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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

APEX: A Prime EXperiment at Jefferson Lab

APEX is an experiment at Thomas Jefferson National Accelerator Facility (JLab) in Virginia, USA, that searches for a new gauge boson ($A^\prime$) with sub-GeV mass and coupling to ordinary matter of $g^\prime \sim (10^{-6} - 10^{-2}) e$. Electrons impinge upon a fixed target of high-Z material. An $A^\prime$ is produced via a process analogous to photon bremsstrahlung, decaying to an $e^+ e^-$ pair. A test run was held in July of 2010, covering $m_{A^\prime}$ = 175 to 250 MeV and couplings $g^\prime/e \; \textgreater \; 10^{-3}$. A full run is approved and will cover $m_{A^\prime} \sim$ 65 to 525 MeV and $g^\prime/e \; \textgreater \; 2.3 \times10^{-4}$.

Beacham, James↗
DOE OSTI2011

Operation Experience with DC Photoemission Guns at Jefferson Lab

The JLab IR FEL injector is driven by a DC photoemission electron gun based on GaAs photocathodes. Since the FEL commissioning in 1998, the DC gun has been rebuilt several times for improved performance and/or for repairs. After demonstrating 9 mA CW and over 7000 Coulombs at 350kV for three consecutive years, the gun was rebuilt in 2008 due to a punctured insulator. Since then, the gun has been operating at 325V (lower voltage due to field emission) and has delivered beam at 65 pC bunch charge for VUV FEL operations, and 135pC for IR FEL operations at beam currents up to 4 mA CW. In February 2011, a copy of that gun was tested in the Gun Test Stand with a partially conductive insulator from Wesgo/Morgan to study bulk conductivity as charge drain for preventing insulator puncture by field emission. Close to 300 hours of high voltage testing showed that processing of field emission with partial pressure of Krypton gas is very effective. The gun held 500kV over 8 hours with 1E-4 Torr of Krypton. However, the gun could not hold more than 440kV under vacuum conditions, at which set point the insulator suffered a puncture. Various observations of Kr processing behavior and voltage-induced gas desorption will be presented. Financial support was provided by the Office of Naval Research, the Army Night Vision Laboratory, the Air Force Research Laboratory, the Joint Technology Office, the Commonwealth of Virginia, and by the U.S. DOE Basic Energy Sciences under contract No. DE-AC05-060R23177.

Hernandez-Garcia, Carlos↗
DOE OSTI2023

Design and Prototyping of a Novel Toroid Magnet System for the MOLLER Experiment at Jefferson Lab

The Thomas Jefferson National Accelerator Facility (JLab) has designed a unique spectrometer system to measure the weak interaction between electrons. The experiment ?Measurement of Lepton-Lepton Electroweak Reaction? (MOLLER) requires leveraging the recent 12 GeV electron beam upgrade and will run in JLab for 3 years. Focusing the signal for the MOLLER experiment requires five water-cooled toroidal magnets, each with unique geometry and with 7-fold symmetry. This system of magnets provides the magnetic field required to separate the incident beam electrons scattered from the target electrons (Møller scattering) and protons (elastic e-p scattering) in a liquid hydrogen target. The conceptual design was developed by the MOLLER collaboration and was given to JLab in the form of amp turns and physical location, with additional physics requirements. This paper presents prototyping of the coils and magnet support system and discusses the lessons learned during the process along with the plans for full magnet testing and installation. The JLab Magnet Group along with the MOLLER collaboration developed the specification document that includes keep out zones to design the set of magnets. JLab contracted the design of the first toroid magnet in the magnet (TM0) to Massachusetts Institute of Technology. The other four toroid magnets (TM1 through TM4) have been designed by JLab and are in the process of fabrication and assembly. Prototype coils of TM1-TM4 have been fabricated by Everson-Tesla Incorporated, PA (USA). The manuscript presents the unique challenges of the design, alignment, high current density, operating range, high radiation dose, and vacuum environment.

Kashy, David↗