Bob H. Smith

Current Regulator for a 10 000‐A dc 7.5‐MW Magnet Power Supply

Design and construction details are discussed for a dc current control system capable of a short term stability of a few parts in 106 and a long term stability of ∼2 parts in 105 when used in conjunction with conventional rotating dc generators powering loads with time constants of approximately 200 msec at levels up to 7.5 MW. Actual performance of the system at various power levels is discussed.

Invited Paper-The Omnitron: A Versatile Medium-Energy Synchrotron for the Acceleration of Light and Heavy Ions

A novel guide-magnet configuration has been devised which makes possible the acceleration of all charge-to-mass ratios from 0.04 to 1. A concentric storage ring, with the associated beam-switching equipment, allows for the extension of beam duty factor to essentially 100%. The storage ring can also be used in a bootstrap acceleration of heavy ions in which the ions are injected at low e/m, accelerated to a moderate velocity, stored while the accelerating ring returns to minimum field, stripped to maximum e/m, and re-injected for further acceleration. With a pressurized 2.5 MV Cockcroft-Walton injector, the proposed system is capable of accelerating all ions from protons to uranium--to energies up to 1.5 BeV for protons and 0.3 to 0.5 BeV/nucleon for the heavier ions. Intensities of 1012 to 1013 nucleons/sec for the lighter ions (M ? 128) are anticipated. The heavy-ion charge-exchange probabilities determine the vacuum requirements of this system. To minimize these requirements and to increase beam intensity, a 60/sec cycling rate has been chosen. The vacuum requirements and the special rf resonator and beam-switching problems attendant with the high cycling rate are discussed.

A 600-kV, 10-mA DC Cockcroft-Walton Rectifier Using Silicon Diodes at 100 kc

In this rectifier high-speed silicon diodes, etched circuit boards, and SF6 are combined in a style of construction that requires only the modest shop facilities of any typical small physics laboratory. This paper covers construction techniques, performance tests, electronic regulation, high-speed protection circuitry, and application of the rectifier to experimental equipment. The technique described can be extended to larger sizes providing several million volts.

Radiofrequency system of the Berkeley 88-inch cyclotron

The design and performance of a single-dee self-excited radio-frequency system that tunes from 5.5 Mc/s to 16.5 Mc/s are discussed. Self-excited radiofrequency systems are compared with driven systems. The multipactoring phenomenon in variable-frequency systems is analyzed and discussed.

Three‐Phase Radiofrequency System for Thomas Cyclotrons

As part of the program to develop high current accelerators several model Thomas cyclotrons employing three‐phase rf were built. The three phase signal was produced by a phase generator which was excited by a crystal oscillator. Each phase was amplified and applied to the corresponding dee, which was kept in tune by means of servomechanisms. Balanced dee voltages require a symmetrical resonator with equal inter‐dee capacitances; stability of the servomechanism requires that the effective inter‐dee capacitances be zero. This last condition was fulfilled by means of neutralizing transmission lines connected from dee stem to dee stem. Thomas cyclotrons appear to be capable of producing megawatts of beam power with an rf efficiency in excess of 70%.

A 3-MV Injector for the Superhilac

Author(s): Spence, D.A.; Gavin, B.F.; Peters, R.; Reginato, L.L.; Smith, B.H.; Wolgast, R.C.

STUDIES WITH A THREE-DEE THREE-PHASE PROTON CYCLOTRON

As part of the program to investigate the properties of the Thomas cyclotron, a 20‐in. diam proton cyclotron was constructed. In such a three‐dee three‐phase system it is possible to accelerate protons, deuterons, and tritons at the same setting of frequency and magnetic field but on different modes of the rf. For stable operation in the proper mode and with balanced voltages, it has been found necessary to provide both phase servos and amplifier efficiency servos. The dees could not be servoed individually until the inter‐dee capacity was neutralized. Under such conditions it was possible to attain steadily 6.0 ma of protons at 1.0 Mev in the forward mode and 6.5 ma of deuterons at 0.5 Mev in the reverse mode.

Simplified Design Techniques for Distributed Power Amplifiers for Synchrotron and Cyclotron Driver Applications

Design of distributed power amplifiers has been simplified through the use of a set of design charts and simplifying circuit techniques. A circuit in which the anode and grid lines are built from bridge-T constant-resistance networks seems to be best. These lines have an image impedance that is resistive and of constant value for all frequencies, and therefore do not require terminating half sections. For a given characteristic impedance and shunt capacitance, the bridge-T lines have about twice the bandwidth of the constant-K lines. The design of the ferrite transformers for matching the anode and grid lines to standard line impedances has been simplified by means of design charts and tables. These amplifiers are simple to build and very stable. A 3.5-kW amplifier which operates from 1.0 to 70 MHz is used to illustrate the technique.

Three Phase, 1.5 MW, Electronic Line Regulator for the Berkeley 88‐Inch Cyclotron

Six hundred power transistors on water‐cooled heatsinks are connected in a Kerns actuator circuit to modulate the power line feeding the Berkeley 88‐Inch Cyclotron. The regulator senses the rectified three phase line voltage and attenuates the frequency components between 0.001 and 200 Hz to 0.03% of the average value. Elimination of these components from the main power line removes the need for expensive wide band regulators for each of the many critical high power loads in the building. The paper discusses the design considerations and construction techniques of this regulator.

A High-Stability, Wide-Band, Low-Noise Transductor Circuit Suitable for High-Precision Magnet-Current Regulators

Typical performance of this transductor circuit includes a long-term stability of a few parts in 105, an output noise level less than 0.002% of full output voltage, and a pass band from 0 to 1 MHz. The circuit provides low-pass, band-pass, and high-pass sections, suitably designed to provide a uniform frequency response. The circuit configuration inherently filters out the commutation noise, thus providing a high signal-to-noise ratio.