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Title: NEW DEVELOPMENTS ON THE E-P INSTABILITY AT THE PROTON STORAGE RING (PSR)

Abstract

New results are reported from an R and D program aimed at greater understanding and control of the e-p instability observed at the Los Alamos Proton Storage Ring (PSR). Numerous characteristics of the electron cloud for both stable and unstable beams in PSR were measured with ANL electron analyzers and various collection plates. Strong suppression of the electron flux density by TiN coating of the vacuum chamber in a straight section was also observed, thereby confirming an essential role for secondary emission at the walls. Landau Damping by a variety of techniques including higher rf voltage, transverse coupling, multipole fields in the lattice, and the use of inductive inserts has been effective in controlling the e-p instability. By these methods, the instability threshold has been raised significantly to 9.7 micro Coulombs per stored pulse.

Authors:
Publication Date:
Research Org.:
Los Alamos National Lab., NM (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
773428
Report Number(s):
LA-UR-01-203
TRN: US0102833
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 Jan 2001
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; TITANIUM NITRIDES; COATINGS; ELECTRONS; FLUX DENSITY; ELECTRON-PROTON INTERACTIONS; INSTABILITY; LANDAU DAMPING; MULTIPOLES; PROTONS; SECONDARY EMISSION; STORAGE RINGS

Citation Formats

R. MACEK. NEW DEVELOPMENTS ON THE E-P INSTABILITY AT THE PROTON STORAGE RING (PSR). United States: N. p., 2001. Web.
R. MACEK. NEW DEVELOPMENTS ON THE E-P INSTABILITY AT THE PROTON STORAGE RING (PSR). United States.
R. MACEK. Mon . "NEW DEVELOPMENTS ON THE E-P INSTABILITY AT THE PROTON STORAGE RING (PSR)". United States. doi:. https://www.osti.gov/servlets/purl/773428.
@article{osti_773428,
title = {NEW DEVELOPMENTS ON THE E-P INSTABILITY AT THE PROTON STORAGE RING (PSR)},
author = {R. MACEK},
abstractNote = {New results are reported from an R and D program aimed at greater understanding and control of the e-p instability observed at the Los Alamos Proton Storage Ring (PSR). Numerous characteristics of the electron cloud for both stable and unstable beams in PSR were measured with ANL electron analyzers and various collection plates. Strong suppression of the electron flux density by TiN coating of the vacuum chamber in a straight section was also observed, thereby confirming an essential role for secondary emission at the walls. Landau Damping by a variety of techniques including higher rf voltage, transverse coupling, multipole fields in the lattice, and the use of inductive inserts has been effective in controlling the e-p instability. By these methods, the instability threshold has been raised significantly to 9.7 micro Coulombs per stored pulse.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2001},
month = {Mon Jan 01 00:00:00 EST 2001}
}

Conference:
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  • Recent observations are consistent with the possibility of an
  • A strong, fast, transverse instability has long been observed at the Los Alamos Proton Storage Ring (PSR) where it is a limiting factor on peak intensity. Most of the available evidence, based on measurements of the unstable proton beam motion, is consistent with an electron-proton two-stream instability. The need for higher beam intensity at PSR and for future high-intensity, proton drivers has motivated a multi-lab collaboration (LANL, ANL, FNAL, LBNL, BNL, ORNL, and PPPL) to coordinate research on the causes, dynamics and cures for this instability. Important characteristics of the electron cloud were recently measured with retarding field electron analyzersmore » and various collection electrodes. Suppression of the electron cloud formation by TiN coatings has confirmed the importance of secondary emission processes in its generation. New tests of potential controls included dual harmonic rf, damping by higher order multipoles, damping by X,Y coupling and the use of inductive inserts to compensate longitudinal space charge forces. With these controls and higher rf voltage the PSR has accumulated stable beam intensity up to 9.7 {micro}C/pulse (6x1013 protons), which is a 60% increase over the previous maximum.« less
  • The frequency dependence of the complex permeability of the ferrite (at room temperature) used in the Inductors at PSR have been determined by comparing the S11 parameters of a jig containing a ferrite core, and a MAFIA simulation of the jig. Both the resonance frequency and the longitudinal impedance of the inductor were obtained by simulating the inductor cavity in MAFIA. Experimental observations of the longitudinal instability caused by the ferrite inductors at room temperature for both DC Coasting beams and Bunched Coasting beams at a variety of intensities have been conducted. Comparisons of observed and calculated growth times, thresholds,more » resonant frequencies, and width of the instability will be discussed.« less
  • An instability in the Proton Storage Ring (PSR) is observed as fast loss of beam during accumulation and storage when the injected beam current exceeds a threshold value. Experimental study results of that instability are presented in this paper. The instability threshold depends significantly on rf voltage, injected momentum spread, PSR sextupole strengths, and also on ring octupole strengths. The results are consistent with the hypothesis that the instability is a transverse instability excited by a transverse impedance Z/sub perpendicular/ with norm of Z/sub perpendicular/approx. = 1 M..cap omega../m. The driving impedance has significant magnitude in the 30 to 300-MHzmore » frequency range. 6 refs., 10 figs., 3 tabs.« less