HB2014 - List of Authors (Argyropoulos, T.)

Paper

Title

Page

Upgrades of the RF Systems in the LHC Injector Complex

165

H. Damerau, M.E. Angoletta, T. Argyropoulos, P. Baudrenghien, A. Blas, T. Bohl, A.C. Butterworth, A. Findlay, R. Garoby, S.S. Gilardoni, S. Hancock, W. Höfle, J.C. Molendijk, E. Montesinos, M.M. Paoluzzi, D. Perrelet, C. Rossi, E.N. Shaposhnikova
CERN, Geneva, Switzerland

In the framework of the LHC Injector Upgrade (LIU) project the radio-frequency (RF) systems of the synchrotrons in the LHC injector chain will undergo significant improvements to reach the high beam intensity and quality required by the High-Luminosity (HL) LHC. Following the recent upgrade of the longitudinal beam control system in the PS Booster (PSB), tests with Finemet cavities are being performed in view of a complete replacement of the existing RF systems in the PSB by ones based on this technology. In the PS a similar wide-band Finemet cavity has been installed as a longitudinal damper. New 1-turn delay feedbacks on the main accelerating cavities to reduce their impedance have also been commissioned. Additional feedback and beam control improvements are foreseen. A major upgrade of the main RF system in the SPS by regrouping sections of its travelling wave cavities, increasing the number of cavities from four to six, will reduce beam-loading and allow higher intensities to be accelerated. The upgrade includes the installation of two new RF power plants and new feedback systems. All upgrades will be evaluated with respect to their expected benefits for the beams to the LHC.

Slides TUO1AB02 [4.317 MB]

THO4LR01

Longitudinal Microwave Instability in a Multi-RF System

404

T. Argyropoulos
CERN, Geneva, Switzerland

The longitudinal microwave instability is observed as a fast increase of the bunch length above some threshold intensity. Recently, this type of instability was seen for a single proton bunch at high energies in the CERN SPS and is proven to be one of the limitations for an intensity increase required by the HL-LHC project. In this paper a theoretical approach to the analysis of the microwave instability is verified by particle simulations. The study is applied to the SPS and is based on the current SPS impedance model. Finally, the effect of the 4th harmonic RF system on the microwave instability threshold is investigated as well.

Slides THO4LR01 [0.855 MB]

THO4LR02

Synchrotron Frequency Shift as a Probe of the CERN SPS Reactive Impedance

409

A. Lasheen, T. Argyropoulos, J.V. Campelo, J.F. Esteban Müller, D. Quartullo, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland

Longitudinal instability in the CERN SPS is a serious limitation for the future increase of bunch intensity required by HiLumi LHC project. The impedance driving this instability is not known precisely and a lot of effort goes into creating an accurate impedance model. The reactive impedance of the machine can be probed by measuring the bunch length oscillations of a mismatched bunch at injection. The frequency of these oscillations as a function of intensity has a slope that depends on the reactive impedance and the emittance. Measurements were done for three values of longitudinal emittances and then compared with particle simulations based on the impedance model using particle distribution close to the measured one. Comparison of measured and calculated frequency shifts gives an estimation of the missing impedance in the model. In addition, scanning of initial emittance for diverse particle distributions in simulations shows that the frequency shift greatly depends on emittance and initial distribution. Small variations of these parameters can lead to very different results and explain partially the discrepancy between measured and calculated values of frequency shifts.

Slides THO4LR02 [1.499 MB]

Paper	Title	Page
TUO1AB02	Upgrades of the RF Systems in the LHC Injector Complex	165
	H. Damerau, M.E. Angoletta, T. Argyropoulos, P. Baudrenghien, A. Blas, T. Bohl, A.C. Butterworth, A. Findlay, R. Garoby, S.S. Gilardoni, S. Hancock, W. Höfle, J.C. Molendijk, E. Montesinos, M.M. Paoluzzi, D. Perrelet, C. Rossi, E.N. Shaposhnikova CERN, Geneva, Switzerland
	In the framework of the LHC Injector Upgrade (LIU) project the radio-frequency (RF) systems of the synchrotrons in the LHC injector chain will undergo significant improvements to reach the high beam intensity and quality required by the High-Luminosity (HL) LHC. Following the recent upgrade of the longitudinal beam control system in the PS Booster (PSB), tests with Finemet cavities are being performed in view of a complete replacement of the existing RF systems in the PSB by ones based on this technology. In the PS a similar wide-band Finemet cavity has been installed as a longitudinal damper. New 1-turn delay feedbacks on the main accelerating cavities to reduce their impedance have also been commissioned. Additional feedback and beam control improvements are foreseen. A major upgrade of the main RF system in the SPS by regrouping sections of its travelling wave cavities, increasing the number of cavities from four to six, will reduce beam-loading and allow higher intensities to be accelerated. The upgrade includes the installation of two new RF power plants and new feedback systems. All upgrades will be evaluated with respect to their expected benefits for the beams to the LHC.
	Slides TUO1AB02 [4.317 MB]

THO4LR01	Longitudinal Microwave Instability in a Multi-RF System	404
	T. Argyropoulos CERN, Geneva, Switzerland
	The longitudinal microwave instability is observed as a fast increase of the bunch length above some threshold intensity. Recently, this type of instability was seen for a single proton bunch at high energies in the CERN SPS and is proven to be one of the limitations for an intensity increase required by the HL-LHC project. In this paper a theoretical approach to the analysis of the microwave instability is verified by particle simulations. The study is applied to the SPS and is based on the current SPS impedance model. Finally, the effect of the 4th harmonic RF system on the microwave instability threshold is investigated as well.
	Slides THO4LR01 [0.855 MB]

THO4LR02	Synchrotron Frequency Shift as a Probe of the CERN SPS Reactive Impedance	409
	A. Lasheen, T. Argyropoulos, J.V. Campelo, J.F. Esteban Müller, D. Quartullo, E.N. Shaposhnikova, H. Timko CERN, Geneva, Switzerland
	Longitudinal instability in the CERN SPS is a serious limitation for the future increase of bunch intensity required by HiLumi LHC project. The impedance driving this instability is not known precisely and a lot of effort goes into creating an accurate impedance model. The reactive impedance of the machine can be probed by measuring the bunch length oscillations of a mismatched bunch at injection. The frequency of these oscillations as a function of intensity has a slope that depends on the reactive impedance and the emittance. Measurements were done for three values of longitudinal emittances and then compared with particle simulations based on the impedance model using particle distribution close to the measured one. Comparison of measured and calculated frequency shifts gives an estimation of the missing impedance in the model. In addition, scanning of initial emittance for diverse particle distributions in simulations shows that the frequency shift greatly depends on emittance and initial distribution. Small variations of these parameters can lead to very different results and explain partially the discrepancy between measured and calculated values of frequency shifts.
	Slides THO4LR02 [1.499 MB]