Thomas Jefferson National Accelerator Facility

The MOLLER experiment at the Thomas Jefferson National Accelerator Facility (JLab) aims to precisely measure the weak interaction between electrons. This experiment leverages the 12 GeV electron beam and will run for three years. A crucial component of MOLLER is a system of five uniquely shaped water-cooled toroidal magnets. These magnets, possessing seven-fold symmetry, are designed to focus particles by separating electrons scattered off hydrogen in a liquid hydrogen target. The five magnets separate electrons scattered off electrons (Møller scattering) and protons (elastic e-p scattering) within target into approximately circular rings at the detector. This paper presents the assembly process for these five toroidal magnets, detailing critical steps including pin insertion, epoxy application, soldering and brazing, coil assembly, and alignment, all performed to meet stringent magnet specifications. Additionally, it discusses challenges encountered during construction and highlights lessons learned, offering insights for future magnet development projects.

Compared to the interaction of electromagnetic particles in matter, that of hadrons is less well measured and there is a need to improve hadron calorimeter performance. One promising method is dual readout, in which both Cherenkov and scintillation light must be detected. Precision crystals like lead tungstate (PWO), where Cherenkov and scintillation light are produced in the same volume, have been of interest for hadronic calorimeters. However, the most recent type of these crystals, the new PWO-II, has never been evaluated in detail. In this article, we perform measurements of the relative contribution of Cherenkov light generated in PbWO4 crystals using cosmic muons. The measurement method is based on the differences in the angular distributions of Cherenkov and scintillation radiations. Light yield generated by cosmic muons passing through the midpoint of a crystal were detected from both Left (L) and Right (R) sides of the crystal. Noticeable dependence of the left-right asymmetry versus the angular orientation of the crystal relative to the incident muons was observed. Based on this angular asymmetry, the contribution of Cherenkov radiation is measured to be at a level of 20–25% relative to the total detected light output. The measured asymmetry is qualitatively well described by the simulation. More studies are needed to confirm these initial observations.

Recently, a new framework for studying generic <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>2</a:mn> <a:mo stretchy="false">→</a:mo> <a:mn>3</a:mn> </a:math> hard exclusive reactions, referred to as single-diffractive hard exclusive processes, has been introduced to provide a cleaner separation of the underlying physical mechanisms. In this work, we expand this formalism to the case of exclusive real-photon electroproduction off a nucleon, <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:mi>e</d:mi> <d:mo stretchy="false">(</d:mo> <d:mo>ℓ</d:mo> <d:mo stretchy="false">)</d:mo> <d:mo>+</d:mo> <d:mi>N</d:mi> <d:mo stretchy="false">(</d:mo> <d:mi>p</d:mi> <d:mo stretchy="false">)</d:mo> <d:mo stretchy="false">→</d:mo> <d:mi>e</d:mi> <d:mo stretchy="false">(</d:mo> <d:msup> <d:mo>ℓ</d:mo> <d:mo>′</d:mo> </d:msup> <d:mo stretchy="false">)</d:mo> <d:mo>+</d:mo> <d:mi>N</d:mi> <d:mo stretchy="false">(</d:mo> <d:msup> <d:mi>p</d:mi> <d:mo>′</d:mo> </d:msup> <d:mo stretchy="false">)</d:mo> <d:mo>+</d:mo> <d:mi>γ</d:mi> <d:mo stretchy="false">(</d:mo> <d:msup> <d:mi>q</d:mi> <d:mo>′</d:mo> </d:msup> <d:mo stretchy="false">)</d:mo> </d:math> , which represents the classical channel for accessing generalized parton distributions (GPDs) in nucleons and nuclei. This extension enables a more systematic and physically transparent formulation of the reaction dynamics, paving the way for improved extractions of GPDs from experimental data as compared to existing approaches.

Abstract The potential of the intense secondary muon, neutrino, and (hypothetical) light dark matter beams at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) is explored. These are produced in the high-power dumps with high-current electron beams. Light dark matter searches with the approved Beam Dump eXperiment (BDX) are driving the realization of a new underground vault behind Hall A that could be extended to a Beamdump Facility with little additional installations. High-energy muons created via the Bethe–Heitler process uniquely do not proceed through the more common pion production and decay channels. Several possible muon physics applications are highlighted. Neutrino detector technologies and experiments suitable for a beamdump facility are outlined.

Workforce reductions, such as those implemented by the Department of Government Efficiency, can have far-reaching effects that extend beyond immediate job losses. This study employs a systems-based modeling approach, combining traditional Input-Output (IO) analysis with the inoperability Input-Output Model (IIM), to investigate how staffing cuts impact economic activity and erode institutional functions across interconnected sectors. The study reveals that reductions in federal staff have a significant impact on industries that rely heavily on government contracts and infrastructure, including aerospace, transportation, and high-tech services. These disruptions create ripple effects throughout supply networks and regional economies, resulting in delays, cancellations, and reduced operational capacity. Notably, the extent and pattern of losses identified here align with findings from independent reports, which highlight hidden costs such as declines in productivity, contract terminations, and maintenance backlogs that often offset the expected savings from workforce reductions. Unlike models that only focus on output, the IIM framework captures functional degradation, providing a more accurate breakdown of impacts on various economic sectors. These findings underscore the limitations of cost-cutting measures that overlook systemic interdependencies, highlighting the need for policies that strike a balance between fiscal objectives and institutional resilience. An adaptive, risk-aware approach to workforce planning can help maintain essential services while managing organizational change.

Atomic Layer Deposition (ALD) inherently yields intrinsic, undoped semiconducting films, necessitating the incorporation of controlled impurity levels to convert them into extrinsic semiconductors. While several in-situ doping strategies—such as delta doping during the ALD process—have been explored, post-deposition doping via ion implantation offers superior control over both dose and doping profile. This study examines the effects of Chromium (Cr⁺) ion implantation at 180 keV on the properties of lead chalcogenide (PbTe) thin films, with the goal of enhancing their thermoelectric figure of merit. A fluence of 5 × 10¹⁵ ions/cm² was employed to achieve an estimated Cr doping concentration of 1%. SRIM (Stopping and Range of Ions in Matter) simulations were used to optimize the implantation energy to align the dopant distribution peak with the ALD film thickness.PbTe thin films were synthesized via ALD on silicon substrates with native oxide layers, using lead(II) bis(2,2,6,6-tetramethyl-3,5-heptanedionato) (Pb(C₁₁H₁₉O₂)₂) and (trimethylsilyl) telluride ((Me₃Si)₂Te) as the precursors for lead and tellurium, respectively. Nitrogen served as both the carrier and purge gas. Prior to deposition, substrate surfaces were functionalized to ensure consistent chemisorption of the ALD precursors. The ALD process was conducted over a temperature range of 130°C to 170°C, with precursor delivery temperatures of 170°C for lead and 45°C for tellurium. The deposition chamber was maintained at a base pressure of 500 mTorr.Comprehensive characterization of the PbTe films was carried out before and after ion implantation. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were used to evaluate film morphology and composition X-ray Diffraction (XRD) analysis confirmed the formation of polycrystalline films with simple cubic structure. Atomic Force Microscopy (AFM) provided detailed information on surface topology, including RMS roughness, grain height, and average grain size. Electrical properties were assessed through temperature-dependent resistivity (ρ(T)), electrical conductivity, Hall mobility, and Seebeck coefficient measurements to evaluate the effects of Cr ion implantation on the thermoelectric performance of the PbTe films.

Measurements of beam single-spin asymmetries in semi-inclusive deep-inelastic electron scattering (SIDIS) with positively charged kaons off protons have been performed with 10.6 and 10.2 GeV incident electron beams using the CLAS12 spectrometer at Jefferson Lab. We report an analysis of the electroproduction of positively charged kaons over a large kinematic range of fractional energy, Bjorken x , transverse momentum, and photon virtualities Q 2 ranging from 1 GeV 2 up to 6 GeV 2 . This is the first published multidimensionally binned CLAS12 measurement of a kaon SIDIS single-spin asymmetry in the valence quark regime. The data provide constraints on the structure function ratio F L U sin ϕ / F U U , where F L U sin ϕ is a quantity with a leading twist of twist-3 that can reveal novel aspects of the quark-gluon correlations within the nucleon. The impact of the data on understanding the underlying reaction mechanisms and their kinematic variation is explored using theoretical models for the different contributing twist-3 parton-distribution functions (PDFs) and fragmentation functions (FFs).

MARCO is the new superconducting solenoid for ePIC, the general-purpose detector capable of delivering the full scientific scope of the Electron-Ion Collider at Brookhaven National Laboratory. This 3.84 m long solenoid, with a bore diameter of 2.84 m, will provide a magnetic field of 2.0 T at the center with a nominal current of 4 kA at 4.5 K, for a total stored energy of 45 MJ. Its conductor is a NbTi Rutherford in Copper Channel (RICC), specially designed to stand the high mechanical loads induced by the magnetic field. Its copper stabilizer will assure the protection in case of quench. The coils are wound into six layers inside a thin external mandrel in brass, with a triple role of mechanical reinforcement, cryogenic support for the thermosiphon circuit and quench-back propagator. With a cold mass average radial thickness of just 7 cm, the magnet fulfills all the criterions of transparency for the particles directed to the hadronic calorimeter forecast around the cryostat. In this paper, the design of MARCO is presented, with a specific focus on the magnetic and quench analysis.