G. E. Fischer

Bunch Lengthening and Related Effects in SPEAR II

In recent years, electron storage ring designers have become aware of the problems caused by the interaction of short, high current bunches with their environment. Important effects are: (1) energy loss can cause local overheating of chamber components; (2) additional rf power is required due to overall energy loss; (3) the increased energy spread requires increased aperture; (4) destructive instabilities could occur. Anomalous bunch lengthening and energy spread, the spectroscopy of longitudinal modes and the shift of synchronous phase were simultaneously measured in order to study the dynamics of the interaction. From the data obtained at SPEAR II one is led to a model of coupling impedance which should be useful in the design of any electron ring.

A large cylindrical drift chamber for the Mark II detector at spear

Abstract We describe a large cylindrical drift chamber designed for the Mark II magnetic detector at the SLAC e + e − storage ring SPEAR. Details on the mechanical construction, electronics readout, and measurements of chamber efficiencies and precision are presented.

Photoproduction of K+ -hyperon from hydrogen and deuterium at 11 GeV☆

Abstract Using an 11-GeV bremsstrahlung beam and the SLAC 20-GeV spectrometer, we have measured K+ missing mass spectra from hydrogen and deuterium at five angles with momentum transfer squared ranging from 0.025 to 0.46 GeV2. Steps in the spectra as a function of missing mass were found corresponding to production of Λ, Σ, Σ1385 + Λ1405 and Λ1520. The ratio Σ− and Σ0 production is not consistent with pure isotopic spin 1 2 in the t-channel for the reaction γN→K+Σ. The cross sections for γN → K+Σ1385 compared with γN→πΔ violate an SU(3) prediction.

Comparison of absorptive one pion exchange model with measurements of π−p → π+π−n

Abstract The results of a wire spark chamber experiment studying the reaction π − p → π + π − n at 15 GeV/ c are compared with the predictions of the absorptive one pion exchange model. The structure at small values of momentum transfer observed in the data is well described by the model.

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.

The SLAC Linear Collider

A brief description of the proposed SLAC Linear Collider is given. This machine would investigate the possibilities and limitations of Linear Colliders while at the same time producing thousands of Z/sup 0/ particles per day for the study of the weak interactions.

Operating Results from SPEAR

Initial operating experience with the SLAC electron-positron storage ring SPEAR is described. A luminosity of 1.2 × 1031 cm-2 sec-1 has been achieved and two-beam interaction effects are described. A single-beam coherent instability, which can be suppressed either by control of the ring chromaticity or by feedback, has been observed. Current-dependent bunch lengthening and widening have been observed, and experiments indicate that these phenomena may be associated with an increase in the energy spread of the beam. Procedures to increase the luminosity to the design value are discussed. Plans to increase the maximum beam energy of SPEAR to 4.5 GeV are described.

SLC ARC transport system-AG-magnet measurement and performance

This paper describes the design, construction, and operation of devices used to rapidly measure the mechanical and magnetic properties of some 950 Alternate gradient magnets1 used in the arc system of the Stanford Linear Collider. The problems of dealing with the measurement of the transverse dimensions to within minute (0.0001 in) resolution of objects that are 8 ft long are discussed. Early results from the production runs of these magnets are presented.

Measurements on Beam-Beam Interaction at SPEAR

Measurements of luminosity at SPEAR, which were performed at different operational conditions of the storage ring are shown and discussed. The parameters varied are: the current in both beams, the minimum betatron amplitude functions at the collision point, the energy and the vertical betatron frequencies. As a result of these measurements we found that the maximum achievable luminosity is much higher than predicted by the incoherent beam-beam limit using ?v = 0.025. We also found that the maximum achievable luminosity is a strong function of the betatron frequencies. After computing the largest linear tuneshifts, we found that the quarter resonance seems to be the limiting effect for beam-beam collision.

Recent Results for e + e − Annihilation at Spear

In this presentation I shall assume that everyone is familiar with the existence of two narrow resonances coupling to electrons1,2,3 at masses of 3.1 and 3.7 GeV. Properties of these resonances will be described at length. I shall also discuss upper limits which we can place for the production of other such resonances in the range 3.2 to 5.9 GeV.4 Lastly, I shall discuss some tantalizing structure at 4.1 GeV.5 This talk will concentrate upon the experimental facts, various speculations will be left for other speakers. It should be emphasized that most results described are preliminary and are subject to refinement.