Publications (11)26 Total impact
-
Article: Laser-driven proton acceleration and applications: Recent results
[show abstract] [hide abstract]
ABSTRACT: The acceleration of high-energy ion beams following the interaction of short (t < 1 ps) and intense (Iλ2 > 1018 W cm-2 μm2) laser pulses with solid targets is a field of research currently attracting high interest in the scientific community, due to some of the unique properties of these ion sources, promising routes toward the optimization of their energy content, and a number of possible, innovative applications in the scientific, technological and medical areas. Work on the characterization and development of these sources has progressed enormously over the past few years, thanks to the contribution of many groups worldwide. This paper will report some recent results, obtained in experiments carried out at the RAL and LULI laboratories, in which we investigated the ion acceleration mechanism, developed a technique to control the ion beam divergence and energy spectrum, and applied a proton radiography technique to investigate electric and magnetic field production following laser-matter interaction.The European Physical Journal Special Topics 04/2012; 175(1):105-110. · 1.56 Impact Factor -
Article: Observation of the transient charging of a laser-irradiated solid
[show abstract] [hide abstract]
ABSTRACT: The proton radiography technique has been used to investigate the incidence of a 3 ×1019W/cm2 infrared pulse with a 125μm-diameter gold wire. The laser interaction is observed to drive the growth of a radial electric field ∼ 1010V/m on the surface of the wire which rises and decays over a temporal window of 20ps. Such studies of the ultrafast charging of a solid irradiated at high-intensity may be of relevance to schemes for laser-driven ion acceleration and the fast-ignitor concept for inertial confinement fusion.The European Physical Journal D 04/2012; 55(2):293-297. · 1.48 Impact Factor -
Article: Weibel-induced filamentation during an ultrafast laser-driven plasma expansion.
[show abstract] [hide abstract]
ABSTRACT: The development of current instabilities behind the front of a cylindrically expanding plasma has been investigated experimentally via proton probing techniques. A multitude of tubelike filamentary structures is observed to form behind the front of a plasma created by irradiating solid-density wire targets with a high-intensity (I ~ 10(19) W/cm(2)), picosecond-duration laser pulse. These filaments exhibit a remarkable degree of stability, persisting for several tens of picoseconds, and appear to be magnetized over a filament length corresponding to several filament radii. Particle-in-cell simulations indicate that their formation can be attributed to a Weibel instability driven by a thermal anisotropy of the electron population. We suggest that these results may have implications in astrophysical scenarios, particularly concerning the problem of the generation of strong, spatially extended and sustained magnetic fields in astrophysical jets.Physical Review Letters 03/2012; 108(13):135001. · 7.37 Impact Factor -
Article: On the investigation of fast electron beam filamentation in laser-irradiated solid targets using multi-MeV proton emission
[show abstract] [hide abstract]
ABSTRACT: The transverse filamentation of beams of fast electrons transported in solid targets irradiated by ultraintense (5 × 1020 W cm−2), picosecond laser pulses is investigated experimentally. Filamentation is diagnosed by measuring the uniformity of a beam of multi-MeV protons accelerated by the sheath field formed by the arrival of the fast electrons at the rear of the target, and is investigated for metallic and insulator targets ranging in thickness from 50 to 1200 µm. By developing an analytical model, the effects of lateral expansion of electron beam filaments in the sheath during the proton acceleration process is shown to account for measured increases in proton beam nonuniformity with target thickness for the insulating targets.Plasma Physics and Controlled Fusion 11/2011; 53(12):124012. · 2.42 Impact Factor -
Article: Modified proton radiography arrangement for the detection of ultrafast field fronts.
[show abstract] [hide abstract]
ABSTRACT: The experimental arrangement for the investigation of high-field laser-induced processes using a broadband proton probe beam has been modified to enable the detection of the ultrafast motion of field fronts. It is typical in such experiments for the target to be oriented perpendicularly with respect to the principal axis of the probe beam. It is demonstrated here, however, that the temporal imaging properties of the diagnostic arrangement are altered drastically by placing the axis (or plane) of the target at an oblique angle to the transverse plane of the probe beam. In particular, the detection of the motion of a laser-driven field front along a wire at a velocity of (0.95+/-0.05)c is described.The Review of scientific instruments 11/2009; 80(11):113506. · 1.52 Impact Factor -
Article: Laser-driven ultrafast field propagation on solid surfaces.
[show abstract] [hide abstract]
ABSTRACT: The interaction of a 3x10;{19} W/cm;{2} laser pulse with a metallic wire has been investigated using proton radiography. The pulse is observed to drive the propagation of a highly transient field along the wire at the speed of light. Within a temporal window of 20 ps, the current driven by this field rises to its peak magnitude approximately 10;{4} A before decaying to below measurable levels. Supported by particle-in-cell simulation results and simple theoretical reasoning, the transient field measured is interpreted as a charge-neutralizing disturbance propagated away from the interaction region as a result of the permanent loss of a small fraction of the laser-accelerated hot electron population to vacuum.Physical Review Letters 06/2009; 102(19):194801. · 7.37 Impact Factor -
Article: Observation of the transient charging of a laser-irradiated solid.
The European Physical Journal D 01/2009; · 1.48 Impact Factor -
Article: Laser-Driven Proton Beams: Acceleration Mechanism, Beam Optimization, and Radiographic Applications
[show abstract] [hide abstract]
ABSTRACT: This paper reviews recent experimental activity in the area of optimization, control, and application of laser-accelerated proton beams, carried out at the Rutherford Appleton Laboratory and the Laboratoire pour lpsilaUtilisation des Lasers Intenses 100 TW facility in France. In particular, experiments have investigated the role of the scale length at the rear of the plasma in reducing target-normal-sheath-acceleration acceleration efficiency. Results match with recent theoretical predictions and provide information in view of the feasibility of proton fast-ignition applications. Experiments aiming to control the divergence of the proton beams have investigated the use of a laser-triggered microlens, which employs laser-driven transient electric fields in cylindrical geometry, enabling to focus the emitted protons and select monochromatic beamlets out of the broad-spectrum beam. This approach could be advantageous in view of a variety of applications. The use of laser-driven protons as a particle probe for transient field detection has been developed and applied to a number of experimental conditions. Recent work in this area has focused on the detection of large-scale self-generated magnetic fields in laser-produced plasmas and the investigation of fields associated to the propagation of relativistic electron both on the surface and in the bulk of targets irradiated by high-power laser pulses.IEEE Transactions on Plasma Science 09/2008; · 1.17 Impact Factor -
Article: Proton probing measurement of electric and magnetic fields generated by ns and ps laser-matter interactions
[show abstract] [hide abstract]
ABSTRACT: The use of laser-accelerated protons as a particle probe for the detection of electric fields in plasmas has led in recent years to a wealth of novel information regarding the ultrafast plasma dynamics following high intensity laser-matter interactions. The high spatial quality and short duration of these beams have been essential to this purpose. We will discuss some of the most recent results obtained with this diagnostic at the Rutherford Appleton Laboratory (UK) and at LULI -Ecole Polytechnique (France), also applied to conditions of interest to conventional Inertial Confinement Fusion. In particular, the technique has been used to measure electric fields responsible for proton acceleration from solid targets irradiated with ps pulses, magnetic fields formed by ns pulse irradiation of solid targets, and electric fields associated with the ponderomotive channelling of ps laser pulses in under-dense plasmas.Laser and Particle Beams 05/2008; 26(02). · 1.62 Impact Factor -
Article: Investigation of transient electric and magnetic fields associated to the propagation of relativistic electron currents
[show abstract] [hide abstract]
ABSTRACT: Introduction Ultra short bursts of high-energy charged particles are produced from high-intensity laser matter interactions, and have many potential applications in advanced science and technology areas [1] . A crucial application of laser-produced MeV electrons is in Inertial Confinement Fusion via Fast Ignition of a pre-compressed fuel [2,3] . Recently, the Fast Ignitor community has focused its attention on a scheme employing a re-entrant cone, which has led to significant increase in neutron yields in experiments performed at ILE, Osaka [4] . By concentrating all the laser energy at the tip of the cone, this scheme was initially envisioned as a way to circumvent the effect of inhomogeneities in the laser focal spot and non-perfect illumination of the imploded target, detrimental to the laser-coupling efficiency. An additional benefit of the cone geometry seems to be the capability of enhancing conversion efficiency into fast electrons and ions [5] . Also, the re-entrant cone geometry could allow fast electron production close to the dense core, reducing electron propagation issues through the dense plasma surrounding it. The propagation of relativistic electrons through dense matter is however a subject still attracting a great deal of experimental and theoretical attention. Scaling laws for the hot electrons produced during ultrahigh intensity interactions give K B T hot ~ U pond ~ 1 MeV • (Iλ 2 /10 19 Wcm -2 µm 2) 0.5 , with up to 30% of the laser energy converted in these relativistic electrons. There is debate on the behaviour of such large currents inside matter, and on the extent to which electromagnetic instabilities will be detrimental to their propagation. A recent experiment has shown that, by adding a thin wire at the tip of a cone one can actually guide a relativistic electron current from the tip of the cone along the wire, effectively creating a guiding device for relativistic electrons with enormous potential for applications [6] . According to simulations interpreting the experimental results, the interplay of electric and magnetic fields near the surface of the wire provides the crucial conditions for collimating and confining the electron flow. Recent work has also highlighted several interesting features of proton acceleration from cone-wire assemblies [7] . Here we report the first results of a campaign investigating the transient fields associated to relativistic electron current flow in cone-wire assemblies and solid/foam targets. These studies were carried out employing the now well-established technique of proton imaging [8] , able to provide high-resolution snapshots of the electric and magnetic field distribution present in and around a laser-irradiated target. -
Article: Relativistic current dynamics investigations by proton probing
Paul R. Bolton et al.: 2nd International Symposium on Laser-Driven Relativistic Plasmas Applied to Science, Industry and Medicine, 319-330 (2009).
Top co-authors
Top Journals
Institutions
-
2009–2012
-
Queen's University Belfast
- • Centre for Plasma Physics (CPP)
- • School of Mathematics and Physics
- • Department of Physics and Astronomy
Belfast, NIR, United Kingdom -
University of Strathclyde
- Department of Physics
Glasgow, SCT, United Kingdom
-
