Polarized positrons in Jefferson lab electron ion collider (JLEIC)

Abstract

Abstract. The Jefferson Lab Electron Ion Collider (JLEIC) is designed to provide collisions of electron and ion beamswith high luminosity and high polarization to reach new frontier in exploration of nuclear structure. The luminosity, exceeding 10 33 cm -2 s -1 in a broad range of the center-of-mass (CM) energy and maximum luminosity above 10 34 cm -2 s -1 , is achieved by high-rate collisions of short small-emittance low-charge bunches with proper cooling of the ion beam and synchrotron radiation damping of the electron beam. The polarization of light ion species (p, d, 3 He) and electron can be easily preserved, manipulated and maintained by taking advantage of the unique figure-8 shape rings. With a growing physics interest, polarized positron-ion collisions are considered to be carried out in the JLEIC to offer an additional probe to study the substructure of nucleons and nuclei. However, the creation of polarized positrons with sufficient intensity is particularly challenging. We propose a dedicated scheme to generate polarized positrons. Rather than trying to accumulate "hot" positrons after conversion, we will accumulate "cold" electrons before conversion. Charge accumulation additionally provides a novel means to convert high repetition rate (>100 MHz) electron beam from the gun to a low repetition rate (<100 MHz) positron beam for broad applications. In this paper, we will address the scheme, provide preliminary estimated parameters and explain the key areas to reach the desired goal.