When EPAC is focussed onto a gas target, a plasma is formed with an extremely high acceleration gradient. This acceleration gradient is about 1000x that achievable with conventional technology, allowing electrons to be accelerated to GeV energies within a few centimetres. The EPAC facility has been designed specifically to develop these Laser-Plasma Accelerators to generate high brightness pulsed laser-driven radiation and particle sources for industry, medicine and defence.

EPAC is capable of producing x-rays using three different techniques, each requiring minimal changes to the beamline and each providing different beam characteristics. This flexibility of the x-ray sources provided by EPAC means that they can be tuneable from few keV to multi-MeV, and can be customised according to user requirements. EPAC will be able to apply these high-quality x-rays for high-resolution imaging and non-destructive evaluation of a wide range of samples.

The first technique, betatron radiation is generated during the acceleration of electrons via laser-plasma acceleration as they oscillate in the wake behind the laser pulse. This process produces low divergence, broad band x-rays typically in the 10 - 100 keV range. The x-ray source size is of order 1 μm, enabling high resolution imaging and providing phase contrast through the spatial coherence of the beam. This technique, improves contrast in weakly absorbing materials, such as soft tissue and carbon composite materials. Laser driven betatron x-rays have been shown to produce bright x-rays; experiments on Gemini have already achieved peak brilliances of >10²³ photons. s^-1. mrad^-2. mm^-2 (0.1% BW) between 20 and 150 keV.

The second technique is Inverse Compton Scattering (ICS), in which the electron beam collides with a short laser pulse coming from the other direction. In a directly counter-propagating geometry, this generates a 4γ² upshift in photon frequency (where γ is the relativistic factor of the electron beam) producing x-rays with a narrow energy spread that can be tuned. Peak photon energies between 50 keV and tens of MeV can be achieved with an x-ray source size of order 10 μm.

The third technique generates bremsstrahlung radiation by interaction of the electron beam with a solid convertor target. This is capable of producing extremely bright broadband x-rays with peak energies of tens of MeV with a sub-100 μm x-ray source size. This has been demonstrated on Gemini producing one of the highest peak brilliances reported in the literature in the MeV range achieving >1.8 ×10²⁰ photons s^-1. mrad^-2. mm^-2 0.1% BW at 15 MeV, a total flux of 10⁷ photons per shot exceeding 6 MeV and energies peaking at 18 MeV.

As the x-ray pulses are delivered in femtosecond-picosecond pulses (dependent on technique), laser-driven, penetrating x-ray beams are brief enough to 'freeze frame' fast processes, such as a turbine spinning at high speed, eliminating the motion blur that can be a problem with conventional NDE technology.

The high brightness of the x-ray pulses will allow EPAC to acquire single-shot images with good signal-to-noise levels at 10 frames per second, allowing micron resolution CT scans to be taken in a matter of minutes; a new high for x-rays produced by laser-plasma acceleration.