skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Microlens Array Laser Transverse Shaping Technique for Photoemission Electron Source

Abstract

A common issue encountered in photoemission electron sources used in electron accelerators is distortion of the laser spot due to non ideal conditions at all stages of the amplification. Such a laser spot at the cathode may produce asymmetric charged beams that will result in degradation of the beam quality due to space charge at early stages of acceleration and fail to optimally utilize the cathode surface. In this note we study the possibility of using microlens arrays to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes at both Fermilab Accelerator Science \& Technology (FAST) facility and Argonne Wakefield Accelerator (AWA). In particular, we discuss the experimental characterization of the homogeneity and periodic patterned formation at the photocathode. Finally, we compare the experimental results with the paraxial analysis, ray tracing and wavefront propagation software.

Authors:
 [1];  [2];  [3];  [4];  [4];  [1];  [4];  [5];  [5];  [5]
  1. Northern Illinois Univ., DeKalb, IL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States); Pohang Univ. of Science and Technology (POSTECH) (Korea, Republic of)
  3. Argonne National Lab. (ANL), Argonne, IL (United States); Tsinghua Univ., Beijing (China)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
  5. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1408329
Report Number(s):
FERMILAB-TM-2634-APC; arXiv:1609.01661
1485409
DOE Contract Number:
AC02-07CH11359
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; PHOTOCATHODES; WAKEFIELD ACCELERATORS; ELECTRON SOURCES; PHOTOEMISSION

Citation Formats

Halavanau, A., Ha, G., Qiang, G., Gai, W., Power, J., Piot, P., Wisniewski, E., Edstrom, D., Ruan, J., and Santucci, J.. Microlens Array Laser Transverse Shaping Technique for Photoemission Electron Source. United States: N. p., 2016. Web. doi:10.2172/1408329.
Halavanau, A., Ha, G., Qiang, G., Gai, W., Power, J., Piot, P., Wisniewski, E., Edstrom, D., Ruan, J., & Santucci, J.. Microlens Array Laser Transverse Shaping Technique for Photoemission Electron Source. United States. doi:10.2172/1408329.
Halavanau, A., Ha, G., Qiang, G., Gai, W., Power, J., Piot, P., Wisniewski, E., Edstrom, D., Ruan, J., and Santucci, J.. 2016. "Microlens Array Laser Transverse Shaping Technique for Photoemission Electron Source". United States. doi:10.2172/1408329. https://www.osti.gov/servlets/purl/1408329.
@article{osti_1408329,
title = {Microlens Array Laser Transverse Shaping Technique for Photoemission Electron Source},
author = {Halavanau, A. and Ha, G. and Qiang, G. and Gai, W. and Power, J. and Piot, P. and Wisniewski, E. and Edstrom, D. and Ruan, J. and Santucci, J.},
abstractNote = {A common issue encountered in photoemission electron sources used in electron accelerators is distortion of the laser spot due to non ideal conditions at all stages of the amplification. Such a laser spot at the cathode may produce asymmetric charged beams that will result in degradation of the beam quality due to space charge at early stages of acceleration and fail to optimally utilize the cathode surface. In this note we study the possibility of using microlens arrays to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes at both Fermilab Accelerator Science \& Technology (FAST) facility and Argonne Wakefield Accelerator (AWA). In particular, we discuss the experimental characterization of the homogeneity and periodic patterned formation at the photocathode. Finally, we compare the experimental results with the paraxial analysis, ray tracing and wavefront propagation software.},
doi = {10.2172/1408329},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 9
}

Technical Report:

Save / Share:
  • In photocathodes the achievable electron-beam parameters are controlled by the laser used to trigger the photoemission process. Non-ideal laser distribution hampers the final beam quality. Laser inhomogeneities, for instance, can be "amplified" by space-charge force and result in fragmented electron beams. To overcome this limitation laser shaping methods are routinely employed. In the present paper we demonstrate the use of simple microlens arrays to dramatically improve the transverse uniformity. We also show that this arrangement can be used to produce transversely-patterned electron beams. Our experiments are carried out at the Argonne Wakefield Accelerator facility.
  • A common issue encountered in photoemission electron sources used in electron accelerators is the transverse inhomogeneity of the laser distribution resulting from the laser-amplification process and often use of frequency up conversion in nonlinear crystals. A inhomogeneous laser distribution on the photocathode produces charged beams with lower beam quality. In this paper, we explore the possible use of microlens arrays (fly-eye light condensers) to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes. We also demonstrate the use of such microlens arrays to generate transversely-modulated electron beams and present a possible application to diagnose the propertiesmore » of a magnetized beam.« less
  • We investigate a novel scheme for significantly increasing the brightness of x-ray light sources based on inverse Compton scattering (ICS) - scattering laser pulses off relativistic electron beams. The brightness of ICS sources is limited by the electron beam quality since electrons traveling at different angles, and/or having different energies, produce photons with different energies. Therefore, the spectral brightness of the source is defined by the 6d electron phase space shape and size, as well as laser beam parameters. The peak brightness of the ICS source can be maximized then if the electron phase space is transformed in a waymore » so that all electrons scatter off the x-ray photons of same frequency in the same direction, arriving to the observer at the same time. We describe the x-ray photon beam quality through the Wigner function (6d photon phase space distribution) and derive it for the ICS source when the electron and laser rms matrices are arbitrary.« less
  • Design of a new aberration corrected Photoemission electron microscope PEEM3 at the Advanced Light Source is outlined. PEEM3 will be installed on an elliptically polarized undulator beamline and will be used for the study of complex materials at high spatial and spectral resolution. The critical components of PEEM3 are the electron mirror aberration corrector and aberration-free magnetic beam separator. The models to calculate the optical properties of the electron mirror are discussed. The goal of the PEEM3 project is to achieve the highest possible transmission of the system at resolutions comparable to the present PEEM2 system (50 nm) and tomore » enable significantly higher resolution, albeit at the sacrifice of intensity. The authors have left open the possibility to add an energy filter at a later date, if it becomes necessary driven by scientific need to improve the resolution further.« less