Magnetized Electron Source for JLEIC Cooler

Magnetized bunched-beam electron cooling is a critical part of the Jefferson Lab Electron Ion Collider (JLEIC). Strong cooling of ion beams will be accomplished inside a cooling solenoid where the ions co-propagate with an electron beam generated from a source immersed in magnetic field. This contribution describes the production and characterization of magnetized electron beam using a compact 300 kV DC high voltage photogun and bialkali-antimonide photocathodes. Beam magnetization was studied using a diagnostic beamline that includes viewer screens for measuring the shearing angle of the electron beamlet passing through a narrow upstream slit. Correlated beam emittance with magnetic field at the photocathode was measured for various laser spot sizes. Measurements of photocathode lifetime were carried out at different magnetized electron beam currents up to 28 mA and high bunch charge up to 0.7 nano-Coulomb was demonstrated

High Current High Charge Magnetized and Bunched Electron Beam From a DC Photogun for JLEIC Cooler

A high current, high charge magnetized electron beamline that has been under development for fast and efficient cooling of ion beams for the proposed Jefferson Lab Electron Ion Collider (JLEIC). In this paper, we present the latest progress over the past year that include the generation of picosecond magnetized beam bunches at average currents up to 28 mA with exceptionally long photocathode lifetime, and the demonstrations of magnetized beam with high bunch charge up to 700 pC at 10s of kHz repetition rates. Detailed studies on a stable drive laser system, long lifetime photocathode, beam magnetization effect, beam diagnostics, and a comparison between experiment and simulations will also be reported. These accomplishes marked an important step towards the essential feasibility for the JLEIC cooler design using magnetized beams

Online Measurement and Tuning of Multipass Recirculation Time in the CEBAF Linac

CEBAF is a recirculating electron accelerator with negligible synchrotron motion of the particles within each bunch. On-crest RF acceleration is used to minimize the time-averaged energy spread of the beam. Previously installed diagnostics** allow us to maintain the relative timing of the beam and the RF, noninvasively compensating for residual drifts of the RF timing system on the first acceleration pass. However, residual setup errors for the path length (recirculation time) and variable path length drift between passes result in relative drifts of beam energy at the 10-4 scale for some passes, even when the energy of any one of the recirculation passes is held fixed by adjusting the RF gradient. We have extended the diagnostic system to the higher acceleration passes and can correct the recirculation timing at the scale of hundreds of femtoseconds (tenths of a degree of 1497 MHz RF phase). Variation in the higher-pass beam to RF timing indicates drift in the beam recirculation time. The previous procedure for measuring and tuning the path length required suspension of beam delivery to the users. These actions can now be done without interruption of beam to the experimenters

Survey and analysis of line-frequency interference in the CEBAF accelerator

Feedthrough of interference from the AC power line into accelerator components is a problem which in pulsed accelerators can be reduced by operation synchronous with the AC line. This means of avoiding line-frequency effects is ineffective for continuous wave machines such as the CEBAF accelerator. We have measured line-frequency perturbations at CEBAF both in beam position and energy by using the beam position monitor system as a multiple-channel sampling oscilloscope. Comparing these data against the measured static optics (taken synchronously with the AC line) we have been able to identify point sources of interference, and resolve line-synchronous variations in the beam energy at a level near 0.001%. 3 refs., 2 figs., 1 tab

Runtime accelerator configuration tools at Jefferson Laboratory

RF and magnet system configuration and monitoring tools are being implemented at Jefferson Lab to improve system reliability and reduce operating costs. They are prototype components of the Momentum Management System being developed. The RF is of special interest because it affects the momentum and momentum spread of the beam, and because of the immediate financial benefit of managing the klystron DC supply power. The authors describe present and planned monitoring of accelerating system parameters, use of these data, RF system performance calculations, and procedures for magnet configuration for handling beam of any of five beam energies to any of three targets