TU Darmstadt, Darmstadt, Germany
The recirculating electron linac S-DALINAC* provides beams with currents up to 20 µA and energies up to 130 MeV. It is planned to extend the beam diagnostics by adding multiple emittance measurement systems in order to investigate the emittance evolution along the beamline. The emittance measurement is based on the quadrupole scan technique and utilizes the existing quadrupoles and newly built optical transition radiation targets. As the targets are heated by the beam and destruction must be avoided, simulations of the thermal behaviour of the target were conducted. In particular, the dependence of the target temperature on the target design, but also variable parameters as beam spot size and current were investigated. This contribution will present these parameter studies.
* N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018)
TU Darmstadt, Darmstadt, Germany
The recirculating superconducting electron accelerator S-DALINAC [1] at TU Darmstadt is capable to run as a onefold or twofold Energy Recovery Linac (ERL) with a maximum energy of approximately 34 or 68 MeV in ERL mode, respectively. After the final acceleration in ERL mode, the momentum spread at the intended interaction point has to be determined. In order to investigate that momentum spread, a nondestructive measurement method is necessary. For this reason, it is planned to expand the beam horizontally in a section close to the interaction point by providing a well-defined horizontal dispersion. Using a wire scanner in this section for measuring the horizontal profile of the electron distribution, one can determine the momentum spread. The method of determining the momentum spread using the horizontal dispersion and the design of the wire scanner will be presented in this contribution.
[1] N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018).
TU Darmstadt, Darmstadt, Germany
For the EPICS-based control system of the superconducting Darmstadt electron linear accelerator S-DALINAC**, supporting infrastructures based on machine learning are currently developed. The most important support for the operators is to assist the beam setup and controlling with reinforcement learning using artificial neural networks. A particle accelerator has a very large parameter space with often hidden relationships between them. Therefore neural networks are a suited instrument to use for approximating the needed value function which represents the value of a certain action in a certain state. Different neural network structures and their training with reinforcement learning are currently tested with simulations. Also there are different candidates for the reinforcement learning algorithms such as Deep-Q-Networks (DQN) or Deep-Deterministic-Policy-Gradient (DDPG). In this contribution the concept and first results will be presented.
**N. Pietralla, Nuclear Physics News, Vol. 28, No.2, 4 (2018)
TU Darmstadt, Darmstadt, Germany
The S-DALINAC* is a thrice-recirculating linear electron accelerator operating in cw-mode at a frequency of 3 GHz. A path-length adjustment system in the second recirculation beam line allows to shift the beam phase by 360° and thus to operate in ERL mode. For the multi-turn ERL operation, the beam will be accelerated twice and subsequently decelerated twice again (not demonstrated yet). For this mode, it is necessary to develop a nondestructive beam diagnostics system in order to measure the beam position, phase and beam current of both, the accelerated and the decelerated beam, simultaneously in the same beamline. A particular challenge will be the operation at low beam currents of 100 nA, which corresponds to bunch charges of about 30 aC. The conceptional study of a 6 GHz resonant cavity beam position monitor will be presented together with alternative solutions.
* N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018)
TU Darmstadt, Darmstadt, Germany
GSI, Darmstadt, Germany
The Superconducting DArmstadt electron LINear ACcelerator S-DALINAC is a thrice-recirculating linac* providing electron beams with energies up to 130 MeV and beam currents up to 20 ¿A for a variety of nuclear physics experiments**. It has been operated as Germany¿s first energy-recovery linac (ERL) in 2017***. The electron beam is produced either in a thermionic gun or a DC photo-gun using GaAs as cathode material****. A new project foresees to use the S-DALINAC for Laser Compton Backscattering (LCB) to produce a monochromatic high-energy photon beam for nuclear photonics applications in photonuclear reactions and atomics physics experiments. Besides this LCB will be used as an additional diagnostic tool for determining electron beam energy and the energy spread at the third recirculation of the S-DALINAC, when the maximum reachable energy at this point (98.8 MeV) yields a scattered photon energy of 179.7 keV. An overview over the desired laser system for LCB at the S-DALINAC will be given, and simulations for the layout and the estimated output of the Compton-backscattering light source will be presented.
*M. Arnold, Diss., TU Darmstadt (2017)
**N. Pietralla, Nucl. Phys. News 28(2), 4(2018)
***M. Arnold et al., Proc. IPAC¿18(4859), 9(2018)
****Y. Poltoratska et al., J.Phys.: Conf. S. 298, 012002(2011)