Colloquium

  • Plasma as a Compact Amplifier and Accelerator

  • Speaker : Prof. Dino Jaroszynski FRSE FInstP, Director of the Scottish Centre for the Application of Plasma-based Accelerators, SCAPA
    Affiliation : Physics Department, University of Strathclyde
    Date : November 1, 2017 4:00 PM
    Place : Building 110 Room N103
    Contact : mshur@unist.ac.kr
    Host : Minsup Hur
  • Abstract

  • Exciting waves in plasma can result in huge electro-static fields, exceeding 1 TV/m, or an optically active medium capable of amplifying light to peak powers that can potentially exceed current laser technologies by orders of magnitude. The talk will review the development of these plasma-based amplifiers, accelerators and radiation sources based on them. These next-generation, ultra-compact devices have niche potential for some applications, and could become widespread because of their lower cost and compactness, when compared with conventional technology. Plasma-based amplifiers based on Raman amplification have the potential to extend the peak power of lasers to exawatts simply by creating a plasma density echelon using colliding laser pulses. Plasma-based laser wakefield accelerators (LWFAs) can be three orders of magnitude shorter than conventional accelerators for the same energy. Their dramatic reduction in size also results in ultra-short electron bunches, which are much shorter than from conventional accelerators. The duration of the electron bunches from the LWFA has been inferred from the spectrum of mid-infrared coherent transition radiation emitted as the bunches pass through a thin metal foil, which has been found it to be consistent with one femtosecond duration electron bunches, which is surprisingly short, and two orders of magnitude shorter than from conventional accelerators. We will also present a theoretical investigation that predicts the production of 100 attosecond electron bunches by controlling injection in a LWFA. A peak current of greater than 10 kA is possible, even for modest charge, which makes the LWFA suitable for driving a free-electron laser (FEL). Though still a challenge, the development of a FEL that is based on the LWFA should be feasible. However, the LWFA has some interesting intrinsic properties, which can be taken advantage of. Their plasma structures have extremely large fields, in excess of 100 GV/m, which also drive transverse “betatron” motion of the accelerating electrons. This gives rise to wiggler-like femtosecond duration pulses of X-ray synchrotron radiation. We will discuss experiments carried out to observe femtosecond duration gamma-ray betatron emission, where photon energies of up to 7 MeV have been measured. The peak brilliances measured are similar to fourth-generation synchrotron sources, but in a photon energy range that is not usually accessible. The electron bunches can also be used to produce unprecedented high intensity, short duration X-ray pulses. Finally, we will discuss several medical applications of these particle and radiation sources, in particular extremely high dose rate radiotherapy and medical imaging. We will also discuss recent work to investigate high gain, high-efficiency plasma-based laser amplifiers through the production of plasma echelons.