W. F. Praeg

A High-Current Low-Pass Filter for Magnet Power Supplies

The majority of high-current dc power supplies for beam bending magnets have well known LCR low-pass ripple filters. To avoid prohibitive heat losses, the filter damping resistor is in series with the capacitor and not in the dc path. Such filters, when critically damped, attenuate high frequencies by 6 dB/octave. This paper analyzes an improved underdamped LCR filter which attenuates high frequencies by 12 dB/octave. Depending on the application, the improved filter can be designed to have an oscillatory or a non-oscillatory response to a step change of the input voltage. Design curves are given which show the frequency response and the time response to a unit step of a normalized improved filter for various degrees of damping.

Results from the Felix experiments on electromagnetic effects in hollow cylinders

The early experiments with the FELIX (Fusion Electromagnetic Induction eXperiments) facility have been devoted to obtaining data which can be used to validate eddy current computer codes. This paper describes experiments on field variation inside conducting cylinders.

Dual Frequency Ring Magnet Power Supply with Flat-Bottom

A power supply is described that furnishes an essentially flat-bottom injection field, followed by a dual frequency cosine field. This results in efficient beam capture during injection and reduces significantly the peak rf power required during acceleration in a rapid-cycling synchrotron.

An Inexpensive Pulsed Power Supply for a Septum Magnet

A 16 ¿H, 6 m¿ septum magnet load must be pulsed while extracting beam from the 200 MeV booster of the Zero Gradient Synchrotron (ZGS). A power supply was designed for this purpose that can deliver ~ 2 ms wide, half sine wave pulses with a PRF of 30 pulses per second. The peak current is adjustable from 3 kA to 10 kA and repeatable within ± 0.05% by means of a novel charging circuit. By providing a transformer between the magnet and the capacitor bank, the overall cost of the system was reduced to less than onehalf of that of a conventional capacitor discharge system. A high-Q choke shunts the negative half wave of the current around the transformer, thereby extending the life expectancy of the magnet and increasing the circuit efficiency.

Control of Ring Magnet Current of the Zero Gradient Synchrotron at Argonne National Laboratory

A comprehensive account is given of the control of the ring magnet current for the 12.5 BeV Zero Gradient Synchrotron (ZGS) at Argonne National Laboratory. Pulsing power is supplied by a motor-generator-flywheel set via four groups of 12-phase rectifiers. The rectifier groups operate alternately as power rectifiers and power inverters as directed by their phase control circuits.

A Multi-Function Ring Magnet Power Supply for Rapid-Cycling Synchrotrons

Ring magnet power supply (RMPS) circuits that produce a wide range of magnet current waveshapes for rapid-cycling synchrotrons (RCS) are described. The shapes range from long flat-tops separated by a biased dual frequency cosine wave to those having a flat-bottom (injection), followed by a lower frequency cosine half wave (acceleration), a flat-top (extraction), and a higher frequency cosine half wave (magnet reset). Applications of these circuits for proposed synchrotrons are outlined. Solid-state switching circuits and the results of proof-of-concept tests are shown.

Phase Lock of Rapid Cycling Synchrotron and Neutron Choppers

The 500 MeV synchrotron of Argonnes Intense Pulsed Neutron Source operates at 30 Hz. Its beam spill must be locked to neutron choppers with a precision of ± 0.5 ¿s. A chopper and an accelerator have large and different inertias. This makes synchronization by phase lock to the 60 Hz power line extremely difficult. We solved the phasing problem by running both the Ring Magnet Power Supply (RMPS) of the synchrotron and the chopper motors from a common oscillator that is stable to 1 ppm and by controlling five quantities of the RMPS. The quantities controlled by feedback loops are dc current, injection current, ejection current, resonant frequency, and the phase shift between the synchrotron peak field and the chopper window.

Shaped Excitation Current for Synchrotron Magnets

A 500 MeV synchrotron at Argonne National Laboratory (ANL) operates at 30 Hz with its beam spill locked to neutron choppers with a precision of ± 0.5 ¿s. The average beam will be increased by running the magnets at 45 Hz. Three 45 Hz circuits are discussed which differ greatly in overall cost and complexity. The first is a conventional 45 Hz sine wave circuit. The reduction in time for beam acceleration results in a costly increase in peak RF power. This problem is avoided in the other two circuits by making the field rise slowly and fall rapidly. The second circuit discussed is resonant at 45 Hz and 90 Hz. Exciting this circuit with a mixture of dc, 45 Hz, and 90 Hz can produce a magnetic field with the same maximum dB/dt as the present 30 Hz field. A third, and possibly least expensive, solution is a novel circuit which produces 30 Hz during acceleration and 90Hz when the magnets are reset. The RF requirements are, of course, identical to present requirements during acceleration. Circuit details are given.

A Transformer Septum Magnet

A pulsed transformer septum magnet is under development for the Intense Pulsed Neutron Source (IPNS-I), 500 MeV accelerator. The septum consists of a copper sheet and a steel sheet. The copper sheet is one side of the shorted single turn transformer secondary. The steel sheet, which is on the stray field side of the septum, is part of the transformer core. External support and cooling structures, as well as the septum itself, can be grounded, which simplifies the design. The design construction and operation will be discussed. The transformer primary is driven by a condenser discharge. A reverse discharge a few ms later recharges the condenser and demagnetizes the septum. Details will be discussed.

A Pulsed Power Supply for Injection Bump Magnets

A very precise and relatively inexpensive charging circuit for an energy storage capacitor bank feeds an efficient thyristor-controlled pulse-forming discharge circuit. These circuits, which generate magnet pulses of 300 joules at a rate of 30 per second, are analyzed in this paper.