Fast electron generation and transport
18 Sep 2012



Experiments on the Vulcan facility have revealed the role played between relativistic electron beams and self-generated magnetic fields in controlling the accelerated electron divergence in a fast ignition scheme.


Isochoric heating of a solid density target by a fast electron beam, generated by an ultra-intense laser-plasma interaction

(Credit: Physical Review Letters 2014)

Controlling relativistic electron beams 

Many of the highly promising applications that are being developed using ultra-high intensity lasers rely on an initial process of creating high flux beams of relativistic electrons. Understanding how these fast electrons are created at the focus of the laser and subsequently transported through a (typically) dense, solid target material remains a highly active area of experimental and theoretical research.

The production of hard X-ray Bremsstrahlung sources [1] or rapid isochoric heating [2] are two applications that could benefit greatly from better control of bright fast electron sources. One high profile example of the latter is the fast ignitor inertial confinement fusion (ICF) concept [3], which aims to use a carefully timed pulse of fast electrons to isochorically heat a pre-compressed fuel capsule, potentially reducing the initial compression requirements and boosting the overall fuel gain. For all of these applications there is a great demand for both improving the diagnosis and control of key electron beam parameters such as temperature, flux and divergence.

The Vulcan laser (and more recently Gemini laser) has been a crucial tool in helping the high power laser user community to not only better understand the fundamental processes of fast electron generation but also to test novel laser and target geometries with the aim of controlling electron beam parameters.

Recent CLF Results

Time-resolved measurements of fast electron recirculation for relativistically intense femtosecond scale laser-plasma interactions - J.S. Green et al. Sci. Rep. 8 4525 (2018)

An experiment on the CLF’s Gemini laser investigated the heating effects of relativistic electrons trapped inside aluminium foils. The researchers used the dual beam capability of Gemini to probe ultra-intense laser interactions and reveal how electrons continue to deposit energy as they recirculate inside targets on a time scale much longer than the pulse duration.

Optically controlled dense current structures driven by relativistic plasma aperture-induced diffraction (link opens in a new window) - B. Gonzalez-Izquierdo et al. Nat. Phys. (2016)

B. Gonzalez-Izquierdo et al.
Simulations illustrate the laser pulse diffracting through the relativistic transparency induced pinhole, causing the accelerated electrons to spiral (Credit: Gonzalez-Izquierdo et al, Nature Physics 2016 )

A team of researchers from the University of Strathclyde have used a relativistic induced transparency effect to diffract ultra-intense laser light. By changing the polarisation of the laser they were able to modify the diffraction pattern and hence the shape of the resulting accelerated electron beam.

Evidence of locally enhanced target heating due to instabilities of counter-streaming fast electron beams (link opens in a new window) - P Koester et al. Phys. Plasmas 22 020701 (2015)

Credit - Physics of Plasmas 2015

An experiment on Vulcan Petawatt aimed to look at the effects of two counter-streaming fast electron beams. Enhancement in energy deposition in the target foil was observed, making this a promising method for generating hot dense matter.

APL Robinson et al. Phys. Plasmas 22 103104 (2015)
Evolution of the angular distribution of laser-generated fast electrons due to resistive self-collimation (link opens in a new window)

DA MacLellan et al. Phys. Rev. Lett.113 185001 (2014)
Tunable Mega-Ampere Electron Current Propagation in Solids by Dynamic Control of Lattice Melt (link opens in a new window)

O Culfa et al. Phys. Plasmas 21 043106 (2014)
Hot electron production in laser solid interactions with a controlled pre-pulse (link opens in a new window)

R Gray et al. New J. Phys.16 113075 (2014)
Laser pulse propagation and enhanced energy coupling to fast electrons in dense plasma gradients (link opens in a new window)

APL Robinson et al.Phys. Rev. Lett.111 65002 (2013)
Generating 'Superponderomotive' Electrons due to a Non-Wake-Field Interaction between a Laser Pulse and a Longitudinal Electric Field (link opens in a new window)

DA MacLellan et al.Phys. Rev. Lett.111 95001 (2013)
Annular Fast Electron Transport in Silicon Arising from Low-Temperature Resistivity (link opens in a new window)


[1] Edwards et al. Appl. Phys. Lett. 80, 2129 (2002)
[2] T.G.White et al. Phys. Rev. Lett. 112, 145005 (2014)
[3] Tabak et al. Phys. Plasmas 1 1626 (1994)

Contact: Green, James (STFC,RAL,CLF)