IBIC2016 - List of Authors (Lefevre, T.)

Paper	Title	Page
TUPG46	Improvements to the LHC Schottky Monitors	453
	M. Wendt, M. Betz, O.R. Jones, T. Lefèvre, T.E. Levens CERN, Geneva, Switzerland
	The LHC Schottky monitors have the potential to measure and monitor some important beam parameters, tune, momentum spread, chromaticity and emittance, in a non-invasive way. We present recent upgrade and improvement efforts of the transverse LHC Schottky systems operating at 4.8 GHz. This includes optimization of the slotted waveguide pickups and a re-design of the RF front-end electronics to detect the weak, incoherent Schottky signals in presence of large, coherent beam harmonics.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG46
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WEPG09	Development of a Prototype Electro-Optic Beam Position Monitor at the CERN SPS	634
	A. Arteche, A. Bosco, S.M. Gibson Royal Holloway, University of London, Surrey, United Kingdom N. Chritin, D. Draskovic, T. Lefèvre, T.E. Levens CERN, Geneva, Switzerland
	Funding: Project funded by UK STFC grant, ST/N001583/1 A novel electro-optic beam position monitor capable of rapidly (<50ps) monitoring transverse intra-bunch perturbations is under development for the HL-LHC project. The EO-BPM relies on the fast optical response of two pairs of electro-optic crystals, whose birefringence is modified by the passing electric field of a 1ns proton bunch. Analytic models of the electric field are compared with electromagnetic simulations. A preliminary opto-mechanical design of the EO-BPM was manufactured and installed at the CERN SPS in 2016. The prototype is equipped with two pairs of 5mm cubic LiNbO3 crystals, mounted in the horizontal and vertical planes. A polarized CW 780nm laser in the counting room transmits light via 160m of PM fibre to the SPS, where delivery optics directs light through a pair of crystals in the accelerator vacuum. The input polarization state to the crystal can be remotely controlled. The modulated light after the crystal is analyzed, fibre-coupled and recorded by a fast photodetector in the counting room. Following the recent installation, we present the detailed setup and report the latest status on commissioning the device in-situ at the CERN SPS.
	Poster WEPG09 [8.441 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG09
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WEPG49	A High Resolution Single-Shot Longitudinal Profile Diagnostic Using Electro-Optic Transposition	752
	D.A. Walsh, S.P. Jamison, E.W. Snedden STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom T. Lefèvre CERN, Geneva, Switzerland
	Funding: This work was funded by CERN through contract KE1866/DG/CLIC and carried out at STFC Daresbury Laboratory. Electro-Optic Transposition (EOT) is the basis for an improved longitudinal bunch profile diagnostic we are developing in ASTeC as part of the CLIC UK research program. The scheme consists of transposing the Cou-lomb field profile of an electron bunch into the intensity envelope of an optical pulse via the mixing processes that occur between a CW laser probe and Coulomb field in an electro-optic material. This transposed optical pulse can then be amplified and characterised using robust laser techniques ' in this case chirped pulse optical parametric amplification and frequency resolved optical gating, allowing the Coulomb field to be recovered. EOT is an improvement over existing techniques in terms of the achievable resolution which is limited by the EO material response itself, reduced complexity of the laser system required since nanosecond rather than femtosecond lasers are used, and insensitivity of the system to bunch-laser arrival time jitter due to using a nanosecond long probe. We present results showing the retrieval of a THz pulse (Coulomb field stand-in) which confirms the principle behind the EOT system.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG49
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WEPG80	Optical Effects in High Resolution and High Dynamic Range Beam Imaging Systems	844
	J. Wolfenden, R.B. Fiorito, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom M. Bergamaschi, R. Kieffer, T. Lefèvre, S. Mazzoni CERN, Geneva, Switzerland P. Karataev, K.O. Kruchinin JAI, Egham, Surrey, United Kingdom
	Optical systems are used to transfer light in beam diagnostics for a variety of imaging applications. The effect of the point spread function (PSF) of these optical systems on the resulting measurements is often approximated or misunderstood. It is imperative that the optical PSF is independently characterised, as this can severely impede the attainable resolution of a diagnostic measurement. A high quality laser and specially chosen optics have been used to generate an intense optical point source in order to accomplish such a characterisation. The point source was used to measure the PSFs of various electron-beam imaging systems. These systems incorporate a digital micro-mirror array, which was used to produce very high (>105) dynamic range images. The PSF was measured at each intermediary image plane of the optical system; enabling the origin of any perturbations to the PSF to be isolated and potentially mitigated. One of the characterised systems has been used for optical transition radiation (OTR) measurements of an electron beam at KEK-ATF2 (Tsukuba, Japan).
	Poster WEPG80 [1.851 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG80
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THAL02	Recent Developments for Instability Monitoring at the LHC	852
	T.E. Levens, K. Łasocha, T. Lefèvre CERN, Geneva, Switzerland
	A limiting factor on the maximum beam intensity that can be stored in the Large Hadron Collider (LHC) is the growth of transverse beam instabilities. Understanding and mitigating these effects requires a good knowledge of the beam parameters during the instability in order to identify the cause and provide the necessary corrections. This paper presents the suite of beam diagnostics that have been put into operation to monitor these beam instabilities and the development of a trigger system to allow measurements to be made synchronously with multiple instruments as soon as any instability is detected.
	Slides THAL02 [15.591 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-THAL02
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Paper

Title

Page

Improvements to the LHC Schottky Monitors

453

M. Wendt, M. Betz, O.R. Jones, T. Lefèvre, T.E. Levens
CERN, Geneva, Switzerland

The LHC Schottky monitors have the potential to measure and monitor some important beam parameters, tune, momentum spread, chromaticity and emittance, in a non-invasive way. We present recent upgrade and improvement efforts of the transverse LHC Schottky systems operating at 4.8 GHz. This includes optimization of the slotted waveguide pickups and a re-design of the RF front-end electronics to detect the weak, incoherent Schottky signals in presence of large, coherent beam harmonics.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG46

Export •

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

WEPG09

Development of a Prototype Electro-Optic Beam Position Monitor at the CERN SPS

634

A. Arteche, A. Bosco, S.M. Gibson
Royal Holloway, University of London, Surrey, United Kingdom
N. Chritin, D. Draskovic, T. Lefèvre, T.E. Levens
CERN, Geneva, Switzerland

Funding: Project funded by UK STFC grant, ST/N001583/1
A novel electro-optic beam position monitor capable of rapidly (<50ps) monitoring transverse intra-bunch perturbations is under development for the HL-LHC project. The EO-BPM relies on the fast optical response of two pairs of electro-optic crystals, whose birefringence is modified by the passing electric field of a 1ns proton bunch. Analytic models of the electric field are compared with electromagnetic simulations. A preliminary opto-mechanical design of the EO-BPM was manufactured and installed at the CERN SPS in 2016. The prototype is equipped with two pairs of 5mm cubic LiNbO3 crystals, mounted in the horizontal and vertical planes. A polarized CW 780nm laser in the counting room transmits light via 160m of PM fibre to the SPS, where delivery optics directs light through a pair of crystals in the accelerator vacuum. The input polarization state to the crystal can be remotely controlled. The modulated light after the crystal is analyzed, fibre-coupled and recorded by a fast photodetector in the counting room. Following the recent installation, we present the detailed setup and report the latest status on commissioning the device in-situ at the CERN SPS.

Poster WEPG09 [8.441 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG09

Export •

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

WEPG49

A High Resolution Single-Shot Longitudinal Profile Diagnostic Using Electro-Optic Transposition

752

D.A. Walsh, S.P. Jamison, E.W. Snedden
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
T. Lefèvre
CERN, Geneva, Switzerland

Funding: This work was funded by CERN through contract KE1866/DG/CLIC and carried out at STFC Daresbury Laboratory.
Electro-Optic Transposition (EOT) is the basis for an improved longitudinal bunch profile diagnostic we are developing in ASTeC as part of the CLIC UK research program. The scheme consists of transposing the Cou-lomb field profile of an electron bunch into the intensity envelope of an optical pulse via the mixing processes that occur between a CW laser probe and Coulomb field in an electro-optic material. This transposed optical pulse can then be amplified and characterised using robust laser techniques ' in this case chirped pulse optical parametric amplification and frequency resolved optical gating, allowing the Coulomb field to be recovered. EOT is an improvement over existing techniques in terms of the achievable resolution which is limited by the EO material response itself, reduced complexity of the laser system required since nanosecond rather than femtosecond lasers are used, and insensitivity of the system to bunch-laser arrival time jitter due to using a nanosecond long probe. We present results showing the retrieval of a THz pulse (Coulomb field stand-in) which confirms the principle behind the EOT system.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG49

Export •

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

WEPG80

Optical Effects in High Resolution and High Dynamic Range Beam Imaging Systems

844

J. Wolfenden, R.B. Fiorito, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
M. Bergamaschi, R. Kieffer, T. Lefèvre, S. Mazzoni
CERN, Geneva, Switzerland
P. Karataev, K.O. Kruchinin
JAI, Egham, Surrey, United Kingdom

Optical systems are used to transfer light in beam diagnostics for a variety of imaging applications. The effect of the point spread function (PSF) of these optical systems on the resulting measurements is often approximated or misunderstood. It is imperative that the optical PSF is independently characterised, as this can severely impede the attainable resolution of a diagnostic measurement. A high quality laser and specially chosen optics have been used to generate an intense optical point source in order to accomplish such a characterisation. The point source was used to measure the PSFs of various electron-beam imaging systems. These systems incorporate a digital micro-mirror array, which was used to produce very high (>105) dynamic range images. The PSF was measured at each intermediary image plane of the optical system; enabling the origin of any perturbations to the PSF to be isolated and potentially mitigated. One of the characterised systems has been used for optical transition radiation (OTR) measurements of an electron beam at KEK-ATF2 (Tsukuba, Japan).

Poster WEPG80 [1.851 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG80

Export •

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

THAL02

Recent Developments for Instability Monitoring at the LHC

852

T.E. Levens, K. Łasocha, T. Lefèvre
CERN, Geneva, Switzerland

A limiting factor on the maximum beam intensity that can be stored in the Large Hadron Collider (LHC) is the growth of transverse beam instabilities. Understanding and mitigating these effects requires a good knowledge of the beam parameters during the instability in order to identify the cause and provide the necessary corrections. This paper presents the suite of beam diagnostics that have been put into operation to monitor these beam instabilities and the development of a trigger system to allow measurements to be made synchronously with multiple instruments as soon as any instability is detected.

Slides THAL02 [15.591 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-THAL02

Export •

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