Slot-coupled beam-signal-pickup development at Argonne National Laboratory

The overall performance of slot couplers, at least for frequenciees below 2 GHz, can probably not match that of stripline based pickups. A measured, typical coupling at 2 GHz correesponds to about 6 to 7 ohms/slot-pair and produces about 8/sup 0/ phase shift/slot on the TEM line. Suppose a 12 to 14 slot array were constructed with these parameters. It would have a total 90/sup 0/ phase shift at about 1.7 GHz, and the coupling would be about 80 ohms at 2.0 GHz. Such an array would be 30 cm long. In a 10 m long straight section, one could place perhaps 25 such modules. After power adding, the net coupling would be about 80 x ..sqrt..25 = 400 ohms. This is 75% of the value which can be obtained by stripline structures (e.g. the FNAL Tevatron-I design). On the other hand, stripline structures may be difficult to construct for, let's say, a 4 to 8 GHz band. Slot coupled devices may then prove to be the more attractive choice. Slot couplers for these higher frequencies will be the subject of our R and D program at this time in the future

Rapid-Cycling Synchrotron extraction-kicker magent-drive system

The Rapid-Cycling Synchrotron (RCS) accelerator of the Intense Pulsed Neutron Source-I (IPNS-I) at Argonne National Laboratory utilizes a fast kicker magnet to provide single-turn extraction for a 500-MeV proton beam at a 30 Hz rate. The single-turn, 0.89-m-long ferrite magnet is broken up into two identical cells with four individual windings. Each winding requires a 4863-A magnetizing current into a 7.0-..cap omega.. load with a rise time of less than 100 ns and a flattop of about 140 ns. Pulse forming network (PFN) charging and switching techniques along with the components used will be described

Intense pulsed neutron source (IPNS-I) accelerator 500 MeV fast kickers

Two ferrite loaded picture frame magnets with a kick of up to 15 mrad each are used to extract 500 MeV protons from the IPNS-I accelerator to the neutron source target at the Argonne National Laboratory. The magnet aperture is 10 cm wide by 5 cm high and the length is 60 cm. The single bunch extraction requires a magnetic field rise time (0 to 100%) of 90 ns and a flattop of 100 ns. The magnets receive the 3600 A maximum current via an array of 50 ..cap omega.. coaxial cables connected in a shunt arrangement. The two legs of each magnet are energized with separate lines to keep the potential to ground to less than 40 kV. The system is designed to run at 30 pulses per second repetition rate. The complete system of control electronics, power supply, deuterium thyratron switch, magnet and resistive load will be described along with some of the problems of stray inductances and the techniques used to reduce them

Rapid Cycling Synchrotron (RCS) sngle-stage kicker magnet

A new single stage kicker magnet system is designed and is being fabricated for the RCS accelerator of the Intense Pulsed Neutron Source (IPNS-I) at the Argonne National Laboratory. This system will replace the two stage kicker in present use. The magnet aperture is 10 cm wide by 5 cm high and the magnetic length is 0.89 m. The magnetic field intensity is 0.1021 T for a 25 milliradian kick to the 500 MeV proton beam. A field rise time (10 to 90%) of 80 ns and a flattop of 100 ns is needed. The magnetic field fall time is not critical so a lumped parameter magnet with a 7.2 ohm load will be used. The electric current required through the single turn magnet is 4863 A. A new energy storage and switching system is designed and is being fabricated for energizing the magnets. The techniques and hardware used will be described along with some of the experience gained in the use of the two stage system which will help to improve the new design

Test facility for relativistic beam pickups

Calibration of beam signal pickup devices is an important but frequently difficult activity associated with the construction of accelerator systems. This is especially true for pickups used in stochastic cooling systems. Here the sensitivity and phase as functions of beam position are frequently critical, fundamental parameters of the system design. The most frequently used method for bench-calibration of pickup devices is that of passing a (usually thin) wire through the device. Electrical excitation of the wire, as a TEM line, simulates a beam and the transfer function of the device is measured directly. As many people have discovered, this procedure can frequently lead to incorrect predictions of pickup response to particle beams. These deficiencies have been eliminated in a facility at ANL which uses a relativistic electron beam to calibrate beam pickups. The facility is extensively used in the development of pickups, and is the primary calibration facility for pickups designed for the FNAL TeV-I antiproton source

Relativistic-beam Pickup Test Facility

The electrical response of pickups and cavities to charged particle beams has been an area of considerable activity and concern for accelerator systems. With the advent of stochastic beam cooling, the position and frequency response of beam pickups has become a crucial parameter in determining the performance of these systems. The most frequently used method for measuring and calibrating beam pickups has been the use of current carrying wires to simulate relativistic beams. This method has sometimes led to incorrect predictions of the pickup response to particle beams. The reasons for the differences are not always obvious but could arise from: (1) wires are incapable of exciting or permitting many of the modes that beams excite or (2) the interaction of the wire with large arrays of pickups produce results which are not easily predicted. At Argonne these deficiencies are resolved by calibrating pickups with a relativistic electron beam. This facility is being used extensively by several groups to measure beam pickup devices and is the primary calibration facility for pickups to be used in the FNAL TEV-I Antiproton Source

Summary of the Argonne Measurements of the LBL Prototype Pickup Characteristics

During the past year the authors have conducted a series of tests on the LBL prototype 1-2 GHz and 2-4 GHz stochastic cooling electrodes at Argonne Chemistry Division's electron LINAC. The electrode geometries are illustrated in Figures 1 and 2. Using the test electron beam, the 16-loop arrays were operated as beam current pickups and their sum and difference mode coupling impedances were measured

ANL stochastic-cooling experiments using the FNAL 200-MeV cooling ring

Studies of stochastic momentum cooling are being conducted on the FNAL 200-MeV Storage Ring. The specific goal of the activity is to establish confidence in the theory and simulation methods used to describe the cooling process, and to develop techniques and devices suitable for use in the antiproton-accumulation scheme now planned for construction at FNAL. A summary of the activity, including hardware design, results of experiments, comparison with theory, and implications for the antiproton accumulator are presented

High energy polarized deuterons at the Argonne National Laboratory zero gradient synchrotron

Modifications made on the ZGS to allow the acceleration of polarized deuterons and the operational experiences with the first production run with this beam are described