Abstract:The 'Frankfurter Neutronenquelle am Stern-Gerlach-Zentrum'(FRANZ), which is currently under development, will be the strongest neutron source in the astrophysically interesting energy region in the world. It will be about three orders of magnitude more intense than the well-established neutron source at the Research Center Karlsruhe (FZK).
The Frankfurt Neutron Source at the Stern-Gerlach-Zentrum (FRANZ) will deliver high neutron fluxes in the energy range of 1 to 500 keV. The Activation Mode provides a high averaged neutron flux created by a cw proton beam of up to 5 mA, while in the Compressor Mode intense neutron pulses of 1 ns length are formed with a repetition rate of up to 250 kHz. The Compressor Mode is well-suited for energy-dependent neutron capture measurements using the Time-of-Flight method in combination with a 4π BaF 2 detector array. The design of the proton driver linac for both operation modes is presented. This includes the volume type ion source, the E×B chopper located in the low energy section, the RFQ-IH combination for beam acceleration and the bunch compressor. Finally, the neutron production at the lithium-7 target and the resulting energy spectrum is described.
We calculate the effect of electron-electron interactions involving vanishing momentum transfer (forward scattering) on the orbital linear magnetic response of disordered metal rings pierced by a magnetic flux . Using the bulk value of the Landau parameter F 0 for copper, we find that in the experiment by Lévy et al. [Phys. Rev. Lett. 64, 2074] the forward-scattering contribution to the linear magnetic response is larger than the corresponding contribution from large momentum transfers considered by Ambegaokar and Eckern [Phys. Rev. Lett. 65, 381 (1990)]. However, outside the regime of the validity of the linear response and to first order in the effective screened interaction the persistent current is dominated by scattering processes involving large momentum transfers.
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