Development of a multi-pulse laser wakefield electron accelerator operating at kHz rep-rate

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics


Laser-driven plasma accelerators can already accelerate electrons to GeV-scale energies in accelerator stages only a few centimetres long. However, the driving lasers used to date can only operate at best at a few pulses per second, and have very low wall-plug efficiencies. The laser-plasma accelerator group at Oxford has pioneered a novel approach for overcoming these limitations: the multi-pulse laser wakefield accelerator (MP-LWFA). In this approach the plasma wakefield is driven by a train of low energy laser pulses. If these pulses are spaced by the plasma period then the wakefields driven by the pulses add coherently, yielding a plasma wave which grows towards the back of the pulse train. The Oxford team recently demonstrated this approach for the first time in experiments performed at the Rutherford Appleton Laboratory (RAL). In that work it was shown that plasma wakefields could indeed be resonantly excited by a train of laser pulses, confirming this validity of this approach. However, to date electrons have not been accelerated by this method since the wakefields driven by MP-LWFA are linear, and as such do not self-trap electrons from the background plasma. The aim of this project is to develop techniques for controlling the injection of electrons into the quasi-linear wakefields driven by a MP-LWFA. Two approaches will be studied. In the first, the use of additional laser pulses to ionize a dopant species will be explored. If a short laser pulse (the "injection" pulse) is focused in the wake driven by the pulse train, then electrons ionized by the second laser pulse can be trapped into the wakefield, and then accelerated. The second approach to be explored will be down-ramp injection. In this method the density of the plasma decreases rapidly with longitudinal position; this slows the wakefield as it moves down the ramp, making it easier for electrons to be trapped, and then accelerated. These injection techniques will be studied through experiments performed in Oxford, at RAL, and, potentially, at other laser facilities, backed up by numerical simulations with particle-in-cell (PIC) codes. If successful this work will open the route to a new generation of very compact plasma accelerators operating at multi-kilohertz pulse repetition rates. These would immediately find applications in driving very compact X-ray sources, with widespread utility in ultrafast science, technology, and medicine.


10 25 50

Studentship Projects

Project Reference Relationship Related To Start End Student Name
ST/R505006/1 30/09/2017 29/09/2021
1937392 Studentship ST/R505006/1 30/09/2017 29/09/2021 Alexander Picksley
Description HOFi Channels with UMD 
Organisation University of Maryland
Country United States 
Sector Academic/University 
PI Contribution I have designed a gas cell and parts for a collabortation with the University of Maryland and will collaborate on a new experiment with them
Collaborator Contribution University of Maryland have offered expertise from their previous research on formation of plasma channels.
Impact A paper will soon be published detailing results of a joint experiment
Start Year 2019