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Helmholtz -Zentrum-Dresden Rossendorf September 2011

Helmholtz -Zentrum-Dresden Rossendorf September 2011. Nuclear Excitation in Plasmas- NEET/NEEC. Ken Ledingham . SUPA, Dept of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland & AWE plc Aldermaston, Reading, RG7 4PR, UK , Helmholtz -Zentrum - Dresden, Rossendorf .

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Helmholtz -Zentrum-Dresden Rossendorf September 2011

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  1. Helmholtz -Zentrum-Dresden Rossendorf September 2011 Nuclear Excitation in Plasmas- NEET/NEEC Ken Ledingham SUPA, Dept of Physics, University of Strathclyde, Glasgow G4 0NG, Scotland & AWE plc Aldermaston, Reading, RG7 4PR, UK , Helmholtz -Zentrum - Dresden, Rossendorf

  2. Vacancy in an inner shell will be immediately filled by electron jumping from an outer orbit • If emission of a real photon takes place then we have X-ray emission • If we have emission of a virtual photon then two further processes can take place • Absorption by an outer electron of the virtual photon leads to Auger electron emission • Absorption of the virtual photon by the nucleus (usually in heavier nuclei) can take place leaving the nucleus excited

  3. Definitions • Internal Conversion (IC) Nuclear de-excitation resulting in the emission of an orbital electron to the continuum • Bound Internal conversion (BIC) Same as IC but electron is promoted to a bound state • NEEC (Nuclear excitation following electron capture from continuum) inverse of IC • NEET (Nuclear Excitation following an electronic de-excitation inverse of BIC

  4. Cartoon of NEET/NEECKritcher et al LLNL

  5. Why are NEET/NEEC Experiments so difficult to perform? • Electron beam, laser induced and synchrotron produced plasmas produce huge numbers of energetic electrons and photons as well as vacancies in electronic shells • The energetic electrons excite the nuclear transition by inelestic scattering • The photons excite the nuclear levels by direct photon interactions • The nuclear transitions are of course also excited by NEET/NEEC • The nuclear de-excitation for all methods of excitation has the same signature

  6. Feynman diagrams for Nuclear Excitation in Plasmas

  7. Production of 235Um in a CO2 laser produced plasma - Izawa 1979 Here the mismatch between electronic and nuclear transitions is considerable Recent experiments have not excited the isomer

  8. 181Ta Excitation – A.V Andreev

  9. Excitation of 181Ta in a Fs Dye Laser Plasma Andreev et al J.Exp.Theor.Phys. 91, 1163 2000 Half life 7± 3 µs in agreement with accepted value. No other group has replicated this including mine.

  10. One of the few accepted experiments which measures NEET – 197 Au Monoenergetic x-rays from a synchrotron were used to ionize the K-shell of gold (81 keV) A similar technique could be used on X-FEL for transitions The NEET probability was determined by comparing the number of de-excitation conversion electrons per photon at photon irradiation above the K-edge and at the nuclear resonance (77.351keV)and was determined to be 5x10-8

  11. NEET/NEEC Programme at Omega Rochester

  12. They intend to use a high resolution crystal spectrometer to detect nuclear photons

  13. The theory is now sufficiently well understood that competing nuclear excitation by scattered electrons and direct photons can easily be calculated leaving NEET/NEEC experimental comparisons with theory meaningful

  14. Can NEET/NEEC excitation from excited states reduce nuclear lifetimes The answer is in principle yes if the half-lives from the upper states are shorter than the isomeric states

  15. 169Tm half life decreases with plasma temperature and with mass density According to Gosselin, Meot and Morel half life is predicted to decrease from ns to ps

  16. Proposed EBIT measurement of 242mAm NEEC(Electron Beam Ion Trap) This is the only proposed NEEC experiment

  17. Ross Marrs LLNL UCRL-PRES-427008

  18. Scaling of NEET & NEEC signal to NIF

  19. According to plasma theorists NEET/NEEC nuclear transitions are among the most important transitions at high temperature and very few cross sections are known

  20. Can these experiments be done at XFEL/PW laser? The PW laser can produce proton beams which can excite NEET isotopes by e.g. (p,n) reactions. The XFEL can create K shell vacancies using monochromatic gamma rays and also measure the direct nuclear photon reaction from which the NEET mcross section can be calculated

  21. Thank you

  22. Proposed Spohr, Ledingham Experiment at NIF What do we intend to do at NIF – modification of the half life of 26Al using the high temps of the multiple laser beams – 108K - 100 times hotter than present lasers.

  23. Motivation Level scheme Skelton R et. al., Phys.Rev. C35(1),45,1987 • 26Al in the astrophysical context using a gamma camera • 1809 keV line in Galaxy Interstellar abundance NASA Compton Gamma Ray observatory (COMPTEL) 1991-2000 & Plüschke S et al., arXiv:astro-ph/0104047v1 Evolution of stellar abundance Voss R et al., Astronomy & Astrophysics, 504, 531, 2009

  24. Al26 Decay scheme

  25. How could NEET/EEC affect the half lives of 26Al • Increase the number of prompt 418 keV γ rays by NEET/NEEC excitation from the ground state • Increase the number of 0.511/1.81 MeV coincidences by NEET/NEEC excitation from the 6 sec isomeric state at 229 keV

  26. How do we make the Al26 -use the PW short pulse laser to generate a proton beam and then use a Mg26(p,n)Al26reaction

  27. Schematic of laser plasma nuclear 26Al experiment Use the NIF PW laser at 1022 W/cm2 'Plasma production pulse' Edriver~15J 'p-production pulse' TSNA I~1018-20 Wcm-2 Plasma medium e.g. Al 26Mg p Shielding Canvas adjustable Diamond Target All within a hohlraum

  28. The experiment entails measuring the 511 keV coincident counting rate or the 511keV and 1.8 MeV coincident counting rate or the 418 prompt counting rate as a function of plasma temperature with semiconductor or scintillation counter systems like the ORGAM system after a rapid transfer of target

  29. ORGAM Detector System

  30. Particle induced Fission Could the no of fragments detected change as a function of temperature because change of half life?

  31. depleted 238U thickness: 8μm encapsulated by Al-foils Fission products & trajectories Al-production target isochoric heated volume Proton beam Laser ~200μm Cu-stack 0-40μm variable Front Al-sheet 1 thickness: 10μm isochoric heated Back Al-sheet 2 thickness:10μm Al-U-Al sandwich target Laser Induced Proton Fission of 238U and Nuclear Fission Yields as a Fn of Temp This was an experiment to be carried out using short pulse laser isochoric heating but could be done by NIF heating. The Al was hot when distance was 40µ and cold at 0µ

  32. ORGAM Detector system

  33. Ross Marrs LLNL UCRL-PRES-427008

  34. First Measure the 26Mg(p,n)26Al cross section (Fazia Hannachi) • Precision measurement of 26Mg(p,n)26Al, with 'ORGAM & Neutron Detection system' 4.9-25 MeV • Nuclear exercise to allow laser plasma driven nuclear investigations in the future i) total neutron yield 26Mg(p,n0)26Al • ORGAM in coincidence with neutron array (neutron wall (GANIL?)) • Ip(max)=6 x 1012 pps , σ~100mb, dtarget~40μg/cm2 estimation of: ii)β+ delayed yield from the isomeric 0+ (T1/2=6.3 s) state at 228 keV: 26Mg(p,n1)26mAl • Bombard and count cycles: 6s/24s, 24s to measure delayed 511 keV radiation • For each Ei:20 cycles of 30s each: ORGAM (Phase I) ε=4.2%, no n-coincidence required • For Ep>16.1 MeV, correction for 2n channel leading to 25Al must be taken iii) prompt yield of 417 keV

  35. 26Mg(p,n)26Al i) total neutrons ii) 411 keV iii) del. 511 keV g.s. calc. OPTMISE the NUCLEAR data to ALLOW the LASER PLASMA Nuclear endeavour on 26Al Norman: total γ-yield No measurement of neutrons

  36. Outlook on future laser nuclear experiments with 100TW e.g DRACO or LULI and the few PW ELI system (2014) • Prima facie study at 100 TW • Firstly, production of 26Al and exposure to hot photon gas and MeV electrons. • How does production of 26mAl scale as beam parameters • Challenge: characterisation of plasma, shot-to-shot fluctuations of pulsed proton energy spectra (1 per 20 mins), deconvolution of proton energy spectra, Delayed 511 keV radiation servers as the measurement • Secondly, exposure of 26Al to WDM matter conditions of ~1 × 106 K = 100eV • A long long, long way from GK, but we have to start!

  37. Preparation for ELI (2014/15) • Intense pulses of mono-energetic protons up to GeV • Creation of GK environments possible, foreseen implementation of a mass separator • Radiation Pressure Acceleration (RPA) regime for ions → Quasi monoenergetic, solid-density bulks of accelerated ions! ~1kJ of laser pulse ≈ n~1013 @ GeV and n~ 1016 @MeV protons, in μm 'sheets', rep. Rate: 1 Hz; implementation of spectrometer & neutron detectors (ELI White book) • The 'ideal' astrophysical laboratory

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