S. Cipiccia

Scottish Universities Physics Alliance, Glasgow, Scotland, United Kingdom

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Publications (20)37.06 Total impact

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    ABSTRACT: New acceleration technology is mandatory for the future elucidation of fundamental particles and their interactions. A promising approach is to exploit the properties of plasmas. Past research has focused on creating large-amplitude plasma waves by injecting an intense laser pulse or an electron bunch into the plasma. However, the maximum energy gain of electrons accelerated in a single plasma stage is limited by the energy of the driver. Proton bunches are the most promising drivers of wakefields to accelerate electrons to the TeV energy scale in a single stage. An experimental program at CERN -- the AWAKE experiment -- has been launched to study in detail the important physical processes and to demonstrate the power of proton-driven plasma wakefield acceleration. Here we review the physical principles and some experimental considerations for a future proton-driven plasma wakefield accelerator.
    01/2014;
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    ABSTRACT: Compton side-scattering has been used to simultaneously downshift the energy of keV to MeV energy range photons while attenuating their flux to enable single-shot, spectrally resolved, measurements of high flux X-ray sources to be undertaken. To demonstrate the technique a 1 mm thick pixelated cadmium telluride detector has been used to measure spectra of Compton side-scattered radiation from a Cobalt-60 laboratory source and a high flux, high peak brilliance X-ray source of betatron radiation from a laser-plasma wakefield accelerator.
    The Review of scientific instruments 11/2013; 84(11):113302. · 1.52 Impact Factor
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    ABSTRACT: The development, understanding and application of laser-driven particle accelerators require accurate measurements of the beam properties, in particular emittance, energy spread and bunch length. Here we report measurements and simulations showing that laser wakefield accelerators can produce beams of quality comparable to conventional linear accelerators.
    AIP Conference Proceedings. 12/2012; 1507(1).
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    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 ϵrms,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 ϵrms,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.
    Journal of Plasma Physics 08/2012; 78(04):393-399. · 0.76 Impact Factor
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    ABSTRACT: Purpose: Progress in the development of compact high-energy pulsed laser- plasma wakefield accelerators is opening up the potential for using Very High Energy Electron (VHEEs) beams in the range of 150 - 250 MeV for biomedical studies. Initial experiments using VHEE for this purpose have been carried out using the ALPHA-X laser-plasma wakefield accelerator beam line at the University of Strathclyde, Glasgow, UK. The purpose of this investigation is to use Monte Carlo simulations to plan experiments and compare with characterization of the interaction of the VHEE beam using a dosimeter. Methods: An experiment using the VHEE beam to irradiate a muscle-equivalent BANG polymer gel dosimeter has been carried out. Simulations have been used to prepare for the experiments. These were undertaken using the expected average energy for a pulse set and an energy spread approximated by Gaussian distribution. The model was implemented in FLUKA Monte Carlo code with follow up modeling using the Geant4 toolkit. The results have been compared with 1mm^3 voxel laser CT based measurements of the dose deposited in the BANG dosimeter and with measurement of the induced radioactivity. Results: The results of the measured dose from induced radioactivity have been compared with data from the FLUKA simulations. 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. Comparison with the dosimeter scanned profiles 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. Such model description of the VHEE beam for the ALPHA-X beam line has been developed. Conclusions: Monte Carlo simulations using the FLUKA code is an efficient way to plan a VHEE experiment and analyze data from measurements.
    Medical Physics 06/2012; 39(6):3813-3814. · 2.91 Impact Factor
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    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 10{sup 9} 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.
    Journal of Applied Physics 03/2012; 111(6). · 2.21 Impact Factor
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    ABSTRACT: This paper presents realisation of linearly tapered capillary discharge waveguides (CDWs), manufactured using a femtosecond laser micromachining technique. Waveguiding of a low power, 50 fs duration laser pulse is demonstrated and, despite a slight mismatch of the laser focal spot size with respect to the capillary entrance size, efficient guiding of the Gaussian-shaped laser pulse is obtained. Energy transmission of 80% is obtained for optimal delay of the laser pulse arrival time with respect to the discharge current pulse.
    Plasma Science (ICOPS), 2012 Abstracts IEEE International Conference on; 01/2012
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    ABSTRACT: 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.
    Plasma Science (ICOPS), 2012 Abstracts IEEE International Conference on; 01/2012
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    ABSTRACT: An intense laser pulse in a plasma can accelerate electrons to GeV energies in centimetres. Transverse betatron motion in the plasma wake results in X-ray photons with an energy that depends on the electron energy, oscillation amplitude and frequency of the betatron motion. Betatron X-rays from laser-accelerator electrons have hitherto been limited to spectra peaking between 1 and 10keV (ref. ). Here we show that the betatron amplitude is resonantly enhanced when electrons interact with the rear of the laser pulse. At high electron energy, resonance occurs when the laser frequency is a harmonic of the betatron frequency, leading to a significant increase in the photon energy. 108 gamma-ray photons, with spectra peaking between 20 and 150keV, and a peak brilliance >1023photonss-1mrad-2mm-2 per 0.1% bandwidth, are measured for 700MeV beams, with 107 photons emitted between 1 and 7MeV. Femtosecond duration gamma-rays may find uses in imaging, isotope production, probing dense matter, homeland security and nuclear physics.
    Nature Physics 09/2011; 7(11):867-871. · 19.35 Impact Factor
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    ABSTRACT: The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme is developing laserplasma accelerators for the production of ultra-short electron bunches with subsequent generation of high brilliance, short-wavelength radiation pulses. Ti:sapphire laser systems with peak power in the range 20-200 TW are coupled into mm- and cm-scale plasma channels in order to generate electron beams of energy 50-800 MeV. Ultra-short radiation pulses generated in these compact sources will be of tremendous benefit for time-resolved studies in a wide range of applications across many branches of science. Primary mechanisms of radiation production are (i) betatron radiation due to transverse oscillations of the highly relativistic electrons in the plasma wakefield, (ii) gamma ray bremsstrahlung radiation produced from the electron beams impacting on metal targets and (iii) undulator radiation arising from transport of the electron beam through a planar undulator. In the latter, free-electron laser action will be observed if the electron beam quality is sufficiently high leading to stimulated emission and a significant increase in the photon yield. All these varied source types are characterised by their high brilliance arising from the inherently short duration (~1-10 fs) of the driving electron bunch.
    Proc SPIE 05/2011;
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    ABSTRACT: The normalised transverse emittance is a measure of the quality of an electron beam from a particle accelerator. The brightness, parallelism and focusability are all functions of the emittance. Here we present a high-resolution single shot method of measuring the transverse emittance of a 125 +/- 3 MeV electron beam generated from a laser wakefield accelerator (LWFA) using a pepper-pot mask. An average normalised emittance of ɛrms,x,y = 2.2 +/- 0.7, 2.3 +/- 0.6 π-mmmrad was measured, which is comparable to that of a conventional linear accelerator. The best measured emittance was ɛrms,x,=1.1 +/- 0.1 π-mm-mrad, corresponding to the resolution limit of our system. The low emittance indicates that this accelerator is suitable for driving a compact free electron laser.
    Proc SPIE 05/2011;
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    ABSTRACT: In this paper, we present a single-shot transverse emittance measurement for 125 ± 3 MeV electron beam using pepper-pot technique. A normalised transverse emittance as low as 1.1 ± 0.1 -mm-mrad was measured using this method. Considering 60 consecutive shots, an average normalised emittance of ε rms,x,y =2.2 ± 0.7, 2.3 ± 0.6 -mm-mrad was obtained, which is comparable to a conventional linear accelerator. We also obtained high energy monoenergetic electron beam with relative energy spread less than 1%. The measured transverse emittance characterises the quality of an electron beam generated from laser-driven accelerator. Brightness, parallelism and focusability are all functions of the emittance. The low emittance and energy spread indicates that this type of accelerator is suitable for compact free electron laser driver.
    DIPAC 2011, Hamburg; 01/2011
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    ABSTRACT: High quality electron beams have been produced in a laser-plasma accelerator driven by femtosecond laser pulses with a peak power of 26 TW. Electrons are produced with an energy up to 150 MeV from the 2 mm gas jet accelerator and the measured rms relative energy spread is less than 1%. Shot-to-shot stability in the central energy is 3%. Pepper-pot measurements have shown that the normalized transverse emittance is ~1π mm mrad while the beam charge is in the range 2–10 pC. The generation of high quality electron beams is understood from simulations accounting for beam loading of the wakefield accelerating structure. Experiments and self-consistent simulations indicate that the beam peak current is several kiloamperes. Efficient transportation of the beam through an undulator is simulated and progress is being made towards the realization of a compact, high peak brilliance free-electron laser operating in the vacuum ultraviolet and soft x-ray wavelength ranges.
    Plasma Physics and Controlled Fusion 11/2010; · 2.37 Impact Factor
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    ABSTRACT: Progress in laser wakefield accelerators indicates their suitability as a driver of compact free-electron lasers (FELs). High brightness is defined by the normalized transverse emittance, which should be less than 1π mm mrad for an x-ray FEL. We report high-resolution measurements of the emittance of 125 MeV, monoenergetic beams from a wakefield accelerator. An emittance as low as 1.1±0.1π mm mrad is measured using a pepper-pot mask. This sets an upper limit on the emittance, which is comparable with conventional linear accelerators. A peak transverse brightness of 5×10¹⁵ A m⁻¹ rad⁻¹ makes it suitable for compact XUV FELs.
    Physical Review Letters 11/2010; 105(21):215007. · 7.94 Impact Factor
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    ABSTRACT: The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme is developing laserplasma accelerators for the production of ultra-short electron bunches with subsequent generation of incoherent radiation pulses from plasma and coherent short-wavelength radiation pulses from a free-electron laser (FEL). The first quantitative measurements of the electron energy spectra have been made on the University of Strathclyde ALPHA-X wakefield acceleration beam line. A high peak power laser pulse (energy 900 mJ, duration 35 fs) is focused into a gas jet (nozzle length 2 mm) using an F/16 spherical mirror. Electrons from the laser-induced plasma are self-injected into the accelerating potential of the plasma density wake behind the laser pulse. Electron beams emitted from the plasma have been imaged downstream using a series of Lanex screens positioned along the beam line axis and the divergence of the electron beam has been measured to be typically in the range 1-3 mrad. Measurements of the electron energy spectrum, obtained using the ALPHA-X high resolution magnetic dipole spectrometer, are presented. The maximum central energy of the monoenergetic beam is 90 MeV and r.m.s. relative energy spreads as low as 0.8% are measured. The mean central energy is 82 MeV and mean relative energy spread is 1.1%. A theoretical analysis of this unexpectedly high electron beam quality is presented and the potential impact on the viability of FELs driven by electron beams from laser wakefield accelerators is examined.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    05/2009;
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    ABSTRACT: The transverse emittance is an important parameter governing the brightness of an electron beam. Here we present the first pepper-pot measurement of the transverse emittance for a mono-energetic electron beam from a laser-plasma wakefield accelerator, carried out on the Advanced Laser-Plasma High Energy Accelerators towards X-Rays (ALPHA-X) beam line. Mono-energetic electrons are passed through an array of 52 μm diameter holes in a tungsten mask. The pepper-pot results set an upper limit for the normalised emittance at 5.5 ± 1 π mm mrad for an 82 MeV beam.
    Proc SPIE 05/2009;
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    ABSTRACT: Electron acceleration using plasma waves driven by ultra-short relativistic intensity laser pulses has undoubtedly excellent potential for driving a compact light source. However, for a wakefield accelerator to become a useful and reliable compact accelerator the beam properties need to meet a minimum standard. To demonstrate the feasibility of a wakefield based radiation source we have reliably produced electron beams with energies of 82+/-5 MeV, with 1+/-0.2% energy spread and 3 mrad r.m.s. divergence using a 0.9 J, 35 fs 800 nm laser. Reproducible beam pointing is essential for transporting the beam along the electron beam line. We find experimentally that electrons are accelerated close to the laser axis at low plasma densities. However, at plasma densities in excess of 1019 cm-3, electron beams have an elliptical beam profile with the major axis of the ellipse rotated with respect to the direction of polarization of the laser.
    Proc SPIE 05/2009;
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    ABSTRACT: The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme is developing laserplasma accelerators for the production of ultra-short electron bunches with subsequent generation of incoherent radiation pulses from plasma and coherent short-wavelength radiation pulses from a free-electron laser (FEL). The first quantitative measurements of the electron energy spectra have been made on the University of Strathclyde ALPHA-X wakefield acceleration beam line. A high peak power laser pulse (energy 900 mJ, duration 35 fs) is focused into a gas jet (nozzle length 2 mm) using an F/16 spherical mirror. Electrons from the laser-induced plasma are self-injected into the accelerating potential of the plasma density wake behind the laser pulse. Electron beams emitted from the plasma have been imaged downstream using a series of Lanex screens positioned along the beam line axis and the divergence of the electron beam has been measured to be typically in the range 1-3 mrad. Measurements of the electron energy spectrum, obtained using the ALPHA-X high resolution magnetic dipole spectrometer, are presented. The maximum central energy of the monoenergetic beam is 90 MeV and r.m.s. relative energy spreads as low as 0.8% are measured. The mean central energy is 82 MeV and mean relative energy spread is 1.1%. A theoretical analysis of this unexpectedly high electron beam quality is presented and the potential impact on the viability of FELs driven by electron beams from laser wakefield accelerators is examined.
    Proc SPIE 05/2009;
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    ABSTRACT: The origin of electron trapping at the back of a ‘bubble’, which is formed when the electrons are expelled from an under-dense plasma by an intense laser pulse, is investigated using a reduced model wakefield. The subsequent acceleration and transverse oscillation produces betatron radiation. Such electromagnetic radiation emitted by trapped electron in an ionic bubble is estimated using the Lienard-Wiechert potential.
    12/2008: pages 543-548;
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    ABSTRACT: The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme at the University of Strathclyde is developing laser-plasma wakefield accelerators to produce high energy, ultra-short duration electron bunches as drivers of radiation sources. Coherent emission will be produced in a free-electron laser by focussing the ultra-short electron bunches into an undulator. To achieve net gain, high peak current, low energy spread and low emittance are required. 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 80 - 200 MeV. Beam transport is monitored using a series of Lanex screens positioned along the beam line. Measurements of the electron energy spectrum, obtained using the ALPHA-X high resolution magnetic dipole spectrometer, are presented. The maximum central energy of the monoenergetic beam is 90 MeV and r.m.s. relative energy spreads as low as 0.8% are measured. The mean central energy is 82 ± 4 MeV and mean energy spread is 1.1 ± 0.4%. We also present pepper-pot measurements of the normalised transverse emittance where mono-energetic electrons are passed through an array of 52µm diameter holes in tungsten. The analysis of the pepper-pot results sets an upper limit for the normalised emittance at 5.5 ± 1π mm mrad for an 82 MeV beam. With further acceleration to 1 GeV, the relative energy spread will reduce giving beam parameters that indicate the feasibility of a compact X-ray FEL driven by a plasma-wakefield accelerator.