Calculation of Impedance from Multibunch Synchronous Phases: Theory and Experimental Results
نویسندگان
چکیده
A novel beam-based method for measuring the longitudinal impedance spectrum is demonstrated using experimental data from the PEP-II High Energy Ring (HER). The method uses a digital longitudinal feedback system from which the charge and synchronous phase are measured for every bucket. Calculation of the transfer function from ll shape to synchronous phase yields the impedance seen by the beam at revolution harmonics. The experimentally-derived longitudinal impedance function and lab measurements of the impedance of parked RF cavities are compared to suggest a mechanism for the occasional instability of low-order coupled bunch modes observed in the HER during commissioning in October 1997. Poster presented at the Sixth European Particle Accelerator Conference Stockholm, Sweden June 22{26 1998 Work supported by Department of Energy contract DE{AC03{76SF00515. CALCULATION OF IMPEDANCE FROM MULTIBUNCH SYNCHRONOUS PHASES: THEORY AND EXPERIMENTAL RESULTS S. Prabhakar, J. Fox, H. Hindi, D. Teytelman, A. Young Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309, USA
منابع مشابه
Commissioning Experience from PEP-II HER Longitudinal Feedback
The DSP-based bunch-by-bunch feedback system installed in the PEPII high-energy ring (HER) has been used to damp instabilities induced by unwanted higher-order modes (HOMs) at beam currents up to 605 mA during commissioning. Beam pseudospectra calculated from feedback system data indicate the presence of coupled-bunch modes that coincide with a previously observed cavity mode (0-M-2). Bunch cur...
متن کاملCharacterization of Longitudinal Impedances in Storage Rings via Multibunch Effects∗
In this paper we present two new techniques for frequency-resolved characterization of longitudinal impedances in storage rings. The first method is based on transient measurements of the growth rates and tune shifts of unstable coupledbunch modes. In the second approach estimates of the impedances are obtained from analysis of the steady-state synchronous phases of the bunches for uneven fill ...
متن کاملImpedance-Based Out-of-Step Protection of Generator in the Presence of STATCOM
This paper presents a novel impedance-based approach for out-of-step (OOS) protection of a synchronous generator. The most popular and commonly used approaches for detecting OOS conditions are based on the measurement of positive sequence impedance at relay location. However, FACTS devices change the measured impedance value and thus disrupt the performance of impedance-based relay function. In...
متن کاملEUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH European Laboratory for Particle Physics Large Hadron Collider Project LHC Project Report 16 Transverse Instabilities in the LHC
I first summarize the impedance model that I will be using (this is compiled from the work of several other authors). I then use the methods described elsewhere [1] to determine mode coupling thresholds and growth rates of multibunch modes, including the effects of multibunch mode coupling (see [1]). The effects of feedback are also considered.
متن کاملCalculation of phononic and thermal properties of the CaB2 using the perturbation density functional theory (Research Article)
In this paper, the phononic structure and Enthalpy of CaB2 compound in simple hexagonal and orthorhombic phase have been investigated. The calculations were performed using the pseudo-potential method in the framework of the density functional theory and using the Quantum-Espresso code. Using the group theory and the characteristic table of the composition point group, the phonon modes were ide...
متن کامل