Neutron emission as high as 10 7 is observed when a high intensity (a few 10 19 W͞cm 2 ) subpicosecond laser pulse at 529 nm wavelength is focused on a deuterated polyethylene target. Neutron emission is also measured in different directions. The emission of neutrons along the laser axis is higher than in the transverse direction. Nonisotropic emission is consistent with neutrons generated by D͑d, n͒-3 He reaction for 0.3 -1 MeV deuterons accelerated in the direction of the laser beam. The energy transferred to the ions is roughly estimated and compared with the energy carried out by the electrons. [S0031-9007(98)08299-4] PACS numbers: 52.40.Nk, 52.50.Jm, 52.70.Nc The development of chirped pulse amplification has made possible the generation of energetic subpicosecond laser pulses [1]. The interaction of the laser pulse with a target generates energetic particles, like MeV electrons and ions [2]. The fast ignitor concept [3], relevant to the inertial confinement fusion (ICF), enhances the interest in this process: Hot particles could heat to thermonuclear temperature an already compressed deuterium-tritium fuel.High-intensity subpicosecond laser pulses produce fast neutrons when they interact with a deuterated target [4]. Hot deuterium ions create neutrons from D͑d, n͒-3 He reaction. Measurements of this neutron emission is a useful method to diagnose fast ions (in the keV to MeV range) generated by the interaction of the laser with the target. Particle-in-cell (PIC) calculations show that highenergy ions are accelerated by a shock wave propagating inside the target [5][6][7]. It knocks the ions along the direction of the laser propagation [8], but collisions stop the ions in the thickness of the target. Neutron emission can identify these ions which cannot be directly measured.Here, we report neutron emission from a deuterated polyethylene target irradiated with a subpicosecond 529 nm laser. The focused intensity is a few 10 19 W͞cm 2 . The experimental conditions are similar to other experiments [1,9]. The laser system provides a chirped pulse with energies up to 30 J at the fundamental wavelength of 1.058 mm. After compression by a pair of diffraction gratings, the pulse duration, measured by an autocorrelation method, is routinely 400 fs. A KH 2 PO 4 (KDP) crystal is used to convert the laser beam to 529 nm with an efficiency of 70%. The pulse duration is less than 300 fs. An f͞3 off-axis parabolic mirror focuses the laser pulse to a 5-mm-diameter spot containing about 30% of the total energy. The highest intensity is 3.5 3 10 19 W͞cm 2 for a laser energy of 7 J at 529 nm.At 1.058 mm, the contrast ratio measured at a few tens of picosecond before the main pulse by a third order cross correlator is 10 8 . Three dichroic mirrors located after the KDP crystal increase the contrast ratio to 10 12 at 529 nm. The optical intensity before the pulse is insufficient to ionize the target, so the pulse interacts directly with the solid target and not with a plasma.The target is made from deuterated polyethylene powd...

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First 14 MeV neutron images of imploded microballoons have been obtained at the Phébus laser facility at CEL-V in 1992 [Garconnet et al. Laser Part Beams 11, 3 (1994)]. The sizes of the neutron source have been measured by using a coded-aperture imaging system and a scintillator array as a detector. The threshold of the experimental setup was typically 2×1010 neutrons/shot. 600–800 μm source sizes in direct drive experiments have been measured with a 130 μm two-point resolution. In 1993 we improved the sensitivity of the camera by increasing the light collection efficiency. It can now work at a neutron yield as small as a few 108. Thanks to this improvement some images in indirect drive experiments have been recorded in the range 3×108–5×109 with a 56 μm two-point resolution. Wiener filter, homomorphic Wiener filter, and Nugent’s ‘‘comb filter’’ methods have been used and compared to deconvolve the penumbral images. Design of the camera and numerical method performances will be discussed.