Ralf Eichhorn

Reactions with polarized electrons and photons at low momentum transfers at the superconducting Darmstadt electron linear accelerator S-DALINAC

A source of polarized electrons has been installed at the superconducting Darmstadt electron linear accelerator S-DALINAC. Experiments with polarized electrons from 100 keV to about 80 MeV are expected to commence in early 2011. This contribution summarizes the status of the polarized source as well as ongoing preparations for the experimental program with polarized beams. In particular, we present results on unpolarized test experiments of the 234,238 U(γ,f) reactions and considerations for the 2 D(� e,ep) and 3 He(� e,ep) reactions.

Status and recent developments at the polarized-electron injector of the superconducting Darmstadt electron linear accelerator S-DALINAC

At the superconducting Darmstadt electron linac a 100 keV source of polarized electrons has been installed. Major components had been tested prior to installation at an offline teststand. Commissioning of the new source at the S-DALINAC will take place early in 2011. We report on the performance of the teststand, simulations, developments on the laser systems, new radio-frequency components for the S-DALINAC injector, and the status of the implementation of the source.

INJECTOR UPGRADE FOR THE SUPERCONDUCTING ELECTRON ACCELERATOR S‐DALINAC

Since 1991 the superconducting Darmstadt linear accelerator S‐DALINAC provides an electron beam of up to 130 MeV for nuclear and astrophysical experiments. The accelerator consists of an injector and four main linac cryostats, where the superconducting cavities are operated in a liquid helium bath at 2 K. Currently, the injector delivers beams of up to 10 MeV with a current of up to 60 μA. The upgrade aims to increase both parameters, the energy to 14 MeV and the current to 150 μA. Due to an increase in the required RF power to 2 kW the old coaxial RF input couplers, being designed for a maximum power of 500 W, have to be replaced by new waveguide couplers. Consequently, modifications to the cryostat‐module had become necessary. We review the design principles, the necessary changes in RF components (i.e. couplers, transition line, stub tuner), the production of the SRF cavities and the new magnetic shielding. A report on the status will be given.

New injector cryostat module based on 3 GHz SRF cavities for the S-Dalinac

Each cryostat module of the superconducting Darmstadt electron linear accelerator S-DALINAC houses two 20 cell elliptical niobium cavities cooled by a helium bath at 2 K. They are operated at a frequency of 3 GHz and used to accelerate electron beams with gradients up to 5 MV/m. The accelerator itself consists of an injector and four main linac cryostats. A new cryostat module has been built to replace the actual injector module. It features a new waveguide transition line and will be operated with new cavities in order to increase the beam current and energy for nuclear physics experiments behind the injector section of the S-DALINAC. In addition, the frequency tuner for the cavities will be equipped with piezoelectric actuators, which will replace the current magnetostrictive fine tuner. We review the latest changes in the design of the module and its RF transition line and present some findings from the production of new cavities. The results of a measurement in liquid helium at 2 K with the piezoelect...

Photo‐fission at the S‐DALINAC

Experiments on photo-induced fission of 238U and 234U using bremsstrahlung with endpoint energies between 6 MeV and 9 MeV have been carried out at the superconducting Darmstadt electron linear acce ...