ORNL, Oak Ridge, Tennessee, USA
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
ORNL RAD, Oak Ridge, Tennessee, USA
Tests were performed at SNS in collaboration with visiting colleagues from ISIS, UK to evaluate the uncesiated beam performance of the SNS RF H− ion sources. Two spare experimental sources, one with internal antenna and one with external antenna were used for the tests. The beam currents achieved with Cs-free operations accounted for about 1/3 to 1/2 of the beam currents produced with cesiated operations. ~17 mA uncesiated H− current was demonstrated within the tested RF power range up to 65 kW with the internal antenna source and ~15 mA with up to 40 kW RF with the external antenna source. In Cs-free operations, the power supply for the electron dumping electrode was loaded down below its set voltage but was not too drastic to tamper the operation.
ANL, Lemont, Illinois, USA
Polarization switching x-ray probes coupled with high-flux provide a unique tool to unraveling the nature of electronic heterogeneity and drive discovery of novel phases of electronic matter. Superconducting Arbitrary Polarization Emitter (SCAPE) is a new concept for a universal undulator, which offers linear or circular polarization states in one device and is ideal for experiments that require polarization switching. Polarization switching relies on modulating the magnetic field in the undulator. This, however, inevitably incurs losses in superconductors, which need to be mitigated. In this study, feasibility of fast switching SCAPE has been investigated through fabricating and testing several short prototype magnets wound with different superconductors and new design concepts. The losses at different frequencies and field amplitudes are measured and details will be discussed.
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.
CCR, San Mateo, California, USA
Fermilab, Batavia, Illinois, USA
CPI, Beverley, Massachusetts, USA
Calabazas Creek Research, Inc., Fermilab, and Communications & Power Industries, LLC, developed a 100 kW peak, 10 kW average, 1.3 GHz, magnetron-based, RF system for driving accelerators. Efficiency varied between 81% and 87%. Phase locking uses a novel approach that provides fast amplitude and phase control when coupled into a superconducting accelerator cavity [1]. The system was successfully tested at Fermilab and produced 100 kW in 1.5 ms pulses at a repetition rate of 2 pps. A locking bandwidth of 0.9 MHz was achieved with a drive signal of 269 W injected through a 4 port circulator. The phase locking signal was 25 dB below the magnetron output power. The spectrum of the phase locked magnetron was suitable for driving accelerator cavities. Phase modulation was demonstrated to 50 kHz (the limit of the available driver source). The average power was limited by available conditioning time. Scaling indicates 42 kW of average power should be achievable. Estimated cost is less than $1/Watt of delivered RF power, exclusive of power supplies or modulators. System design and performance measurements will be presented.
[1] B. Chase, R. Pasquinelli, E. Cullerton, P. Varghese, "Precision Vector Control of a Superconducting RF Cavity driven by an Injection Locked Magnetron," Jou. of Instrumentation, Vol. 10 March 2015.
ANL, Lemont, Illinois, USA
Orbit stabilization to 10% of the expected small beam sizes for Advanced Photon Source Upgrade (APS-U) requires pushing the state of the art in fast orbit feedback (FOFB) control, both in the spatial domain and in dynamical performance. We are building a Matlab/Simulink fast orbit feedback system model to guide decisions about APS-U fast orbit feedback system implementation and to provide a test bench for optimal-control methodologies and orbit correction algorithms applicable to the APS-U. A transfer function model was built from open-loop frequency-response and step-response measurements of the present APS and subsequently validated against closed-loop measurements. A corresponding model for APS-U fast orbit feedback was generated by substituting measured responses of APS-U prototype corrector magnets and power supplies into this same model. Stabilizing PID gains are designed using model, and simulated dynamic performance of the new controller is validated through experiments.
LANL, Los Alamos, New Mexico, USA
From 2014-2016, the three highest power 201 MHz power amplifier (PA) systems were replaced at the Los Alamos Neutron Science Center 100 MeV DTL. The initial DTL cavity provides 4.25 MeV of energy gain and has been powered by a Photonis (RCA) 4616 tetrode driving a 7835 triode PA for over 30 years. It consumes 110 kW of electrical power for tube filaments, power supplies and anode modulator. The modulator is not required with modern tetrode amplifiers. In 2020 we plan to replace this obsolete 6 tube transmitter with a design using a single tetrode PA stage without anode modulator, and a 20 kW solid-state driver stage. This transmitter needs to produce no more than 400 kW, and will use a coaxial circulator. Cooling water demand will reduce from 260 to 70 gal/min of pure water. High voltage DC power comes from the same power supply/capacitor bank that supplied the old system. The old low-level RF controls will be replaced with digital LLRF with learning capability for feedforward control, I/Q signal processing, and PI feedback. All high power components have been assembled in a complete mockup system for extended testing. Installation of the new RF system begins in January of 2020.
ORNL, Oak Ridge, Tennessee, USA