Abstract
We describe a new technique for low-emittance tuning of electron and positron storage rings. This technique is based on calibration of the beam position monitors (BPMs) using excitation of the normal modes of the beam motion, and has benefits over conventional methods. It is relatively fast and straightforward to apply, it can be as easily applied to a large ring as to a small ring, and the tuning for low emittance becomes completely insensitive to BPM gain and alignment errors that can be difficult to determine accurately. We discuss the theory behind the technique, present some simulation results illustrating that it is highly effective and robust for low-emittance tuning, and describe the results of some initial experimental tests on the CesrTA storage ring.
Highlights
Lepton storage rings often require tuning to achieve very low vertical emittance: in light sources, this increases the beam brightness; in colliders, it improves luminosity
Calibration of beam position monitors (BPMs) using normal mode beam excitation offers the possibility of a novel technique for lowemittance tuning in storage rings
This technique has a number of potential advantages over conventional techniques, such as orbit response matrix (ORM) analysis
Summary
Lepton storage rings often require tuning to achieve very low vertical emittance: in light sources, this increases the beam brightness; in colliders, it improves luminosity. A common technique is to perform an analysis of the measured orbit response matrix (ORM) to determine the sources of error [5]. This includes diagnostic errors such as tilts of the beam position monitors (BPMs). Fitting a model to the measured data (to determine the errors present in the ring) involves numerically intensive computation, and can be time consuming For large rings, such as those proposed, for example, for the damping rings of the International Linear Collider [6], it may become impractical to perform ORM analysis on a routine basis to achieve and maintain the specified vertical emittance.
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