Characterization of Li7(p,n)7Be neutron yields from laser produced ion beams for fast neutron radiography

Abstract

Investigations of 7 Li(p,n) 7 Be reactions using Cu and CH primary and LiF secondary targets were performed using the VULCAN laser ͓C.N. Danson et al., J. Mod. Opt. 45, 1653 ͑1997͔͒ with intensities up to 3ϫ10 19 W cm Ϫ2. The neutron yield was measured using CR-39 plastic track detector and the yield was up to 3ϫ10 8 sr Ϫ1 for CH primary targets and up to 2ϫ10 8 sr Ϫ1 for Cu primary targets. The angular distribution of neutrons was measured at various angles and revealed a relatively anisotropic neutron distribution over 180°that was greater than the error of measurement. It may be possible to exploit such reactions on high repetition, table-top lasers for neutron radiography.

Temporal Narrowing of Neutrons Produced by High-Intensity Short-Pulse Lasers

“…The CR-39 and bubble detectors recorded yields of 7 AE 4 and 8 AE 4 × 10 5 n=MeV=sr=shot, respectively, in the S1 case. We note that these yields are lower than those presently achievable on some laser systems due to the higher laser intensity and contrast of such systems [5,8,[10][11][12][13].…”

“…In fact, such high-intensity lasers have previously produced monoenergetic neutron bunches of 0.2 ns duration [9] via irradiation of deuterium clusters (D-D reactions). However, this method is limited to monoenergetic neutrons and has a low neutron yield (∼10 5 n=J) compared to methods based on laser-accelerated protons impinging on solid material slabs, a technique shown to create up to and above 10 8 n=sr=shot (∼10 7 n=J) [5,8,[10][11][12][13]. On the other hand, a major challenge when using solid targets is that the interaction creates large numbers of highenergy charged particles and x rays, which could damage a test sample and create a high-noise environment for sensitive diagnostics.…”

High Power Lasers and Their New Applications

“…Fusion neutrons from the explosion of deuterium clusters were observed with a compact Ti:sapphire laser [60]. The neutron production by (, ) and (, ) reactions induced by laser driven -rays and proton beams were also demonstrated [61,62]. For D-T fusion and proton induced nuclear reaction, 10 9 neutrons/J and ~10 7 neutrons /J have been achieved, respectively.…”

Ultra-High-Contrast Laser Acceleration of Relativistic Electrons in Solid Targets

“…[19] The accelerated ions can potentially be used for medical oncology treatments or to produce high energy neutron sources. [20][21][22] These high-intensity lasers can create extremely high electron currents. If we consider the Titan laser system, average electron energies are on the order of 1 MeV, with 150 J of laser energy and a conversion efficiency of 20%, and the pulse length about 700 fs in duration.…”