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Fundamental limits on beam stability at the Advanced Photon Source.

Description: Orbit correction is now routinely performed at the few-micron level in the Advanced Photon Source (APS) storage ring. Three diagnostics are presently in use to measure and control both AC and DC orbit motions: broad-band turn-by-turn rf beam position monitors (BPMs), narrow-band switched heterodyne receivers, and photoemission-style x-ray beam position monitors. Each type of diagnostic has its own set of systematic error effects that place limits on the ultimate pointing stability of x-ray beams supplied to users at the APS. Limiting sources of beam motion at present are magnet power supply noise, girder vibration, and thermal timescale vacuum chamber and girder motion. This paper will investigate the present limitations on orbit correction, and will delve into the upgrades necessary to achieve true sub-micron beam stability.
Date: June 18, 1998
Creator: Decker, G. A.
Partner: UNT Libraries Government Documents Department

Operational aspects of experimental accelerator physics

Description: During the normal course of high energy storage ring operations, it is customary for blocks of time to be allotted to something called ``machine studies,`` or more simply, just ``studies.`` It is during these periods of time that observations and measurement of accelerator behavior are actually performed. Almost invariably these studies are performed in support of normal machine operations. The machine physicist is either attempting to improve machine performance, or more often trying to recover previously attained ``good`` operation, for example after an extended machine down period. For the latter activity, a good portion of machine studies time is usually devoted to ``beam tuning`` activities: those standard measurements and adjustments required to recover good operations. Before continuing, please note that this paper is not intended to be comprehensive. It is intended solely to reflect one accelerator physicist`s impressions as to what goes on in an accelerator control room. Many topics are discussed, some in more detail than others, and it is not the intention that the techniques described herein be applied verbatim to any existing accelerator. It is hoped,, however, that by reading through the various sections, scientists, including accelerator physicists, engineers, and accelerator beam users, will come to appreciate the types of operations that are required to make an accelerator work.
Date: July 1, 1995
Creator: Decker, G.A.
Partner: UNT Libraries Government Documents Department

Optimization of compact synchrotron optics for x-ray lithography

Description: The production of integrated circuits having sub-micron component dimensions has motivated the development of compact electron storage rings to provide synchrotron x-ray radiation. This paper presents considerations for optimizing the optics for small radius rings using superconducting dipole magnets. The key parameters are the sizes and angular divergences of the source points illuminating the different ports. Two ring designs are compared in terms of theoretical beam parameters achievable using idealized optics.
Date: March 1, 1987
Creator: Decker, G.A. & Craft, B.C.
Partner: UNT Libraries Government Documents Department

Beam position monitor data acquisition for the Advanced Photon Source

Description: This paper describes the Beam Position Monitor (BPM) data acquisition scheme for the Advanced Photon Source (APS) storage ring. The storage ring contains 360 beam position monitors distributed around its 1104-meter circumference. The beam position monitor data acquisition system is capable of making turn-by-turn measurements of all BPMs simultaneously. It is VXI-based with each VXI crate containing the electronics for 9 BPMS. The VXI Local Bus is used to provide sustained data transfer rates of up to 13 mega-transfers per second to a scanner module. The system provides single-bunch tracking, bunch-to-bunch measurements, fast digital-averaged positions, beam position history buffering, and synchronized multi-turn measurements. Data is accessible to the control system VME crates via an MXI bus. Dedicated high-speed ports are provided to supply position data to beam orbit feedback systems.
Date: January 1, 1993
Creator: Lenkszus, F.R.; Kahana, E.; Votaw, A.J.; Decker, G.A.; Chung, Y.; Ciarlette, D.J. et al.
Partner: UNT Libraries Government Documents Department