In order to meet the beam quality constrains of the experiments as well as to provide very high beam current at the position of the experimental setups, great attention needs to be paid at the low energy beam transport and the first stages of acceleration in the injection linacs of accelerators in general and of ERLs in particular. Project Area B of AccelencE adresses this topic through studies of relevant parameters, like space charge effects, beam quality deterioration through higher order modes, β-grading and novel materials for cavities.
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Designstudie von β-gradierten SRF-Kavitäten für den Injektor des S-DALINAC
Design study of β-graded SRF cavities for the S-DALINAC injector
The current setup of the capture section of the S-DALINAC injector is one of the main sources of the increased longitudinal energy spread of the beam. In that regard, the 5-cell β = 1 superconducting radio-frequency (SRF) cavity needs to be upgraded. The suggested layout of the cavity for the upgrade is the 6-cell reduced-β SRF structure that allows to accelerate low energy electron beams from the energies of 200 keV up to 1.5 MeV with moderate electric field on the central axis of the cavity with minimised longitudinal energy spread. The designed cavity allows to operate it with the existing cooling cryostat and the existing RF tuning system.
Author: M.Sc. Dmitry Bazyl
Niderenergie-Strahlführung von MESA (Match)
Low-energy beam transport system for MESA (match)
An important part of the new accelerator MESA (Mainz Energy-recovering Superconducting Accelerator) is the low energy beam transport system connecting the 100 keV electron source with the injector accelerator. The present setup includes the chopper- and bunching system. The devices are of most importance in order to achieve sufficient bunch compression particularly at higher bunch charges and currents. With the circular deflecting cavity of the chopper system it is possible to measure the longitudinal dimension of the bunches upstream of the buncher whereas downstream the longitudinal size will be measured by Smith-Purcell radiation. Based on experimental results obtained from this setup we will discuss the beam parameter and compare them with simulations of the beamline.
Author: Dipl.-Phys. Christoph Matejcek
Supervisor: Dr. Robert Heine
Installation und Inbetriebnahme der verbesserten Einfangssektion des S-DALINAC Injektors
Installation and comissioning of the improved capture section for the S-DALINAC injector
For the installation of the new superconducting capture structure designed in the project of D. Bazyl, the first module of the superconducting part of the S-DALINAC injector has to be modified. The tuner frame and other surrounding parts of the cavity have to be adapted to the new geometry of the capture structure in order to prepare the module for the upcoming upgrade. Furthermore, the beam dynamics of the bunched electron beam have to be studied: A diagnostic setup at the end of the normal conducting injector is being planned to characterize the thermionic gun beam parameters in detail, which contributes to a successful commissioning of the new capture section. This project includes the preparation, installation and commissioning of the upgraded injector section and corresponding diagnostics which will contribute to an improved beam quality of the S-DALINAC.
Currently, a state funded capture cavity with β = 0,86 is under construction at Research Instruments (RI).
Author: M.Sc. Simon Weih
Charakterisierung von Oberflächen neuer Materialien für Beschleuniger-Kavitäten (Match)
Surface characterization of novel materials for accelerator cavities (match)
Niobium is the standard material for superconducting RF (SRF) cavities. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram the cubic δ-phase of NbN has the highest critical temperature (16 K). Already slight nitrogen doping of the α-Nb phase results in higher quality factors.
Nb samples are doped with nitrogen in the refurbished UHV furnace at IKP Darmstadt. The doped samples are investigated at the Advanced Thin Film group of the Materials Research department to select the best procedure for cavity treatment.
Author: Dr. Marton Major
Supervisor: Prof. Dr. Lambert Alff