JLab, Newport News, Virginia, USA
ODU, Norfolk, Virginia, USA
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.
BNL, Upton, New York, USA
Brookhaven National Laboratory is constructing a 350 kV DC high voltage photogun to provide spin-polarized electron beam for the proposed eRHIC facility. The photogun employs a compact inverted-tapered-geometry ceramic insulator that extends into the vacuum chamber and mechanically holds the cathode electrode. By operating at high voltage, the photogun will provide lower beam emittance, thereby improving the beam transmission through the injector apertures, and prolong the operating lifetime of the photogun. However, high voltage increases the field emission, which can result in high voltage breakdown and even lead to irreparable damage of the ceramic insulator. This work describes the methods to minimize the electric field near the metal-vacuum-insulator interface, and to avoid high voltage breakdown and ceramic insulator damage. The triple point junction shields are designed. The simulated electric field, field emission and beam transportation will be presented.
ORNL RAD, Oak Ridge, Tennessee, USA
The Spallation Neutron Source (SNS) extraction kicker 60Hz pulsed system uses 14 Blumlein pulse-forming network (PFN) modulators that require timing synchronization with stable rise times. A replacement design has been investigated and the kickers have been converted over to use a solid-state switch design, eliminating the lifetime and stability issues associated with thyratrons and subsequent maintenance costs. All kickers have been converted, preventing thyratron jitter from impacting the beam performance and allowing higher-precision target impact. This paper discusses the completion of the conversion of the high-voltage switch from a thyratron to a solid-state switch with improved stability of the extraction system and associated accelerator beam stability.
BNL, Upton, New York, USA
The NSLS-II synchrotron light-source at BNL uses three S-band, 45MW klystrons in its injector LINAC. At the core of the klystron station design is the novel solid-state switching modulators (or SSM). Compared to the conventional PFN klystron modulators, the main advantages of the SSM include the compact size requiring a smaller footprint in the LINAC, and a very flat top in the produced klystron HV pulses. The flatness of the HV pulses is very important for NSLS-II LINAC that runs multi-bunch beams to keep the beam energy dispersion within the tolerance. The principle of the SSM is fairly simple. It uses a large number of relatively low-voltage switched charging capacitor cells (or SU’s) in parallel. A specially designed, high step-up ratio, pulse transformer in the oil-tank with the same number of primary windings (as SU’s) combines the power from all the SU’s, and steps up to the required ~300kV klystron beam voltage. The operation experience at NSLS-II has proven the performance and reliability of the SSM’s. The BNL Model K2 SSM’s are currently being upgraded to Model K300 to run more powerful, and more cost-effective Canon’s E37302A klystrons.
ANL, Lemont, Illinois, USA
Euclid Beamlabs LLC, Bolingbrook, USA
The RF system of Argonne Wakefield Accelerator (AWA) facility has grown over the years from one RF power station into 4 RF power stations. The demand for RF power keeps growing as the capability of AWA continues to grow. Now the 5th RF station is needed to fulfill the RF power needs of AWA facility. Some details regarding the construction and commissioning of the 5th RF station of AWA facility are documented in this paper.
Fermilab, Batavia, Illinois, USA
A Marx-topology modulator has been designed and developed at the Fermi National Accelerator Laboratory under the Proton Improvement Plan (PIP). This modulator replaces the previous triode hard-tube design, increasing reliability, lowering operational costs, and maintaining waveform accuracy. The Marx modulator supplies the anode of the 7835 VHF power triode tube with a 35 kV, 375 Amp, 460 µs pulse at 15 Hz. It consists of 54 individual Marx cells, each containing a 639 µF capacitor charged to 900 Volts, combined in series with IGBT switches to create the desired output waveform. This requires variable rise and fall times, flattening of capacitive droop, and feedforward beam loading compensation. All five 201.25 MHz RF systems have been upgraded to Marx modulators to ensure continued operation of the linear accelerator.
ORNL, Oak Ridge, Tennessee, USA