Author: Hoffstaetter, G.H.
Paper Title Page
WEOAA2
 Cornell ERL Update  
 
  • G.H. Hoffstaetter, C.E. Mayes
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Cornell University has pioneered the design and hardware for ERL lightsources. This preparatory research for ERL-lightsource construction will be discussed. Important milestones have been achieved in Cornell's prototype ERL injector, including the production of a prototype SRF cavity that exceeds design specifications, the regular production of long-lived and low emittance cathodes, the acceleration of ultra-low emittance bunches, and the world-record of 75 mA current from a photoemission DC gun. We believe that demonstration of the practical feasibility of these technologies have progressed sufficiently to allow the construction of an ERL-based lightsource like the Cornell ERL.  
slides icon Slides WEOAA2 [7.762 MB]  
 
WEPAC09 A Temperature-Mapping System for Multi-Cell SRF Accelerator Cavities 805
 
  • G.M. Ge, G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  A Temperature mapping (T-map) system for Superconducting Radio Frequency (SRF) cavities consists of a thermometer array positioned precisely on an exterior cavity wall, capable of detecting small increases in temperature; therefore it is a powerful tool for research on the quality factor (Q0) of SRF cavities. A new multi-cell T-mapping system is has been developed at Cornell University. The system has nearly two thousand thermometers to cover 7-cell SRF cavities for Cornell’s ERL project. A new multiplexing scheme was adopted to reduce number of wires. A 1mK resolution of the temperature increase ΔT is achieved. A 9-cell cavity of TESLA geometry was tested with the T-map system. By converting ΔT to power loss and quality factor, it has been found that for this cavity, most surface losses were generated by the first cell when the accelerating gradient is increased above 15MV/m. Effective and intuitive ways of displaying surface properties of the cavity interior, e.g. the residual resistivity, will be shown.  
 
WEPAC10 Investigation of the Surface Resistivity of SRF Cavities via theHEAT and SRIMP Program as well as the Multi-cell T-Map System 808
 
  • G.M. Ge, G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  A high-sensitive temperature mapping system for multi-cell SRF cavities has been constructed at Cornell University. The resolution of the system is 1mK. Hence it’s able to detect small temperature increases when cavities reach at low accelerating gradients e.g. 3MV/m. The surface resistivity of superconductor under radio-frequency electromagnetic field can be calculated from the temperature increases. In this contribution, the surface resistance map of multi-cell SRF cavities is shown. The temperature mapping result is possible to establish a relationship between the surface resistivity and the magnetic field as well. Unlike the RF method which is average value of the surface resistance, the T-map results give local surface resistivity versus magnetic field. BCS theory assumes the surface resistivity is independent to the magnetic field. The T-map results, however, suggest that the surface resistance at high-loss region is field dependent and caused Q-slope.  
 
WEPAC11 Cornell's Main Linac Cryo-module Prototype 811
 
  • R.G. Eichhorn, G.M. Ge, Y. He, G.H. Hoffstaetter, M. Liepe, T. O'Connel, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: Supported by NSF award DMR-0807731
In preparation to built an energy-recovery linac (ERL) based synchrotron-light facility at Cornell University which can provide greatly improved X-ray beams due to the high electron-beam quality that is available from a linac, a phase 1 R&D program was launched, adressing critical challenges in the design. One of them being a full linac cryo-module, housing 6 superconducting cavities (operated at 1.8 K in cw mode), 7 HOM absorbers and 1 magnet/ BPM section. The final design will be presented and a report on the fabrication status that started in late 2012 will be given 		 
 
THPMA07 Cryomodule Performance of the Main Linac Prototype Cavity for Cornell's Energy Recovery Linac 1367
 
  • N.R.A. Valles, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, S. Posen, P. Quigley, J. Sears, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: NSF Grants: NSF DMR-0807731 and NSF PHY-1002467
Energy Recovery Linacs (ERLs) require strong damping of higher-order modes in main linac cavities to avoid beam loss from beam break-up effects. In addition, the cavities need to have very high intrinsic quality factors to minimize the size of cryogenic plants in CW cavity operation. We present world record results for a fully equipped multicell cavity in a cryomodule, reaching intrinsic quality factors at operating accelerating field of Q0(E =16.2 MV/m, 1.8~K) > 6.0\ee10 and Q0(E =16.2 MV/m, 1.6~K) = 1.0\ee{11}, corresponding to a residual surface resistance of 1.1~nΩ.