D. E. Suddeth

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.

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.

The Rapid Cycling Synchrotron Extraction Kicker Magnet 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 ¿ 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.

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.

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 ¿ 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.

Zero Gradient Synchrotron Booster Injection

Fig. 1 is the phase space diagram illustrating the injection of two booster beam bunches into one ZGS rf bucket. The expected highest and lowest energy beams are shown to illustrate how each contributes to the final beam width. The first booster beam is bumped onto the equilibrium orbit in the straight section threeeighths of a revolution from the injection point. For v = 0. 833 the kicker is at 1120 in betatron phase. I;o achieve the minimum beam width (4 900) the booster beam is injected at a slight positive angle. For betatron motion:

Main Magnet Coil Diagnostic Tests at the Zero Gradient Synchrotron (ZGS)

To establish a meaningful history of the electrical condition of our main magnet coils, various instruments and techniques were developed for a diagnostic program.

Pole Face Winding (PFW) Equipment for Eddy Current Correction at the Zero Gradient Synchrotron (ZGS)

The titanium vacuum chambers installed in the ZGS this past summer were equipped with PFWs. In this paper, the operation and monitoring of the windings used to flatten the guide field in the ZGS will be described. The physical and electrical characteristics of the system will be discussed along with a computer program which calculates the magnetic field shape in the vacuum chamber as a function of PFW current and other machine parameters.

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, lets 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.

Improvements in the Zero Gradient Synchrotron (ZGS) Main Magnet Coil Protection

Two main coil failures in a one-year period initiated a review of on-line protective circuitry. Two existing circuits, which would limit damage, were made more reliable. Four new circuits were added to monitor coil condition and protect against voltage transients.