Bonn 2010 – wissenschaftliches Programm
HK 71.4: Vortrag
Freitag, 19. März 2010, 14:45–15:00, HG ÜR 8
Characterization and Tuning of High-Gradient Miniature Quadrupoles — •Sebastian Raith1,2, Stefan Becker1,2, Carlo Frevert1,2, and Florian Grüner1,2 — 1Department für Physik, Ludwig-Maximilians-Universität, Am Coulombwall 1, 85748 Garching, Germany — 2Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany
To guide and shape laser-wakefield-accelerated electron bunches while maintaining the intrinsically ultra-short pulse lengths, we use segmented Halbach quadrupole lenses. They consist of 12 segments made of permanent magnet material with a remanence of 1.3 T. Together with an aperture of 6 mm, large gradients of about 500 T/m can be achieved. However, a small aperture increases the effect of disturbing higher order multipoles which destroys the beam quality. To preserve the beam quality, it is mandatory to reduce them. This is achieved by precisely shifting the individual segments and hence introducing additional higher orders, but with a phase opposing the one of the present multipoles. Being of iterative nature, this process requires a fast determination of the higher-order field components. We have developed a measurement technique relying on a Fourier expansion of the field which dramatically reduces the measurement effort.