IPAC2012 - List of Authors (Liu, X.)

Paper

Title

Page

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 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 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.

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 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 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.