Plasma Channels and Laser Pulse Tailoring for GeV Laser-Plasma Accelerators

Downer, M. C.; Chiu, Charles B.; Fomyts’kyi, Mykhailo V.; Gaul, E.; Grigsby, F.; Matlis, N. H.; Shim, Bonggu; Smith, Peter J.; Zgadzaj, Rafal

doi:10.1063/1.1524920

Cited by 6 publications

(8 citation statements)

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“…Included are the laser and pulse amplification systems that are common to most LWFA experiments as well as a proposed option for a plasma-gas cylinder. 9,24 High intensities are achieved by amplifying the laser pulse and focusing the laser pulse within the gas target. The laser source must be capable of generating pulses with intensity ͑irradiance͒ on the order of 10 18 W cm Ϫ2 .…”

Section: Iib Lwfa Accelerator Designmentioning

confidence: 99%

Dose properties of a laser accelerated electron beam and prospects for clinical application

et al. 2004

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Laser wakefield acceleration (LWFA) technology has evolved to where it should be evaluated for its potential as a future competitor to existing technology that produces electron and x-ray beams. The purpose of the present work is to investigate the dosimetric properties of an electron beam that should be achievable using existing LWFA technology, and to document the necessary improvements to make radiotherapy application for LWFA viable. This paper first qualitatively reviews the fundamental principles of LWFA and describes a potential design for a 30 cm accelerator chamber containing a gas target. Electron beam energy spectra, upon which our dose calculations are based, were obtained from a uniform energy distribution and from two-dimensional particle-in-cell (2D PIC) simulations. The 2D PIC simulation parameters are consistent with those reported by a previous LWFA experiment. According to the 2D PIC simulations, only approximately 0.3% of the LWFA electrons are emitted with an energy greater than 1 MeV. We studied only the high-energy electrons to determine their potential for clinical electron beams of central energy from 9 to 21 MeV. Each electron beam was broadened and flattened by designing a dual scattering foil system to produce a uniform beam (103%>off-axis ratio>95%) over a 25 x 25 cm2 field. An energy window (deltaE) ranging from 0.5 to 6.5 MeV was selected to study central-axis depth dose, beam flatness, and dose rate. Dose was calculated in water at a 100 cm source-to-surface distance using the EGS/BEAM Monte Carlo algorithm. Calculations showed that the beam flatness was fairly insensitive to deltaE. However, since the falloff of the depth-dose curve (R10-R90) and the dose rate both increase with deltaE, a tradeoff between minimizing (R10-R90) and maximizing dose rate is implied. If deltaE is constrained so that R10-R90 is within 0.5 cm of its value for a monoenergetic beam, the maximum practical dose rate based on 2D PIC is approximately 0.1 Gy min(-1) for a 9 MeV beam and 0.03 Gy min(-1) for a 15 MeV beam. It was concluded that current LWFA technology should allow a table-top terawatt (T3) laser to produce therapeutic electron beams that have acceptable flatness, penetration, and falloff of depth dose; however, the dose rate is still 1%-3% of that which would be acceptable, especially for higher-energy electron beams. Further progress in laser technology, e.g., increasing the pulse repetition rate or number of high energy electrons generated per pulse, is necessary to give dose rates acceptable for electron beams. Future measurements confirming dosimetric calculations are required to substantiate our results. In addition to achieving adequate dose rate, significant engineering developments are needed for this technology to compete with current electron acceleration technology. Also, the functional benefits of LWFA electron beams require further study and evaluation.

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Section: Iib Lwfa Accelerator Designmentioning

confidence: 99%

Dose properties of a laser accelerated electron beam and prospects for clinical application

et al. 2004

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“…Much higher net energy gains can be realized for the same amount of input laser power by extending the acceleration distance beyond Z R . Guiding concepts relying on the use of preformed channels are being studied by several groups around the world (Volfbeyn et al 1999;Geddes et al 2004a;Alexeev et al 2003;Downer et al 2003;Tochitsky et al 2004;Sprangle et al 2001;Spence & Hooker 2001;Zhidkov et al 2004;Lopes et al 2003;Chen et al 2004;Cros et al 2002). At LBNL, using the ignitor-heater concept (Volfbeyn et al 1999), we have recently produced plasma channels that have guided, to our knowledge, the highest peak power and the highest intensity in a preformed channel (Geddes et al 2004a).…”

Section: Channel Guiding: Scaling Laws and Experimentsmentioning

confidence: 99%

Laser guiding for GeV laser–plasma accelerators

Leemans

Esarey

Geddes

et al. 2006

Phil. Trans. R. Soc. A.

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Guiding of relativistically intense laser beams in preformed plasma channels is discussed for development of GeV-class laser accelerators. Experiments using a channel guided laser wakefield accelerator (LWFA) at LBNL have demonstrated that near mono-energetic 100 MeV-class electron beams can be produced with a 10 TW laser system. Analysis, aided by particle-in-cell simulations, as well as experiments with various plasma lengths and densities, indicate that tailoring the length of the accelerator, together with loading of the accelerating structure with beam, is the key to production of mono-energetic electron beams. Increasing the energy towards a GeV and beyond will require reducing the plasma density and design criteria are discussed for an optimized accelerator module. The current progress and future directions are summarized through comparison with conventional accelerators, highlighting the unique short term prospects for intense radiation sources based on laser-driven plasma accelerators.

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“…As discussed, the lower plasma densities for a centimeter scale laser-driven hydrodynamic expansion waveguide made that approach unpractical because low efficiency heating needs high energy heater. The Ignitor -heater concept [114,115,123] was not the only way to achieve a guiding of an intense laser, and however, other guiding concepts relying on the use of preformed plasma channels have been pursued by several groups around the world [124][125][126][127][128]. An alternative plasma channel technology, based on capillary discharge guides (CDG), was developed at Oxford University [129][130][131].…”

Section: Loasis Laser Plasma Based Acceleratorsmentioning

confidence: 99%

Control of Laser Plasma Based Accelerators up to 1 GeV

Nakamura

2007

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This dissertation documents the development of a broadband electron spectrometer (ESM) for GeV class Laser Wakefield Accelerators (LWFA), the production of high quality GeV electron beams (e-beams) for the first time in a LWFA by using a capillary discharge guide (CDG), and a statistical analysis of CDG-LWFAs.An ESM specialized for CDG-LWFAs with an unprecedentedly wide momentum acceptance, from 0.01 to 1.1 GeV in a single shot, has been developed. Simultaneous measurement of e-beam spectra and output laser properties as well as a large angular acceptance (> ±10 mrad) were realized by employing a slitless scheme. A scintillating screen (LANEX Fast back ,LANEX-FB) -camera system allowed faster than 1 Hz operation and evaluation of the spatial properties of e-beams. The design provided sufficient resolution for the whole range of the ESM (below 5% for beams with 2 mrad divergence).The calibration between light yield from LANEX-FB and total charge, and a study on the electron energy dependence (0.071 to 1.23 GeV) of LANEX-FB were performed at the Advanced light source (ALS), Lawrence Berkeley National Laboratory (LBNL). Using this calibration data, the developed ESM provided a charge measurement as well.The production of high quality electron beams up to 1 GeV from a centimeter-scale ii accelerator was demonstrated. The experiment used a 310 µm diameter gas-filled capillary discharge waveguide that channeled relativistically-intense laser pulses (42 TW, A statistical analysis of the CDG-LWFAs' performance was carried out. By taking advantage of the high repetition rate experimental system, several thousands of shots were taken in a broad range of the laser and plasma parameters. An analysis program was developed to sort and select the data by specified parameters, and then to evaluate performance statistically.The analysis suggested that the generation of GeV-level beams comes from a highly unstable and regime. By having the plasma density slightly above the threshold density for self injection, 1) the longest dephasing length possible was provided, which led to the generation of high energy e-beams, and 2) the number of electrons injected into the wakefield was kept small, which led to the generation of high quality (low energy spread) e-beams by minimizing the beam loading effect on the wake. The analysis of the stable half-GeV beam regime showed the requirements for stable self injection and acceleration. A small change of discharge delay t dsc , and input energy E in , significantly affected performance.The statistical analysis provided information for future optimization, and suggested possible schemes for improvment of the stability and higher quality beam generation. A CDG-LWFA is envisioned as a construction block for the next generation accelerator, enabling significant cost and size reductions.

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Plasma Channels and Laser Pulse Tailoring for GeV Laser-Plasma Accelerators

Cited by 6 publications

References 0 publications

Dose properties of a laser accelerated electron beam and prospects for clinical application

Dose properties of a laser accelerated electron beam and prospects for clinical application

Laser guiding for GeV laser–plasma accelerators

Control of Laser Plasma Based Accelerators up to 1 GeV

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