CEBAF Lifetime tests with our present CEBAF photoguninjector

CEBAF • Lifetime tests with our present CEBAF photogun/injector (m. A current, voltage, active area, laser spot size, Wien ON/OFF, strained vs bulk, etc. , ) • 200 k. V Wien, rebuild 2 -Wien spin flipper • Operate our 130 k. V gun at 200 k. V (tee-shaped electrode, or with spherical electrode and shed), or replace our 130 k. V inverted gun chamber with our 350 k. V chamber • Finish today’s 5 Me. V Mott paper • Consider Mott part 2: different energies and different Zs, improve/expand Marty’s GEANT model • Brock harmonically resonant cavity at Me. V location, one beam and two beams • Resonant polarimeter tests • Stern Gerlach deflection • Stewart platform for pockels cell • Assist Kent with RTP cell studies, quantify the benefits of the Paschke method of PC alignment • Bubble Chamber experiment, fluorine and oxygen • SRF cavities at 4 K • AOM laser/AOM light + Compton scattering/AOM electron beams

Photocathode R&D at TL 1137 : alkali-antimonides • Finish evaluating Cs. K 2 Sb photocathode on Nb substrate: spectral response measurements at 100 C, RT, 0 C, dry ice, and LN 2 • Make alkali antimonide photocathodes using hydroxides in crucibles, Cs. OH and KOH • Make alkali-antimonide photocathodes with Na • Brock cavity RF gun: need waveguide couplers, need calculation of expected E field. Install cavity below the chemical sources of Mamun’s depo chamber, install small beamline and dipole magnet spectrometer. Illuminate photocathode with gain switched diode laser. Make 10 ke. V beam with RF structure, seen on viewer and dump, that would be a big deal (because it could be scaled to higher energy with SRF cavity). • Thin Cs. K 2 Sb photocathode on Ga. As, measure polarization in mini-Mott. Cs. K 2 Sb photocathode could be fabricated in depo chamber and moved to mini. Mott…. need a load lock. Could use brute force - with long bellows and long stalks. Or with Mamun’s puck holding scheme • Drop a permanent magnet into stalk and make “magnetized” beam at 1137…can do this at mini. Mott too, but suspect this would only serve to mis-steer the beam. Does magnetization manifest itself in ways we can “see”?

Photocathode R&D at TL 1137: polarized photocathodes • Polarization vs NEA layer, cleave plane, dopant density and temperature. Quantify depolarization terms for a monte carlo simulation that others want to create • Evaluate our stock of Ga. As. Sb/Al. Ga. As and Ga. As. Sb/Al. Ga. As. P photocathodes from SVT: mini. Mott and then inside UITF gun. These photocathodes are supposed to be more rugged, with improved lifetime. • Cool Ga. As/Ga. As. P photocathode to 77 K and obtain highest polarization ever recorded at JLab. For bulk Ga. As, polarization increased by 20+% at 77 K. For 90% photocathode at RT, what will polarization be at 77 K? • Improve our mini. Mott, or make a new one? • Spintronics photocathodes, halfmetals, chalcopyrites? Ag. Ga. Se 2: Zn. Se • If we think Cs. K 2 Sb photocathodes exhibit long lifetime because the alkali is infused throughout the photocathode, can we find a polarized photocathode with alkali infused throughout? • Alternatives to Ga. As (it will be a big deal for someone to demonstrate polarized beam from any other photocathode): Zn. Cd. Se QW, wurtzite In. Ga. N QW, Ga. Mn. As, Zn. Si. As 2 and Zn. Ge. As 2, Ferromagnetic thin films: Gadolinium or Europium • Use nanostructure to demonstrate a “dark” photocathode, 100% absorption. Increased QE due to 100% absorption, make sure polarization is maintained

GTS • High current inverted gun at 350 k. V with long lifetime • Emittance vs alkali-antimonide photocathode recipe, Cs. K 2 Sb vs Cs 3 Sb • Magnetized beam (dc laser, rf structure low and high bunch charge) • Hollow beam • High average current, High bunch charge operation • Precipitator tests • Fast kicker tests with Brock harmonic cavity as selective energy booster, or Rimmer subharmonic cavity • Field emission tests: Ti. N-Al, Ti. N-Cu, barrel polishing evaluation, Nb electrode

Lasers • High power lasers at visible and IR wavelengths, picosecond pulses • Improved reliability • Less DC light • Hollow beams • Vortex laser/vortex light

UITF • Polarized high current inverted gun at 350 k. V • m. A polarized beam lifetime tests, lifetime vs laser spot size, vs gun voltage • Ga. As/Ga. As. P with and without DBR, Ga. As. Sb/Al. Ga. As, and Ga. As. Sb/Al. Ga. As. P photocathode lifetime tests (harder now that YQ has left SVT) • Ga. As activated with Cs and Li: bi-alkali lifetime tests • 200 ke. V Wien, with beam-based evaluation of performance • Polarized positron proposal • Brock cavities • Bubble Chamber

Vacuum • Phil’s -12 Torr demonstration with only homemade NEG coating and 20 L/s pump • Gauge comparison • Cryopumping to reach -13 Torr? It’s time to remove Leybold pump and replace with BNNT cryopump, right? • BNNT cryopump, improve capacity, write it up • Use VTA as our cryostat, build a chamber with -12 Torr vacuum, immerse in LHe, bottom out a gauge…. • Means to reduce outgassing rate below our -13 TL/scm 2 value obtained via 400 C bakeout • Revisit the modulated Bayard-Alpert gauge to improve gauge S/N ratio, and accurately measure lower pressures

JLEIC/e. RHIC • Magnetized beam • High average current unpolarized beam • High bunch charge unpolarized beam • Fast kickers • High current, high bunch charge polarized beam • 500 k. V guns • 10 -13 Torr guns • Alternatives to Ga. As

LERF • Begin designing the 500 k. V inverted gun with large FEL insulator • Improve the depo chamber design to accommodate bigger pucks • Replace the modelocked Time. Bandwidth master oscillator laser with gain switched diode and fiber amp • Add beamline for bubble chamber, astrophysics experiments, NASA tests, etc. , • Characterize H-cleaned metal photocathodes, add plasmonic structure

Staff Scientist I Work should result in primary authorship of at least one refereed publication annually, in addition to conference papers/ posters and internal technical notes. Staff Scientist II Work should result in primary authorship of one or more refereed publications annually, in addition to significant contributions to other refereed publications and conference papers/ posters and internal technical notes. Staff Scientist III Fewer publications as first author in favor of an increasing number of publications as team leader. Senior Staff Scientist Invited talks and review papers should dominate the publication record. • Are these reasonable expectations? I think so…especially now that CEBAF is running smoothly • Scientists like to “measure things”. There’s plenty to measure, many problems to solve. Let’s agree to measure something important • It’s a privilege to work at a National Lab – it is easier for us to do research compared to universities • More importantly to me, writing a paper means we learned something, we brought something to conclusion. • Doing publishable work is our “responsibility”

CIS Publications per Year 7 6 5 4 Making CEBAF and LERF operate reliably 3 2 1 0 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 • CIS includes seven staff scientists. Per Skills Matrix, CIS should produce > 13 publications per year! • Sure, fewer publications if scientists work together on projects…. • Plot shows a great trend, but clearly, the Promotion Review Board has not been looking at our publication record!

• The Cornell Group represents a good model for CIS. Like Cornell, we’ve done the hard work of building machines and test stands, now let’s reap rewards • Adjusting to our new normal: More competitive environment, limited resources. Doing good work that has an impact, that leads to something new, like a new capability, it makes JLab look good, we maintain our credibility. And we absolutely need credibility…. credibility will bring us funding, which is needed in our “new normal” • Note, in past 5 years, most of the research appears to happen as a result of students and/or postdocs. Only small fraction originates from non-student work. So scientists need to step it up, or get students…. • Advice to you and me: step away from your desk • We sometimes convince ourselves we can’t do something because of lack of money, but there might still be ways to get things done with what we have, or by exploiting the good relationships we have with other groups