Neutron Emission from Laser-Produced Plasmas

McCall, Gene H.; Young, F.C.; Ehler, A. W.; Kephart, J. F.; Godwin, R. P.

doi:10.1103/physrevlett.30.1116

Cited by 42 publications

(12 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recent experiments of laser-pellet interactions 1 have demonstrated the existence of energetic ions of 10-30 keV which carry approximately half the energy absorbed by the plasma. These energetic ions could also be important in explaining the observation of neutrons.…”

Section: Ion Acceleration In Strong Electromagnetic Interactions Withmentioning

confidence: 99%

Ion Acceleration in Strong Electromagnetic Interactions with Plasmas

Wong¹,

Stenzel²

1975

Phys. Rev. Lett.

View full text Add to dashboard Cite

Energetic ions of energy up to 7kT e are detected when an inhomogeneous plasma (T e / T {^1 0) is irradiated by microwave pulses (jE 0 2 /4imkT e &10~2) of short durations (r approximately twice the ion-plasma period). Time-and space-resolved analyses trace their origin to the generation of density cavitons by ponderomotive forces. The axially directed energetic-ion flux carries a significant fraction of incident electromagnetic energy.Recent experiments of laser-pellet interactions 1 have demonstrated the existence of energetic ions of 10-30 keV which carry approximately half the energy absorbed by the plasma. These energetic ions could also be important in explaining the observation of neutrons. There are also a number of experiments 2 in which ion heating is observed when microwave fields are radiated upon the plasmas, Such an increase in ion temperatures has been described in terms of interactions between particles and a turbulent wave spectrum,, In this paper we present experimental evidence to demonstrate a new mechanism which accelerates ions by sharply localized electric fields, a concept which should be applicable to a wide range of experiments involving strong fields E 2 /4nnkT e xl created by external electromagnetic (EM) fields or strong electron or ion beams. In our particular experiment where ionization effects are negligible the ponderomotive force V(E 2 )/Sir which arises from the sharply localized electric field near the resonant layer a> 0 = u) p (z) in a nonuniform plasma is found to be mainly responsible for driving these ions out of the resonant layer, leaving a density cavity behind. 3 The experiment is performed in QUIPS, the large TRW quiescent-plasma device (2 m diam and 4 m long). A 1-GHz 40-kW pulsed microwave source (Applied Microwaves) is used with a large horn antenna (14.4 dB gain, linear polarization) at one end of the chamber. Short microwave pulses of typical duration 0.4 Msec are radiated onto the plasma-density profile which rises from the antenna end to a maximum density near the opposite end (3 m away). The argon-plasma characteristics are 1.5 eV

show abstract

Section: Ion Acceleration In Strong Electromagnetic Interactions Withmentioning

confidence: 99%

Ion Acceleration in Strong Electromagnetic Interactions with Plasmas

Wong¹,

Stenzel²

1975

Phys. Rev. Lett.

View full text Add to dashboard Cite

show abstract

“…Experimental efforts to optimize laser-based neutron generators have been reported for over four decades [6][7][8][9]. Two experiments in the past year [4,10,11] reported lasergenerated neutron yields as high as 10 10 n/sr per laser shot.…”

Section: Pacsmentioning

confidence: 99%

Ultrashort Pulsed Neutron Source

et al. 2014

View full text Add to dashboard Cite

“…McCall et al 76 at Los Alamos argued that the neutrons could be produced in the blowoff plasma by fast ions generated through electrostatic acceleration. They showed that neutrons could arise from deuterium monolayers deposited on the chamber wall.…”

Section: A the Quest For Neutronsmentioning

confidence: 99%

“…They showed that neutrons could arise from deuterium monolayers deposited on the chamber wall. They obtained neutrons using a short-pulse laser (17 J, 25 76 that in the case of tight focusing on a solid target, the neutrons were produced external to the plasma from accelerated deuterons. However, they found that in a multibeam irradiation geometry with spherical targets, the neutrons were thermal, on the basis of the width of the energy spectrum of the neutrons.…”

Section: A the Quest For Neutronsmentioning

confidence: 99%

Direct-drive inertial confinement fusion: A review

et al. 2015

View full text Add to dashboard Cite

The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. The problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 μm—the third harmonic of the Nd:glass laser—and 0.248 μm (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be nonlocal in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [Haynam et al., Appl. Opt. 46(16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.

show abstract

Neutron Emission from Laser-Produced Plasmas

Cited by 42 publications

References 12 publications

Ion Acceleration in Strong Electromagnetic Interactions with Plasmas

Ion Acceleration in Strong Electromagnetic Interactions with Plasmas

Ultrashort Pulsed Neutron Source

Direct-drive inertial confinement fusion: A review

Contact Info

Product

Resources

About