Measurements of high-order magnetic field components of permanent quadrupole magnets for a laser-plasma-driven undulator x-ray source

Abstract

Laser wake-field accelerators as a novel sources of high-energy electron beam are prominent candidates to drive a next generation of compact light sources. Howev-er, to preserve the unique properties of laser-plasma driv-en electron beams, it is crucial to capture the beam direct-ly after the target using quadrupole magnets with ex-tremely high field gradient. We designed and manufac-tured compact permanent quadrupole magnets based on a Halbach design using 12 NdFeB wedges with 1.02 T remanent field which provide field gradients up to ~500 T/m at an aperture radius of only of a few mm. We meas-ured the magnetic field of the permanent magnet quadru-poles using both the pulsed-wire and rotating-coil tech-nique. Here, we present a first analysis of the magnetic field quality, the integrated field gradient and high-order field components. We briefly discuss the influence of field imperfections on the electron beam quality and its consequences for application in the transport line of a laser-plasma-driven undulator X-ray source