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Characterization and minimization of the half-integer stop band with space charge in hadron synchrotrons

Rabusov, Dmitrii (2023)
Characterization and minimization of the half-integer stop band with space charge in hadron synchrotrons.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00023222
Ph.D. Thesis, Primary publication, Publisher's Version

Abstract

This work characterizes the half-integer stop band for various beam distributions in hadron synchrotrons using simulation models with self-consistent space charge and experimental data. Synchrotrons for hadron beams are an important tool in fundamental research (particle and nuclear physics) and applied sciences (medical technology, materials science, industry). However, they are subject to undesirable effects, which degrade the quality of the beam. In any hadron synchrotron, the half-integer resonance is among the strongest effects that limit the maximum achievable beam intensity. The heavy-ion superconducting synchrotron SIS100, currently under construction at GSI, together with the already operating SIS18 synchrotron at GSI, should provide intense beams for future FAIR experiments. Using SIS100 as an example, this work develops a quantitative framework for characterizing the half-integer stop band for realistic, Gaussian-like distributed bunched beams in simulations. The developed framework is tested in a dedicated experiment in SIS18. In any synchrotron, gradient errors in quadrupole magnets induce the half-integer resonance. Due to the half-integer resonance, the beam intensity is limited, which is often referred to as the space-charge limit. To minimize the half-integer stop band for a bunched beam, and hence increase the maximum achievable intensity, lattice corrections are applied. Including space charge in the optimization procedure yields results equivalent to a conventional lattice correction. We validate in long-term simulations, that conventional correction tools are sufficient for increasing the gradient-error-induced space-charge limit of synchrotrons. This study identifies the tune areas affected by the half-integer resonance for varying space-charge strengths. The role of synchrotron motion in providing continuous emittance growth across the bunch is investigated. A key insight of this analysis is that, for bunched beams, a relatively small gradient error can result in a large half-integer stop-band width. The maximum achievable bunch intensity is thus reduced significantly. This contrasts with the findings in existing studies in literature based on more simplified beam distributions, where the space-charge limit does not depend on the strength of gradient errors. The reason for the discrepancy is identified in the increasing stop-band width for Gaussian distributions when space charge becomes stronger, which appears on time scales relevant for synchrotrons.

Item Type: Ph.D. Thesis
Erschienen: 2023
Creators: Rabusov, Dmitrii
Type of entry: Primary publication
Title: Characterization and minimization of the half-integer stop band with space charge in hadron synchrotrons
Language: English
Referees: Boine-Frankenheim, Prof. Dr. Oliver ; Khan, Prof. Dr. Shaukat
Date: 2023
Place of Publication: Darmstadt
Collation: VIII, 112 Seiten
Refereed: 5 December 2022
DOI: 10.26083/tuprints-00023222
URL / URN: https://tuprints.ulb.tu-darmstadt.de/23222
Abstract:

This work characterizes the half-integer stop band for various beam distributions in hadron synchrotrons using simulation models with self-consistent space charge and experimental data. Synchrotrons for hadron beams are an important tool in fundamental research (particle and nuclear physics) and applied sciences (medical technology, materials science, industry). However, they are subject to undesirable effects, which degrade the quality of the beam. In any hadron synchrotron, the half-integer resonance is among the strongest effects that limit the maximum achievable beam intensity. The heavy-ion superconducting synchrotron SIS100, currently under construction at GSI, together with the already operating SIS18 synchrotron at GSI, should provide intense beams for future FAIR experiments. Using SIS100 as an example, this work develops a quantitative framework for characterizing the half-integer stop band for realistic, Gaussian-like distributed bunched beams in simulations. The developed framework is tested in a dedicated experiment in SIS18. In any synchrotron, gradient errors in quadrupole magnets induce the half-integer resonance. Due to the half-integer resonance, the beam intensity is limited, which is often referred to as the space-charge limit. To minimize the half-integer stop band for a bunched beam, and hence increase the maximum achievable intensity, lattice corrections are applied. Including space charge in the optimization procedure yields results equivalent to a conventional lattice correction. We validate in long-term simulations, that conventional correction tools are sufficient for increasing the gradient-error-induced space-charge limit of synchrotrons. This study identifies the tune areas affected by the half-integer resonance for varying space-charge strengths. The role of synchrotron motion in providing continuous emittance growth across the bunch is investigated. A key insight of this analysis is that, for bunched beams, a relatively small gradient error can result in a large half-integer stop-band width. The maximum achievable bunch intensity is thus reduced significantly. This contrasts with the findings in existing studies in literature based on more simplified beam distributions, where the space-charge limit does not depend on the strength of gradient errors. The reason for the discrepancy is identified in the increasing stop-band width for Gaussian distributions when space charge becomes stronger, which appears on time scales relevant for synchrotrons.

Alternative Abstract:
Alternative abstract Language

In dieser Arbeit wird die transversale quadrupolare Resonanz bei halbzahligen Arbeitspunkten für verschiedene Strahlverteilungen in Hadron-Synchrotrons anhand von Simulationsmodellen mit selbstkonsistenter Raumladung und experimentellen Daten charakterisiert. Synchrotrone spielen in der Forschung (Teilchenphysik, Kernphysik) und den Anwendungen (Medizintechnik, Materialwissenschaft, Industrie) eine wichtige Rolle. Bei ihrem Betrieb treten jedoch unerwünschte Effekte auf, welche die Strahlqualität beeinträchtigen. Die quadrupolare Resonanz gehört zu den stärksten (kollektiven) Effekten, welche die maximal erreichbare Strahlintensität in Hadronensynchrotrons begrenzen. Das aus supraleitenden Magneten bestehende Schwerionensynchrotron SIS100, das derzeit an der GSI entsteht, soll zusammen mit dem bereits an der GSI in Betrieb befindlichen Synchrotron SIS18 intensive Ionenstrahlen für zukünftige FAIR Experimente bereitstellen. In dieser Arbeit wird am Beispiel des SIS100 ein Modell zur quantitativen Charakterisierung des quadrupolaren Stoppbandes für realistische Ionenbunche entwickelt. Das entwickelte Modell wurde in einem dedizierten Experiment im SIS18 getestet. Um das halbzahlige Stoppband für einen gebunchten Strahl zu minimieren und somit die maximal erreichbare Intensität zu erhöhen, werden Korrekturmagnete verwendet. Das in dieser Arbeit entwickelte Optimierungsverfahren bezieht die Raumladung ein für die Bestimmung der Stärken der Korrekturmagnete. Die Ergebnisse weichen nicht wesentlich von denen konventioneller Tools ab. Aus dieser Erkenntnis folgt, dass konventionelle Korrekturverfahren ausreichen, um die durch Gradientenfehler verursachte Raumladungsgrenze in Synchrotronen zu erhöhen. In dieser Arbeit werden Tunebereiche für Raumladungsfelder verschiedener Stärken identifiziert, die von der durch Gradientenfehler angeregten quadrupolare Resonanz betroffen sind. Die Rolle der Synchrotronbewegung bei dem beobachteten kontinuierlichen Anstieg der Emittanz über den Bunch hinweg wird untersucht. Eine wichtige Erkenntnis dieser Analyse ist, dass ein relativ kleiner Gradientenfehler zu einer großen Breite des quadrupolaren Stoppbandes führen kann. Die maximal erreichbare Strahlintensität, oft als Raumladungsgrenze bezeichnet, wird dadurch erheblich reduziert. Dies steht im Gegensatz zu den Ergebnissen vorheriger Studien in der Literatur, in denen vereinfachte Strahlverteilungen verwendet wurden. Als Grund für diese Diskrepanz wurde die für stärker werdende Raumladung zunehmende Stoppbandbreite identifiziert, wie sie auf für Synchrotrone relevanten Zeitskalen auftritt.

German
Status: Publisher's Version
URN: urn:nbn:de:tuda-tuprints-232225
Classification DDC: 500 Science and mathematics > 530 Physics
Divisions: 18 Department of Electrical Engineering and Information Technology
18 Department of Electrical Engineering and Information Technology > Institute for Accelerator Science and Electromagnetic Fields > Accelerator Physics
18 Department of Electrical Engineering and Information Technology > Institute for Accelerator Science and Electromagnetic Fields
Date Deposited: 16 Feb 2023 13:08
Last Modified: 21 Feb 2023 14:44
PPN:
Referees: Boine-Frankenheim, Prof. Dr. Oliver ; Khan, Prof. Dr. Shaukat
Refereed / Verteidigung / mdl. Prüfung: 5 December 2022
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