Marco Brunken

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.

Polarized Electrons in Darmstadt: Recent Developments

The injector of the superconducting Darmstadt electron linear accelerator S‐DALINAC will soon be extended by a source of polarized electrons. A test set‐up of the future source consists of a 100 keV GaAs polarized gun and associated beamline including an assembly for polarization manipulation and determination. We give a short overview of the existing and planned polarimeters at the different accelerator sites, introduce briefly the future implementation of the polarized source at the S‐DALINAC and list experiments that are planned with polarized electron and photon beams.

A compact autocorrelator for the wavelength range between 4 and 10 μm

Abstract A compact autocorrelator suitable for the measurement of the optical pulse length of the infrared free electron laser (IR-FEL) at the S-DALINAC is described. It allows to investigate the energy transfer process from the electrons into the laser light within the undulator of the FEL. The autocorrelator utilizes the second harmonic generation (SHG) and it provides the possibility of a background-free measurement at wavelengths between 4 and 10 μm . Simulations for three different crystals used for SHG show that the largest efficiency for SHG and the best temporal resolution is achieved with a ZnGeP2 crystal at a length of 2 mm . A test experiment at the free electron laser for infrared experiments confirmed the expected high efficiency of about 7.5% of SHG for the ZnGeP2 crystal as well as the easy handling and fast adjustment of the system.

Status Report of the New Darmstadt Polarized Electron Injector

We present the status of the polarized injector for the superconducting Darmstadt electron linear accelerator S‐DALINAC. An offline teststand of the source was built to test all components of the S‐DALINAC polarized injector SPIN. The new electron source will deliver a 100 keV polarized beam and complement the present thermionic source operating at 250 kV. Results of the beam properties measurements will be introduced and an outlook on the upcoming installation of the new injector at the S‐DALINAC will be given.

Influence of doping the pump-chamber material in a flashlamp pumped Er:YAG laser

Abstract The influence of the conversion of pump light of wavelengths below 400 nm into pump light with a central wavelength of 500 nm in a Europium doped quartzglass pump chamber has been investigated. The results are compared to the ones from an undoped quartzglass. The measurements resulted in a reduction of the slope efficiency by a factor of two for the doped quartzglass compared to the undoped one. Furthermore, the pump-pulse lengths around 80 μs lead to a decrease in the slope efficiency compared to pump-pulse lengths above 100 μs .

Polarimetry at the Superconducting Darmstadt Electron Linac S‐DALINAC

A spin polarized electron source will be installed at the S‐DALINAC to extend the existing experimental capabilities polarization. In order to manipulate and monitor the beam polarization a Wien filter and different polarimeters will be installed. The already installed Wien filter and 100 keV Mott polarimeter and the planned 5 MeV Mott, 30–130 MeV Mo/ller and Compton transmission polarimeters are described.

3 GHz Waveguide-to-Coax Transition for RF Input Power Couplers

A 3 GHz waveguide-to-coax transition for rf input power couplers is presented. It is part of a new design of an input coupler for the Superconducting Darmstadt Electron Linear Accelerator (S-DAUNAC). The 3 GHz operating frequency of the accelerator and the fixed dimensions of the coaxial side of the coupler require a special suppression mechanism of the Hn coaxial mode, which can propagate, to keep transverse electric and magnetic fields on the beam axis of the coupler small. Therefore a simple doorknob transition can not be used for the new coupler design. Results from CST MICROWAVE STUDIO® simulations are presented. Index Terms RF input power coupler, S-DALINAC, waveguide-to-coax transition

Investigation of short pulse effects in IR FELs and new simulation results

Abstract The Darmstadt IR FEL is designed to generate wavelengths between 3 and 10 μm and driven by the superconducting electron linear accelerator. The pulsed electron beam has a peak current of 2.7 A leading to a small signal gain of 5%. Currently, investigations of the energy transfer process inside the undulator are performed using the 1D time-dependent simulation code FAST1D-OSC. We present simulation results for the power vs. different desynchronization and tapering parameters as well as a comparison with experimental data from the S-DALINAC IR-FEL. Furthermore, a compact autocorrelation system assuring a background-free measurement of the optical pulse length is described. In a first test experiment at FELIX, the autocorrelator has been tested at wavelengths 5.7 ≤λ≤9.0 μm. The frequency doubling in a 2 mm-long ZnGeP 2 -crystal resulted in a time resolution of 300 fs and a conversion efficiency of 5%.© 2003 Elsevier Science B.V. All rights reserved. PACS: 41.60. Cr; 42.60. Fe; 42.65. Ky; 42.65. Re