Ramped Electron Bunch Experiment

Permanent Magnet Quadrupoles

To obtain a sufficiently high beam density for matching of the electron beam into a potential plasma source, a permanent magnet quadrupole final focusing system is being developed for the S-Bahn beamline. This final focus incorporates the Permanent Magnet Quadrupole Design developed for the Neptune Nonlinear Inverse Compton Scattering Experiment. A photograph of the assembled PMQ focusing triplet is shown below.

The magnets are a hybrid design with either four or eight (for either the 1 or 2 cm long design) cubes of NdFeB permanent magnet material serving as the field sources, surrounding four precisely machined (EDMed) hyperbolic poles held in alignment by an aluminum keeper. The magnetic circuit is completed by an iron yoke which holds both the NdFeB cubes and the keeper in place. There are two models of different lengths (1cm and 2cm) which have measured field strengths of 90 T/m and 110 T/m respectively.