Author: Pietralla, N.
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MOPLR014 Construction of a Third Recirculation for the S-DALINAC* 168
 
  • M. Arnold, T. Kürzeder, J. Pforr, N. Pietralla, M. Steinhorst
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
 
  Funding: * Work supported by DFG through CRC 634 and RTG 2128
Since 1991 the superconducting recirculating electron accelerator S-DALINAC is running at TU Darmstadt. Its designated design energy of 130 MeV wasn't reached yet due to a lower quality factor of the 3 GHz cavities and thus a higher dissipated power to the helium bath. To increase the maximum achievable energy in cw operation from approx. 85 MeV to the design value of 130 MeV the main accelerator will be passed a fourth time. In this configuration the accelerating gradients of the cavities can be lowered, so that the resulting dissipated power will match the available cooling power of the cryo plant. To realize an additional main linac pass a new recirculation beam line is needed. The most crucial points are the design of the separation dipole and its mirrored version as well as a properly calculated lattice. For the implementation of a new recirculation beam line the existing sections must be adapted to fit the new boundary conditions. This contribution will present some aspects of the design and will report on the actual status of this project.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR014  
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MOPLR032 Preparation for Cavity Material Studies at the Vertical High-Temperature UHV-Furnace of the S-DALINAC 209
 
  • R. Grewe, L. Alff, J. Conrad, T. Kürzeder, M. Major, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
 
  Funding: Work supported by the Federal Ministry of Education and Research through grant No. 05H15RDRBA.
Since 2005 the Institute for Nuclear Physics at the Technische Universität Darmstadt operates a high temperature vacuum furnace. It is designed to reach temperatures of up to 1800°C. It has been used for baking out several niobium superconducting RF cavities at 850°C with proven success*. Current research for improving the performance of SRF cavities is focused on nitrogen treatment of such cavities. Nitrogen doping of SRF cavtities results in an up to four times higher quality-factor as compared to untreated cavities**. At higher temperatures between 1300°C and 1700°C the so-called delta-phase of NbN forms, which is highly interesting for applications to superconducting accelerator technology***. The UHV-furnace at the S-DALINAC offers the possibility to treat niobium samples at considerably higher temperatures than what has been done up to now in order to study the effect of delta-phase NbN and N-doping on superconducting properties. The furnace has been refurbished and recommissioned to realize research on nitrogen treatment of niobium samples. We will report on our first experiences with operating the upgraded furnace.
*Araz et al., Proceedings of SRF05, 2015
**Grasselino et al., Superconducting Science and Technology, 2013
***Pham Tu et al., Proceedings of SRF87, 1987
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR032  
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THOP04 Measurements of the Beam Break-Up Threshold Current at the Recirculating Electron Accelerator S-DALINAC 751
THPLR001   use link to see paper's listing under its alternate paper code  
 
  • T. Kürzeder, M. Arnold, L.E. Jürgensen, J. Pforr, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
 
  Funding: *Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05K13RDA.
Linear accelerators, in particular those with a recirculating design and superconducting cavities, have to deal with the problem of Beam Break-Up (BBU). This instability can limit the maximum beam current in such accelerators. Knowing the effectiveness of prevention strategies is of great interest especially for future accelerators like energy recovery linacs (ERL) which aim for high beam currents. One option is to optimize the cavities and higher order mode couplers of those machines. In addition one may adapt the beam line lattice for further suppressing BBU. The superconducting recirculating accelerator S-DALINAC at the Technische Universität Darmstadt provides electron beams in c.w. for nuclear physics experiments since 1991. As the SRF components were never optimized for higher order mode suppression the S-DALINAC suffers from BBU at relatively low beam currents of a few μA. While those currents are sufficient for most nuclear physics experiments we can investigate BBU with respect to the beam optics. We will report on first measurements of threshold currents at different beam energies of the S-DALINAC. The results of a first test to increase the BBU limit by using skew quadrupoles will be presented.
 
slides icon Slides THOP04 [1.473 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP04  
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