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Jefferson Lab's Center for Injectors and Sources (CIS) develops and maintains the sources of high polarization (85%) electron beams used in the CEBAF accelerator at Jefferson Lab. These sources are based upon photoemission from prepared gallium arsenide semiconductor material. Our group is involved in state-of-the-art technologies of electron gun design, radio-frequency syncrhonized lasers, ultra-high vacuum and electron beam polarimetry.
CIS members are (l to r) Jim Clark, Matt Poelker (Group Leader), Steve Covert,
Phil Adderley, Riad Suleiman, John Hansknecht, Marcy Stutzman, Joe Grames.
It has been a long while since updating this page. Our group has been busy - a new Inverted Electron Gun has been commissioned and running the CEBAF program since 2009, the polarized electron source beam line has been rebuilt in Spring, 2010 to include additional spin rotators for full 4pi coverage, the PV experiment PREX is nearly finished and the next high current (180uA) PV experiment QWeak is about to begin. The group has also been busy commissioning a second Inverted Gun to 200kV, extending our measurements of photocathode lifetime at milliAmp beam current, extending studies at Extreme High Vacuum (XHV). Graduate students are involved in novel experiments to investigate two-photon excitation of GaAs and to test a concept to make polarized positrons using the CEBAF polarized electron source.
Installed and commissioned two-Wien flipper system for beam based spin reversal in injector.
Completed installation of the inverted ceramic loadlock gun in tunnel.
Jefferson Lab and CIS host PESP 2008, a gathering of scientists and engineers from around the globe who have a common interest in the physics, vacuum, and mechanics of Polarized Electron Sources and Polarimeters. Unique to this 2008 workshop was the expansion of topics to include high brightness unpolarized sources and the growing experimental field of Rf photo-emission sources. The open channel of communication between laboratories was benificial to all participants.
HGun 2 replaced with LLGun2 (tee-style) commissioned in the Injector Test Cave.
Upon completion of a one month summer shutdown, all halls are being driven by fiber lasers. Hall C has a dedicated fiber laser. Hall A&B are sharing a second fiber laser.
Ti-Sapphire lasers are no longer needed. This would not have been possible had it not been for the advancements in photo-cathode material. Superlattice cathodes provide excellent polarization at the 780nm wavelength produced by the fiber lasers.
John Hansknecht and Matt Poelker describe the new fiber laser system in a recently published paper, "Synchronous Photoinjection using a Frequency-Doubled Gain-Switched Fiber-Coupled Seed Laser and ErYb-Doped Amplifier".
A significant portion of the CEBAF program was recently run using the new optical fiber based laser system built by John Hansknecht and Matt Poelker. This laser will replace our mode-locked Ti:Sapphire lasers owing to their permanent synchronization with the accelerator radio-frequency and exceptionally higher power output (>700 mW at 780 nm).
Marcy Stutzman and the electron gun group are recognized in the laboratory newsletter OnTarget for contributing to the viability of high polarization superlattice photocathodes for the CEBAF program.
February 28, 2006
A defining moment in CEBAF history. At 22:30 the Hall C drive laser was switched from a Ti-Sapphire laser to the new experimental fiber laser. It was never to return.
A fruitful time for meetings and discussion - Marcy Stutzman and Phil Adderley just returned from the AVS 2005 (American Vacuum Society) meeting in Boston, MA and Matt Poelker is preparing for PST 2005 (Polarized Sources and Targets) in Tokyo, Japan. Locally, the Hall A Proton Parity EXperiment (HAPPEX) has been running with high polarization (86%) from strained superlattice GaAs and our best ever parity quality beam.
Jennifer Cooper, a student intern with our group last summer, has published her results from our Injector Test Stand in the undergraduate, peer-reviewed The Journal of Young Investigators. You can find her submission here, for which she won the Best Undergraduate Paper/Poster Award at the Davidson College Society of Physics Students conference in Charlottle, NC last year.
Happy New Year! We began the year by delivering high average current (>200 microAmps) at high polarization (~85%) from a high polarization superlattice photocathode.
This month Daniel Charles, a student in our group, receives his Bachelor of Science in Physics degree from Christopher Newport University (click here). Congratulations Daniel !
Phil presents a poster at the American Vacuum Society 53rd International Symposium.
Matt & Joe make presentations at the PESP 2004 workshop hosted in Mainz, Germany.
A superlattice GaAs photocathode has been sucessfully installed and activated in Gun 3. It provided the highest polarization ever measured in the CEBAF accelerator (81%), with high quantum efficiency. It will be provide beam to the next experiment.
Our Gun3 strained layer GaAs photocathode has delivered above 70% polarization for more than a year with only three activations.
The CEBAF injector is augmented with two identical 100 keV polarized electron guns.
Last maintained on 11-22-11 by email@example.com.