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Energy recovery is coming to plasma acceleration

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The JAI team has made an important step towards the prospects of energy recovery in plasma accelerators.

The JAI team led by Prof Simon Hooker has initiated, couple years ago, research towards novel approach for plasma acceleration – so called MP-LWFA, i.e. multi-pulse laser wakefield acceleration. The key idea of this approach is that plasma can be excited (see illustration) by a train of low energy laser pulses separated by the plasma wavelength. The beauty of this idea is that the energy required to drive the plasma wave is delivered over several plasma periods, opening plasma accelerators to emerging laser technologies such as fibre and thin-disk lasers. These new laser systems can deliver the required energy at pulse repetition rates of tens of kHz, whereas the traditional Ti:Sapphire lasers, can at most work at 10 Hz. Moreover, fibre lasers have much higher wall-plus efficiency – more than 20%, in comparison with modest 0.1% efficiency of Ti:Sapphire lasers.

It is certainly the case that the high rep-rate and higher wall-plug efficiency are very attractive features of the MP-LWFA scheme. But this is not yet the whole story. Any plasma acceleration facility, light source or plasma acceleration-based collider, would strongly benefit from minimizing the overall power consumption of the facility. Meanwhile, when the exited plasma has done its job – accelerated beams of electrons, there is still quite a lot of energy remaining in the wake.

The recent research by the JAI team has shown that in fact a trailing, out-of-resonance laser pulse could extract the unused wakefield energy via blue-shifting the laser pulse, and therefore this energy in principle could be recycled. This achievement - In addition to showing that laser pulse trains could drive plasma wakefields – has been recently highlighted in the APS Physics Synopsis following the publication in the Phys Rev Letters.

We congratulate Prof Simon Hooker and his team for this achievement – demonstration of the possibility of the energy recovery in MP-LWFA, and with verification of MP-LWFA feasibility with 7-pulse experiment performed at the UK Central Laser Facility.

For more details also see this blog