from inner surface of the pocket and venting through jet array • R&D Guidance - aerosol behavior in out-of-pocket region needs to be better understood - comprehensive model required including ablation source term, gas dynamics, condensation and aerosol formation and dynamics - condensation dynamics for prototypical material and conditions needs to be studied experimentally • Documentation - as part of town meeting paper

10. Liquid Jet Dynamics • Key Issues - liquid jet reformation - droplets formation • Results and Findings - possible droplets formation from criss-crossing series of jet could lead to unacceptable aerosol densities affecting driver transmission • R&D Guidance - Combination of scaled experimental and modeling studies to better understand droplet formation and behavior in a chamber-like jet geometry • Documentation - partly in overall thick liquid wall paper - fully described in separate paper?

11. Shielding of Driver Components • Key Issues - final magnet shielding • Results and Findings - should liquid shield be replaced by solid shielding block? • R&D Guidance - • Documentation - as part of overall thick liquid wall paper

12. Structural Material Assessment • Key Issue - Choice of structural material for thick liquid wall chamber of HYLIFE IFE power plant • Results and Findings - Initial choice of 304SS to alleviate need for advanced structural material development. However, this raises possible swelling, activation and He embrittlement concerns - Swelling and activation issues could perhaps be alleviated by compliant design and drastically reducing Nb and Mo impurities - He embrittlement issue and thermal creep limits would seriously impact the operating temperature window (<~550C) when utilized in conjunction with a flibe blanket - Recommendation that other structural materials (in particular ODS FS) be considered for power plant application • R&D Guidance - R&D info on advanced structural material, including ODS FS • Documentation - already documented as a UCSD technical report - part of overall thick liquid wall paper

13. Suggested List of Papers for ARIES-IFE Study on Thick Liquid Wall Overall thick liquid wall paper: “Title to be confirmed” Chamber dynamics paper based on town meeting presentations and discussion: “Thick Liquid Wall Chamber Dynamics: Key Issues, Existing Models and Experiments, and Future R&D” Paper on ablation mechanisms: “IFE Liquid Wall Response to the Prompt X-ray Energy Deposition:Investigation of Physical Processes and Assessment of Ablated Material” Paper on liquid jet dynamics including droplet formation: (separate or as part of overall paper?) 5. Other paper(s)?

14. “Thick Liquid Wall Chamber Dynamics: Key Issues, Existing Models and Experiments, and Future R&D” R. Raffray, W. Meier, S. Abdel-Khalik, R. Bonazza, P. Calderoni, C. Debonnel, Z. Dragojlovic, L. El-Guebaly, D. Haynes, J. Latkowski, C. Olson, P. Peterson, S. Reyes, P. Sharpe, M. Tillack and M. Zaghloul Outline (some sections already written) • Introduction (~1 page) • 2. TLW Chamber Concept and Operation (~2 pages) • - General description of TLW concept • - Example HYLIFE-II design with HI driver and ID target • - Driver and target constraints • 3. Chamber/Liquid Wall Dynamics (~5-7 pages) • Describe mechanisms with illustrative analytical results (as needed) • - Liquid wall response to threats and early chamber dynamics (to ~1 ms) • - Chamber clearing mechanisms (to ~100 ms) • 4. Existing Models (~5-7 pages) • (capabilities to simulate mechanisms described above, example results • and planned improvement) (~0.5-1 page per model) • 5. Existing Experimental Facilities (~5-7 pages) • (capabilities to simulate and measure mechanisms described above, • 6. R&D Needs • 7. Conclusions

15. “IFE Liquid Wall Response to the Prompt X-ray Energy Deposition:Investigation of Physical Processes and Assessment of Ablated Material”M. Zaghloul, R. Raffray, and the ARIES Team Outline (paper being written) 1. Introduction 2. X-ray Energy Deposition - X-ray Spectra - Photon Energy Deposition in The Cavity and Wall - Cold Opacities of Candidate Materials - Profiles of the Percentage of Energy Deposition in the Cavity and Wall 3. Wall Response (Physical Processes and Material Removal Mechanisms) - Thermal Response and Phase Transitions - Normal (Surface) Vaporization - Normal Boiling (Vaporization into HeterogeneousNuclei) - Phase Explosion (Explosive Boiling) and HomogeneousNucleation - Mechanical Response and Ruptures - Fractures and Spall 4. Material Properties - Relevant Material Properties of Candidate Materials - Theoretical Spall Strength and EOS 5. Modelling Approaches - Volumetric vs. Kinetic - Justification for the Volumetric Approach 6. Scoping Results - Results for different ablated amounts - Pb, flibe - Comparison with ABLATOR 7. Discussion and Conclusions