Positron Annihilation Lifetime Spectroscopy (PALS) is a unique and non-destructive method for characterizing atomistic defects in a wide range of materials. The use of positron beams for PALS offers significant advantages, such as the ability to probe thin layers, multilayers, and to obtain lifetime spectra with the highest quality.
The generation of positron beams for PALS experiments...
Attempts to utilize positronium (Ps)—a hydrogen-like bound state of an electron and a positron—as an energy-tunable beam have been ongoing since the 1980s. To achieve this, a technique was developed whereby a slow positron beam is injected into a dilute gas, where charge exchange generates a Ps beam [1]. Ps beams generated in this manner have been utilized for experiments involving specular...
We present the beamline design for a high power 10 MeV electron injector to be installed at the Low Energy Recirculator Facility (LERF). The injector is designed to provide beam power of up to 100 kW for testing positron source target candidates. We discuss the results of beam dynamics simulations conducted using the General Particle Tracer (GPT) software, where electromagnetic beamline...
The parity-violating electron scattering program at Jefferson Lab has been a remarkable success. In particular, the PREX and CREX campaigns have provided for the first time, model-independent information on the neutron distribution of medium to heavy nuclei that is free from the uncertainties inherent to hadronic probes. In this presentation I will discuss the far reaching implications of...
Precision studies of the electric dipole moment (EDM) and search for the ultra-light axion particles are much discussed and very important research areas related to wider efforts for exploring new physics beyond the Standard Model and CP violation problem. Highly specialized room-size storage rings utilizing 1 MeV or, sub-MeV scale polarized electron/positron beams are excellent devices to...
Positronium is a Hydrogen-like bound state of an electron and positron, and is an eigenstate of both Charge and Parity transformations. Spin-1 ortho-positronium primarily decays to three photons. Observation of a parity violating angular correlation among the decay products would be a clean indication of combined CP-violation, that cannot be mimicked by final state interactions. We present an...
The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) is the first particle accelerator to employ superconducting radio-frequency (SRF) cavities for generating continuous-wave (CW) high-intensity polarized electron beams. These beams enable detailed investigations of nucleon structure, protons and neutrons, and the strong nuclear force that governs their...
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...
This talk will describe physics motivations for understanding of low-energy (<100 MeV) neutrino-nucleus interactions, and will consider what could be gained with the use of low-energy beams at JLab.
The development of a compact slow positron source at SLAC relies upon the optimization of every component of the linac based source. Current plans involve testing novel systems by using an electron beam incident upon a tungsten target which can then be followed by a tungsten moderator to convert the fast positrons into a low emittance, high brightness positron beam. Moderators are known to...
We examine the sensitivity of the beam normal spin asymmetry in Bhabha scattering to beyond the Standard Model (BSM) mediators, in the context of the JLab polarized positron program. A key property of this observable is that the Standard Model contribution exhibits a zero crossing at a fixed scattering angle, providing a clean, effectively background-free point for these searches. We consider...
Precise measurements of energy intervals of positronium, the bound-state of an electron and a positron, can be used to test quantum electrodynamics theory and constrain parameters related to physics not included in the framework [1]. Despite this promise current measurements of the n=2 fine-structure...
The search proposed here uses a missing mass method in one photon final state for a reaction of a positron-electron annihilation.Muon and electron g-2 measurements are the only other comparable approaches which are able to give a model independent constraint on the electron-axion (A’) coupling constant.The proposed experiment with a 100 MeV beam in 30-days run will reach a sensitivity for the...
We review the physics opportunities, both at high energies and low energies, that present themselves with a positron beam at Jefferson Lab.
McMule (Monte Carlo for Muons and other Leptons) is a powerful tool for fully differential higher-order QED calculations of scattering and decay processes involving leptons. It provides various types of observables, such as cross-sections and branching ratios.
In this work we show, with McMule, the importance of the radiative corrections up to and including next-to-next-to leading order...
Positron annihilation spectroscopy (PAS) is a powerful, non-destructive method in modern materials science. Slow mono-energetic positron beams with variable energy enable depth-resolved characterization of atomistic open-volumes in solids. Positrons are highly sensitive to lattice defects, since they can be trapped at vacancies or vacancy clusters, resulting in a change of their lifetimes and...
The physics program using the polarized low energy electron/positron beam at CE$^+$BAF will require multiple forms of precise beam polarimetry.
The spin dependent synchrotron radiation (SR), called “spin-light,” is a
well known phenomena routinely used to polarize electron/positron beams in
storage rings. The use of spin-light for monitoring beam polarization of
transversely polarized...
The 100-year old theory proposed by E. Fermi and further developed by Weizsaker and Williams can be tested by using Compton scattering of quasi-real photons from atomic electrons.Currently known tests have a few percent accuracy which could be improved by at least a factor of 10. The proposed experiment will use an H(e, e_1 + e_2 + \gamma) reaction with selection of the events with the...
