Laser and preparation laboratory

 

View of the laser lab, showing the oscillator and two power amplifiers. The 12 fs pulse from the oscillator is stretched, amplified to 800 mJ and recompressed

Situated above the tunnel of FLASHForward are two associated laboratories. One of them houses the 25 TW laser that is used as in ignitor for the plasma channel. The laser compressor is situated in this lab, with a nearly 60 m beam transport line delivering the 25 fs duration pulses into the experimental chamber in the FLASHForward beam line. Next to the laser lab is an experimental area which can also receive the compressed laser pulses. This area is essential in delivering successful experiments in the main tunnel as most components and diagnostics are developed and tested here.

View of the vacuum chamber used for laser wakefield acceleration experiments

The experimental lab is currently divided between two main experiments. One of these works on characterising the plasma targets used on the FLASHForward experiments. All new plasma targets are developed and first tested here. Advanced diagnostics are employed to measure the plasma density, uniformity and temperature, parameters that are vital for accurate evaluation of the experimental results obtained with the electron beam driver.
The other experiments performed in the experimental area focus on generating electron beams via laser wakefield acceleration (LWFA). Here, instead of the electron beam, the laser pulse itself is used to drive a highly relativistic and non-linear plasma wave, capable of accelerating electrons to energies of a few hundred megaelectronvolts in mere millimeters. Research is focused on, among other things, x-rays emitted by these electrons, called betatron radiation, to understand how the betatron beam parameters relate to the electron beam itself.
As a test-bed for advanced electron beam diagnostics many other novel diagnostics, which will eventually be used to understand the behavior of the electron beams in FLASHForward, will be tested here. These include cavity based charge diagnostics, transition radiation based longitudinal phase space diagnostics, Thomson scattering setup and many more. Particular attention is given to plasma lenses, compact plasma based focussing optics for electron beams. The flexibility of the setup and surrounding infrastructure allows any new idea to be quickly prototyped and tested for proof of principle.

CAD rendering of the complete beam transport line from the laser system to the FLASHForward beamline