IPAC2013 - List of Authors (Skowronski, P.K.)

Paper

Title

Page

Determination of Octupole and Sextupole Polarities in the LHC

655

M.J. McAteer, Y.I. Levinsen, E.H. Maclean, T. Persson, P. Skowroński, R.J. Steinhagen, R. Tomás
CERN, Geneva, Switzerland

We report the results of measurements to verify the polarity of the LHC’s lattice focusing and defocusing octupoles (MOF and MOD), spool piece octupole correctors (MCO), arc skew sextupole correctors (MSS), and interaction region sextupoles (MCSX and MCSSX). Octupole polarities were determined by measuring the change to second order chromaticity when a magnet family was trimmed. The MSS skew sextupole corrector polarities were checked by measuring the change to chromatic coupling when a magnet family was trimmed. The polarities of the MCSSX skew sextupoles in IR 1 and the MCSX normal sextupoles in IR 5 were checked by measuring the tune shift due to a magnet trim. Comparison of measurements with model predictions indicates that the polarities of the octupoles and the IR sextupoles are correct, and the polarities of the MSS skew sextupole correctors are reversed.

TUPFI039

Optics Performance of the LHC During the 2012 Run

1433

P. Skowroński, T. Bach, M. Giovannozzi, A. Langner, Y.I. Levinsen, E.H. Maclean, T. Persson, S. Redaelli, T. Risselada, M. Solfaroli Camillocci, R. Tomás, G. Vanbavinckhove
CERN, Geneva, Switzerland
M.J. McAteer
The University of Texas at Austin, Austin, USA
R. Miyamoto
ESS, Lund, Sweden
T. Persson
Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden

During 2012 the LHC was operating at 4TeV with beta star at ATLAS and CMS interaction points of 0.6m. During dedicated machine studies the nominal LHC optics was also setup with beta star of 0.4m. A huge effort was put into the optics commissioning leading to a record low peak beta-beating of around 7%. We describe the correction procedures and discuss the measurement results.

TUPFI040

Experimental Verification of the CLIC Two-Beam Acceleration Technology in CTF3

1436

P. Skowroński, A. Andersson, J. Barranco, B. Constance, R. Corsini, S. Döbert, A. Dubrovskiy, W. Farabolini, E. Ikarios, R.L. Lillestøl, T. Persson, F. Tecker
CERN, Geneva, Switzerland
W. Farabolini
CEA/DSM/IRFU, France
E. Ikarios
National Technical University of Athens, Athens, Greece
M. Jacewicz, A. Palaia, R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden
R.L. Lillestøl
University of Oslo, Oslo, Norway
T. Persson
Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden

The Compact Linear Collider (CLIC) International Collaboration is pursuing an extensive R&D program towards a multi-TeV electron-positron collider. In particular, the development of two beam acceleration technology is the focus of the CLIC test facility CTF3. In this paper we summarize the most recent results obtained at CTF3: the results of the studies on the drive beam generation are presented, the achieved two beam acceleration performance is reported and the measured break-down rates and related observations are summarized. The stability of deceleration process performed over 13 subsequent modules and the comparison of the obtained results with the theoretical expectations are discussed. We also outline and discuss the future experimental program.

TUPFI041

Operating the LHC Off-momentum for p-Pb Collisions

1439

R. Versteegen, R. Bruce, J.M. Jowett, A. Langner, Y.I. Levinsen, E.H. Maclean, M.J. McAteer, T. Persson, S. Redaelli, B. Salvachua, P. Skowroński, M. Solfaroli Camillocci, R. Tomás, G. Valentino, J. Wenninger
CERN, Geneva, Switzerland
E.H. Maclean
JAI, Oxford, United Kingdom
M.J. McAteer
The University of Texas at Austin, Austin, USA
T. Persson
Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
G. Valentino
University of Malta, Information and Communication Technology, Msida, Malta
S.M. White
BNL, Upton, Long Island, New York, USA

The first high-luminosity p-Pb run at the LHC took place in January-February 2013 at an energy of 4 Z TeV per beam. The RF frequency difference of proton and Pb is about 60 Hz for equal magnetic rigidities, which means that beams move slightly to off-momentum, non-central, orbits during physics when frequencies are locked together. The resulting optical perturbations ("beta-beating") restrict the available aperture and required a special correction. This was also the first operation of the LHC with low beta in all four experiments and required a specific collimation set up. Predictions from offline calculations of beta-beating correction are compared with measurements during the optics commissioning and collimator set up.

TUPME039

The Drive Beam Phase Stability in CTF3 and its Relation to the Bunch Compression Factor

1655

E. Ikarios, A. Andersson, J. Barranco, B. Constance, R. Corsini, A. Gerbershagen, T. Persson, P. Skowroński, F. Tecker
CERN, Geneva, Switzerland

The proposed Compact Linear Collider (CLIC) is based on a two-beam acceleration scheme. The energy needed to accelerate a low intensity "main" beam is provided by a high intensity, low energy "drive" beam. The precision and stability of the phase relation between two beams is crucial for the performance of the scheme. The tolerable phase jitter is 0.2 deg rms at 12GHz. For this reason it is fundamental to understand the main possible causes of the drive beam timing jitter. Experimental work aimed at such understanding was done in the CLIC Test Facility (CTF3) where a drive beam with characteristics similar to the CLIC one is produced. Several phase measurements allowed us to conclude that the main source of phase jitter is energy jitter of the beam transformed and amplified into phase jitter when passing through a magnetic chicane. This conclusion is supported by measurements done with different momentum compaction values in the chicane. In this paper the results of these several phase measurements will be presented and compared with expectations.

TUPWO048

Understanding the Tune, Coupling, and Chromaticity Dependence of the LHC on Landau Octupole Powering

1976

E.H. Maclean, M. Giovannozzi, W. Herr, Y.I. Levinsen, G. Papotti, T. Persson, P. Skowroński, R. Tomás, J. Wenninger
CERN, Geneva, Switzerland

During the 2012 LHC run there were several observations of unexpectedly large shifts to the tune, chromaticity, and coupling which were correlated with changes in the powering of Landau octupoles (MO). Understanding the chromaticity dependence is of particular importance given it's influence on instabilities. This paper summarizes the observations and our attempts to-date to understand the relationship between Q, Q', c- and the MO powering.

TUPWO049

Automatic Correction of Betatron Coupling in the LHC using Injection Oscillations

1979

T. Persson, T. Bach, D. Jacquet, V. Kain, Y.I. Levinsen, E.H. Maclean, M.J. McAteer, P. Skowroński, R. Tomás, G. Vanbavinckhove
CERN, Geneva, Switzerland
R. Miyamoto
ESS, Lund, Sweden

The control of the betatron coupling at injection and during the energy ramp is critical for the safe operation of the tune feedback and for the dynamic aperture. In the LHC every fill is preceded by the injection of a pilot bunch with low intensity. Using the injection oscillations from the pilot bunch we are able to measure the coupling at each individual BPM. The measurement is used to calculate a global coupling correction. The correction is based on the use of two orthogonal knobs which correct the real and imaginary part of the difference resonance term f1001, respectively. This method to correct the betatron coupling has been proven successful during the normal operation of the LHC. This paper presents the method used to calculate the corrections and its performance.

WEOBB203

Design of Phase Feed Forward System in CTF3 and Performance of Fast Beam Phase Monitors

2097

P. Skowroński, A. Andersson, A. Gerbershagen, E. Ikarios, J. Roberts
CERN, Geneva, Switzerland
P. Burrows, G.B. Christian, A. Gerbershagen, C. Perry, J. Roberts
JAI, Oxford, United Kingdom
P. Burrows, G.B. Christian, A. Gerbershagen, C. Perry
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
A. Ghigo, F. Marcellini
INFN/LNF, Frascati (Roma), Italy
E. Ikarios
National Technical University of Athens, Athens, Greece

Funding: Work supported by the European Commission under the FP7 Research Infrastructures project Eu- CARD, grant agreement no. 227579
The CLIC two beam acceleration technology requires a drive beam phase stability of better than 0.3 deg rms at 12 GHz, corresponding to a timing stability below 50 fs rms. For this reason the CLIC design includes a phase stabilization feed-forward system. It relies on precise beam phase measurement and its subsequent correction in a chicane with help of fast kickers. A prototype of such a system is being installed in CLIC Test Facility CTF3. In this paper we describe in detail its design and implementation. Additionally, we present and discuss the performance of the precision phase monitor prototypes installed at the end of the CTF3 linac, measured with the drive beam.
We would like to acknowledge support of G.Sensolini, A.Zolla (INFN/LNF Frascati), N.S.Chritin and J-M.Scigliuto (CERN) in design and fabrication of components.

Slides WEOBB203 [6.770 MB]

WEPEA069

Review of the Drive Beam Stabilization in the CLIC Test Facility CTF3

2666

A. Dubrovskiy, L. Malina, P. Skowroński, F. Tecker
CERN, Geneva, Switzerland
T. Persson
Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden

CTF3 is a Test Facility focusing on beam-based studies of the key concepts of the Compact Linear Collider CLIC. Over the past several years many aspects the CLIC two-beam acceleration scheme were studied in CTF3, including the crucial issue of drive beam stability. The main sources of drifts and instabilities have been identified and mitigated, helping to improve the machine performance and showing significant progress towards the experimental demonstration of the very stringent requirements on current, energy and phase stability needed in CLIC. In this paper, the more effective techniques and feed-backs are summarized. The latest measurements on beam stability are reported and their relevance to CLIC is discussed.

Paper	Title	Page
MOPME076	Determination of Octupole and Sextupole Polarities in the LHC	655
	M.J. McAteer, Y.I. Levinsen, E.H. Maclean, T. Persson, P. Skowroński, R.J. Steinhagen, R. Tomás CERN, Geneva, Switzerland
	We report the results of measurements to verify the polarity of the LHC’s lattice focusing and defocusing octupoles (MOF and MOD), spool piece octupole correctors (MCO), arc skew sextupole correctors (MSS), and interaction region sextupoles (MCSX and MCSSX). Octupole polarities were determined by measuring the change to second order chromaticity when a magnet family was trimmed. The MSS skew sextupole corrector polarities were checked by measuring the change to chromatic coupling when a magnet family was trimmed. The polarities of the MCSSX skew sextupoles in IR 1 and the MCSX normal sextupoles in IR 5 were checked by measuring the tune shift due to a magnet trim. Comparison of measurements with model predictions indicates that the polarities of the octupoles and the IR sextupoles are correct, and the polarities of the MSS skew sextupole correctors are reversed.

TUPFI039	Optics Performance of the LHC During the 2012 Run	1433
	P. Skowroński, T. Bach, M. Giovannozzi, A. Langner, Y.I. Levinsen, E.H. Maclean, T. Persson, S. Redaelli, T. Risselada, M. Solfaroli Camillocci, R. Tomás, G. Vanbavinckhove CERN, Geneva, Switzerland M.J. McAteer The University of Texas at Austin, Austin, USA R. Miyamoto ESS, Lund, Sweden T. Persson Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
	During 2012 the LHC was operating at 4TeV with beta star at ATLAS and CMS interaction points of 0.6m. During dedicated machine studies the nominal LHC optics was also setup with beta star of 0.4m. A huge effort was put into the optics commissioning leading to a record low peak beta-beating of around 7%. We describe the correction procedures and discuss the measurement results.

TUPFI040	Experimental Verification of the CLIC Two-Beam Acceleration Technology in CTF3	1436
	P. Skowroński, A. Andersson, J. Barranco, B. Constance, R. Corsini, S. Döbert, A. Dubrovskiy, W. Farabolini, E. Ikarios, R.L. Lillestøl, T. Persson, F. Tecker CERN, Geneva, Switzerland W. Farabolini CEA/DSM/IRFU, France E. Ikarios National Technical University of Athens, Athens, Greece M. Jacewicz, A. Palaia, R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden R.L. Lillestøl University of Oslo, Oslo, Norway T. Persson Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
	The Compact Linear Collider (CLIC) International Collaboration is pursuing an extensive R&D program towards a multi-TeV electron-positron collider. In particular, the development of two beam acceleration technology is the focus of the CLIC test facility CTF3. In this paper we summarize the most recent results obtained at CTF3: the results of the studies on the drive beam generation are presented, the achieved two beam acceleration performance is reported and the measured break-down rates and related observations are summarized. The stability of deceleration process performed over 13 subsequent modules and the comparison of the obtained results with the theoretical expectations are discussed. We also outline and discuss the future experimental program.

TUPFI041	Operating the LHC Off-momentum for p-Pb Collisions	1439
	R. Versteegen, R. Bruce, J.M. Jowett, A. Langner, Y.I. Levinsen, E.H. Maclean, M.J. McAteer, T. Persson, S. Redaelli, B. Salvachua, P. Skowroński, M. Solfaroli Camillocci, R. Tomás, G. Valentino, J. Wenninger CERN, Geneva, Switzerland E.H. Maclean JAI, Oxford, United Kingdom M.J. McAteer The University of Texas at Austin, Austin, USA T. Persson Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden G. Valentino University of Malta, Information and Communication Technology, Msida, Malta S.M. White BNL, Upton, Long Island, New York, USA
	The first high-luminosity p-Pb run at the LHC took place in January-February 2013 at an energy of 4 Z TeV per beam. The RF frequency difference of proton and Pb is about 60 Hz for equal magnetic rigidities, which means that beams move slightly to off-momentum, non-central, orbits during physics when frequencies are locked together. The resulting optical perturbations ("beta-beating") restrict the available aperture and required a special correction. This was also the first operation of the LHC with low beta in all four experiments and required a specific collimation set up. Predictions from offline calculations of beta-beating correction are compared with measurements during the optics commissioning and collimator set up.

TUPME039	The Drive Beam Phase Stability in CTF3 and its Relation to the Bunch Compression Factor	1655
	E. Ikarios, A. Andersson, J. Barranco, B. Constance, R. Corsini, A. Gerbershagen, T. Persson, P. Skowroński, F. Tecker CERN, Geneva, Switzerland
	The proposed Compact Linear Collider (CLIC) is based on a two-beam acceleration scheme. The energy needed to accelerate a low intensity "main" beam is provided by a high intensity, low energy "drive" beam. The precision and stability of the phase relation between two beams is crucial for the performance of the scheme. The tolerable phase jitter is 0.2 deg rms at 12GHz. For this reason it is fundamental to understand the main possible causes of the drive beam timing jitter. Experimental work aimed at such understanding was done in the CLIC Test Facility (CTF3) where a drive beam with characteristics similar to the CLIC one is produced. Several phase measurements allowed us to conclude that the main source of phase jitter is energy jitter of the beam transformed and amplified into phase jitter when passing through a magnetic chicane. This conclusion is supported by measurements done with different momentum compaction values in the chicane. In this paper the results of these several phase measurements will be presented and compared with expectations.

TUPWO048	Understanding the Tune, Coupling, and Chromaticity Dependence of the LHC on Landau Octupole Powering	1976
	E.H. Maclean, M. Giovannozzi, W. Herr, Y.I. Levinsen, G. Papotti, T. Persson, P. Skowroński, R. Tomás, J. Wenninger CERN, Geneva, Switzerland
	During the 2012 LHC run there were several observations of unexpectedly large shifts to the tune, chromaticity, and coupling which were correlated with changes in the powering of Landau octupoles (MO). Understanding the chromaticity dependence is of particular importance given it's influence on instabilities. This paper summarizes the observations and our attempts to-date to understand the relationship between Q, Q', c- and the MO powering.

TUPWO049	Automatic Correction of Betatron Coupling in the LHC using Injection Oscillations	1979
	T. Persson, T. Bach, D. Jacquet, V. Kain, Y.I. Levinsen, E.H. Maclean, M.J. McAteer, P. Skowroński, R. Tomás, G. Vanbavinckhove CERN, Geneva, Switzerland R. Miyamoto ESS, Lund, Sweden
	The control of the betatron coupling at injection and during the energy ramp is critical for the safe operation of the tune feedback and for the dynamic aperture. In the LHC every fill is preceded by the injection of a pilot bunch with low intensity. Using the injection oscillations from the pilot bunch we are able to measure the coupling at each individual BPM. The measurement is used to calculate a global coupling correction. The correction is based on the use of two orthogonal knobs which correct the real and imaginary part of the difference resonance term f1001, respectively. This method to correct the betatron coupling has been proven successful during the normal operation of the LHC. This paper presents the method used to calculate the corrections and its performance.

WEOBB203	Design of Phase Feed Forward System in CTF3 and Performance of Fast Beam Phase Monitors	2097
	P. Skowroński, A. Andersson, A. Gerbershagen, E. Ikarios, J. Roberts CERN, Geneva, Switzerland P. Burrows, G.B. Christian, A. Gerbershagen, C. Perry, J. Roberts JAI, Oxford, United Kingdom P. Burrows, G.B. Christian, A. Gerbershagen, C. Perry Oxford University, Physics Department, Oxford, Oxon, United Kingdom A. Ghigo, F. Marcellini INFN/LNF, Frascati (Roma), Italy E. Ikarios National Technical University of Athens, Athens, Greece
	Funding: Work supported by the European Commission under the FP7 Research Infrastructures project Eu- CARD, grant agreement no. 227579 The CLIC two beam acceleration technology requires a drive beam phase stability of better than 0.3 deg rms at 12 GHz, corresponding to a timing stability below 50 fs rms. For this reason the CLIC design includes a phase stabilization feed-forward system. It relies on precise beam phase measurement and its subsequent correction in a chicane with help of fast kickers. A prototype of such a system is being installed in CLIC Test Facility CTF3. In this paper we describe in detail its design and implementation. Additionally, we present and discuss the performance of the precision phase monitor prototypes installed at the end of the CTF3 linac, measured with the drive beam. We would like to acknowledge support of G.Sensolini, A.Zolla (INFN/LNF Frascati), N.S.Chritin and J-M.Scigliuto (CERN) in design and fabrication of components.
	Slides WEOBB203 [6.770 MB]

WEPEA069	Review of the Drive Beam Stabilization in the CLIC Test Facility CTF3	2666
	A. Dubrovskiy, L. Malina, P. Skowroński, F. Tecker CERN, Geneva, Switzerland T. Persson Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
	CTF3 is a Test Facility focusing on beam-based studies of the key concepts of the Compact Linear Collider CLIC. Over the past several years many aspects the CLIC two-beam acceleration scheme were studied in CTF3, including the crucial issue of drive beam stability. The main sources of drifts and instabilities have been identified and mitigated, helping to improve the machine performance and showing significant progress towards the experimental demonstration of the very stringent requirements on current, energy and phase stability needed in CLIC. In this paper, the more effective techniques and feed-backs are summarized. The latest measurements on beam stability are reported and their relevance to CLIC is discussed.