Pathways towards break even for low convergence ratio direct-drive inertial confinement fusion

Journal of Plasma Physics Cambridge University Press 88:3 (2022) 905880314

Authors:

Rw Paddock, H Martin, Rt Ruskov, Rhh Scott, W Garbett, Bm Haines, Ab Zylstra, Em Campbell, Tjb Collins, Rs Craxton, Ca Thomas, Vn Goncharov, R Aboushelbaya, Qs Feng, Mw von der Leyen, I Ouatu, Bt Spiers, R Timmis, Rhw Wang, Pa Norreys

Abstract:

Following indirect-drive experiments which demonstrated promising performance for low convergence ratios (below 17), previous direct-drive simulations identified a fusion-relevant regime which is expected to be robust to hydrodynamic instability growth. This paper expands these results with simulated implosions at lower energies of 100 and 270 kJ, and ‘hydrodynamic equivalent’ capsules which demonstrate comparable convergence ratio, implosion velocity and in-flight aspect ratio without the need for cryogenic cooling, which would allow the assumptions of one-dimensional-like performance to be tested on current facilities. A range of techniques to improve performance within this regime are then investigated, including the use of two-colour and deep ultraviolet laser pulses. Finally, further simulations demonstrate that the deposition of electron energy into the hotspot of a low convergence ratio implosion through auxiliary heating also leads to significant increases in yield. Results include break even for 1.1 MJ of total energy input (including an estimated 370 kJ of short-pulse laser energy to produce electron beams for the auxiliary heating), but are found to be highly dependent upon the efficiency with which electron beams can be created and transported to the hotspot to drive the heating mechanism.

L-Shell X-ray conversion yields for laser-irradiated tin and silver foils

Laser and Particle Beams Hindawi 2022 (2022) 3234804

Authors:

Rl Singh, S White, M Charlwood, Fp Keenan, C Hyland, D Bailie, T Audet, G Sarri, Sj Rose, J Morton, C Baird, C Spindloe, D Riley

Abstract:

We have employed the VULCAN laser facility to generate a laser plasma X-ray source for use in photoionization experiments. A nanosecond laser pulse with an intensity of order 1015 Wcm−2 was used to irradiate thin Ag or Sn foil targets coated onto a parylene substrate, and the L-shell emission in the 3.3–4.4 keV range was recorded for both the laser-irradiated and nonirradiated sides. Both the experimental and simulation results show higher laser to X-ray conversion yields for Ag compared with Sn, with our simulations indicating yields approximately a factor of two higher than those found in the experiments. Although detailed angular data were not available experimentally, the simulations indicate that the emission is quite isotropic on the laser-irradiated side but shows close to a cosine variation on the nonirradiated side of the target as seen experimentally in the previous work.

An Experimental Study of Magnetic Flux Penetration in Radiatively Driven Plasma Flows

Institute of Electrical and Electronics Engineers (IEEE) 00 (2022) 1-1

Authors:

JWD Halliday, A Crilly, J Chittenden, S Merlini, S Rose, D Russell, LG Suttle, RC Mancini, V Valenzuela-Villaseca, SN Bland, SV Lebedev

Absolute calibration of Fujifilm BAS-TR image plate response to laser driven protons up to 40 MeV

Review of Scientific Instruments American Institute of Physics 93:5 (2022) 53303

Authors:

P Martin, H Ahmed, D Doria, A Alejo, R Clarke, S Ferguson, J Fernández-Tobias, Rr Freeman, J Fuchs, A Green, Js Green, D Gwynne, F Hanton, J Jarrett, D Jung, Kf Kakolee, Ag Krygier, Cls Lewis, A McIlvenny, P McKenna, Jt Morrison, Z Najmudin, K Naughton, G Nersisyan, P Norreys, M Notley, M Roth, Ja Ruiz, C Scullion, M Zepf, S Zhai, M Borghesi, S Kar

Abstract:

Image plates (IPs) are a popular detector in the field of laser driven ion acceleration, owing to their high dynamic range and reusability. An absolute calibration of these detectors to laser-driven protons in the routinely produced tens of MeV energy range is, therefore, essential. In this paper, the response of Fujifilm BAS-TR IPs to 1-40 MeV protons is calibrated by employing the detectors in high resolution Thomson parabola spectrometers in conjunction with a CR-39 nuclear track detector to determine absolute proton numbers. While CR-39 was placed in front of the image plate for lower energy protons, it was placed behind the image plate for energies above 10 MeV using suitable metal filters sandwiched between the image plate and CR-39 to select specific energies. The measured response agrees well with previously reported calibrations as well as standard models of IP response, providing, for the first time, an absolute calibration over a large range of proton energies of relevance to current experiments.

Production of high fluence laser beams using ion wave plasma optics

Applied Physics Letters AIP Publishing 120 (2022) 200501

Authors:

Robert Kirkwood, Patrick Poole, Dan Kalantar, Thomas Chapman, Scott Wilks, Matthew Edwards, David Turnbull, Pierre Michel, Laurent Divol, Nathaniel Fisch, Peter Norreys, Wojciech Rozmus, Jeffrey Bude, Brent Blue, Kevin Fournier, Bruno Van Wonterghem, Andrew MacKinnon, Peter Norreys

Abstract:

Optical components for laser beams with high peak and averaged powers are being developed worldwide using stimulated plasma scattering that occurs when plasmas interact with intense, coherent light. After decades of pursuit of pulse compressors, mirrors, and other plasma based components that can be created by stimulated scattering from electron density perturbations forming on ultra-short time scales (e.g., via Stimulated Raman Scattering), more recent work has produced optical components on longer time scales allowing ion motion as well [via Stimulated Brillouin Scattering (SBS)]. In the most recent work, ion wave plasma optics have had success in producing pulses of focusable coherent light with high energy and fluence by operating on ns time scales and now promise to enable numerous applications. Experiments have further shown that in some parameter regimes, even simple plasma response models can describe the output of such optics with sufficient accuracy that they can be used as engineering tools to design plasma optics for future applications, as is already being done to control power deposition in fusion targets. In addition, the development of more sophisticated models promises to enable still higher performance from SBS driven plasma optical components under a wider range of conditions. The present status and most promising directions for future development of ion wave plasma optic techniques are discussed here.