P-4: Transverse Laser Probe

Principle Investigator:
Lucas Schaper

Contact in absentia:
Alexander Knetsch, Pardis Niknejadi

Description and goals:
The diagnostic developed here will allow for first measurements of the longitudinal electron bunch structure, as well as the bunch-induced effects on the plasma, at FLASHForward. For full characterisation of the  variety of electron bunches used in the different experiments at FLASHForward knowledge of not only the transverse projection but also of their temporal profile is crucial. Currently there is no transverse deflection structure installed at FLASHForward (installation is planned for Summer 2019). Therefore, an alternative method, based on the induced change of a laser beam's plane of polarisation by the plasma-related magnetic field (the so called Faraday effect), will be investigated. The data obtained will allow for reconstruction of the longitudinal beam and plasma substructure. This will lead to real-time observation of plasma dynamics, including nonlinear focusing and defocusing forces, which can reduce the quality of the accelerating electron bunch. 

  • Reconstructing the density modulation of the plasma and beam for a PWFA
  • Measuring the jitter between the laser and the electron beam
  • Calibration of beam influencing elements upstream of the interaction point, e.g. the scraper
  • Study CSR effect and hosing instability and mitigation
  • Benchmarking and parallel measurements with an Electro Optical Sampling set up (P-10) and X-band TDS (P-9)
  • Long term: Increasing sensitivity by usage of longer wavelength (Near IR) optical beam