IPAC2016 - List of Authors (Grudiev, A.)

Paper	Title	Page
MOPOR010	Impedance Measurements and Simulations on the TCTP and TDI LHC Collimators	610
	N. Biancacci, F. Caspers, A. Grudiev, J. Kuczerowski, I. Lamas Garcia, A. Lechner, E. Métral, A. Passarelli, A. Perillo Marcone, B. Salvant, J.A. Uythoven CERN, Geneva, Switzerland O. Frasciello, M. Zobov INFN/LNF, Frascati (Roma), Italy A. Mostacci Rome University La Sapienza, Roma, Italy N. Mounet EPFL, Lausanne, Switzerland
	The LHC collimation system is a critical element for the safe operation of the LHC machine and is subject to continuous performance monitoring, hardware upgrade and optimization. In this work we will address the impact on impedance of the upgrades performed on the TDI injection protection collimator, where the absorber material has been changed to mitigate the device heating observed in machine operation, and on selected secondary (TCS) and tertiary (TCT) collimators, where beam position monitors (BPM) have been embedded for faster jaw alignment. Concerning the TDI, we will present the RF measurements performed before and after the upgrade, comparing the result to heating and tune shift beam measurements. For the TCTs, we will study how the higher order modes (HOM) introduced by the BPM addition have been cured by means of ferrite placement in the device. The impedance mitigation campaign has been supported by RF measurements whose results are in good agreement with GdfidL and CST simulations. The presence of undamped low frequency modes is proved not to be detrimental to the safe LHC operation.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR010
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WEOBB02	Status of Wakefield Monitor Experiments at the CLIC Test Facility	2099
	R.L. Lillestøl, E. Adli, J. Pfingstner University of Oslo, Oslo, Norway N. Aftab, S. Javeed PINSTECH, Islamabad, Pakistan R. Corsini, S. Döbert, W. Farabolini, A. Grudiev, W. Wuensch CERN, Geneva, Switzerland
	For the very low emittance beams in CLIC, it is vital to mitigate emittance growth which leads to reduced luminosity in the detectors. One factor that leads to emittance growth is transverse wakefields in the accelerating structures. In order to combat this the structures must be aligned with a precision of a few um. For achieving this tolerance, accelerating structures are equipped with wakefield monitors that measure higher-order dipole modes excited by the beam when offset from the structure axis. We report on such measurements, performed using prototype CLIC accelerating structures which are part of the module installed in the CLIC Test Facility 3 (CTF3) at CERN. Measurements with and without the drive beam that feeds rf power to the structures are compared. Improvements to the experimental setup are discussed, and finally remaining measurements that should be performed before the completion of the program are summarized.
	Slides WEOBB02 [2.928 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEOBB02
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WEPOR016	Pre-alignment of Accelerating Structures for Compact Acceleration and High Gradient using In-situ Radiofrequency Methods	2696
SUPSS078	use link to see paper's listing under its alternate paper code
	N. Galindo Munoz, N. Catalán Lasheras, A. Grudiev CERN, Geneva, Switzerland V.E. Boria DCOM-iTEAM-UPV, Valencia, Spain A. Faus-Golfe IFIC, Valencia, Spain
	Funding: PACMAN is founded under the European Union's 7th Framework Program Marie Curie Actions, grant PITN-GA-2013-606839 To achieve a high accelerating gradient of 100 MV/m, the CLIC project under study at CERN uses a 23 cm long tapered normal-conducting travelling wave Accelerating Structure (AS) operating at 12 GHz. Minimisation of the long-range wakefields (WF) is assured by damping of the HOM through four radial waveguides in each cell without distorting the accelerating mode. As an extension of them, there are four bent waveguides called WF monitors (WFM) in the middle cell with two RF pick-ups. To obtain a small beam emittance in the collision point, micro-metric pre-alignment of the AS is required. We work to find the electrical centre of the AS through the use of the asymmetry in the RF scattering parameters created by an off-centre conductive wire, stretched along the axis. The accuracy required is of 7 μm with a resolution of 3.5 μm for the WFM signals including the acquisition electronics. Our simulations have shown that a resolution of 1 μm is possible using a calibrated VNA. Measurement results and improvements of the final accuracy will be presented and discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR016
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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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THPOR042	New Quantity Describing the Pulse Shape Dependence of the High Gradient Limit in Single Cell Standing-Wave Accelerating Structures	3878
	J. Shi, H.B. Chen, X.W. Wu TUB, Beijing, People's Republic of China V.A. Dolgashev SLAC, Menlo Park, California, USA A. Grudiev, W. Wuensch CERN, Geneva, Switzerland Y. Higashi KEK, Ibaraki, Japan B. Spataro INFN/LNF, Frascati (Roma), Italy
	A new quantity has been developed to study the relationship among the breakdown rate, the pulse width and the gradient. Difference pulse shapes can be treated by introducing a Green's function. This paper describes the quantity and the results while it is applied to the data of many high-power test runs of different single-cell standing wave accelerating structures. A remarkably similar relationship between the new quantity and breakdown rate is observed from all of the test results.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR042
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Paper

Title

Page

Impedance Measurements and Simulations on the TCTP and TDI LHC Collimators

610

N. Biancacci, F. Caspers, A. Grudiev, J. Kuczerowski, I. Lamas Garcia, A. Lechner, E. Métral, A. Passarelli, A. Perillo Marcone, B. Salvant, J.A. Uythoven
CERN, Geneva, Switzerland
O. Frasciello, M. Zobov
INFN/LNF, Frascati (Roma), Italy
A. Mostacci
Rome University La Sapienza, Roma, Italy
N. Mounet
EPFL, Lausanne, Switzerland

The LHC collimation system is a critical element for the safe operation of the LHC machine and is subject to continuous performance monitoring, hardware upgrade and optimization. In this work we will address the impact on impedance of the upgrades performed on the TDI injection protection collimator, where the absorber material has been changed to mitigate the device heating observed in machine operation, and on selected secondary (TCS) and tertiary (TCT) collimators, where beam position monitors (BPM) have been embedded for faster jaw alignment. Concerning the TDI, we will present the RF measurements performed before and after the upgrade, comparing the result to heating and tune shift beam measurements. For the TCTs, we will study how the higher order modes (HOM) introduced by the BPM addition have been cured by means of ferrite placement in the device. The impedance mitigation campaign has been supported by RF measurements whose results are in good agreement with GdfidL and CST simulations. The presence of undamped low frequency modes is proved not to be detrimental to the safe LHC operation.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR010

Export •

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

WEOBB02

Status of Wakefield Monitor Experiments at the CLIC Test Facility

2099

R.L. Lillestøl, E. Adli, J. Pfingstner
University of Oslo, Oslo, Norway
N. Aftab, S. Javeed
PINSTECH, Islamabad, Pakistan
R. Corsini, S. Döbert, W. Farabolini, A. Grudiev, W. Wuensch
CERN, Geneva, Switzerland

For the very low emittance beams in CLIC, it is vital to mitigate emittance growth which leads to reduced luminosity in the detectors. One factor that leads to emittance growth is transverse wakefields in the accelerating structures. In order to combat this the structures must be aligned with a precision of a few um. For achieving this tolerance, accelerating structures are equipped with wakefield monitors that measure higher-order dipole modes excited by the beam when offset from the structure axis. We report on such measurements, performed using prototype CLIC accelerating structures which are part of the module installed in the CLIC Test Facility 3 (CTF3) at CERN. Measurements with and without the drive beam that feeds rf power to the structures are compared. Improvements to the experimental setup are discussed, and finally remaining measurements that should be performed before the completion of the program are summarized.

Slides WEOBB02 [2.928 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEOBB02

Export •

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

WEPOR016

Pre-alignment of Accelerating Structures for Compact Acceleration and High Gradient using In-situ Radiofrequency Methods

2696

SUPSS078

use link to see paper's listing under its alternate paper code

N. Galindo Munoz, N. Catalán Lasheras, A. Grudiev
CERN, Geneva, Switzerland
V.E. Boria
DCOM-iTEAM-UPV, Valencia, Spain
A. Faus-Golfe
IFIC, Valencia, Spain

Funding: PACMAN is founded under the European Union's 7th Framework Program Marie Curie Actions, grant PITN-GA-2013-606839
To achieve a high accelerating gradient of 100 MV/m, the CLIC project under study at CERN uses a 23 cm long tapered normal-conducting travelling wave Accelerating Structure (AS) operating at 12 GHz. Minimisation of the long-range wakefields (WF) is assured by damping of the HOM through four radial waveguides in each cell without distorting the accelerating mode. As an extension of them, there are four bent waveguides called WF monitors (WFM) in the middle cell with two RF pick-ups. To obtain a small beam emittance in the collision point, micro-metric pre-alignment of the AS is required. We work to find the electrical centre of the AS through the use of the asymmetry in the RF scattering parameters created by an off-centre conductive wire, stretched along the axis. The accuracy required is of 7 μm with a resolution of 3.5 μm for the WFM signals including the acquisition electronics. Our simulations have shown that a resolution of 1 μm is possible using a calibrated VNA. Measurement results and improvements of the final accuracy will be presented and discussed.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR016

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)

THPOR042

New Quantity Describing the Pulse Shape Dependence of the High Gradient Limit in Single Cell Standing-Wave Accelerating Structures

3878

J. Shi, H.B. Chen, X.W. Wu
TUB, Beijing, People's Republic of China
V.A. Dolgashev
SLAC, Menlo Park, California, USA
A. Grudiev, W. Wuensch
CERN, Geneva, Switzerland
Y. Higashi
KEK, Ibaraki, Japan
B. Spataro
INFN/LNF, Frascati (Roma), Italy

A new quantity has been developed to study the relationship among the breakdown rate, the pulse width and the gradient. Difference pulse shapes can be treated by introducing a Green's function. This paper describes the quantity and the results while it is applied to the data of many high-power test runs of different single-cell standing wave accelerating structures. A remarkably similar relationship between the new quantity and breakdown rate is observed from all of the test results.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR042

Export •

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