Richard Talman

The CLEO detector

Abstract The construction and performance of a large aperture magnetic detector designed for use at the Cornell Electon Storage Ring is descr bed.

On the statistics of particle identification using ionization

Abstract First an analytic expression is obtained for the distribution in energy losses of high energy particles traversing a thin sample. It generalizes the theories of Landau and of Blunck and Leisegang by taking into account of the atomic energy levels. Secondly a statistical procedure is described for estimating a location and a width parameter of the distribution from a set of energy loss measurements. These determine the particle velocity even in the vicinity of the ionization minimum and the confidence with which particle identification can be obtained from such measurements is discussed.

Unified accelerator libraries

A “Universal Accelerator Libraries” (UAL) environment is described. Its purpose is to facilitate program modularity and inter-program and inter-process communication among heterogeneous programs. The goal ultimately is to facilitate model-based control of accelerators.

The Cornell ERL prototype project

Synchrotron light sources based on Energy Recovery Linacs (ERLs) show promise to deliver X-ray beams with both brilliance and X-ray pulse duration far superior to the values that can be achieved with storage ring technology. Cornell University, in collaboration with Jefferson Laboratory, has proposed the construction of a prototype ERL. This 100MeV, 100mA CW superconducting electron accelerator will be used to study and resolve the many accelerator physics and technology issues of this type of machine. These studies are essential before ERLs can be confidently proposed for large-scale applications such as synchrotron light sources. Key issues include the generation of high average current, high brightness electron beams; acceleration and transport of these beams while preserving their brightness; adequate damping of higher order modes (HOMs) to assure beam stability; removal of large amounts of HOM power from the cryogenic environment; stable RF control of cavities operating at very high external Q; reduction of beam losses to very low levels; and the development of precision non-intercepting diagnostics to allow beam setup, control and characterization. Our prototype design allows us to address these and other issues over a broad range of parameter space. This design, along with recent progress on understanding these issues, will be presented.

New method for a continuous determination of the spin tune in storage rings and implications for precision experiments

A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune-defined as the number of spin precessions per turn-is given by ν(s)=γG (γ is the Lorentz factor, G the gyromagnetic anomaly). At 970  MeV/c, the deuteron spins coherently precess at a frequency of ≈120  kHz in the Cooler Synchrotron COSY. The spin tune is deduced from the up-down asymmetry of deuteron-carbon scattering. In a time interval of 2.6 s, the spin tune was determined with a precision of the order 10^{-8}, and to 1×10^{-10} for a continuous 100 s accelerator cycle. This renders the presented method a new precision tool for accelerator physics; controlling the spin motion of particles to high precision is mandatory, in particular, for the measurement of electric dipole moments of charged particles in a storage ring.

New energy recovery linac source of synchrotron X-rays

Introduction Cornell University and Jefferson Laboratory physicists have been studying the properties of a new type of synchrotron radiation machine, called an Energy Recovery Linac (ERL), based on a superconducting linac configured for energy recovery with a return ring. A high energy, high current ERL could produce electron beams of order 10 microns in diameter. These could be used as an ultra-high brilliance x-ray source with many desirable characteristics, including: transversely coherent, diffraction-limited hard x-ray beams, very short (~100 fs) frequent (1 – 2 GHz) pulses, no limits on beam lifetime, and very flexible modes of operation. This combination of characteristics opens up new possibilities and could significantly advance the state of the art in x-ray research.

Beam Diagnostic Instrumentation at CESR

We discribe various beam diagnostic devices in use at CESR, an 8 GeV electron-positron storage ring operating primarily in the 4.7 to 5.5 GeV beam energy range. Getting the last 20% of performance depends to some extent on empirical tuning and appropriate presentation of various parameters is very important. Several devices are most useful in machine studies and we describe their operation. The individually regulated quadrupoles in CESR provide unique opportunities for lattice measurements and calibration of beam position monitors.

Status of A Plan for an ERL Extension to CESR

We describe the status of plans to build an Energy-Recovery Linac (ERL) X-ray facility at Cornell University. This 5 GeV ERL is an upgrade of the CESR ring that currently powers the Cornell High Energy Synchrotron Source (CHESS) [1]. Due to its very small electron-beam emittances, it would dramatically improve the capabilities of the light source and result in X-ray beams orders of magnitude better than any existing storage-ring light source. The emittances are based upon simulations for currents that are competitive with ring-based sources [2, 4]. The ERL design that is presented has to allow for non-destructive trans port of these small emittances. The design includes a series of X-ray beamlines for specific areas of research. As an upgrade of the existing storage ring, special attention is given to reuse of many of the existing ring components. Bunch compression, tolerances for emittance growth, simulations of the beam-breakup instability and methods of increasing its threshold current are mentioned. This planned upgrade illustrates how other existing storage rings could be upgraded as ERL light sources with vastly improved beam qualities.

The Energy Recovery Linac (ERL) as a driver for X-ray producing insertion devices

Storage rings have served well as X-ray sources, achieving continued increases in flux and brilliance. While further improvements in performance may still be expected, the performance of these machines is constrained by radiation fluctuations and by the Touschek effect. The practical effect of the radiation fluctuations is to limit the minimum 6D emittance of the rings in general, and particularly the bunch length. The Touschek effect limits the lifetime and the bunch charge density. These effects can be ameliorated by using a linac to accelerate the beam to the requisite energy before passing it through undulators to produce the X-rays. If the beam is discarded after producing X-rays, radiation and collision effects are no longer limiting. This approach has not been used because prohibitive amounts of energy would be required to produce the beam. However, by using energy recovery in a superconducting linac, the energy can be recycled to accelerate new electrons. This would allow the use of currents comparable to those in storage rings, but with superior emittance, bunch length and flexibility. The concept of a 5-7 GeV facility using this principle is described and parameter goals given.

A universal algorithm for accelerator correction

A general formalism for compensating accelerator lattice functions is described. It is applied to the special cases of orbit smoothing, tune adjustment, beta function compensation, local and global decoupling, and vertical dispersion suppression. Some of these algorithms are implemented, and have performed robustly, in the thin element modeling code TEAPOT, analyzing the SSC circular accelerators, sometimes with a few beam‐position monotors assumed to be malfunctioning.