IPAC2011 - List of Authors (Barnes, M.J.)

Paper	Title	Page
MOPS078	Coaxial Wire Measurements of Ferrite Kicker Magnets	784
	H.A. Day, R.M. Jones UMAN, Manchester, United Kingdom M.J. Barnes, F. Caspers, H.A. Day, E. Métral, B. Salvant, C. Zannini CERN, Geneva, Switzerland
	Fast kicker magnets are used to inject beam into and eject beam out of the CERN accelerator rings. These kickers are generally transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the yoke can provoke significant beam induced heating, especially for high intensities. In addition the impedance may contribute to beam instabilities. The results of longitudinal and transverse impedance measurements, for various kicker magnets, are presented and compared with analytical calculations: in addition predictions from a numerical analysis are discussed.

TUPC011	Striplines for CLIC Pre-Damping and Damping Rings*	1012
	C. Belver-Aguilar, A. Faus-Golfe IFIC, Valencia, Spain M.J. Barnes, G. Rumolo CERN, Geneva, Switzerland F. Toral CIEMAT, Madrid, Spain C. Zannini EPFL, Lausanne, Switzerland
	The Compact Linear Collider (CLIC) study explores the scheme for an electron-positron collider with high luminosity and a nominal center-of-mass energy of 3 TeV: CLIC would complement LHC physics in the multi-TeV range. The CLIC design relies on the presence of Pre-Damping Rings (PDR) and Damping Rings (DR) to achieve, through synchrotron radiation, the very low emittance needed to fulfil the luminosity requirements. The specifications for the kicker systems are very challenging and include very low beam coupling impedance and excellent field homogeneity: striplines have been chosen for the kicker elements. Analytical calculations have been carried out to determine the effect of tapering upon the high frequency beam coupling impedance. In addition detailed numerical modeling of the field homogeneity has been performed and the sensitivity of the homogeneity to various parameters, including stripline cross-section, has been studied. This paper presents the main conclusions of the beam impedance calculations and field homogeneity predictions.

TUPC137	UFOs in the LHC	1347
	T. Baer, M.J. Barnes, B. Goddard, E.B. Holzer, J.M. Jimenez, A. Lechner, V. Mertens, E. Nebot Del Busto, A. Nordt, J.A. Uythoven, B. Velghe, J. Wenninger, F. Zimmermann CERN, Geneva, Switzerland
	One of the major known limitations for the performance of the Large Hadron Collider are so called UFOs (”Unidentified Falling Objects”). UFOs were first observed in July 2010 and have since caused numerous protection beam dumps. UFOs are thought to be micrometer sized dust particles which lead to fast beam losses with a duration of about 10 turns when they interact with the beam. In 2011, the diagnostics for such events was significantly improved which allows estimates of the properties, dynamics and production mechanisms of the dust particles. The state of knowledge and mitigation strategies are presented.

THPO022	Risk Assessment of the Chopper Dipole Kicker Magnets for the MedAustron Facility	3388
	T. Kramer, T. Stadlbauer EBG MedAustron, Wr. Neustadt, Austria M.J. Barnes, M. Benedikt, T. Fowler CERN, Geneva, Switzerland
	The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and ions for both cancer therapy and research. Different types of kicker magnets will be used in the facility, including fast beam chopper dipoles: these allow the beam to be switched on and off for routine operational reasons or in case of emergency. One of the main requirements for the beam chopper system is reliability. A criticality analysis, to chart the probability of failure modes against the severity of their consequences of the fault, has been carried out for the chopper dipole system. This “Failure Mode, Effects, and Criticality Analysis” (FMECA), has been used to highlight failure modes with relatively high probability and severity of consequences: conservative ratings of critical components and appropriate redundancy, together with measurements and interlocks, have been used to reduce the probability and criticality of faults. This paper presents the results of the FMECA.

THPO032	Preliminary Design of an Inductive Adder for CLIC Damping Rings	3409
	J. Holma, M.J. Barnes CERN, Geneva, Switzerland
	The Compact Linear Collider (CLIC) study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC damping rings will produce ultra-low emittance, with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse power modulators for the damping rings kickers must provide extremely flat, high-voltage pulses: specifications call for a 160 ns duration flattop of 12.5 kV, 250 A, with a combined ripple and droop of not more than ±0.02 %. A solid-state modulator, the inductive adder, is a very promising approach to meeting the demanding specifications; this topology allows the use of both digital and analogue modulation. To effectively use modulation techniques to achieve such low ripple and droop requires an in-depth knowledge of the behaviour of the solid-state switching components and their gate drivers, as well as a good understanding of the overall circuit behaviour. This paper describes the initial design of the inductive adder.

THPO033	Calculation of Metallization Resistivity and Thickness for MedAustron Kicker Systems	3412
	M.J. Barnes CERN, Geneva, Switzerland T. Kramer, T. Stadlbauer EBG MedAustron, Wr. Neustadt, Austria
	The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and ions for both cancer therapy and research. Different types of kicker magnets will be used in the facility. The kicker magnets are outside machine vacuum: each kicker magnet has a ceramic beam chamber whose inner surface is metallized. The resistivity and thickness of the metallization are chosen such that the induced eddy currents, resulting from the pulsed kicker magnetic field, do not unduly affect the rise/fall times or homogeneity of the magnetic field. A comparison of an analytical calculation and measurement is reported for the effect of metallization of the ceramic beam chamber of an existing kicker system at CERN. For a MedAustron kicker the result of an analytical calculation is compared with predictions from electromagnetic simulations: conclusions concerning the metallization of the ceramic beam chambers, for the MedAustron kicker magnets, are presented.

Paper

Title

Page

Coaxial Wire Measurements of Ferrite Kicker Magnets

784

H.A. Day, R.M. Jones
UMAN, Manchester, United Kingdom
M.J. Barnes, F. Caspers, H.A. Day, E. Métral, B. Salvant, C. Zannini
CERN, Geneva, Switzerland

Fast kicker magnets are used to inject beam into and eject beam out of the CERN accelerator rings. These kickers are generally transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the yoke can provoke significant beam induced heating, especially for high intensities. In addition the impedance may contribute to beam instabilities. The results of longitudinal and transverse impedance measurements, for various kicker magnets, are presented and compared with analytical calculations: in addition predictions from a numerical analysis are discussed.

TUPC011

Striplines for CLIC Pre-Damping and Damping Rings*

1012

C. Belver-Aguilar, A. Faus-Golfe
IFIC, Valencia, Spain
M.J. Barnes, G. Rumolo
CERN, Geneva, Switzerland
F. Toral
CIEMAT, Madrid, Spain
C. Zannini
EPFL, Lausanne, Switzerland

The Compact Linear Collider (CLIC) study explores the scheme for an electron-positron collider with high luminosity and a nominal center-of-mass energy of 3 TeV: CLIC would complement LHC physics in the multi-TeV range. The CLIC design relies on the presence of Pre-Damping Rings (PDR) and Damping Rings (DR) to achieve, through synchrotron radiation, the very low emittance needed to fulfil the luminosity requirements. The specifications for the kicker systems are very challenging and include very low beam coupling impedance and excellent field homogeneity: striplines have been chosen for the kicker elements. Analytical calculations have been carried out to determine the effect of tapering upon the high frequency beam coupling impedance. In addition detailed numerical modeling of the field homogeneity has been performed and the sensitivity of the homogeneity to various parameters, including stripline cross-section, has been studied. This paper presents the main conclusions of the beam impedance calculations and field homogeneity predictions.

TUPC137

UFOs in the LHC

1347

T. Baer, M.J. Barnes, B. Goddard, E.B. Holzer, J.M. Jimenez, A. Lechner, V. Mertens, E. Nebot Del Busto, A. Nordt, J.A. Uythoven, B. Velghe, J. Wenninger, F. Zimmermann
CERN, Geneva, Switzerland

One of the major known limitations for the performance of the Large Hadron Collider are so called UFOs (”Unidentified Falling Objects”). UFOs were first observed in July 2010 and have since caused numerous protection beam dumps. UFOs are thought to be micrometer sized dust particles which lead to fast beam losses with a duration of about 10 turns when they interact with the beam. In 2011, the diagnostics for such events was significantly improved which allows estimates of the properties, dynamics and production mechanisms of the dust particles. The state of knowledge and mitigation strategies are presented.

THPO022

Risk Assessment of the Chopper Dipole Kicker Magnets for the MedAustron Facility

3388

T. Kramer, T. Stadlbauer
EBG MedAustron, Wr. Neustadt, Austria
M.J. Barnes, M. Benedikt, T. Fowler
CERN, Geneva, Switzerland

The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and ions for both cancer therapy and research. Different types of kicker magnets will be used in the facility, including fast beam chopper dipoles: these allow the beam to be switched on and off for routine operational reasons or in case of emergency. One of the main requirements for the beam chopper system is reliability. A criticality analysis, to chart the probability of failure modes against the severity of their consequences of the fault, has been carried out for the chopper dipole system. This “Failure Mode, Effects, and Criticality Analysis” (FMECA), has been used to highlight failure modes with relatively high probability and severity of consequences: conservative ratings of critical components and appropriate redundancy, together with measurements and interlocks, have been used to reduce the probability and criticality of faults. This paper presents the results of the FMECA.

THPO032

Preliminary Design of an Inductive Adder for CLIC Damping Rings

3409

J. Holma, M.J. Barnes
CERN, Geneva, Switzerland

The Compact Linear Collider (CLIC) study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC damping rings will produce ultra-low emittance, with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse power modulators for the damping rings kickers must provide extremely flat, high-voltage pulses: specifications call for a 160 ns duration flattop of 12.5 kV, 250 A, with a combined ripple and droop of not more than ±0.02 %. A solid-state modulator, the inductive adder, is a very promising approach to meeting the demanding specifications; this topology allows the use of both digital and analogue modulation. To effectively use modulation techniques to achieve such low ripple and droop requires an in-depth knowledge of the behaviour of the solid-state switching components and their gate drivers, as well as a good understanding of the overall circuit behaviour. This paper describes the initial design of the inductive adder.

THPO033

Calculation of Metallization Resistivity and Thickness for MedAustron Kicker Systems

3412

M.J. Barnes
CERN, Geneva, Switzerland
T. Kramer, T. Stadlbauer
EBG MedAustron, Wr. Neustadt, Austria

The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and ions for both cancer therapy and research. Different types of kicker magnets will be used in the facility. The kicker magnets are outside machine vacuum: each kicker magnet has a ceramic beam chamber whose inner surface is metallized. The resistivity and thickness of the metallization are chosen such that the induced eddy currents, resulting from the pulsed kicker magnetic field, do not unduly affect the rise/fall times or homogeneity of the magnetic field. A comparison of an analytical calculation and measurement is reported for the effect of metallization of the ceramic beam chamber of an existing kicker system at CERN. For a MedAustron kicker the result of an analytical calculation is compared with predictions from electromagnetic simulations: conclusions concerning the metallization of the ceramic beam chambers, for the MedAustron kicker magnets, are presented.