Effects of front surface plasma expansion on proton acceleration in ultraintense laser irradiation of foil targets

McKenna, P.; Carroll, D. C.; Lundh, Olle; Nürnberg, F.; Markey, K.; Bandyopadhyay, S.; Batani, D.; Evans, R. G.; Jafer, R.; Kar, S.; Neely, D.; Pepler, D.; Quinn, M. N.; Redaelli, R.; Roth, Markus; Wahlström, Claes‐Göran; Yuan, Xiaohui; Zepf, Matthew

doi:10.1017/s0263034608000657

Cited by 104 publications

(69 citation statements)

References 34 publications

(22 reference statements)

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“…The higher ion energy can be understood by larger laser power and intensity which was achieved without the saturable absorber, by increased absorption in the preformed plasma, [16] - [18] and by the laser pulse self-focusing in the preplasma with the optimum scale length. [19] 0 200 400 600 800 0 [12] with the additional limit of the acceleration length equals the sheath diameter. [13] x, µm Although the optimum preplasma allowed achieving higher proton energies, the proton acceleration was less stable than in the case of high laser contrast.…”

Section: Results Of Proton Accelerationmentioning

confidence: 99%

Laser-driven proton acceleration and plasma diagnostics with J-KAREN laser

et al. 2009

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We describe results of experiments on laser-driven proton acceleration and corresponding laser-plasma diagnostics performed with the multi-10-TW J-KAREN laser. The laser consists of a high-pulse-energy oscillator, saturable absorber, stretcher, Optical Parametric Chirped Pulse Amplifier (OPCPA), two 4-pass Ti:Sapphire amplifiers, and compressor. The final amplifier is cryogenically cooled down to 100 K to avoid thermal lensing. The laser provides ~30 fs, ~ 1 J, high-contrast pulses with the nanosecond contrast better than 10 10 . The peak intensity is 10 20 W/cm 2 with the 3-4 μm focal spot. Using few-μm tape and sub-μm ribbon targets we produced protons with the energies up to 4 MeV. The tape target and repetitive laser operation allowed achieving proton acceleration at 1 Hz. We found significant differences in stability and angular distribution of proton beam in high-contrast and normal-contrast modes. The plasma diagnostics included interferometry and measurement of the target reflectivity. The latter provides convenient diagnostics of the laser contrast in the ion acceleration, harmonics generation, and other laser -solid target interaction experiments.

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Section: Results Of Proton Accelerationmentioning

confidence: 99%

Laser-driven proton acceleration and plasma diagnostics with J-KAREN laser

et al. 2009

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“…Plasma mirrors for the incoming laser light have been utilized to increase the laser contrast so as to enable high power laser irradiance onto essentially unperturbed solid target surfaces [5,6]. Alternatively, the production of high-energy electrons, ions, and radiation can be enhanced by deliberately creating gradients of density [7][8][9][10]. Culfa et al [11] measured the changes of fast electron temperatures and the number of fast electrons with varying plasma scale length.…”

Section: Introductionmentioning

confidence: 99%

Plasma scale-length effects on electron energy spectra in high-irradiance laser plasmas

et al. 2016

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An analysis of an electron spectrometer used to characterize fast electrons generated by ultraintense (10 20 W cm −2 ) laser interaction with a preformed plasma of scale length measured by shadowgraphy is presented. The effects of fringing magnetic fields on the electron spectral measurements and the accuracy of density scale-length measurements are evaluated. 2D EPOCH PIC code simulations are found to be in agreement with measurements of the electron energy spectra showing that laser filamentation in plasma preformed by a prepulse is important with longer plasma scale lengths (>8 μm).

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“…The D 2 O stream will not have sharp boundaries predominantly because the main laser shot is preceded by a pre-pulse [24][25][26][27][28] , which ablates the material and generates a pre-plasma surrounding the water target. The creation of this pre-plasma is beneficial as it increases the coupling efficiency of the laser energy to the production of hot electrons, whose improvement enhances the energy of the deuterons.…”

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High repetition-rate neutron generation by several-mJ, 35 fs pulses interacting with free-flowing D2O

Hah

Petrov

Nees

et al. 2016

Applied Physics Letters

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Using several-mJ energy pulses from a high-repetition rate ( 1 ⁄2 kHz), ultrashort (35 fs) pulsed laser interacting with a ∼ 10 µm diameter stream of free-flowing heavy water (D 2 O), we demonstrate a 2.45 MeV neutron flux of 10 5 /s. Operating at high intensity (of order 10 19 Wcm −2 ), laser pulse energy is efficiently absorbed in the pre-plasma, generating energetic deuterons. These collide with deuterium nuclei in both the bulk target and the large volume of low density D 2 O vapor surrounding the target to generate neutrons through d (d, n) 3 He reactions. The neutron flux, as measured by a calibrated neutron bubble detector, increased as the laser pulse energy was increased from 6 mJ to 12 mJ. A quantitative comparison between the measured flux and results derived from 2D particle-in-cell simulations show comparable neutron fluxes for similar laser characteristics to the experiment. The simulations reveal that there are two groups of deuterons; forward moving deuterons generate D−D fusion reactions in the D 2 O stream and act as a point source of neutrons, while backward moving deuterons propagate through the low-density D 2 O vapor filled chamber and yield a volumetric source of neutrons.Energetic neutrons have numerous applications in many fields, including medicine 1 , homeland security 2 , and material science 3 . Conventional fast neutron sources include deuterium−deuterium (D−D) and deuteriumtritium (D−T) fusion generators, as well as light-ion, photoneutron and spallation sources. Laser plasma interactions in the relativistic regime can also generate charged particles and subsequently accelerate them to energies high enough to trigger nuclear fusion reactions, resulting in neutron production [4][5][6][7][8][9][10][11][12][13][14][15][16] . Recent advances in ultra-high power laser technology now enable tabletop scale systems, which may be further reduced in size for use as drivers for portable neutron generators in the future. One of the methods for neutron production is through the acceleration of high-energy ions (keV-MeV) impinging upon an appropriate converter target, such as deuterated plastic. Typically, thin solid targets are used in these experiments to accelerate deuterons.Using solid targets in the form of a thin (1µm) foil has some drawbacks for high repetition-rate (>kHz) operation; for example, one has to replace the target after each shot. To resolve target life-time issues, fast target replacement schemes have been introduced by some groups 8,15,[17][18][19] . In particular, using ∼ 100 mJ of pulse energy at 10 Hz repetition-rate, Ditmire et. al. 8 used deuterium clusters, which were rapidly heated by the laser pulse (on a femtosecond time scale) and launched few a) Now at Physics Department, Lancaster University, UK keV deuterons to drive D−D fusion reactions.In this Letter, we report the production of neutrons using a high repetition-rate ( 1 ⁄2 kHz) femtosecond laser at high intensities (> 10 19 Wcm −2 for vacuum focus) but low pulse energies (several-mJ) interacting with a heavy...

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Effects of front surface plasma expansion on proton acceleration in ultraintense laser irradiation of foil targets

Cited by 104 publications

References 34 publications

Laser-driven proton acceleration and plasma diagnostics with J-KAREN laser

Laser-driven proton acceleration and plasma diagnostics with J-KAREN laser

Plasma scale-length effects on electron energy spectra in high-irradiance laser plasmas

High repetition-rate neutron generation by several-mJ, 35 fs pulses interacting with free-flowing D2O

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