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HK: Physik der Hadronen und Kerne

HK 18: Instrumentation und Anwendungen II

HK 18.13: Vortrag

Dienstag, 18. März 2003, 18:30–18:45, C

Magnet Design Perspectives for Polarized Atomic Beam Sources — •G. Tenckhoff, R. Emmerich, and H. Paetz gen. Schieck — IKP, Universität zu Köln, Zülpicher Straße 77, 50937 Köln

Atomic-beam type polarized sources have made possible numerous measurements of polarization observables with increasing accuracy. While there is still a need for an increase in atomic or ionic flux at high polarization from these sources, their development over 40 years has reached a kind of saturation. As the polarization is near the theoretical maximum for nearly all running sources the output flux stagnates near 10¹⁶ atoms/(s· cm²) (two spin states). This atomic flux has been achieved with focussing NdFeB sextupoles in the "Halbach" design. This material presently has the highest energy density known and therefore allowed the increase in pole-tip field strength at a given sextupole bore to a typical value of 1.8 T/5 mm. Assuming that the exponential attenuation by the gas from the defocussed part of the beam is the flux-limiting factor, the need for sextupoles with still higher pole-tip field strength at even larger bore diameter becomes obvious. However, the lack of higher-strength magnetic materials has halted the development until M. Kumada [1] recently presented a Halbach-type dipole magnet with a pole-tip field strength of almost 4 T at a gap width of 3 mm. The principle can be roughly circumscribed by field concentration in soft-iron pole tips and can be transferred to the sextupole design. Different design approaches and first results from numerical field calculations will be presented.

[1] M.Kumada et al., IEEE Trans. Appl. Supercond. 12(1), 2002