A targeted way tomanipulate beams of protons accelerated using ultrashort and ultra-intense laserpulses has been demonstrated by a team of researchers led by the University of Strathclydeand performed using the Gemini laser at the Central Laser Facility.
Schematic of a beam of intense light passing through a 'relativistically transparent' aperture in a thin foil target.
Credit: University of Strathclyde
The research was enabledby recent technological developments including ultrahigh intensity contrast(which enables the use of ultrathin foils) and the deployment of an adaptiveoptic to produce a high quality focal spot.
The discovery could havea major impact on advancing smaller, cheaper, laser-driven particleaccelerators and their potential applications.
By using the diffraction of intense laser light as it passes through aself-generated ‘relativistically transparent’ aperture in an expanding thinfoil target, the researchers demonstrated that they can manipulate the strongelectrostatic fields responsible for ion acceleration
Dr. Rajeev Pattathil, Gemini Group Leader at CLF said "Being ableto optically control accelerated beams is an important step in the field oflaser-driven accelerators. This new finding from the Strathclyde team is a realbreakthrough in this field and potentially should make a considerable differencein the development of the next generation of laser driven particleaccelerators.”
“The CLF team’s bigcontribution to the research has been in facilitating the experiment usingGemini and working in collaboration with the experimental team to prepare theultra-thin foil targets and field diagnostics.”
Professor Paul McKenna,of Strathclyde’s Department of Physics, leads the project. He said: “Compactlaser-driven particle accelerators have many potential applications in science,industry and medicine. Controlling the collective motion of plasma electrons andions displaced by intense laser fields is key to the development of thesepromising sources.
“Our discovery that thediffraction of intense laser light as it passes through an ultra-thin foil stronglyinfluences the formation of electrostatic fields opens up a potential new routeto controlling laser-driven ion sources.”
The findings of theresearch, published in the journal Nature Communications, demonstrate that the collectivemotion of electrons and ions – the constituents of plasma - can be controlledby variation of the near-field, or Fresnel, diffraction pattern of intenselaser light as it passes through the aperture. It is shown that by varying thepolarisation of the laser light, the profile of the beam of accelerated protonscan be manipulated.
The study involvesresearchers at the CLF, University of Strathclyde, Queen’s University Belfast,the University of York and the Centro de Laseres Pulsados, Salamanca.
The next step in thisresearch will be to get follow-up access to the Gemini laser to continue to investigate this approach to controlling the collective behaviour of plasmaelectrons and ions. This finding is the first demonstration of this newapproach and will require time to develop and determine if it is feasible forapplications.
The research issupported by EPSRC funding and was performed using the Gemini laser at the STFC’s Central Laser Facility, at the Rutherford Appleton Laboratory. Simulationswere carried out using the ARCHIE-WeSt (University of Strathclyde) and ARCHER(Edinburgh) high performance computers. Furtherinformation:
Towards optical polarization control of laser-driven proton acceleration in foils undergoing relativistic transparency
Bruno Gonzalez-Izquierdo, Martin King, Ross J. Gray, Robbie Wilson, Rachel J. Dance, Haydn Powell,David A. Maclellan, John McCreadie, Nicholas M. H. Butler, Steve Hawkes, James S. Green, Chris D. Murphy, Luca C. Stockhausen, David C. Carroll, Nicola Booth, Graeme G. Scott, Marco Borghesi,David Neely & Paul McKenna
Nature Communications 7, 12891 (2016). doi:10.1038/ncomms12891 (link opens in a new window). Open access.
More information on Gemini
CLF Contact: David Neely