IPAC2021 - List of Authors (Damerau, H.)

Paper	Title	Page
WEPAB243	Longitudinal Microwave Instability Study at Transition Crossing with Ion Beams in the CERN PS	3197
	A. Lasheen, H. Damerau, A. Huschauer, B.K. Popovic CERN, Geneva, Switzerland
	The luminosity of lead ion collisions in the Large Hadron Collider (LHC) was significantly increased during the 2018 ion run by reducing the bunch spacing from 100 ns to 75 ns, allowing to increase the total number of bunches. With the new 75 ns variant, three instead of four bunches are generated each cycle in the Low Energy Ion Ring (LEIR) and the Proton Synchrotron (PS) with up to 30% larger intensity per bunch. The beam was produced with satisfactory quality but at the limit of stability in the injectors. In particular, the minimum longitudinal emittance in the PS is limited by a strong longitudinal microwave instability occurring just after transition crossing. The uncontrolled blow-up generates tails, which translate into an unacceptably large satellite population following the RF manipulations prior to extraction from the PS. In this paper, instability measurements are compared to particle simulations using the latest PS impedance model to identify the driving impedance sources. Moreover, means to mitigate the instability are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB243
About •	paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 29 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB244	Optimization and Machine Learning Applied to the RF Manipulations of Proton Beams in the CERN PS	3201
	A. Lasheen, H. Damerau, S.C. Johnston CERN, Meyrin, Switzerland
	The 25 ns bunch spacing in the LHC is defined by a sequence of RF manipulations in the Proton Synchrotron (PS). Multiple RF systems covering a large range of revolution harmonics (7 to 21, 42, 84, 168) allow performing RF manipulations such as beam splitting, and non-adiabatic bunch shortening. For the nominal beam sent to LHC, each bunch is split in 12 in the PS. The relative amplitude and phase settings of the RF systems need to be precisely adjusted to minimize the bunch-by-bunch variations in intensity, longitudinal emittance, and bunch shape. However, due to transient beam-loading, the ideal settings, as well as the best achievable beam quality, vary with beam intensity. Slow drifts of the hardware may also affect beam quality. In this paper, automatized optimization routines based on particle simulations with intensity effects are presented, together with the first considerations of machine learning. The optimization routines are used to assess the best achievable longitudinal beam quality expected with the PS RF systems upgrades, in the framework of the LHC Injector Upgrade project.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB244
About •	paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 24 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Longitudinal Microwave Instability Study at Transition Crossing with Ion Beams in the CERN PS

3197

A. Lasheen, H. Damerau, A. Huschauer, B.K. Popovic
CERN, Geneva, Switzerland

The luminosity of lead ion collisions in the Large Hadron Collider (LHC) was significantly increased during the 2018 ion run by reducing the bunch spacing from 100 ns to 75 ns, allowing to increase the total number of bunches. With the new 75 ns variant, three instead of four bunches are generated each cycle in the Low Energy Ion Ring (LEIR) and the Proton Synchrotron (PS) with up to 30% larger intensity per bunch. The beam was produced with satisfactory quality but at the limit of stability in the injectors. In particular, the minimum longitudinal emittance in the PS is limited by a strong longitudinal microwave instability occurring just after transition crossing. The uncontrolled blow-up generates tails, which translate into an unacceptably large satellite population following the RF manipulations prior to extraction from the PS. In this paper, instability measurements are compared to particle simulations using the latest PS impedance model to identify the driving impedance sources. Moreover, means to mitigate the instability are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB243

About •

paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 29 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB244

Optimization and Machine Learning Applied to the RF Manipulations of Proton Beams in the CERN PS

3201

A. Lasheen, H. Damerau, S.C. Johnston
CERN, Meyrin, Switzerland

The 25 ns bunch spacing in the LHC is defined by a sequence of RF manipulations in the Proton Synchrotron (PS). Multiple RF systems covering a large range of revolution harmonics (7 to 21, 42, 84, 168) allow performing RF manipulations such as beam splitting, and non-adiabatic bunch shortening. For the nominal beam sent to LHC, each bunch is split in 12 in the PS. The relative amplitude and phase settings of the RF systems need to be precisely adjusted to minimize the bunch-by-bunch variations in intensity, longitudinal emittance, and bunch shape. However, due to transient beam-loading, the ideal settings, as well as the best achievable beam quality, vary with beam intensity. Slow drifts of the hardware may also affect beam quality. In this paper, automatized optimization routines based on particle simulations with intensity effects are presented, together with the first considerations of machine learning. The optimization routines are used to assess the best achievable longitudinal beam quality expected with the PS RF systems upgrades, in the framework of the LHC Injector Upgrade project.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB244

About •

paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 24 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)