IPAC2019 - List of Authors (Dehler, M.M.)

Paper	Title	Page
TUPGW066	Exploring the Potential of the Swiss Light Source	1554
	M. Aiba, M. Böge, A. Citterio, M.M. Dehler, A. Lüdeke, C. Ozkan Loch, L. Stingelin, A. Streun PSI, Villigen PSI, Switzerland
	Swiss Light Source (SLS) has been on-line since 2001. Although its performance meets the specifications, it still has a potential to achieve better storage ring beam parameters. We explore two possible improvements. The first one is for the beam lifetime. There are 480 rf buckets while normally 390 bunches are stored. The gap in filing pattern (90 empty buckets) is held to suppress ion instability. After many years of operation, however, the vacuum condition is much better than that of the time when the SLS was turned on. Hence it is possible to shorten the gap. The beam lifetime can then be prolonged due to less bunch current while keeping the net beam current. The study may be also useful to predict possible filling patter in SLS2, which is the SLS upgrade planned. The second one is for the beam emittance. The nominal energy closed orbit coincides with the axes of quadrupole magnets. An off-momentum closed orbit is therefore off-centered through quadrupoles, resulting in a damping partition shift. The beam emittance can be decreased at the expense of a larger energy spread. This was successfully achieved in the ESRF booster. We study whether it is applicable to the SLS storage ring.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW066
About •	paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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TUPGW107	Overview of Collective Effects in SLS 2.0	1658
	M.M. Dehler, M. Aiba, A. Citterio, L. Stingelin PSI, Villigen PSI, Switzerland
	At the end of 2017, the conceptual design for an upgrade of the Swiss Light Source was finished, promising a 40 fold smaller emittance and a corresponding increase of the spectral brightness from the current value. From the point of view of collective effects, the main changes in the new design are a reduced chamber size, fully coated with NEG, and operation at small and negative momentum compaction with low synchrotron frequency. We give an overview of the latest results for the ring. Most critical is the threshold for the longitudinal single bunch instability. Taking into account the combined effect of wake impedances and CSR, we have to rely on bunch stretching by a higher harmonic system to achieve stable operation at nominal current.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW107
About •	paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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TUPGW108	Characterization of NEG Coatings for SLS 2.0	1662
	M.M. Dehler, A. Citterio PSI, Villigen PSI, Switzerland S. Alberti, J.P. Hogge SPC-EPFL, Lausanne, Switzerland M. Hahn, H.P. Marques ESRF, Grenoble, France X.Y. Liu USTC/NSRL, Hefei, Anhui, People’s Republic of China
	To limit desorption and ameliorate pumping of the narrow 20 mm aperture vacuum chamber of SLS2.0, it is planned to fully coat it with nonevaporable getter (NEG) material. NEG coating can be produced with different structural characteristics, from dense films to columnar growth, with corresponding distinct electrical properties affecting the machine impedance and the instability threshold of the accelerator. In order to evaluate and characterize the coating process for geometries similar to the SLS chamber, we measured the resonance properties of coated and uncoated shorted waveguide pieces. First tests were done with standard X band waveguides at 12 and 7 GHz. Test setups using elliptical cross sections are in preparation, also for higher frequencies allowing the characterization of thin NEG layers. The final goal is to have a standardized process to test of samples coated by external producers. We describe the setups and first results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW108
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEPGW080	Design of Resonant Stripline BPM for an IR-FEL Project at NSRL	2665
	X.Y. Liu, B.G. Sun USTC/NSRL, Hefei, Anhui, People’s Republic of China M. Bopp, M.M. Dehler, X.Y. Liu, A. Scherer PSI, Villigen PSI, Switzerland
	Funding: Work supported by the National Science Foundation of China (11575181, 21327901, 11705203); X. Y. Liu was supported by the China Scholarship Council for a 2-year study at PSI (Grant No. 201706340057). This paper presents the design of a 476MHz resonant stripline beam position monitor (BPM) for an IR-FEL machine at NSRL. This type of BPM was developed based on stripline BPM by moving the coupling feedthrough closer to the short end downstream. This modification introduces a resonance that gives this BPM a better capability to detect lower beam currents compared to broadband devices like button and stripline BPM. Meanwhile, the change is small enough to use the same type of electronics [1-3]. In the following sections, the basic principle, nonlinear effect, sensitivity, the filtered sum and difference signals, and the mechanical design of this BPM will be mainly discussed. Email address: xiaoyu.liu@psi.ch
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW080
About •	paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Exploring the Potential of the Swiss Light Source

1554

M. Aiba, M. Böge, A. Citterio, M.M. Dehler, A. Lüdeke, C. Ozkan Loch, L. Stingelin, A. Streun
PSI, Villigen PSI, Switzerland

Swiss Light Source (SLS) has been on-line since 2001. Although its performance meets the specifications, it still has a potential to achieve better storage ring beam parameters. We explore two possible improvements. The first one is for the beam lifetime. There are 480 rf buckets while normally 390 bunches are stored. The gap in filing pattern (90 empty buckets) is held to suppress ion instability. After many years of operation, however, the vacuum condition is much better than that of the time when the SLS was turned on. Hence it is possible to shorten the gap. The beam lifetime can then be prolonged due to less bunch current while keeping the net beam current. The study may be also useful to predict possible filling patter in SLS2, which is the SLS upgrade planned. The second one is for the beam emittance. The nominal energy closed orbit coincides with the axes of quadrupole magnets. An off-momentum closed orbit is therefore off-centered through quadrupoles, resulting in a damping partition shift. The beam emittance can be decreased at the expense of a larger energy spread. This was successfully achieved in the ESRF booster. We study whether it is applicable to the SLS storage ring.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW066

About •

paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

Export •

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

TUPGW107

Overview of Collective Effects in SLS 2.0

1658

M.M. Dehler, M. Aiba, A. Citterio, L. Stingelin
PSI, Villigen PSI, Switzerland

At the end of 2017, the conceptual design for an upgrade of the Swiss Light Source was finished, promising a 40 fold smaller emittance and a corresponding increase of the spectral brightness from the current value. From the point of view of collective effects, the main changes in the new design are a reduced chamber size, fully coated with NEG, and operation at small and negative momentum compaction with low synchrotron frequency. We give an overview of the latest results for the ring. Most critical is the threshold for the longitudinal single bunch instability. Taking into account the combined effect of wake impedances and CSR, we have to rely on bunch stretching by a higher harmonic system to achieve stable operation at nominal current.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW107

About •

paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

Export •

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

TUPGW108

Characterization of NEG Coatings for SLS 2.0

1662

M.M. Dehler, A. Citterio
PSI, Villigen PSI, Switzerland
S. Alberti, J.P. Hogge
SPC-EPFL, Lausanne, Switzerland
M. Hahn, H.P. Marques
ESRF, Grenoble, France
X.Y. Liu
USTC/NSRL, Hefei, Anhui, People’s Republic of China

To limit desorption and ameliorate pumping of the narrow 20 mm aperture vacuum chamber of SLS2.0, it is planned to fully coat it with nonevaporable getter (NEG) material. NEG coating can be produced with different structural characteristics, from dense films to columnar growth, with corresponding distinct electrical properties affecting the machine impedance and the instability threshold of the accelerator. In order to evaluate and characterize the coating process for geometries similar to the SLS chamber, we measured the resonance properties of coated and uncoated shorted waveguide pieces. First tests were done with standard X band waveguides at 12 and 7 GHz. Test setups using elliptical cross sections are in preparation, also for higher frequencies allowing the characterization of thin NEG layers. The final goal is to have a standardized process to test of samples coated by external producers. We describe the setups and first results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW108

About •

paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

Export •

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

WEPGW080

Design of Resonant Stripline BPM for an IR-FEL Project at NSRL

2665

X.Y. Liu, B.G. Sun
USTC/NSRL, Hefei, Anhui, People’s Republic of China
M. Bopp, M.M. Dehler, X.Y. Liu, A. Scherer
PSI, Villigen PSI, Switzerland

Funding: Work supported by the National Science Foundation of China (11575181, 21327901, 11705203); X. Y. Liu was supported by the China Scholarship Council for a 2-year study at PSI (Grant No. 201706340057).
This paper presents the design of a 476MHz resonant stripline beam position monitor (BPM) for an IR-FEL machine at NSRL. This type of BPM was developed based on stripline BPM by moving the coupling feedthrough closer to the short end downstream. This modification introduces a resonance that gives this BPM a better capability to detect lower beam currents compared to broadband devices like button and stripline BPM. Meanwhile, the change is small enough to use the same type of electronics [1-3]. In the following sections, the basic principle, nonlinear effect, sensitivity, the filtered sum and difference signals, and the mechanical design of this BPM will be mainly discussed.
Email address: xiaoyu.liu@psi.ch

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW080

About •

paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

Export •

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