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Title: A Study of Longitudinal Coherent Effects of Unbunched Beams Near Transition in the Fermilab Accumulator

Abstract

The Fermilab Accumulator was built primarily as an 8 Ge V kinetic energy antiproton storage ring. Recently it was modified for use in a medium energy experiment studying charmonium states. In the experiment, an intense antiproton beam was decelerated from the operating energy to specific energies in the charmonium region between 6.8 Ge V and 3.8 Ge V, and collided with protons from an internal hydrogen gas jet target. In order to decelerate the beam below 5 Ge V, transition must be crossed. The method adopted for Accumulator transition crossing was to raise the value of $$\gamma t$$ slowly while the antiproton beam circulated in the ring unbunched. During Accumulator transition crossing with this coasting beam, longitudinal coherent instability was observed which limited the machine performance. Measurements for identifying the major source of the longitudinal instability were made with a resistive wall current monitor and a dedicated Schottky detector. Measurement results are presented and compared with the simulations. The Accumulator operation in the experiment is also recorded in this thesis, which includes deceleration of the $$\bar{p}$$ beam, transition crossing, and measurements of the beam energy and energy spread. In addition, since knowledge of the longitudinal impedance is important for instabilitymore » studies, beam-based measurements of the Accumulator longitudinal impedance is described. The principle, the experimental setup, and measurement results are discussed.« less

Authors:
 [1]
  1. IIT, Chicago
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP)
OSTI Identifier:
1425860
Report Number(s):
FERMILAB-THESIS-1991-20; UMI-92-06439
325160
DOE Contract Number:  
AC02-07CH11359
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Wang, Xiao-qing. A Study of Longitudinal Coherent Effects of Unbunched Beams Near Transition in the Fermilab Accumulator. United States: N. p., 1991. Web. doi:10.2172/1425860.
Wang, Xiao-qing. A Study of Longitudinal Coherent Effects of Unbunched Beams Near Transition in the Fermilab Accumulator. United States. https://doi.org/10.2172/1425860
Wang, Xiao-qing. 1991. "A Study of Longitudinal Coherent Effects of Unbunched Beams Near Transition in the Fermilab Accumulator". United States. https://doi.org/10.2172/1425860. https://www.osti.gov/servlets/purl/1425860.
@article{osti_1425860,
title = {A Study of Longitudinal Coherent Effects of Unbunched Beams Near Transition in the Fermilab Accumulator},
author = {Wang, Xiao-qing},
abstractNote = {The Fermilab Accumulator was built primarily as an 8 Ge V kinetic energy antiproton storage ring. Recently it was modified for use in a medium energy experiment studying charmonium states. In the experiment, an intense antiproton beam was decelerated from the operating energy to specific energies in the charmonium region between 6.8 Ge V and 3.8 Ge V, and collided with protons from an internal hydrogen gas jet target. In order to decelerate the beam below 5 Ge V, transition must be crossed. The method adopted for Accumulator transition crossing was to raise the value of $\gamma t$ slowly while the antiproton beam circulated in the ring unbunched. During Accumulator transition crossing with this coasting beam, longitudinal coherent instability was observed which limited the machine performance. Measurements for identifying the major source of the longitudinal instability were made with a resistive wall current monitor and a dedicated Schottky detector. Measurement results are presented and compared with the simulations. The Accumulator operation in the experiment is also recorded in this thesis, which includes deceleration of the $\bar{p}$ beam, transition crossing, and measurements of the beam energy and energy spread. In addition, since knowledge of the longitudinal impedance is important for instability studies, beam-based measurements of the Accumulator longitudinal impedance is described. The principle, the experimental setup, and measurement results are discussed.},
doi = {10.2172/1425860},
url = {https://www.osti.gov/biblio/1425860}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 01 00:00:00 EST 1991},
month = {Tue Jan 01 00:00:00 EST 1991}
}

Thesis/Dissertation:
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