JLab, Newport News, Virginia, USA
RadiaSoft LLC, Boulder, Colorado, USA
BNL, Upton, New York, USA
DESY, Hamburg, Germany
Cornell University, Ithaca, New York, USA
Tech-X, Boulder, Colorado, USA
SLAC, Menlo Park, California, USA
ANL, Lemont, Illinois, USA
ODU, Norfolk, Virginia, USA
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Douglas Consulting, York, Virginia, USA
Muons, Inc, Illinois, USA
Northern Illinois University, DeKalb, Illinois, USA
Stanford University, Stanford, California, USA
Texas A&M University, College Station, USA
Fermilab, Batavia, Illinois, USA
FRIB, East Lansing, Michigan, USA
CalPoly, San Luis Obispo, California, USA
MIT, Cambridge, Massachusetts, USA
LBNL, Berkeley, California, USA
Dimtel, Redwood City, California, USA
NSCL, East Lansing, Michigan, USA
JLab, Newport News, Virginia, USA
ODU, Norfolk, Virginia, USA
Magnetized bunched-beam electron cooling is a critical part of the Jefferson Lab Electron Ion Collider (JLEIC). Strong cooling of ion beams will be accomplished inside a cooling solenoid where the ions co-propagate with an electron beam generated from a source immersed in magnetic field. This contribution describes the production and characterization of magnetized electron beam using a compact 300 kV DC high voltage photogun and bialkali-antimonide photocathodes. Beam magnetization was studied using a diagnostic beamline that includes viewer screens for measuring the shearing angle of the electron beamlet passing through a narrow upstream slit. Correlated beam emittance with magnetic field at the photocathode was measured for various laser spot sizes. Measurements of photocathode lifetime were carried out at different magnetized electron beam currents up to 28 mA and high bunch charge up to 0.7 nano-Coulomb was demonstrated.
Euclid Beamlabs LLC, Bolingbrook, USA
GWU, Washington, USA
University of Arkansas, Fayetteville, Arkansas, USA
JLab, Newport News, Virginia, USA
We present progress on incorporation of nanopillar arrays into spin-polarized gallium arsenide photocathodes in pursuit of record high tolerance to ion back-bombardment. Our goal is to exceed the 400 Coulomb record for a high polarization milliampere-class electron source set at Jefferson Laboratory in 2017, while maintaining high quantum efficiency (QE) and spin polarization with a superlattice. Because the Mie effect is resonant, uniformity and careful control over nanostructure geometry is key. We report excellent uniformity and straight sidewall geometry with improved optical absorption using a painstakingly optimized inductively coupled plasma reactive ion etch. We also report the application of Kerker theory to spin-polarized photocathode nanopillar arrays, setting new requirements on nanostructure dimensions to avoid spoiling spin polarization. Finally, we also report initial steps toward re-establishing U.S. production of strained superlattice photocathodes towards integration with nanopillar arrays.
Euclid Beamlabs LLC, Bolingbrook, USA
Euclid TechLabs, LLC, Solon, Ohio, USA
JLab, Newport News, Virginia, USA
Euclid Beamlabs is developing a new "Black Gun" concept in direct current (DC) photoinjectors. To reduce electron-stimulated desorption indirectly influenced by stray photoemission, we are testing advanced optical coatings and low-scattering optics compatible with the extreme high vacuum (XHV) environment of modern DC photoinjectors. Stray light in DC photoinjectors (in proportion to the photoemitted charge) causes off-nominal photoemission, initiating electron trajectories which intercept downstream surfaces. This causes electron-stimulated desorption of atoms, which ionize and may back-bombard the cathode, reducing its charge lifetime. Back-bombardment is key for high average current or high repetition rate. First, we report on progress developing optical skimmers based on Butler baffles to collimate both incoming and outgoing laser beams. Second, we describe candidate coatings for reduction of scattered light. Requirements for these coatings are that they be conducting, optically black at the drive laser wavelength, conformally applied to complex geometry, and XHV-compatible with negligible outgassing.
ODU, Norfolk, Virginia, USA
JLab, Newport News, Virginia, USA