D-D NUCLEAR FUSION PROCESSES INDUCED IN POLYEHTYLENE BY TW LASER-GENERATED PLASMA

Transcription

1 D-D NUCLEAR FUSION PROCESSES INDUCED IN POLYEHTYLENE BY TW LASER-GENERATED PLASMA L. Torrisi 1, M. Cutroneo, S. Cavallaro 1 and J. Ullschmied 3 1 Physics Department, Messina University, V.le S. D Alcontres 31, S. Agata (ME), Italy Institute of Nuclear Physics, ASCR-Rez, Czech Republic 3 PALS Laboratory, Institute of Plasma Physics ASCR, 1800 Prague 8, Czech Republic International Conference Dark Matter, Hadron Physics and Fusion Physics Messina (Italy) - September 4-6, 014

2 Asterix Laser- PALS Lab, ASCR Prague, Czech Republic Properties Laser Asterix Focal dimension 70 mm Power density W/cm Beam profile Gaussian Maximum Energy 1 kj Beam diameter 9 cm Pulse duration 300 ps Power 3 TW Wavelenght 1315 nm 438 nm Repetition rate 1 shot/0 min

3 y x B o E o ee dv x (t) 0 cos( t kz) dt m e z The Ponderomotive Force dv dt The integral of the electron equation of motion gives: z eb 0 vx cos( t kz) me vosc v x (t) vosc sin( t kz 0); x(t) cos( t kz 0); ee0 v (electron quiver velocity) d E osc m e Fd E(t)cos t ee kin me d (maximum deplacement) * Valence ionization processes d = nm lattice spacings in a solid ee e 0 m * (e-e) and (e-i) collisions 3kT/ * Due to collisions electrons gain energy from laser

4 Matter under extreme conditions I = W cm - E ~ 109 V/cm q V E. x x + High intensity Photoeletric Effect Rapid ionization of valence electrons ad of the most external electrons

5 1. Backward Plasma Acceleration (BPA) Thick target ions W/cm Laser -1. Laser-electron interaction -. Electron-crystal lattice interaction - Photo-thermal effects with IR, metals and ns lasers -Photo -chemical effects with UV, insulators and fs lasers Advantages 1) High ion yield ) High ion current using repetition rates; 3) Use of post ion acceleration methods and ion implantation Disadvantages 1) Low ion energy (below 1 MeV/z) ) Plasma expansion toward the laser lens 3) Roto-translating targets for repetitive laser shots 4) Large angular distribution of ions and electrons T ~ 1-10 kev; n ~ /cm 3

6 I > W/cm. Normal Target Sheath Acceleration (TNSA) Thin target ( um) E=kT e /el D - Laser-electron interaction - Electrons penetrate the solid target - Formation of charge separation in the rear side - Coulomb Explosion of the target - Driven ion acceleration from the rear side Advantages 1) High electron energy ) High ion energy (>1 MeV/z) 3) High directivity 4) Diagnostics in forward along the target normal direction Electrons penetrate the solid target T ~ 10 kev-10 MeV; n ~ 10 0 /cm 3 Disadvantages 1) Low ion yield ) Large movements for next laser shot 3) Surface deformation in thin films 4) Laser energy loss for transmission effects ~ 1 mm

7 Coulomb-Shifted-Boltzmann function Roger Kelly theory: shifted-maxwell distribution (non-coulombian interactions) Torrisi et al.: Coulomb-Boltzmann-shifted distribution (coulombian interactions) T v C u v v kt : plasma temperature; g adiabatic coefficient; V 0 : Coulombian Potential T k u m v v T k m A v f B B ) ( exp ) ( 3 3/ T k v u m v v T k m A v f B C B ) ( exp ) ( 3 3/ m ezv v C 0 m T k u B 1 m T k v B T 3 L. Torrisi et al. Rad. Eff. and Def. in Solids 157 (00) 333 Polyethylene

8 Plasma parameters depends on: 1. Laser properties: Plasma properties dedends on the Il factor; Laser polarization, pulse duration,.... Irradiation conditions: Focal position with respect to target surface, laser spot, self focusing, prepulse, polarization, Target: Composition, geometry, optical properties, (absorption, transmission, reflectivity, scattering),...

9 Plasma Diagnostics on line : TOF: IC, IC & abs, Si, SiC, Monocrystalline Diamonds; IEA : TOF tech. to determine E/z ratio, Energy and Charge state distributions; TPS-MCP: Ion Momentum, Enery, mass, charge state, X-ray Streak camera imaging: Expansion velocity, plasma density and temperature,.. Optical spectroscopy: Electonic plasma temperature and density Mass quadrupole spectrometry: ablated elements and chemical compounds Interferometric imaging: interference fringes modified by plasma expansion Plasma Diagnostics off line : Optical and Scanning electron microscopy of the irradiated targets; Surface profilers: Crater volume and shape; Track detectors and Gaf-chromic detectors: Cr39, PM 355, dosimeters, Ion Implantation: RBS analysis implanted substrates Target and/or substrate modifications (PLD, welding, )

10 Laser Thick CD target Deuterium ion acceleration Backward plasma Low density (Foams) (~10 mg/cm 3 ) Porouses CD (10 mg/cm 3 ) Target holder for Thin Targets (TNSA regime) TNSA Thin target Laser Forward plasma High density CD (0.95 g/cm 3 ) 5-50 mm CD

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12 ION COLLECTOR SiC DETECTOR H + (3 MeV) H + (.1 MeV) Thin CD Target (5 um) C n+ ions, ~ MeV/z D + (4. MeV) L. Torrisi et Al., Acta Polytechnica 53():41 45, 013

13 Nuclear applications: D-D Fusion investigation H + H 50% 3 H (1.01 MeV) + 1 H (3.0 MeV) 50% 3 He (0.8 MeV) + n (.45 MeV) 3 MeV Flux <sv> d-d f(kt)

14 S. Cavallaro and L. Torrisi, 41-EPS Conf., 3-7 June, Berlin, P.115 E L =600 J, l=1315 nm, Dt=300 ps, I=10 16 W/cm, 70 um spot TNSA regime, d=.6 m in air, forward 0, NE-10A Plastic scintillator- TOF configuration

15 Al absorber Neutron detection through elastic scattering with protons, in CR-39 track detectors, DE =.5 MeV-0. Detector covered with 6 um Al absorber. Cr-39 detector Microscopic liquid droplets form bubbles of trapped gas upon contact with neutrons. Number of bubbles is indicative of the neutron radiation field intensity Bubble neutron detectors, calibrated for MeV neutrons, Sensitivity= 4. b/mrem=4. b/10 msv Bubble Technology Industries Inc., Canada

16 Literature Data comparison Laser Phys. 16, JETP. 98, Eur. Phys. J. D 54, 93 Plasma Phys. Control. Fusion 47, L49 L56. J. Korean Phys. Soc. 55, 543 Plasma Phys. Contr. Fusion 40, 175 Our data: CD 7x10 5 1x x10 16 PALS, Torrisi et Al.

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18 Discussion & Conclusions 1) A laser pulse at W/cm, 1.3 mm wavelength, 300 ps pulse duration accelerates deuterons at energies of the order of -5 MeV (along the normal to the target surface) in TNSA approach. ) The number of fusion events depends on: the laser parameters, irradiation conditions and target composition and geometry. 3) The number of events can be calculated in different way. A simple method by using the bubble neutron dosimeters, giving, on the total solid angle, a flux of about F ~ 10 x10 8 n/laser shot 4) Increment of the Number of fusion events using secondary CD targets 5) Fusions are not due to plasma temperature but to MeV ion accelerated deuterons. 6) Production of monoenergetic Protons (3.0 MeV) and Neutrons (.5 MeV) streams for each laser shot using TNSA regime.

19 International Conference Dark Matter, Hadron Physics and Fusion Physics Messina (Italy) - September 4-6, 014 Thanks for Your kindly attention