IPAC2016 - List of Authors (Argyropoulos, T.)

Paper	Title	Page
MOPOY058	Removing Known SPS Intensity Limitations for High Luminosity LHC Goals	989
	E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, P. Cruikshank, B. Goddard, T. Kaltenbacher, A. Lasheen, J. Perez Espinos, J. Repond, B. Salvant, C. Vollinger CERN, Geneva, Switzerland
	In preparation of the SPS as an LHC injector its impedance was significantly reduced in 1999 - 2000. A new SPS impedance reduction campaign is planned now for the High Luminosity (HL)-LHC project, which requires bunch intensities twice as high as the nominal one. One of the known intensity limitations is a longitudinal multi-bunch instability with a threshold 3 times below this operational intensity. The instability is presently cured using the 4th harmonic RF system and controlled emittance blow-up, but reaching the HL-LHC parameters cannot be assured without improving the machine impedance. Recently the impedance sources responsible for this instability were identified and implementation of their shielding and damping is foreseen during the next long shutdown (2019 - 2020) in synergy with two other important upgrades: amorphous carbon coating of (part of) the vacuum chamber against the e-cloud effect and rearrangement of the 200 MHz RF system. In this paper the strategy of impedance reduction is presented together with beam intensity achievable after its realisation. The potential effect of other proposals on remaining limitations is also considered.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY058
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TUPOR008	Effect of the Various Impedances on Longitudinal Beam Stability in the CERN SPS	1666
	A. Lasheen, T. Argyropoulos, J. Repond, E.N. Shaposhnikova CERN, Geneva, Switzerland
	The High Luminosity (HL)-LHC project at CERN aims at a luminosity increase by a factor ten and one of the necessary ingredients is doubling the bunch intensity to 2.4x10¹¹ ppb for beams with 25 ns bunch spacing. Many improvements are already foreseen in the frame of the LHC Injector Upgrade (LIU) project, but probably this intensity would still not be reachable in the SPS due to longitudinal instabilities. Recently a lot of effort went into finding the impedance sources of the instabilities. Particle simulations based on the latest SPS impedance model are now able to reproduce the measured instability thresholds and were used to determine the most critical impedance sources by removing them one by one from the model. It was found that impedance of vacuum flanges and of the already damped 630 MHz HOM of the main RF system gave for 72 bunches the comparable intensity thresholds. Possible intensity gains are defined for realistic impedance modifications and for various beam configurations (number of bunches, longitudinal emittances) and RF programs (single and double RF). The results of this study are used as a guideline for planning of a new campaign of the SPS impedance reduction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR008
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THPOR031	Beam-Loading Effect on Breakdown Rate in High-Gradient Accelerating Structures	3848
	F. Tecker, T. Argyropoulos, N. Catalán Lasheras, R. Corsini, A. Degiovanni, D. Gamba, J. Giner Navarro, A. Grudiev, G. McMonagle, J.L. Navarro Quirante, R. Rajamaki, E. Senes, I. Syratchev, B.J. Woolley, W. Wuensch CERN, Geneva, Switzerland T. Argyropoulos, J. Giner Navarro IFIC, Valencia, Spain A. Degiovanni, J.L. Navarro Quirante ADAM, Geneva, Switzerland D. Gamba JAI, Oxford, United Kingdom R. Rajamaki Aalto University, School of Science and Technology, Aalto, Finland E. Senes Torino University, Torino, Italy J. Tagg National Instruments Switzerland, Ennetbaden, Switzerland
	The Compact Linear Collider (CLIC) study for a future electron-positron collider with a center-of-mass energy up to 3 TeV aims for an accelerating gradient of 100 MV/m. The gradient is limited by RF breakdowns, and the luminosity requirements impose a limit on the admissible RF breakdown rate. RF testing of 12 GHz structure prototypes has shown that gradients in excess of 100 MV/m can be reached with the required breakdown rate. However at CLIC, the structures will be operated with significant beam-loading, modifying the field distribution inside. The effect of the beam-loading must be well understood but has not been previously measured. The commissioning and operation of an experiment to measure the effect of beam-loading on breakdown rate and the measurement results are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR031
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Paper

Title

Page

Removing Known SPS Intensity Limitations for High Luminosity LHC Goals

989

E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, P. Cruikshank, B. Goddard, T. Kaltenbacher, A. Lasheen, J. Perez Espinos, J. Repond, B. Salvant, C. Vollinger
CERN, Geneva, Switzerland

In preparation of the SPS as an LHC injector its impedance was significantly reduced in 1999 - 2000. A new SPS impedance reduction campaign is planned now for the High Luminosity (HL)-LHC project, which requires bunch intensities twice as high as the nominal one. One of the known intensity limitations is a longitudinal multi-bunch instability with a threshold 3 times below this operational intensity. The instability is presently cured using the 4th harmonic RF system and controlled emittance blow-up, but reaching the HL-LHC parameters cannot be assured without improving the machine impedance. Recently the impedance sources responsible for this instability were identified and implementation of their shielding and damping is foreseen during the next long shutdown (2019 - 2020) in synergy with two other important upgrades: amorphous carbon coating of (part of) the vacuum chamber against the e-cloud effect and rearrangement of the 200 MHz RF system. In this paper the strategy of impedance reduction is presented together with beam intensity achievable after its realisation. The potential effect of other proposals on remaining limitations is also considered.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY058

Export •

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

TUPOR008

Effect of the Various Impedances on Longitudinal Beam Stability in the CERN SPS

1666

A. Lasheen, T. Argyropoulos, J. Repond, E.N. Shaposhnikova
CERN, Geneva, Switzerland

The High Luminosity (HL)-LHC project at CERN aims at a luminosity increase by a factor ten and one of the necessary ingredients is doubling the bunch intensity to 2.4x10¹¹ ppb for beams with 25 ns bunch spacing. Many improvements are already foreseen in the frame of the LHC Injector Upgrade (LIU) project, but probably this intensity would still not be reachable in the SPS due to longitudinal instabilities. Recently a lot of effort went into finding the impedance sources of the instabilities. Particle simulations based on the latest SPS impedance model are now able to reproduce the measured instability thresholds and were used to determine the most critical impedance sources by removing them one by one from the model. It was found that impedance of vacuum flanges and of the already damped 630 MHz HOM of the main RF system gave for 72 bunches the comparable intensity thresholds. Possible intensity gains are defined for realistic impedance modifications and for various beam configurations (number of bunches, longitudinal emittances) and RF programs (single and double RF). The results of this study are used as a guideline for planning of a new campaign of the SPS impedance reduction.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR008

Export •

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

THPOR031

Beam-Loading Effect on Breakdown Rate in High-Gradient Accelerating Structures

3848

F. Tecker, T. Argyropoulos, N. Catalán Lasheras, R. Corsini, A. Degiovanni, D. Gamba, J. Giner Navarro, A. Grudiev, G. McMonagle, J.L. Navarro Quirante, R. Rajamaki, E. Senes, I. Syratchev, B.J. Woolley, W. Wuensch
CERN, Geneva, Switzerland
T. Argyropoulos, J. Giner Navarro
IFIC, Valencia, Spain
A. Degiovanni, J.L. Navarro Quirante
ADAM, Geneva, Switzerland
D. Gamba
JAI, Oxford, United Kingdom
R. Rajamaki
Aalto University, School of Science and Technology, Aalto, Finland
E. Senes
Torino University, Torino, Italy
J. Tagg
National Instruments Switzerland, Ennetbaden, Switzerland

The Compact Linear Collider (CLIC) study for a future electron-positron collider with a center-of-mass energy up to 3 TeV aims for an accelerating gradient of 100 MV/m. The gradient is limited by RF breakdowns, and the luminosity requirements impose a limit on the admissible RF breakdown rate. RF testing of 12 GHz structure prototypes has shown that gradients in excess of 100 MV/m can be reached with the required breakdown rate. However at CLIC, the structures will be operated with significant beam-loading, modifying the field distribution inside. The effect of the beam-loading must be well understood but has not been previously measured. The commissioning and operation of an experiment to measure the effect of beam-loading on breakdown rate and the measurement results are presented.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR031

Export •

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