High energy density nuclear physics at UC Berkeley, LLNL, and LBNL. Karl van Bibber & Lee Bernstein

Transcription

1 High energy density nuclear physics at UC Berkeley, LLNL, and LBNL Karl van Bibber & Lee Bernstein

2 HFNG NIF A Bay Area collaboration has formed to study Nuclear Plasma Interactions and related phenomena Primary tools are NIF and other Laser HED platforms Supporting measurements and instrument development at the LBNL 88 cyclotron, and the UC Berkeley HFNG We acknowledge funding by the UC Office of the President A major proposal for a UC HED S&T Center involving four campuses & three labs has just been submitted 88

3 The HFNG primarily designed for 39 Ar/ 40 Ar dalng technique for geochronology and paleochronology requires 39 K(n,p) 39 Ar Our design enables both 2.45 MeV and thermal neutrons, either internal to the target or in an external beamline Team HFNG UC Berkeley Ka- Ngo Leung Cory Waltz Leo Kirsch Jay James Karl van Bibber Keeton Ross Joe Labrum BGC Paul Renne Tim Becker LLNL Lee Bernstein LBNL Rick Firestone MSU/UMass Lowell Andy Rogers

4 Background of the High Flux Neutron Generator (HFNG) HFNG designed by Ka- Ngo Leung for the Berkeley Geochronology Center Supported by NSF ARRA funding Expected Neutron Flux (over 4π) neutrons/sec D- D Fusion ReacLon: Deuteron Deuteron 3 He Neutron D + D 3 He + n Q = 2.45 MeV

5 The Generator Matching networks for RF Cooling ConnecLons Shielding Target Turbopump RF Ion Source Major components: 120 kv, 200 A Power supply 30 A RF Generators Impedance Matching Networks for RF Turbopump Cooling System Poly Shielding

6 Opera=on Deuterium Injected RF Ion Source RF ON Enough deuterium Deuterium imbeds imbedded D- D Fusion! in target for into target collisions to occur Target High Voltage ON RF Ion Source RF ON

7 115 In (n,n ) 115m In ( 4.49 h, 336 kev γ ) First neutrons were produced on July 25, kv anode voltage 1 ma ion current (0.2-2) 10 8 n/sec The Indium disk used to measure the neutron flux from HFNG was the idenkcal foil which measured the first neutrons from NIF in 2010

8 Next steps: suppression of backstreaming electrons to enable current to reach goal of ~ 1 A & thus ~ 1011 n/sec Strategy for suppression involves both permanent magnets in the anode, and a shroud to capture electrons Movie (right): Plasma without magnets & graphite shield Movie (left): Plasma with magnets & graphite shield We can now run with ~ 4 ma A full shield is being designed with the assistance of Comsol modeling

9 Our collaboration is pursuing a multi-component program to measure nuclear-plasma interactions in HED plasmas Mau Chen, Andrea Kritcher, Bob Heeter, Darren Bleuel, Dawn Shaughnessy, Carol Velsko, Bill Cassata, Laura Hopkins, K. Moody, N. Gharibyan, D.H.G. Schneider LLNL Bethany Goldblum, Brian Daub, Karl Van Bibber, Jasmina Vujic, Joshua Brown, Nick Brickner, O. Clamens, O. Nunez University of California - Berkeley Vincent Meot, Gilbert Gosselin, Pascal Morel, Phillipe Franck, Charles Reverdin CEA-DAM A. Yasunobu, M. Nakai, H. Azechi ILE-Osaka This work was performed under the auspices of the U.S. DOE by 9

10 Classes of Nuclear Plasma Interactions (NPI) Photo-absorption Time Reverse: γ-ray decay Atomic-nuclear (electron) interactions NEEC, NEET, IES* Time Reverse: IC-decay e free e bound N N* HEDP electrons Photons Atom Photons N N* photons Nucleus This work was performed under the auspices of the U.S. DOE by 10

11 NPI-induced population of low-lying excited states changes the spin of the compound nucleus leading to alterations in neutron capture rates in stellar plasmas S n NEEC/T SEF ( kt ) = σ HEDP = σ GS i=0 A Z ( 2J i +1)σ E x = E i ( ) σ GS ( 2J i +1) i=0 e E i /kt e E i /kt A+1 Z LIfetime of s Lifetime (ps) J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= Higher spin states are less Likely emit neutrons Energy (MeV) These rates remain entirely unmeasured This work was performed under the auspices of the U.S. DOE by under contract DE-AC52-07NA *Bao Lawrence & Kappeler Livermore At. Dat. National Nucl. Dat. Security, Tables LLC 76, (2000) J/pi= 0.0+ J/pi= 1.0+ J/pi= 2.0+ J/pi= 3.0+ J/pi= 4.0+ J/pi= 5.0+ J/pi= 6.0+ J/pi= 7.0+ J/pi= 8.0+ J/pi= 9.0+ J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= J/pi=

12 We have attempted to observe NPI-induced population of low-lying nuclear states through the observation of prompt γ-rays in a HEDP formed using a high energy laser The Omega laser at LLE 60 beams 30 kj at 3ω Variable pulse shape P 60TW This work was performed under the auspices of the U.S. DOE by 12

13 The experiments at Omega were designed to directly detect NEEC decay in hohlraum targets 1 ns laser pulses were used to heat the interior of the Tm hohlraum to > 5 kev. -Tm atoms undergo NEEC to 8.41 kev excited state closely matches L-shell e- energies 3/ Tm 8.4 kev 4.1 ns -gamma decay is measured 2-4 ns later using Omega x-ray diagnostics 38 drive beams" 169 Tm hohlraum (10 μm thick)" 1/2+ 0 This work was performed under the auspices of the U.S. DOE by 13

14 8-9 kev γ-rays can be detected with standard crystal x-ray spectrometers at Omega High collection efficiency Bragg crystal allows γ s to be seen above x-ray background XRFC & FILM! θ Bragg =12 o! Source! F=12.5 cm! Highly Oriented Pyrolytic Graphite (HOPG) crystal Spectral Range: kev Reflectivity ~3 mrad Solid angle Ω det ~ This work was performed under the auspices of the U.S. DOE by 14

15 Our first LLE experiments in 2012 produced confusing results: Did we observe NEEC or atomic metastable states in 169 Tm? NEEC rate in blowoff plasma Au HED plasmas: M.B. Schneider et al, Phys. Plasmas 13, (2006) Detected late time spectrum Metastable state NEEC?? M. Chen simulakons This work was performed under the auspices of the U.S. DOE by 15

16 On May 7 we revisited this approach at Omega using 187 Os (test case), 192 Os (control) and 169 Tm half-raums Ti Th/Os plume The candidate peak is still there The 2012 phantom is gone 169 Tm t = 3 ns t = 4 ns t = 5 ns t = 6 ns Half-raum with washer reduces blow-off plasma location ambiguity. 3/2-1/2-2+ NEEC 187 Os 9.76 kev γ (2.4ns) 0 kev 206 kev Arbitrary Units Arbitrary Units Os Osmium 3ns Osmium 3ns E (ev) Osmium 4ns Osmium 4ns The control allows us to separate nuclear from atomic physics effects: 0+ Control 192 Os 0 kev Arbitrary Units E (ev) Osmium 5ns Osmium 5ns This work was performed under the auspices of the U.S. DOE by E (ev) 16

17 Isomer de-excitation can be used to observe NPIs on excited states in HED plasmas as well* Via discrete states Via the quasi-continuum X+ΔE kev f X kev t 1/2 > 20 ps e - γ i A Z g S n Ideal case Γ f i Γ f g *G. Gosselin & P. Morel Phys. Rev. C (2004) A Z Ground State A-1 Z Isomer m g This work was performed under the auspices of the U.S. DOE by 17

18 The National Ignition Facility (NIF) at LLNL provides an HEDP with 20x longer confinement times than LLE 192 beams 1.8 MJ at 3ω Variable pulse shape (20ns) P ~ 500TW Up to neutrons which can be used to make isomers This work was performed under the auspices of the U.S. DOE by 18

19 Our programs also includes a component focused on NPI-induced reactions taking place on highly-excited states altering the population of isomers B f S n +E n NEE*/NRF? S n A Z Current AssumpLon A+1 Z Lifetime (ps) LIfetime of s J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= Energy (MeV) The situation could be even more complicated if fission is an open channel (e.g., the r-process) Whether this happens depends on τ(j), σ NPI, and Φ e,γ J/pi= 0.0+ J/pi= 1.0+ J/pi= 2.0+ J/pi= 3.0+ J/pi= 4.0+ J/pi= 5.0+ J/pi= 6.0+ J/pi= 7.0+ J/pi= 8.0+ J/pi= 9.0+ J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= J/pi= This work was performed under the auspices of the U.S. DOE by 19

20 A NIF experiment using this approach is planned using a 134 Xe-doped exploding pusher to make 133m Xe and 133g Xe in and out of a HEDP We maximize both neutron flux and plasma density by placing a 134 Xe dopant nuclei in a direct-drive target Glass/CH pusher (10 µm) d 2.19 d 133 Xe 11/2-3/2 + plus a control sample outside the plasma in a sample positioner 50cm from the target DT gas 0.03% 134 Xe R DIGS N 133m Xe RAGS N 133m Xe DIM Fusion neutrons interact with Xe on way out of target N 133g Xe RAGS N 133g Xe DIM 1 NPI 50 cm All of the Xe gets hots None of the Xe gets hots This work was performed under the auspices of the U.S. DOE by 20

21 The radiochemical team at NIF has shown that it can collect radioactive Xenon from exploding pushers with high efficiency From NIF chamber turbo pumps Exploding pusher 2 mm 0.03% Xenon > 50% of gaseous material in NIF chamber can be retrieved This work was performed under the auspices of the U.S. DOE by 21

22 A beam-foil experiment is scheduled for 10/14 at LBNL to try and observe NPIs on highly excited state in 196 Au via isomer de-excitation 100 µm metal foil + 1 µm 13 C target 197 Au beam Excited 198/196 Au* residuals made via binary transfer from 13 C recoils into a Bismuth foil plasma target 196,198 Au*** In the close target NEEC can occur on quasi-continuum states. 196,198 Au In the far target, Au has decayed to ground state or isomer, and NEEC will occur on these states. This work was performed under the auspices of the U.S. DOE by 22

23 In preparation for this experiment we performed an excitation function measurement that has produced a publication worthy result in its own right Gold Target Layers (1 micron) Gold Monitor Foil 130 MeV 13 C Aluminum Degrader Foils (25 microns) Aluminum Stopping Foils Maximum m/g ratio occurs at 8.5 MeV/nucleon. This work was performed under the auspices of the U.S. DOE by 23

24 We are now planning to develop enhanced debris collection techniques at ILE-Osaka using radioactive Au nuclei produced at the RCNP cyclotron Step 1 Make radioaclve gold using the RCNP AVF cyclotron via nat Pt(p,xn). Proton Beam: 20 MeV, 1μA (min), 1.5cm diameter GEKKO chamber Step 2 Count aclvity of radioaclve targets Isotope: 194Au; Peak Energy: keV; Peak Intensity: 60.4% Step 3 Step 4 Collect debris with our models in GEKKO XII Target Chamber Various models, with different sizes and materials Perform chemistry to prepare a sample for counlng using HPGe detector RCNP collimator Debris Collector Step 5 Count again and compare with the results in Step 3 to obtain the colleclon efficiency Many thanks to the team at ILE, including Dr. Arikawa Yasunobu! This work was performed under the auspices of the U.S. DOE by 24

25 Summary 1 A multi-institutional collaboration has been assembled at and around UCB 1 To pursue neutron-induced nuclear science measurements 2 To study the elusive topic of nuclear-plasma interactions 2 We are pursuing a multi-component approach to try and observe the elusive phenomena of NPIs: 1 On nuclear ground states using Laser-driven HEDPs at Omega in 169 Tm and 187 Os 2 On excited nuclear states via isomer de-excitation in 133 Xe at NIF 3 On excited states via isomer de-excitation in 196,198 Au using the LBNL 88-Inch cyclotron. 3 We are also working to develop enhanced debris collection at ILE-Osaka 1 This is the 1 st step toward using a combination of long- and short-pulse lasers to observe NPIs Thanks for your attention! This work was performed under the auspices of the U.S. DOE by 25