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Title: Emittance growth saturation effect in synchrotron machines due to point-like perturbations

Abstract

Analytical estimation of the transverse emittance growth due to a point-like perturbation is performed for a proton synchrotron machine. This emittance growth is caused by the tune spread within the bunch. However, the emittance growth suffers a saturation effect caused by the same tune spread. Computer simulations on the emittance growth due to resistive wall instabilities and feedback systems verify qualitatively this emittance growth saturation effect. These simulations were accomplished in the Medium Energy Booster of the Superconducting Super Collider using the TADIMMI computer code.

Authors:
;
Publication Date:
Research Org.:
Superconducting Super Collider Lab., Dallas, TX (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
71705
Report Number(s):
SSCL-Preprint-539
ON: DE95011029; TRN: 95:015248
DOE Contract Number:
AC35-89ER40486
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Nov 1993
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; SUPERCONDUCTING SUPER COLLIDER; BEAM EMITTANCE; DISTURBANCES; TUNING; BEAM BUNCHING; COMPUTERIZED SIMULATION; PARTICLE BOOSTERS; INSTABILITY; FEEDBACK; BEAM POSITION; BEAM MONITORING

Citation Formats

Lopez, G., and Chen, S.. Emittance growth saturation effect in synchrotron machines due to point-like perturbations. United States: N. p., 1993. Web. doi:10.2172/71705.
Lopez, G., & Chen, S.. Emittance growth saturation effect in synchrotron machines due to point-like perturbations. United States. doi:10.2172/71705.
Lopez, G., and Chen, S.. Mon . "Emittance growth saturation effect in synchrotron machines due to point-like perturbations". United States. doi:10.2172/71705. https://www.osti.gov/servlets/purl/71705.
@article{osti_71705,
title = {Emittance growth saturation effect in synchrotron machines due to point-like perturbations},
author = {Lopez, G. and Chen, S.},
abstractNote = {Analytical estimation of the transverse emittance growth due to a point-like perturbation is performed for a proton synchrotron machine. This emittance growth is caused by the tune spread within the bunch. However, the emittance growth suffers a saturation effect caused by the same tune spread. Computer simulations on the emittance growth due to resistive wall instabilities and feedback systems verify qualitatively this emittance growth saturation effect. These simulations were accomplished in the Medium Energy Booster of the Superconducting Super Collider using the TADIMMI computer code.},
doi = {10.2172/71705},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Nov 01 00:00:00 EST 1993},
month = {Mon Nov 01 00:00:00 EST 1993}
}

Technical Report:

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  • A four-dipole bunch compressor chicane has recently been installed in the SLAC linac at 9 GeV and is capable of compressing a 3.4-nC electron bunch to an rms length of 50 microns, resulting in a peak current of nearly 10 kA [1]. The electron bunch is extracted from a damping ring with normalized horizontal emittance of {approx} 30 {micro}m. We present preliminary measurements of the initial and final emittance in the chicane and compare these to 1D and 3D calculations of the effects of coherent synchrotron radiation (CSR).
  • If the energies of individual particles in a bunch change as the bunch traverses a bending system, even if it is achromatic, betatron oscillations can be excited. Consequently, the transverse emittance of the bunch will grow as it moves downstream. Short bunches may be particularly susceptible to emission of coherent synchrotron radiation which can act back on the particles to change their energies and trajectories. Because a bend spans a well-defined length and angle, the bunch-excited wakefield and its effect back on the bunch are inherently transient. We outline a recently developed theory of this effect and apply it tomore » example bending systems.« less
  • The problem of emittance growth due to random fluctuations of the magnetic field in a hadron collider is considered. The results of computer simulations are compared with the analytical theory developed earlier. A good agreement was found between the analytical theory predictions and the computer simulations for the collider tunes located far enough from high order betatron resonances. The dependencies of the emittance growth rate on noise spectral density, beam separation at the Interaction Point (IP) and value of beam separation at long range collisions are studied. The results are applicable to the Superconducting Super Collider (SSC).
  • The problem of emittance growth due to random fluctuation of the magnetic field in hadron colliders is considered. Based on a simple one-dimensional linear model, a formula for an emittance growth rate as a function of the noise spectrum is derived. Different sources of the noise are analyzed and their role is estimated for the Superconducting Super Collider (SSC). A theory of feedback suppression of the emittance growth is developed which predicts the residual growth of the emittance in the accelerator with a feedback system.
  • Emittance growth of the beam caused by power supply ripple in the Superconducting Super Collider (SSC) is studied. We find that due to nonlinear terms in the equation of the betatron oscillations, the emittance grows only during an initial transient period, after which its increase saturates at some level. An analytical formula is derived that gives the fractional increase of the emittance as a function of the amplitude of the ripple. Numerical estimates for the SSC are presented.