Researches on Thermal Emittance of Metal Cathode in Photoinjectors

HE Xiao-Zhong; TANG Chuan-Xiang; HUANG Wen-Hui; LIN Yu-Zheng

Chinese Physics C> 2004, Vol. 28> Issue(9) : 1007-1012

Researches on Thermal Emittance of Metal Cathode in Photoinjectors

Department of Engineering Physics,Tsinghua University,Beijing 100084,China

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Abstract：
Theoretical analysis of thermal emittance of photoinjectors is presented in this paper.Thermal emittance of metal photo-cathode mainly consists of two parts.One is due to thermal emittance of ideal flat metal cathode,and the other is due to surface roughness.To analyze the former part of the thermal emittance,a new model for the electron distribution emitted from the photocathode is presented,and a formula of the thermal emittance of an idea flat cathode is derived according to this model,which is ε n,rms,flat=R2·hυ-3m 0c2.As to the influence on the thermal emittance from the roughness of the cathode,we also give the analy-tical results with a simplified model.Surface profile measurement of Copper and Magnesium after diamond cutting shows normalized RMS thermal emittance due to surface roughness is about 0.4mm·mrad.Thermal emittance expressions analytical given in this paper can explain some of the existing experimental results very well.

References

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. Lcls Design Group.Lcls Conceptual Design Report2. TESLA Design Group. TESLA Conceptual Design Report3. Recommendations of Basic Energy Sciences Advisory Committee (BES-AC) Panel on Novel ,Coherent Light Sources. http ://www. er. doe. gov/production/bes/BESAC/pubs. html4. Schoenlein R W et al . Science ,1996 ,274 :236 —2385. Yorozu M et al . Jpn. J . Appl . Phys. ,2001 ,40 :4228 —42326. HUANG Wen-Hui ,HE Xiao-Zhong et al . HEPNP ,2004 ,28(4) :304 (in Chinese)(黄文会,何小中等. 高能物理与核物理,2004 ,28(4) :304)7. Batchelor K,Farrell J P ,Dudnikova G. A High Current ,High Gradient ,Laser Excited ,Pulsed Electron Gun. Proceeding of EPAC 988. de Loos M J ,van der Geer S B , Kiewiet F B et al . A High-Brightness Pre-accelerated RF-photo Injector. Proceeding of EPAC 20029. Clendenin J E ,Mulhollan G A , High Quantum Yield ,Low Emittance Electron Sources. SLAC-PUB-7760 ,199810. Palmer D T. The Next Generation Photoinjector. Doctor Thesis ,199811. Wang X J ,Babzien M,Malone R et al . Mg Cathode and Its ThermalEmittance. Proceeding of LINAC 200212. Graves W S ,DiMauro L F ,Heese R et al . Thermal Emittance Measurement of Copper Cathode. PAC 200113. Bluem H ,Cole M D ,Todd A M M et al . Photocathode Electron SourceDevelopment at Advanced Energy Systems. Proceeding of EPAC 200214. Bradley D J ,Allenson M B , Holeman B R. The Transverse Energy of Electrons Emitted from GaAs Photocathodes. J . Phys. D:Appl . Phys. ,1997 ,10 :111—125

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HE Xiao-Zhong, TANG Chuan-Xiang, HUANG Wen-Hui and LIN Yu-Zheng. Researches on Thermal Emittance of Metal Cathode in Photoinjectors[J]. Chinese Physics C, 2004, 28(9): 1007-1012.

HE Xiao-Zhong, TANG Chuan-Xiang, HUANG Wen-Hui and LIN Yu-Zheng. Researches on Thermal Emittance of Metal Cathode in Photoinjectors[J]. Chinese Physics C, 2004, 28(9): 1007-1012. shu

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Received: 2004-03-24
Revised: 1900-01-01

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沈阳化工大学材料科学与工程学院沈阳 110142

Researches on Thermal Emittance of Metal Cathode in Photoinjectors

Corresponding author: HE Xiao-Zhong,

Department of Engineering Physics,Tsinghua University,Beijing 100084,China

Received Date: 2004-03-24
Accepted Date: 1900-01-01
Available Online: 2004-09-05

Abstract: Theoretical analysis of thermal emittance of photoinjectors is presented in this paper.Thermal emittance of metal photo-cathode mainly consists of two parts.One is due to thermal emittance of ideal flat metal cathode,and the other is due to surface roughness.To analyze the former part of the thermal emittance,a new model for the electron distribution emitted from the photocathode is presented,and a formula of the thermal emittance of an idea flat cathode is derived according to this model,which is ε n,rms,flat=R2·hυ-3m 0c2.As to the influence on the thermal emittance from the roughness of the cathode,we also give the analy-tical results with a simplified model.Surface profile measurement of Copper and Magnesium after diamond cutting shows normalized RMS thermal emittance due to surface roughness is about 0.4mm·mrad.Thermal emittance expressions analytical given in this paper can explain some of the existing experimental results very well.