An Overview of Laser-Driven Magnetized Liner Inertial Fusion on OMEGA 4 compression beams MIFEDS coils B z ~ 1 T Preheat beam from P9 1 mm Ring 3 Rings 4 Ring 3 Target support Fill-tube pressure transducer J. R. Davies University of Rochester Laboratory for Laser Energetics 46th Annual Anomalous Absorption Conference Old Saybrook, CT 1 6 May 216 1
Summary Laser-driven magnetized liner inertial fusion (MagLIF) is being developed on OMEGA to study MagLIF scaling A energy scaled point design for laser-driven MagLIF on OMEGA has been developed that is 1 smaller in linear dimensions than Z targets* The key elements of preheating to >1 ev and uniform cylindrical compression at ~1 km/s have been demonstrated in experiments The first integrated laser-driven MagLIF experiment will be carried out later this year E24972 * S. A. Slutz et al., Phys. Plasmas 17 5633 (21); M. R. Gomez et al., Phys. Rev. Lett. 113 1553 (214); P. F. Schmit et al., Phys. Rev. Lett. 113 1554 (214). 2
Collaborators D. H. Barnak, R. Betti, E. M. Campbell, P.-Y. Chang, 1 G. Fiksel, 2 J. P. Knauer, and S. P. Regan University of Rochester Laboratory for Laser Energetics A. Harvey-Thompson, K. J. Peterson, A. B. Sefkow, D. B. Sinars, and S. A. Slutz Sandia National Laboratories 1 Currently at National Cheng Kung University, Taiwan 2 Currently at University of Michigan 3
MagLIF is an inertial confinement fusion (ICF) scheme using magnetized preheated fuel to allow for cylindrical implosions with lower velocities and lower convergence ratios than conventional ICF * Laser entrance hole with CH foil Laser entrance hole with CH foil Laser beam Axial field compressed by implosion 5 to 1 mm Azimuthal drive field Axial magnetic field Liner (Al or Be) Cold DT gas (fuel) Laser-heated fuel Start of liner compression Liner unstable but sufficiently intact Compressed fuel at fusion temperatures An axial magnetic field lowers electron thermal conductivity, allowing for a near-adiabatic compression at lower implosion velocities and confines alpha particles, allowing for a lower areal density Laser preheating to ~1 ev makes it possible for >1 kev to be reached at a convergence ratio <3 I2185c *S. A. Slutz et al., Phys. Plasmas 17, 5633 (21). 4
A point design for laser-driven MagLIF on OMEGA has been developed by scaling down the Z point design* by a factor of 1 in drive energy 4 compression beams SG2 phase plates up to 15.8 kj in 1.5 ns Preheat beam from P9 2- phase plate up to 395 J in 1.5 ns 1 mm MIFEDS** coils B z ~ 1 T Target support Fill-tube pressure transducer r (mm) Dr (mm) r/dr Ring 3 Rings 4 Ring 3 t fuel (mg/cm 3 ) B (T) T (ev) V imp (km/s) Convergence ratio T max (kev) Z 3.48.58 6 3 (DT) 3 25 7 25 8. OMEGA.3.3 1 2.4 (D 2 ) 1 2 154 26 2.9 TC12449a *S. A. Slutz et al., Phys. Plasmas 17, 5633 (21). **MIFEDS: magneto-inertial fusion electrical discharge system 5
The first two shot days were supported by the Laboratory Basic Science (LBS) program and Sandia National Laboratories (SNL) Laser entrance foil only targets (1.84 polyimide) Soft x-ray emission calorimeter Beam 46 Full targets Beam 25 3 (24.8 ) 25 ( ) H17C (16.6 ) Time-resolved spectra 3 (24.8 ) 25 ( ) H17C (16.6 ) Time-resolved spectra soft x-ray emission Soft x-ray diagnostic window optical emission Beam 25 3 (24.8 ) 25 ( ) H17C (16.6 ) Time-resolved spectra soft x-ray emission TC12451a Empty cylinders were used for compression-only shots 6
Foil transmission exceeds 5% with no backscatter from the gas and less than 1% sidescatter of transmitted light Intensity (MW/cm 2 ).5.4.3.2.1 Backscattered intensities measured for a full target and a foil...5 1. Cylinder 25 Cylinder H17C Cylinder 3 Foil 25 Foil H17C Foil 3 1.5 2. 2.5 Power (TW) Total transmitted and backscattered powers calculated from two foil shots.1 63.4% forward transmission.8 Laser.6.4.2.. 27% absorbed 8.7% sidescattered transmission.5% backscattered.5 1. 1.5 2. 2.5 3. Time (ns) Time (ns) Backscatter from foils and from full targets are very similar and contain a negligible amount of the laser energy. TC12456a 7
Three-channel soft x-ray imaging of the side window shows a gas temperature of >1 ev Transmission ( 1 22 cm 2 /ster) 6 4 2 Soft x-ray framing camera (SXR) response Channel 3 Channel 1 Channel 2 1 2 3 4 5 Photon energy (kev) SXR is not absolutely calibrated so it gives two channel ratios Used Spect3D to generate channel ratios for a range of gas and wall temperatures and densities (assumed uniform): four free parameters to fit the 2 channel ratios With the constraint T gas > T wall, one can determine T gas > 1 ev Channel 2/Channel 3 1.2 1..8.6.4.2. Lower bound solution 1 1.3 ns T gas = 17 ev Shot 2 Shot 3 T gas = 1 ev Shot 1 2 3 4 Wall temperature (ev) T gas = 5 ev TC12574a According to 1-D models there is a preheat threshold of 1 ev. 8
X-ray emission recorded by Dante shows window, gas, and wall heating B52 Dante view 1 mm.54 mm Volume that Dante sees Diode (V).5.4.3.2.1. Channel 6 (9 to 98 ev) Foil only Cylinder with B = Signal from gas and wall Signal from foil Cylinder with B = 15 T 2 4 6 8 1 Time (ns) TC12575a 9
Two-dimensional hydrocode predictions are in reasonable agreement with Dante measurements Channel 2 Channel 6 Signal (V).8.6.4.2. 1. 1.5 2. 2.5 3. E = 195.6 J E = 198.4 J FLASH E = 2 J Signal (V).25.2.15.1.5. 1. 1.5 2. 2.5 3. Time (ns) Time (ns) TC12575b 1
Streaked optical pyrometry (SOP) of the cylinder surface demonstrates energy coupling to the central.8 mm SOP view.8 mm Shield Laser Distance from laser entrance hole () 14 13 12 11 1 9 8 7 6 Streaked optical pyrometry image Inner surface heats up Blanking Outer surface heats up Shock breakout 1 2 3 4 5 6 7 8 Time (ns) E24973 11
The implosion of empty cylinders with rings 3 and 4 was measured separately using x-ray framing cameras Laser power (TW/cm 2 ) 25 2 15 1 5 Intensity on target Position of peak x-ray self-emission 6 31.5 Ring 3 8.75 Ring 4 5 Ring 3.5..5 z (cm) R () 4 3 Ring 4 1. 1.5 2. 2.5 3. Time (ns) Ring 3 only t = 2.55 ns (end of laser pulse) Ring 4 only 52!19 V ring3 = 124.3!4. km/s 312!11 V ring3 = 178.1!1.2 km/s E24974 Overlap rings 3 at center and drive the ends with rings 4 12
A nine-shot day program is now being suported by the Advanced Research Projects Agency-Energy (ARPA-E) 1. Optimize ring-3 and ring-4 energy balance without preheat (1 Sept 15) 2. Complete optimization of ring-3 and ring-4 drive and reduce shell thickness without preheat (24 Nov 15) 3. Optimize preheat timing and vary preheat energy (19 July 16) 4. Complete B/no-B and preheat level dataset (22 Sept 16) 5. Measure axial B-field evolution 1: proton probing with D 3 He backlighter using H 2 fill to avoid proton production from target 6. Axial B-field evolution 2: use OMEGA EP if D 3 He is unsuccessful or extend dataset 7. Complete initial B-field scan including a higher value, if possible, with two MIFEDS and/or transformer coils (under development) with preheat 8. Fill-density and shell-thickness scans with B and preheat 9. Contingency: fill in missing data, address unforeseen issues, or extend dataset E24975 13
Compression-only shots have shown that axial uniformity can be controlled by beam balance and a.7-mm-long region can be compressed at >1 km/s r Sample x-ray framing camera (XRFC) Radius () of peak x-ray self-emission at 2.55 ns (end of laser pulse) 3 24 1 z r () 18 12 1% ring 3 6 9% ring 3 8% ring 3 (r 43.8 ) 6 3 3 6 z () 4--thick shells with 12 kj in 2.5 ns TC12532a 14
Hot-core formation and expansion have been observed with side-on x-ray framing cameras 5 2.2 to 2.25 ns 4 3 2 1 2 4 6 8 1 3--thick shell with 13.2 kj in 2 ns E24976 15
Hot-core formation and expansion have been observed with side-on x-ray framing cameras 5 2.5 to 2.55 ns 4 3 2 1 2 4 6 8 1 3--thick shell with 13.2 kj in 2 ns E24977 16
Hot-core formation and expansion have been observed with side-on x-ray framing cameras 5 2.65 to 2.7 ns 4 3 2 1 2 4 6 8 1 3--thick shell with 13.2 kj in 2 ns E24977a 17
Hot-core formation and expansion have been observed with side-on x-ray framing cameras 5 2.9 to 2.95 ns 4 3 2 1 2 4 6 8 1 3--thick shell with 13.2 kj in 2 ns E24977b 18
End-on x-ray framing-camera images show core emission earlier and a pentagonal structure to the shell Shadow of uncompressed end 2. ns 2.25 ns 6 5 4 3 2 1 2 4 6 2 4 6 3--thick shell with 13.2 kj in 2 ns E24978 19
End-on x-ray framing-camera images show core emission earlier and a pentagonal structure to the shell Shadow of uncompressed end 2. ns 2.25 ns 6 5 4 3 2 1 2 4 6 2 4 6 3--thick shell with 13.2 kj in 2 ns E24978a 2
End-on x-ray framing-camera images show core emission earlier and a pentagonal structure to the shell Emission from laser-heated plasma 2. ns 2.25 ns 6 5 4 3 2 1 2 4 6 2 4 6 3--thick shell with 13.2 kj in 2 ns E24978b 21
End-on x-ray framing camera images show core emission earlier and a pentagonal structure to the shell No emission from cold gas inside shell 2. ns 2.25 ns 6 5 4 3 2 1 2 4 6 2 4 6 3--thick shell with 13.2 kj in 2 ns E24978c 22
End-on x-ray framing-camera images show core emission earlier and a pentagonal structure to the shell Shock convergence heats gas 2. ns 2.25 ns 6 5 4 3 2 1 2 4 6 2 4 6 3--thick shell with 13.2 kj in 2 ns E24978d 23
The pentagon corresponds to the azimuthal beam distribution in ring 4 and can be removed by repointing Standard beam distribution Direct laser power deposited (TW/cm 2 ) Uniform beam distribution Azimuthal angle ( ) 3 2 1.1..1 z (cm) P laser (direct) 3 2 1 E24979 24
A 3~ beam from P9 using Beam 35 is being implemented for preheating Current P9 system provides 2~ or 4~ using Beam 25 2~ has too low a critical density; 4~ has no diagnostics and no phase plate Beam 25 is required for compression A project to move Beam 35 at 3~ into P9 is underway First use date is 19 July 216 Current capabilities will be maintained P9 New 3~ lens Periscope (moveable) Final mirror Beam 35 Carts for 2~ and 3~ pickoff and final mirrors E2533 25
Summary/Conclusions Laser-driven magnetized liner inertial fusion (MagLIF) is being developed on OMEGA to study MagLIF scaling A energy scaled point design for laser-driven MagLIF on OMEGA has been developed that is 1 smaller in linear dimensions than Z targets* The key elements of preheating to >1 ev and uniform cylindrical compression at ~1 km/s have been demonstrated in experiments The first integrated laser-driven MagLIF experiment will be carried out later this year E24972 * S. A. Slutz et al., Phys. Plasmas 17 5633 (21); M. R. Gomez et al., Phys. Rev. Lett. 113 1553 (214); P. F. Schmit et al., Phys. Rev. Lett. 113 1554 (214). 26