1. PEPPo : Polarized Positron Production
Phys. Rev. Lett (2016)
APS Focus Article
Editor’s Suggestion
For these data we had at 4 MeV yield of ~10-5 e+/e-

2. High Impact Potential – Based upon JLab expertise in polarized electron beams
CEBAF - NP
Jefferson Lab Positron Working Group (JLAB-PWG) formed in 2016
120 members (>90% are JLab Users) and 39 Institutions
Letter of Intent “Physics Program with Positron Beams at CEBAF 12 GeV” to PAC46 (2018)
“These measurements all have significant physics interest.”
Jefferson Lab Accelerator Advisory Committee, November 2018
Two recommendations (R27 and R28) to assess conceptual design
EIC - NP
Enables new probe for flavor/amplitude separation
Standard Model (2g/DVCS, neutral/charged current DIS)
Beyond Standard Model (PVDIS, Right handed W boson, SUSY)
LEPTON COLLIDERS - HEP
New interest expressed at LCWS 2018 to consider PEPPo for conventional source at ILC
New research topic on polarized positron production proposed to US-Japan HEP collaboration
LOW ENERGY SCIENCE – BES/NSF
Invited talk at International Conference of Positron Annihilation 2018
Community has interest to have new US facility providing intense polarized positron beams

3. PhD quality research that can be performed at the UITF
Polarization Transfer Experiments
Test single-converter thickness – complete an original PEPPo goal to benchmark polarization transfer on target thickness (affects EM shower and spin-filtering of low-E positrons)
Test double-converter design – test original PEPPo design to separate gamma converter “beam dump” and generate positrons in a second “quiet” target (only photons go in).
Develop Compton transmission polarimeter at UITF – measure longitudinal spin polarization of electrons or positrons readily, using CEBAF Mott as a basis for calibration
Target and Yield Experiments
Build our first positron collection beam line – learn how to optimize collection and manage beam power at target for useful cw re-acceleration (i.e. we don’t need to re-accelerate, but rather measure distributions transverse/longitudinal).
Test high power targets (at low power!) – composed of moving or composite materials such as liquid lead bismuth targets already developed for JLab in SBIR-II.
Physics Experiments
Do Physics – Bowling Green State University to use polarized gamma and polarized positrons at MeV energies (unmoderated) to study magnetic nanostructures and bulk magnetic properties.

4. Beam Requirements at the UITF
Parameter
UITF e- Beam
Comment
Energy
1-10 MeV
OK if dp/p is high
Intensity
1-10 uA
>10uA OK for “high-power” targets
Rep Rate
750 MHz (or sub)
62.5 MHz useful for ToF
Duty Factor
Any
CW preferred
Spin Polarization
Typical >80%
Tests w/ low- or no-P OK
Helicity Reversal
Typical 30 Hz
Faster clock for noise measurements
We retained many useful components from PEPPo, and gained useful experience for next measurements.