Speaker
Description
We describe a compact upgrade to the LERF at Jefferson Lab that enables a monochromatic, slow-positron beam (few-eV) with projected intensity >10¹⁰ e⁺/s and ~10⁴× higher brightness than existing facilities, within the capabilities of the current LERF accelerator. The concept uses an electron beam up to 120 MeV incident on a rotating gamma converter, able to absorb 30 kW of linac power. A key novelty is e⁻/e⁺ separation and downstream transport of positrons with kinetic energy (T+ < 600 keV) from the pair-production target to a low-radiation, low-temperature area, where moderation is performed using a high-efficiency cryogenic rare-gas moderator (solid neon). This yields ≥10× higher moderation efficiency than conventional tungsten moderators.
We performed Monte Carlo studies of a very-large-acceptance guiding solenoid with a novel endcap design, including optimization of (i) electron/positron beam energies and converter thickness, (ii) transport from converter to moderator, (iii) extraction of the e⁺ beam from the magnetic channel, (iv) a synchronized raster system, and (v) moderator efficiency. To enable efficient extraction, a magnetic field terminator-plug prototype has been built; performance measurements demonstrating effective field termination will be presented. Thermal management of the converter and radiation-protection measures have also been analyzed.
If realized, this source would represent one of the most significant advances in positron science in decades, enabling experiments currently out of reach: positronium (Ps) Bose–Einstein condensates, antihydrogen production, precision Ps 1S–2S spectroscopy for QED tests, searches for Ps antigravity, creation of positron plasmas, and large-quantity e⁺ storage for portable sources. High-density e⁺ applications, such as proposed e⁺ superconductors, e⁺ field-effect transistors (FETs), annihilation gamma-ray lasers, and density probes for laser-fusion capsules and exploding foils, become feasible. The unique beam characteristics will also unlock advanced characterization and modification techniques across solid-state and materials science, molecular science, nanotechnology, and industrial applications, substantially enhancing Jefferson Lab’s scientific visibility.
