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Title: Benchmarking of Touschek Beam Lifetime Calculations for the Advanced Photon Source

Abstract

Particle loss from Touschek scattering is one of the most significant issues faced by present and future synchrotron light source storage rings. For example, the predicted, Touschek-dominated beam lifetime for the Advanced Photon Source (APS) Upgrade lattice in 48-bunch, 200-mA timing mode is only ~ 2 h. In order to understand the reliability of the predicted lifetime, a series of measurements with various beam parameters was performed on the present APS storage ring. This paper first describes the entire process of beam lifetime measurement, then compares measured lifetime with the calculated one by applying the measured beam parameters. The results show very good agreement.

Authors:
;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1389082
DOE Contract Number:
AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Conference: 2016 North American Particle Accelerator Conference, 10/09/16 - 10/14/16, Chicago, IL, US
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Xiao, A., and Yang, B. Benchmarking of Touschek Beam Lifetime Calculations for the Advanced Photon Source. United States: N. p., 2017. Web. doi:10.18429.
Xiao, A., & Yang, B. Benchmarking of Touschek Beam Lifetime Calculations for the Advanced Photon Source. United States. doi:10.18429.
Xiao, A., and Yang, B. 2017. "Benchmarking of Touschek Beam Lifetime Calculations for the Advanced Photon Source". United States. doi:10.18429. https://www.osti.gov/servlets/purl/1389082.
@article{osti_1389082,
title = {Benchmarking of Touschek Beam Lifetime Calculations for the Advanced Photon Source},
author = {Xiao, A. and Yang, B.},
abstractNote = {Particle loss from Touschek scattering is one of the most significant issues faced by present and future synchrotron light source storage rings. For example, the predicted, Touschek-dominated beam lifetime for the Advanced Photon Source (APS) Upgrade lattice in 48-bunch, 200-mA timing mode is only ~ 2 h. In order to understand the reliability of the predicted lifetime, a series of measurements with various beam parameters was performed on the present APS storage ring. This paper first describes the entire process of beam lifetime measurement, then compares measured lifetime with the calculated one by applying the measured beam parameters. The results show very good agreement.},
doi = {10.18429},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2017,
month = 6
}

Conference:
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  • When a positron`s energy deviation {delta}E/E exceeds the rf acceptance, or when it receives an angular kick for the betatron motion that exceeds some limiting admittance, the positron will be lost. The main contributions to the total beam lifetime come from single Coulomb and Touschek scattering. In this report we investigate the dependence of the residual gas pressure and the vertical aperture of the Advanced Photon Source storage ring on the total beam. lifetime. We present results of calculating the total beam lifetime as a function of vertical aperture for varying average ring pressure, beam current, and coupling coefficient.
  • Total beam lifetime consists of two components: the residual-gas-scattering lifetime and Touschek lifetime. The residual-gas lifetime is comprised of the elastic and inelastic scattering on electrons and elastic and inelastic scattering on nuclei. Touschek scattering involves scattering of particles within the bunch. One usually calculates only the elastic scattering on nuclei (single Coulomb scattering) and inelastic scattering on nuclei (bremsstrahlung) of the residual-gas-scattering lifetime component. Experience gained from computing the beam lifetime in the Advanced Photon Source (APS) storage ring shows that the electron scattering should not be neglected, particularly the inelastic contribution. Given the measured quantities from the APSmore » storage ring, one can compare theoretical predictions with experimental results. Uncertainties in calculating the various contributions to lifetime will be discussed.« less
  • The beam lifetime in most medium energy synchrotron radiation sources is limited by the Touschek effect, which describes the momentum transfer from the transverse into the longitudinal direction due to binary collisions between electrons. While an analytical formula exists to calculate the resulting lifetime, the actual momentum acceptance necessary to perform this calculation can only be determined by tracking. This is especially the case in the presence of small vertical apertures at insertion devices. In this case, nonlinear betatron coupling leads to beam losses at these vertical aperture restrictions. In addition, a realistic model of the storage ring is necessarymore » for calculation of equilibrium beam sizes (particularly in the vertical direction) which are important for a self-consistent lifetime calculation.« less
  • The Touschek effect limits the lifetime for NSLS-II. The basic mechanism is Coulomb scattering resulting in a longitudinal momentum outside the momentum aperture. The momentum aperture results from a combination of the initial betatron oscillations after the scatter and the non-linear properties determining the resultant stability. We find that higher order multipole errors may reduce the momentum aperture, particularly for scattered particles with energy loss. The resultant drop in Touschek lifetime is minimized, however, due to less scattering in the dispersive regions. We describe these mechanisms, and present calculations for NSLS-II using a realistic lattice model including damping wigglers andmore » engineering tolerances.« less
  • Electron beam loss due to intra-beam scattering, the Touschek effect, in a storage ring depends on the electron beam polarization. The polarization of an electron beam can be determined from the difference in the Touschek lifetime compared with an unpolarized beam. In this paper, we report on a systematic experimental procedure recently developed at Duke FEL laboratory to study the radiative polarization of a stored electron beam. Using this technique, we have successfully observed the radiative polarization build-up of an electron beam in the Duke storage ring, and determined the equilibrium degree of polarization and the time constant of themore » polarization build-up process.« less