Showing papers by "Dino A. Jaroszynski published in 2012"
TL;DR: In this paper, the authors show that a source based on this emission process can produce more than 109 photons per pulse with a mean energy of 10 MeV, and compare the experimental results with GEANT4 Montecarlo simulations, which also give the scaling required to evaluate its suitability as method to produce radioisotopes via photo-nuclear reactions or for imaging applications.
Abstract: The laser driven plasma wakefield accelerator is a very compact source of high energy electrons. When the quasi-monoenergetic beam from these accelerators passes through dense material, high energy bremsstrahlung photons are emitted in a collimated beam with high flux. We show how a source based on this emission process can produce more than 109 photons per pulse with a mean energy of 10 MeV. We present experimental results that show the feasibility of this method of producing high energy photons and compare the experimental results with GEANT4 Montecarlo simulations, which also give the scaling required to evaluate its suitability as method to produce radioisotopes via photo-nuclear reactions or for imaging applications.
45 citations
TL;DR: In this article, a femtosecond laser micromachining technique is used to produce a linearly tapered plasma density, which enables the energy of the accelerator to be enhanced significantly.
Abstract: Gas-filled capillary discharge waveguides are commonly used as media for plasma wakefield accelerators. We show that effective waveguides can be manufactured using a femtosecond laser micromachining technique to produce a linearly tapered plasma density, which enables the energy of the accelerator to be enhanced significantly. A laser guiding efficiency in excess of 82% at sub-relativistic intensities has been demonstrated in a 40 mm long capillary with a diameter tapering from 320 μm to 270 μm, which gives rise to an on-axis, time-averaged plasma density that varies from 1.0 × 1018 cm−3 to 1.6 × 1018 cm−3.
19 citations
TL;DR: The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) program at the University of Strathclyde is developing laser-plasmas accelerators for the production of ultra-short high quality electron bunches.
Abstract: The Advanced Laser–Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme at the University of Strathclyde is developing laser– plasma accelerators for the production of ultra-short high quality electron bunches. Focussing such LWFA bunches into an undulator, for example, requires particular attention to be paid to the emittance, electron bunch duration and energy spread. On the ALPHA-X wakefield accelerator beam line, a high intensity ultra-short pulse from a 30 TW Ti:Sapphire laser is focussed into a helium gas jet to produce femtosecond duration electron bunches in the range of 90–220 MeV. Measurements of the electron energy spectrum, obtained using a high resolution magnetic dipole spectrometer, show electron bunch r.m.s. energy spreads down to 0.5%. A pepper-pot mask is used to obtain transverse emittance measurements of a 128±3 MeV mono-energetic electron beam. An average normalized emittance of erms,x,y = 2.2±0.7, 2.3±0.6 π-mm-mrad is measured, which is comparable to that of a conventional radio-frequency accelerator. The best measured emittance of erms,x, = 1.1±0.1 π-mm-mrad corresponds to the resolution limit of the detection system. 3D particle-in-cell simulations of the ALPHA-X accelerator partially replicate the generation of low emittance, low energy spread bunches with charge less than 4 pC and gas flow simulations indicate both long density ramps and shock formation in the gas jet nozzle.
9 citations
TL;DR: In this paper, a kinetic theory is developed to describe radiating electrons whose motion is governed by the Lorentz-Dirac equation, which gives rise to a generalized Vlasov equation coupled to an equation for the evolution of the physical submanifold of phase space.
Abstract: A kinetic theory is developed to describe radiating electrons whose motion is governed by the Lorentz-Dirac equation. This gives rise to a generalized Vlasov equation coupled to an equation for the evolution of the physical submanifold of phase space. The pathological solutions of the 1-particle theory may be removed by expanding the latter equation in powers of $\tau := q^2/ 6\pi m$. The radiation-induced change in entropy is explored, and its physical origin is discussed. As a simple demonstration of the theory, the radiative damping rate of longitudinal plasma waves is calculated.
8 citations
TL;DR: The beam model based on an average energy of particles in irradiation gives an acceptable estimate of the induced radioactivity and the dose deposited in the BANG dosimeter and shows that the structure of the spectra of VHEE beams in the experiment and secondary scattered particles in the beam line should be accounted for in any model.
Abstract: This meeting abstract looks at the characterization of the very high energy electrons, 150-250 MeV (VHEE) beam generated by ALPHA-X laser wakefield accelerator beam line for utilization in Monte Carlo simulation for biomedical experiment planning
4 citations
TL;DR: In this paper, a straight and linearly tapered capillary discharge waveguide was produced using femtosecond laser micromachining technique, which can achieve up to 82% energy transmission of the fundamental Gaussian mode of a low intensity, 50 fs duration laser pulse for both types of waveguide.
Abstract: Gas-filled capillary discharge waveguides are a commonly employed medium in laser–plasma interaction applications, such as the laser wakefield accelerator, because they can simultaneously guide high-power laser pulses while acting as the medium for acceleration. In this paper, the production of both straight and linearly tapered capillaries using a femtosecond laser micromachining technique is presented. A tapered capillary is shown to possess a smooth variation in diameter (from 305 μm to 183 μm) along its entire 40 mm length, which would lead to a longitudinal plasma density gradient, thereby dramatically improving the laser–plasma interaction efficiency in applications. Efficient guiding with up to 82% energy transmission of the fundamental Gaussian mode of a low intensity, 50 fs duration laser pulse is shown for both types of capillary waveguide.
2 citations
08 Jul 2012
TL;DR: The gas-filled capillary discharge waveguide (CDW) is a commonly applied accelerating structure for the laser wakefield accelerator (LWFA) because an intense femtosecond laser pulse can be successfully guided over several centimetres, leading to the generation of GeV-scale electron beams.
Abstract: Summary form only given. The gas-filled capillary discharge waveguide (CDW) is a commonly applied accelerating structure for the laser wakefield accelerator (LWFA) because an intense femtosecond laser pulse can be successfully guided over several centimetres, leading to the generation of GeV-scale electron beams. Simulations have shown that tapering the longitudinal plasma density leads to significant enhancement of the final electron energy in a single accelerating stage.
08 Jul 2012
TL;DR: In this article, it is shown that some parts of the terahertz frequency components have been cut off by plasma, and with the density of plasma rising, the starting frequency of THz prohibited by plasma is going higher.
Abstract: Summary form only given. Research on terahertz wave transmission through plasma is significant for researches on plasma itself and transmission discipline of terahertz wave through plasma. It is possible for plasma with suitable density to be an available stealth outerwear for plane or missile in THz waveband. In this paper, plasma is gotten by ionizing inert gases such as argon and helium gases with pulsed high alternating voltage. With electro-optic pump-probe measurement, THz transmission phenomena through plasma have been studied. The experiments show that some parts of THz frequency components have been cut off by plasma, and with the density of plasma rising, the starting frequency of THz prohibited by plasma is going higher. Experiments also provide an assistant scheme for plasma diagnose with terahertz technique.
08 Jul 2012
TL;DR: In this article, the energy spread for a relatively small electron bunch is affected by beam loading in the bubble regime, and the results have a strong impact on emerging applications such as short-pulse and short-wavelength radiation sources.
Abstract: Summary form only given. Acceleration of particles driven by the interaction of a relativistic laser intensity, having femtosecond duration, with an under-dense plasma can produce plasma wave, in the form of bubble, delivering several hundred gigavolts per meter accelerating electric fields [1] and deliver high quality femtosecond-scale electron beams with relatively narrow energy spread [2] and low emittance [3]. We will discuss how the energy spread for such relatively small electron bunch is affected by beam loading in the bubble regime. Electrons that are accelerated in the wakefield also oscillate transversely and emit very bright x-rays and gamma-rays due to a harmonically resonant betatron oscillation [4]. This synchrotron-like radiation occurs in a “wiggler” formed by the electrostatic forces of the plasma wave. These results will have a strong impact on emerging applications such as short-pulse and short-wavelength radiation sources.