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Hannon, Fay E.

Publications and source records attributed to Hannon, Fay E..

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Electrostatic design and conditioning of a triple point junction shield for a –200 kV DC high voltage photogun [Electrostatic design of a triple point junction shield for a -200 kV DC high voltage photogun using COMSOL]

Nuclear physics experiments performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at the Jefferson Lab require a DC high voltage photogun to generate polarized electron beams from GaAs photocathodes. The photogun uses a tapered ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. Increasing the operating voltage from nominal –130 kV to –200 kV will provide lower beam emittance, better transmission through injector apertures, and improved photocathode lifetime. This desire to increase the photogun operating voltage led to the design of a triple-point-junction shield electrode which minimizes the electric field at the delicate insulator-metal-vacuum interface and linearizes the potential across the insulator, thus reducing the risk of arcing along the ceramic insulator. Furthermore, this work describes the results obtained using COMSOL® electrostatic-field simulation software and presents the high voltage conditioning results of the upgraded –200 kV CEBAF photogun.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

952.6 MHz SRF cavity development for JLEIC

JLab is developing new SRF cavity designs at 952.6 MHz for the proposed Jefferson Lab Electron-Ion Collider (JLEIC). New cavities will be required for the ion ring, cooler ERL and booster and eventually for the electron ring to allow the highest possible bunch collision rate. The challenges include the need for strong HOM damping, high fundamental mode power couplers and high HOM power. Initial focus is on the cooler ERL five- cell cavity as this is a critical component for the strong, high energy, bunched-beam cooling concept. One-cell and five-cell Nb prototype cavities have been designed and fabricated. Details concerning the cavity fabrication and test results for the will be presented.

Rimmer, Robert A.↗
DOE OSTI2018

Simulation Study of the Magnetized Electron Beam

Electron cooling of the ion beam plays an important role in electron ion colliders to obtain the required high luminosity. This cooling efficiency can be enhanced by using a magnetized electron beam, where the cooling process occurs inside a solenoid field. This paper compares the predictions of ASTRA and GPT simulations to measurements made using a DC high voltage photogun producing magnetized electron beam, related to beam size and rotation angles as a function of the photogun magnetizing solenoid and other parameters.

Wijethunga, W M Sajini↗
DOE OSTI2018

PERLE - Lattice Design and Beam Dynamics Studies

PERLE (Powerful ERL for Experiments) is a novel ERL test facility, initially proposed to validate choices for a 60 GeV ERL foreseen in the design of the LHeC and the FCC-eh. Its main thrust is to probe high current, CW, multi-pass operation with superconducting cavities at 802 MHz (and perhaps testing other frequencies of interest). With very high virtual beam power (~ 10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERL design; becoming a ‘stepping stone' between present state-of-art 1 MW ERLs and future 100 MW scale applications. PERLE design features Flexible Momentum Compaction lattice architecture for six vertically stacked return arcs and a high-current, 6 MeV, photo-injector. With only one pair of 4 cavity cryomodules, 400 MeV beam energy can be reached in 3 re-circulation passes, with beam currents in excess of 15 mA. The beam is decelerated in 3 consecutive passes back to the injection energy, transferring virtually stored energy back to the RF. This unique facility will serve as a test-bed for high current ERL technologies, as well as a user facility in low energy electron and photon physics.

Bogacz, Alex↗
DOE OSTI2018

Production of magnetized electron beam from a DC high voltage photogun

Bunched-beam electron cooling is a key feature of all proposed designs of the future electron-ion collider, and a requirement for achieving the highest promised collision luminosity. At the Jefferson Lab Electron Ion Collider (JLEIC), fast cooling of ion beams will be accomplished via so-called 'magnetized cooling' implemented using a recirculator ring that employs an energy recovery linac. In this contribution, we describe the production of magnetized electron beam using a compact 300 kV DC high voltage photogun with an inverted insulator geometry, and using alkali-antimonide photocathodes. Beam magnetization was assessed using a modest diagnostic beamline that includes YAG view screens used to measure the rotation of the electron beamlet passing through a narrow upstream aperture. Magnetization results are presented for different gun bias voltages and for different laser spot sizes at the photocathode, using 532 nm lasers with DC and RF time structure. Photocathode lifetime was measured at currents up to 4.5 mA, with and without beam magnetization.

Al Mamun, Md Abdullah↗
DOE OSTI2018

300 kV DC High Voltage Photogun with Inverted Insulator Geometry and CsK2sb Photocathode

A compact DC high voltage photogun with inverted-insulator geometry was designed, built and operated reliably at 300 kV bias voltage using alkali-antimonide photocathodes. This presentation describes key electrostatic design features of the photogun with accompanying emittance measurements obtained across the entire photocathode surface that speak to field non-uniformity within the cathode/anode gap. A summary of initial photocathode lifetime measurements at beam currents up to 4.5 mA is also presented.

Wang, Yan↗
DOE OSTI2018

Development of a Bunched Beam Electron Cooler based on ERL and Circulator Ring Technology for the Jefferson Lab Electron-Ion Collider

Jefferson Lab is in the process of designing an electron ion collider with unprecedented luminosity at a 45 GeV center-of-mass energy. This luminosity relies on ion cooling in both the booster and the storage ring of the accelerator complex. The cooling in the booster will use a conventional DC cooler similar to the one at COSY. The high-energy storage ring, operating at a momentum of up to 100 GeV/nucleon, requires novel use of bunched-beam cooling. There are two designs for such a cooler. The first uses a conventional Energy Recovery Linac (ERL) with a magnetized beam while the second uses a circulating ring to enhance both peak and average currents experienced by the ion beam. This presentation will describe the design of both the Circulator Cooling Ring (CCR) design and that of the backup option using the stand-alone ERL operated at lower charge but higher repetition rate than the ERL injector required by the CCR-based design.

Benson, Stephen V.↗
DOE OSTI2015

Observation of High Field Q-Slope in 3 GHz Nb Cavities

A degradation of the unloaded quality factor is commonly observed above about 100 mT in elliptical niobium cavities. The cause of this degradation has not been fully understood yet, but the empirically found solution of heating to about 100-120 C for 24-48 hrs. eliminates the degradation in electropolished fine grain or large grain niobium cavities. While numerous experiments related to this phenomenon have been done at 1.3 GHz and 1.5 GHz, little data exists at other frequencies, and the frequency dependence of this degradation is not clear. We have measured the unloaded quality factor of 3 GHz fine grain niobium cavities, which were chemically polished as the final treatment before RF tests in a vertical Dewar and observed the characteristic degradation in two cavities. The measurement of the quality factor degradation at different bath temperatures points to a field-dependent rather than a temperature-related effect.

Eremeev, Grigory V.↗