J.-L. Pellegrin

Monitoring of the Stanford Linac Microbunches' Position

A new hardware has been developed to measure the trajectory of microbunches along the Stanford Linac. To be suitable for the operation of the SLAC Single Pass Collider, the bunches absolute position must be kept within ±100 microns of the accelerator center, and the acquisition of this measurement must be made along the machine in a snapshot fashion. Typically, the position of three bunches will be monitored during subsequent shots; we expect a minimum charge of 109 particles per bunch and a time spacing between bunches of 50 nanoseconds. The mechanics of the position detectors is described as well as the general system organization and the calibration of various components.

RF System for the PEP Storage Ring

The main parameters of the rf system for the PEP storage ring are given. A total of 6 MW will be provided by twelve klystrons, each capable of delivering 500 kW of continuous rf power. Each klystron feeds two accelerating cavity sections, each 2.1 meters in length. The general layout is shown. The klystrons are housed in shelters above ground. The wave guides run through vertical penetrations to connect the klystrons to the accelerating cavities in the tunnel. The shelters are placed at three symmetrical regions around the ring. At each of regions 4, 8, and 12 there will be four klystrons and their eight cavities with the eight cavities all being grouped together in the long straight section on one side of an interaction region. The klystron power supplies are on pads outside the shelters. They are unregulated but their voltage may be slowly varied over a 40 percent range by means of variable voltage transformers in the 12 kV input line to each power supply. The output of each power supply passes into the shelter to a high voltage cabinet which contains filter capacitors, crowbars, interlock circuits, and control and metering circuits.

Single Bunch Beam Measurements for the Proposed SLAC Linear Collider

Single S-band bunches of ~ 109 electrons have been used to study the characteristics of the SLAC linac in anticipation of its operation as a linear collider. Emittance measurements have been made, the longitudinal charge distribution within single bunches has been determined and transverse emittance growth has been produced by deliberately missteering the beam. New equipment is being installed and checked out, and the sensitivity of new traveling-wave beam position monitors has been measured.

Spear II Performance

The single beam and colliding beam performance of the SLAC electron-positron storage ring SPEAR II is described. The sevenfold increase in harmonic number in SPEAR II in comparison to SPEAR I has made significant changes in single beam behavior. Strong synchrobetatron resonances and a new transverse instability are observed and our first studies of these phenomena are described, Measurements on current dependent bunch lengthening are presented.

Parasitic Mode Losses versus Signal Sensitivity in Beam Position Monitors

A beam position monitor (BPM) for a storage or damping ring may be subject to heating problems due to the parasitic mode (PM) losses, beam interception and synchrotron radiation interception. In addition, high PM losses can cause beam instabilities under some conditions. Recessing and/or masking the BPM may increase the PM losses in the process of solving the latter two problems. This paper presents three complementary methods for estimating the PM losses and for improving the design of a stripline directional coupler type of BPM: bench measurements, computer modeling (TBCI) and an equivalent circuit representation. These methods lead to a decrease in PM losses without significant reduction in output signal for the north SLC damping ring BPMs.

Operation of the PEP Transverse Beam Feedback

The PEP Storage Ring has been equipped with a wide band beam feedback system capable of damping the vertical and horizontal motion of six bunches. The oscillation detection is done at a symmetry point on the Storage Ring and feedback is applied at the same location one orbital period later. The signal is synchronously gated and the system appears as twelve independent feedback loops, operating on the two coordinates of each of the six bunches. Two beam deflection electrodes are driven each by a low-Q push-pull amplifier which is tuned at the 72nd harmonic of the revolution frequency and suppressed-carrier modulation is generated by a sequence of the detected bunch oscillations. The design parameters are reviewed as well as the salient features of the hardware, and the impact of this system on the machine operation is evaluated in the light of experimental results.

A Proportional Wire Chamber Electronics System Utilizing CAMAC

This report describes a system of electronics to be used with a proportional wire chamber hodoscope. The system, which uses CAMAC packaging and data handling philosophy, consists of octo (8 channel) wire signal amplifiers, octo 4-bit per wire latch modules, gate fanout modules, crate controllers, and two types of data processor-interface units to the SDS 9300 computer. System operation is explained, and each component is described.