Polarised particle beams are indispensable for the study of spin-dependent processes . The LEAP (Laser Electron Acceleration with Polarisation) project at DESY aims to demonstrate the acceleration of polarised electrons in the extremely high fields enabled by laser plasma accelerators to create high energy electron beams in ultra-compact footprint. In this proof of principle experiment, spin-polarised electron beams with energies of tens of MeV will be generated in a sub-millimetre long plasma source. For electron beams of such energies, Compton transmission polarimetry is the ideal method to measure the polarisation. Gamma rays produced by bremsstrahlung are transmitted through an iron absorber core magnetised by a surrounding solenoid, with rate and energy spectrum depending on the relative orientation of the gamma spin and the magnetisation direction of the iron. The transmission asymmetry with respect to the direction of the magnetisation is proportional to the initial electron polarisation. In this contribution, an overview of the LEAP project is presented, detailing the setup of the polarimeter as well as its implementation and commissioning status.

Compton transmission polarimetry of laser-plasma accelerated electron beams