IPAC2016 - Classification: 01 Circular and Linear Colliders / T12 Beam Injection/Extraction and Transport

Paper	Title	Page
THPMW034	Review on the Effects of Characteristic Impedance Mismatching in a Stripline Kicker	3627
	C. Belver-Aguilar, M.J. Barnes, L. Ducimetière CERN, Geneva, Switzerland
	A stripline kicker operates as two coupled transmission lines, with two TEM operating modes, known as odd and even modes. The characteristic impedance of these two modes is generally different, both only tend to the same value either when the electrodes are widely separated or when the electrodes are very close to the beam pipe wall. In all other cases, the even mode characteristic impedance is always higher than the odd mode characteristic impedance. The specifications required for a kicker operating in a low emittance ring are usually very challenging. In this situation it is desirable to match the even mode characteristic impedance of the striplines to the resistance of their termination. However a mismatched odd mode impedance can significantly influence the striplines performance. This paper presents predictions for the influence of the odd mode characteristic impedance upon the contribution of each field component, electric and magnetic, to the deflection angle. In addition, the variation of the characteristic impedance and field homogeneity with frequency are presented.
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THPMW035	Considerations on an Upgrade Possibility of the LHC Beam Dump Kicker System	3631
	M.A. Fraser, W. Bartmann, C. Bracco, L. Ducimetière, B. Goddard, T. Kramer, V. Senaj CERN, Geneva, Switzerland
	The LHC Beam Dump System (LBDS) is designed to safely dispose the circulating beams over a wide range of energy from 450 GeV up to 7 TeV, where the maximum stored energy is 362 MJ per beam. One of the most critical components of the LBDS are the extraction kickers that must reliably switch on within the 3 us particle-free abort gap. To ensure this functionality, even in the event of a power-cut, the power generator capacitors remain charged and hence the Gate Turn-Off (GTO) switch stack has to hold the full voltage throughout beam operation. The increase of the LHC collision energy to 13 TeV has increased the voltage levels at the GTO stacks and during re-commissioning an increased rate of high-voltage (HV) related issues at the level of the GTO stack was observed. Different solutions have been analysed and an improved GTO stack will be implemented. This paper also outlines the benefit of adding more kicker magnets to improve the voltage hold off issues and to improve the tolerance to missing kickers during extraction.
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THPOR051	Beam Based Measurements to Check Integrity of LHC Dump Protection Elements	3908
	C. Bracco, W. Bartmann, M.A. Fraser, B. Goddard, A. Lechner CERN, Geneva, Switzerland
	LHC operation is approaching its nominal operating goals and several upgrades are also being prepared to increase the beam intensity and brightness. In case of an asynchronous beam dump at 6.5 - 7 TeV a non-negligible fraction of the stored energy (360 MJ during nominal operation) will be deposited on the protection elements (TCDQ and TCDS) located downstream of the extraction kickers. These elements are designed to protect the machine aperture from the large amplitude particles resulting from the asynchronous dump. A number of checks and measurements with beam have been worked out to verify the integrity of these elements, after a potentially harmful event, without opening the machine vacuum. Details on measurements and simulations performed to evaluate the validity of the proposed method are presented in this paper.
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THPOR052	A Beam-based Measurement of the LHC Beam Dump Kicker Waveform	3911
	M.A. Fraser, W. Bartmann, C. Bracco, E. Carlier, B. Goddard, V. Kain, N. Magnin, J.A. Uythoven, F.M. Velotti CERN, Geneva, Switzerland
	The increase of the LHC collision energy to 13 TeV after Long Shutdown 1 has doubled the operational energy range of the LHC beam dump system (LBDS) during Run 2. In preparation for the safe operation of the LHC, the waveform of the LBDS extraction kicker was measured using beam-based measurements for the first time during the machine's re-commissioning period. The measurements provide a reference for a more precise synchronisation of the dump system and abort-gap timing, and provide an independent check of the system's calibration. The precision of the beam-based technique allowed the necessary adjustments to the LBDS trigger delays to ensure the synchronous firing of the LBDS at all beam energies up to 6.5 TeV. In this paper the measurement and simulation campaign is described and the performance of the system reported.
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Paper

Title

Page

Review on the Effects of Characteristic Impedance Mismatching in a Stripline Kicker

3627

C. Belver-Aguilar, M.J. Barnes, L. Ducimetière
CERN, Geneva, Switzerland

A stripline kicker operates as two coupled transmission lines, with two TEM operating modes, known as odd and even modes. The characteristic impedance of these two modes is generally different, both only tend to the same value either when the electrodes are widely separated or when the electrodes are very close to the beam pipe wall. In all other cases, the even mode characteristic impedance is always higher than the odd mode characteristic impedance. The specifications required for a kicker operating in a low emittance ring are usually very challenging. In this situation it is desirable to match the even mode characteristic impedance of the striplines to the resistance of their termination. However a mismatched odd mode impedance can significantly influence the striplines performance. This paper presents predictions for the influence of the odd mode characteristic impedance upon the contribution of each field component, electric and magnetic, to the deflection angle. In addition, the variation of the characteristic impedance and field homogeneity with frequency are presented.

Export •

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

THPMW035

Considerations on an Upgrade Possibility of the LHC Beam Dump Kicker System

3631

M.A. Fraser, W. Bartmann, C. Bracco, L. Ducimetière, B. Goddard, T. Kramer, V. Senaj
CERN, Geneva, Switzerland

The LHC Beam Dump System (LBDS) is designed to safely dispose the circulating beams over a wide range of energy from 450 GeV up to 7 TeV, where the maximum stored energy is 362 MJ per beam. One of the most critical components of the LBDS are the extraction kickers that must reliably switch on within the 3 us particle-free abort gap. To ensure this functionality, even in the event of a power-cut, the power generator capacitors remain charged and hence the Gate Turn-Off (GTO) switch stack has to hold the full voltage throughout beam operation. The increase of the LHC collision energy to 13 TeV has increased the voltage levels at the GTO stacks and during re-commissioning an increased rate of high-voltage (HV) related issues at the level of the GTO stack was observed. Different solutions have been analysed and an improved GTO stack will be implemented. This paper also outlines the benefit of adding more kicker magnets to improve the voltage hold off issues and to improve the tolerance to missing kickers during extraction.

Export •

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

THPOR051

Beam Based Measurements to Check Integrity of LHC Dump Protection Elements

3908

C. Bracco, W. Bartmann, M.A. Fraser, B. Goddard, A. Lechner
CERN, Geneva, Switzerland

LHC operation is approaching its nominal operating goals and several upgrades are also being prepared to increase the beam intensity and brightness. In case of an asynchronous beam dump at 6.5 - 7 TeV a non-negligible fraction of the stored energy (360 MJ during nominal operation) will be deposited on the protection elements (TCDQ and TCDS) located downstream of the extraction kickers. These elements are designed to protect the machine aperture from the large amplitude particles resulting from the asynchronous dump. A number of checks and measurements with beam have been worked out to verify the integrity of these elements, after a potentially harmful event, without opening the machine vacuum. Details on measurements and simulations performed to evaluate the validity of the proposed method are presented in this paper.

Export •

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

THPOR052

A Beam-based Measurement of the LHC Beam Dump Kicker Waveform

3911

M.A. Fraser, W. Bartmann, C. Bracco, E. Carlier, B. Goddard, V. Kain, N. Magnin, J.A. Uythoven, F.M. Velotti
CERN, Geneva, Switzerland

The increase of the LHC collision energy to 13 TeV after Long Shutdown 1 has doubled the operational energy range of the LHC beam dump system (LBDS) during Run 2. In preparation for the safe operation of the LHC, the waveform of the LBDS extraction kicker was measured using beam-based measurements for the first time during the machine's re-commissioning period. The measurements provide a reference for a more precise synchronisation of the dump system and abort-gap timing, and provide an independent check of the system's calibration. The precision of the beam-based technique allowed the necessary adjustments to the LBDS trigger delays to ensure the synchronous firing of the LBDS at all beam energies up to 6.5 TeV. In this paper the measurement and simulation campaign is described and the performance of the system reported.

Export •

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