Author: Liu, X.
Paper Title Page
MOOAA01 Performance of the Cornell High-Brightness, High-Power Electron Injector 20
  • B.M. Dunham, A.C. Bartnik, I.V. Bazarov, L. Cultrera, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter, R.P.K. Kaplan, V.O. Kostroun, Y. Li, M. Liepe, X. Liu, F. Löhl, P. Quigley, D.H. Rice, E.N. Smith, K.W. Smolenski, M. Tigner, V. Veshcherevich, Z. Zhao
    CLASSE, Ithaca, New York, USA
  • S.S. Karkare, H. Li, J.M. Maxson
    Cornell University, Ithaca, New York, USA
  Funding: NSF DMR-0807731
The last year has seen significant progress in demonstrating the feasibility of a high current, high brightness photoinjector as required for the Energy Recovery Linac driven X-ray source at Cornell University. Both low emittances (0.4 mm-mrad rms normalized for 100% of the beam at 20 pC per bunch and 0.15 mm-mrad rms core emittance with 70% of the beam, and twice these values at 80 pC per bunch) and high average currents with a good lifetime well in excess of 1000 Coulombs at 5 MeV, 20 mA have been demonstrated. If these beams can be accelerated to 5 GeV without diluting the phase space, it would already provide a beam brightness higher than any existing storage ring. Operational experience, results, and the outlook for the future will be presented.
slides icon Slides MOOAA01 [1.424 MB]  
TUPPR064 Time-resolved Shielded-Pickup Measurements and Modeling of Beam Conditioning Effects on Electron Cloud Buildup at CesrTA 1966
  • J.A. Crittenden, Y. Li, X. Liu, M.A. Palmer, S. Santos, J.P. Sikora
    CLASSE, Ithaca, New York, USA
  • S. Calatroni, G. Rumolo
    CERN, Geneva, Switzerland
  • S. Kato
    KEK, Ibaraki, Japan
  Funding: Work supported by the US National Science Foundation PHY-0734867, PHY-1002467, and the U.S. Department of Energy DE-FC02-08ER41538.
The Cornell Electron Storage Ring Test Accelerator program includes investigations into electron cloud buildup in vacuum chambers with various coatings. Two 1.1-m-long sections located symmetrically in the east and west arc regions are equipped with BPM-like pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. We present new measurements of the effect of beam conditioning on a newly-installed amorphous carbon coated chamber, as well as on a diamond-like carbon coating. The ECLOUD modeling code is used to quantify the sensitivity of these measurements to model parameters, differentiating between photoelectron and secondary-electron production processes.
WEOAB02 Photocathode R&D at Cornell University 2137
  • L. Cultrera, I.V. Bazarov, J.V. Conway, B.M. Dunham, Y. Hwang, Y. Li, X. Liu, R. Merluzzi, T.P. Moore, K.W. Smolenski
    CLASSE, Ithaca, New York, USA
  • S.S. Karkare, J.M. Maxson, W.J. Schaff
    Cornell University, Ithaca, New York, USA
  Funding: This work has been supported by NSF DMR-0807731 and by DOE DE-SC0003965.
A wide R&D program is pursued at Cornell University aimed at preparation and characterization of high efficiency photocathodes for the Energy Recovery Linac photoinjector. The currently investigated photoemitters include both positive and negative electron affinity materials such as respectively bi-alkali antimonide and III-V semiconductors activated with Cs and either O or F. Analysis techniques as Scanning Auger Spectroscopy, Low Energy Electron Diffraction, Reflected High Energy Electron Diffraction and work function measurements are used to characterize the surfaces properties of the specimens. Spectral response, photoemission uniformity, electron energy distributions are used to characterize the quality of the photoelectron beam and to relate it to the measured surface properties.
slides icon Slides WEOAB02 [6.934 MB]  
WEPPD082 Characterization of Photocathode Damage during High Current Operation of the Cornell ERL Photoinjector 2717
  • J.M. Maxson, S.S. Karkare
    Cornell University, Ithaca, New York, USA
  • I.V. Bazarov, S.A. Belomestnykh, L. Cultrera, D.S. Dale, J. Dobbins, B.M. Dunham, K. Finkelstein, R.P.K. Kaplan, V.O. Kostroun, Y. Li, X. Liu, F. Löhl, B. Pichler, P. Quigley, D.H. Rice, K.W. Smolenski, M. Tigner, V. Veshcherevich, Z. Zhao
    CLASSE, Ithaca, New York, USA
  The Cornell ERL Photoinjector prototype has recently demonstrated successful operation at 20 mA for 8 hours using a bi-alkali photocathode grown on a Si substrate. The photocathode film was grown off center, and remained relatively undamaged; however, upon removal from the gun, the substrate at the gun electrostatic center displayed significant visible damage. Here we will describe not only the parameters of that particular high current run, but a suite of post-operation surface morphology and crystallographic measurements, including X-ray fluorescence, X-ray diffraction, contact profilometry, scanning electron microscopy, performed about the damage site and photocathode film. The data indicate violent topological changes to the substrate surface, as well as significant induced crystallographic strain. Ion back-bombardment is proposed as a possible mechanism for damage, and a simple model for induced crystal strain is proposed (as opposed to ion induced sputtering), and is shown to have good qualitative agreement with the spatial distribution of damage.  
THPPD053 Study on Eddy Current Power Losses in Insulated Core Transformer Primary Coil 3632
  • L. Yang, X. Liu, Y.Q. Xiong, J. Yang
    Huazhong University of Science and Technology (HUST), Wuhan, People's Republic of China
  • T. Yu
    HUST, Wuhan, People's Republic of China
  Insulated core transformer (ICT) high-voltage DC power supply is widely used in electron beam accelerator. With air gap in ICT, the reluctance of magnetic circuit is larger than other transformers, and the transverse magnetic flux leakage around the primary coil is more serious. Because the magnetic flux on the radial direction of coil cannot be ignored, the eddy current loss on the wire should be discussed. In this paper, simulation and analysis of the eddy current loss is presented. The relationship between the sizes of the coil wire is also discussed. An optimal design of the primary coil is shown.