Yan<i>et al.</i>Reply:

Yan, Xueqing; Lin, Chen; Sheng, Z. M.; Guo, Zhiyu; Liu, B. C.; Lu, Yuanrong; Jx, Fang; Chen, J. E.

doi:10.1103/physrevlett.102.239502

Cited by 58 publications

(87 citation statements)

References 6 publications

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“…Moreover, distribution properties are likely to vary significantly as techniques employed evolve (e.g., use of curved emission foils to control incident envelope divergence). Although techniques exist to produce relatively monochromatic proton beams with short pulse lasers [40][41][42][43][44], in typical TNSA produced proton beams the coherent beam energy spectrum is broad with particle counts decaying nearly exponentially with energy [10,[13][14][15][16]. For the PHELIX facility, the variation of the TNSA produced proton distribution (f) in coherent energy for the situation outlined in Sec.…”

Section: Particle-in-cell Simulationsmentioning

confidence: 99%

“…If desired, form factors for other smooth charge-density profiles can be calculated explicitly using Eq. (43) in either the continuous approximation or with full z variation. Simulations or higher level theory can be applied to model the evolution more consistently if more accuracy in F is necessary.…”

Section: Foilmentioning

confidence: 99%

“…This is a strong idealization of typical TNSA proton beams which have a broad, roughly exponentially varying energy spectrum. However, methods exist to produce a more monochromatic energy distribution by restricting the source region within the TNSA context to a small volume [40][41][42], or alternatively, through exploiting a radiation-pressureinduced acceleration mechanism [43,44]. The initial (z¼z i ¼0) rms-beam width x ðz¼z i Þ¼ xi and divergence…”

Section: Example: Application Of the Envelope Model To An Idealizementioning

confidence: 99%

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Envelope model for passive magnetic focusing of an intense proton or ion beam propagating through thin foils

Lund

Cohen

2013

Phys. Rev. ST Accel. Beams

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Ion beams (including protons) with low emittance and high space-charge intensity can be propagated with normal incidence through a sequence of thin metallic foils separated by vacuum gaps of order the characteristic transverse beam extent to transport/collimate the beam or to focus it to a small transverse spot. Energetic ions have sufficient range to pass through a significant number of thin foils with little energy loss or scattering. The foils reduce the (defocusing) radial electric self-field of the beam while not altering the (focusing) azimuthal magnetic self-field of the beam, thereby allowing passive self-beam focusing if the magnetic field is sufficiently strong relative to the residual electric field. Here we present an envelope model developed to predict the strength of this passive (beam generated) focusing effect under a number of simplifying assumptions including relatively long pulse duration. The envelope model provides a simple criterion for the necessary foil spacing for net focusing and clearly illustrates system focusing properties for either beam collimation (such as injecting a laser-produced proton beam into an accelerator) or for magnetic pinch focusing to a small transverse spot (for beam driven heating of materials). An illustrative example is worked for an idealization of a recently performed laser-produced proton-beam experiment to provide guidance on possible beam focusing and collimation systems. It is found that foils spaced on the order of the characteristic transverse beam size desired can be employed and that envelope divergence of the initial beam entering the foil lens must be suppressed to limit the total number of foils required to practical values for pinch focusing. Relatively modest proton-beam current at 10 MeV kinetic energy can clearly demonstrate strong magnetic pinch focusing achieving a transverse rms extent similar to the foil spacing (20-50 m gaps) in beam propagation distances of tens of mm. This is a surprisingly optimistic result since placing many foils per characteristic beam radius, which one might expect to be necessary to strongly attenuate the self-electric field, would likely result in excessive scattering and loss of focusing from the current neutralization due to the beam propagating too far through solid metal. Results from the envelope model are compared with particle-in-cell simulations to help clarify limits related to envelope-model idealizations. Possible degradations of focusing in situations where strong halo can be generated and where pulse duration is short are clarified.

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Section: Particle-in-cell Simulationsmentioning

confidence: 99%

Section: Foilmentioning

confidence: 99%

Section: Example: Application Of the Envelope Model To An Idealizementioning

confidence: 99%

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Envelope model for passive magnetic focusing of an intense proton or ion beam propagating through thin foils

Lund

Cohen

2013

Phys. Rev. ST Accel. Beams

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“…[1][2][3][4][5][6][7][8][9] Considerable effort has been put into both the theoretical and, more recently, the experimental aspects 10 of this problem. RPA has been classified into two modes: "hole-boring" 3,[11][12][13][14][15][16] (HB) and "light-sail" (LS).…”

Section: Introductionmentioning

confidence: 99%

Production of high energy protons with hole-boring radiation pressure acceleration

Robinson¹

2011

Physics of Plasmas

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The possibility of producing energetic protons with energies in the range of 100–200 MeV via hole-boring (HB) radiation pressure acceleration (RPA) at intensities around 1021 W cm−2 is reexamined. It is found that hole-boring RPA can occur well below the relativistically corrected critical density in numerical simulations, with average proton energies in good agreement with established formulas. This suggests that protons in this energy range can be produced via HB RPA at around 1021 W cm−2. It is also shown that the prospects of doing this could be improved by using lasers of the same intensity but longer wavelength.

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“…Experiments, currently exploiting micrometer foil targets for target normal sheath acceleration (TNSA) [6] , provide a world record of maximum proton energy beyond 85 MeV [7] . With nm thin foils, novel acceleration mechanisms such as radiation pressure acceleration (RPA) [8][9][10][11][12][13][14] and breakout afterburner (BOA) [15,16] have already demonstrated a higher conversion efficiency and faster energy scaling which are in favor for potential applications [17] .…”

Section: Introductionmentioning

confidence: 99%

An automated, 0.5 Hz nano-foil target positioning system for intense laser plasma experiments

Gao

Haffa

et al. 2017

High Pow Laser Sci Eng

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We report on a target system supporting automated positioning of nano-targets with a precision resolution of 4 µm in three dimensions. It relies on a confocal distance sensor and a microscope. The system has been commissioned to position nanometer targets with 1 Hz repetition rate. Integrating our prototype into the table-top ATLAS 300 TW-laser system at the Laboratory for Extreme Photonics in Garching, we demonstrate the operation of a 0.5 Hz laser-driven proton source with a shot-to-shot variation of the maximum energy about 27% for a level of confidence of 0.95. The reason of laser shooting experiments operated at 0.5 Hz rather than 1 Hz is because the synchronization between the nano-foil target positioning system and the laser trigger needs to improve.

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Yanet al.Reply:

Cited by 58 publications

References 6 publications

Envelope model for passive magnetic focusing of an intense proton or ion beam propagating through thin foils

Envelope model for passive magnetic focusing of an intense proton or ion beam propagating through thin foils

Production of high energy protons with hole-boring radiation pressure acceleration

An automated, 0.5 Hz nano-foil target positioning system for intense laser plasma experiments

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