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Title: Electron proton two-stream instability at the PSR.

Abstract

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 [1] 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 analyzers 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 (6 x 10{sup 13} protons), which is a 60% increase over the previous maximum.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab., IL (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
793052
Report Number(s):
ANL/ASD/CP-106950
TRN: US0200900
DOE Contract Number:
W-31-109-ENG-38
Resource Type:
Conference
Resource Relation:
Conference: 2001 Particle Accelerator Conference (PAC 2001), Chicago, IL (US), 06/18/2001--06/22/2001; Other Information: PBD: 19 Feb 2002
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; ELECTRONS; INSTABILITY; PROTON BEAMS; PROTONS; SECONDARY EMISSION; SPACE CHARGE; STORAGE RINGS; TWO-STREAM INSTABILITY

Citation Formats

Macek, R. J., Browman, A., Fitzgerald, D., McCrady, R., Merrill, F., Plum, M., Spickermann, T., Wang, T. S., Griffin, J., Ng, K. Y., Wildman, D., Harkay, K., Kustom, R., and Rosenberg, R. Electron proton two-stream instability at the PSR.. United States: N. p., 2002. Web.
Macek, R. J., Browman, A., Fitzgerald, D., McCrady, R., Merrill, F., Plum, M., Spickermann, T., Wang, T. S., Griffin, J., Ng, K. Y., Wildman, D., Harkay, K., Kustom, R., & Rosenberg, R. Electron proton two-stream instability at the PSR.. United States.
Macek, R. J., Browman, A., Fitzgerald, D., McCrady, R., Merrill, F., Plum, M., Spickermann, T., Wang, T. S., Griffin, J., Ng, K. Y., Wildman, D., Harkay, K., Kustom, R., and Rosenberg, R. 2002. "Electron proton two-stream instability at the PSR.". United States. doi:. https://www.osti.gov/servlets/purl/793052.
@article{osti_793052,
title = {Electron proton two-stream instability at the PSR.},
author = {Macek, R. J. and Browman, A. and Fitzgerald, D. and McCrady, R. and Merrill, F. and Plum, M. and Spickermann, T. and Wang, T. S. and Griffin, J. and Ng, K. Y. and Wildman, D. and Harkay, K. and Kustom, R. and Rosenberg, R.},
abstractNote = {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 [1] 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 analyzers 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 (6 x 10{sup 13} protons), which is a 60% increase over the previous maximum.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2002,
month = 2
}

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  • 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
  • This paper is an analytical investigation of the trans-verse electron-proton (e-p) two-stream instability in a pro-ton bunch propagating through a stationary electron back-ground. The equations of motion, including the effect of damping, are derived for the centroids of the proton beam and the electron cloud. An approach is developed to solve the coupled linear centroid equations in the time domain describing the e-p instability in proton bunches with non-uniform line densities. Examples are presented for proton line densities corresponding to uniform and parabolic profiles.
  • For intense proton beams, the focus of recent two-stream instability analyses has been on the transverse instability observed in the Proton Storage Ring (PSR) at Los Alamos National Laboratory. The PSR stores a long proton bunch with a near triangular line density profile for a duration of about one millisecond. The instability is observed as rapidly growing transverse oscillations of the stored beam, usually occuring when the beam intensity reaches 2.5 x 10{sup 13} ppp or higher, causing fast beam loss. Experimental results support the conjecture that the instability in PSR is due to the two-stream interaction between the circulatingmore » proton beam and the electrons created in the ring, i.e., the so called e-p instability. However, the understanding of the physics of this instability is usually based on the theory developed for a continuous beam of uniform line density. Although computer simulations have been implemented or are being developed to study the e-p instability in bunched beams, a companion analytical theory still remains to be developed. The present work is an attempt to investigate the transverse e-p instability in a proton bunch using an analytical approach based on the centroid model built on the 'one-pass' interaction between the protons and the electrons. This paper is an analytical investigation of the transverse electron-proton (e-p) two-stream instability in a proton bunch propagating through a stationary electron background. The equations of motion, including the effect of damping, are derived for the centroids of the proton beam and the electron cloud. An approach is developed to solve the coupled linear centroid equations in the time domain describing the e-p instability in proton bunches with nonuniform line densities. Examples are presented for proton line densities corresponding to uniform and parabolic profiles.« less
  • The electron-proton instability of a long, intense, and partially neutralized proton bunch is studied by numerically solving the equations of motion for the line centroid of the proton beam and the line centroid of the trapped electrons. The formalism takes into account the effects of variable line densities and alternating-gradient focusing. Good qualitative agreement between the computational results and experimental observations was obtained when applying the theory to the Los Alamos Proton Storage Ring (PSR). Both the case of a clean extraction gap and the case with a few percent of protons in the extraction gap were studied. It ismore » found that with only a few percent neutralization, the PSR beam can become unstable in both cases. The same equations and method were used to study the stability of the proton beam in the accumulator ring of the proposed LANSCE II spallation-neutron source. The results indicate that the e-p instability can also occur in the LANSCE II accumulator ring for only a few percent neutralization.« less
  • No abstract prepared.