HB2012 - List of Authors (Papotti, G.)

Paper

Title

Page

Colliding High Brightness Beams in the LHC

180

T. Pieloni, X. Buffat, R. Giachino, W. Herr, E. Métral, G. Papotti
CERN, Geneva, Switzerland

The CERN-LHC is a high energy particle collider, where intense proton bunches are brought into collision. In order to achieve optimum performance, the bunches must have a high brightness, leading to strong and significant beam-beam effects. Experimental tests during the first two years of its operation have shown that beams with very high brightness can be collided head-on without detrimental effects on the beam dynamics. Such head-on collisions are therefore not expected to limit the LHC performance. Long range beam-beam interactions dominate the adverse effects on the dynamics but can profit from an increased beam brightness, in particular from small emittances. We summarize the experimental results and compare with the theoretical expectations. This allows to optimize the performance for future operation and a definition of promising upgrade scenarios.

MOP252

Measurements of the LHC Longitudinal Resistive Impedance with Beam

183

J.F. Esteban Müller, T. Argyropoulos, T. Bohl, T. Mastoridis, N. Mounet, G. Papotti, B. Salvant, E.N. Shaposhnikova, D. Valuch
CERN, Geneva, Switzerland

The resistive part of the longitudinal impedance contributes to the heat deposition on different elements in the LHC ring including the beam screens, where it has to be absorbed by the cryogenic system and can be a practical limitation for the maximum beam intensity. In this paper, we present the first measurements of the LHC longitudinal resistive impedance with beam, done through synchronous phase shift measurements during Machine Development sessions in 2012. Synchronous phase shift is measured for different bunch intensities and lengths using the high-precision LHC Beam Phase Module and then data are post-processed to further increase the accuracy. The dependence of the energy loss per particle on bunch length is then obtained and compared with the expected values found using the LHC impedance model.

WEO1C06

Measurement and Simulation of Luminosity Leveling in LHC via Beam Separation

451

S. Paret, J. Qiang
LBNL, Berkeley, California, USA
R. Alemany-Fernandez, R. Calaga, R. Giachino, W. Herr, D. Jacquet, G. Papotti, T. Pieloni, L. Ponce, M. Schaumann
CERN, Geneva, Switzerland
R. Miyamoto
ESS, Lund, Sweden

Funding: This work supported by the US LHC Accelerator Research Program and the National Energy Research Scientific Computing Center of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Leveling of the luminosity in LHC by means of separating the beams colliding at an interaction point is examined. An experiment in which the separation of the beams was stepwise increased to up to 2.5 times the beam width is presented. The luminosity at all IPs and emittance of the beams were measured to detect possible side effects of the collision with an offset. Strong-strong simulations that closely follow the experimental setup are discussed and compared with the measurements. Finally, potential alternatives for luminosity leveling are briefly described.

Slides WEO1C06 [1.031 MB]

Paper	Title	Page
MOP250	Colliding High Brightness Beams in the LHC	180
	T. Pieloni, X. Buffat, R. Giachino, W. Herr, E. Métral, G. Papotti CERN, Geneva, Switzerland
	The CERN-LHC is a high energy particle collider, where intense proton bunches are brought into collision. In order to achieve optimum performance, the bunches must have a high brightness, leading to strong and significant beam-beam effects. Experimental tests during the first two years of its operation have shown that beams with very high brightness can be collided head-on without detrimental effects on the beam dynamics. Such head-on collisions are therefore not expected to limit the LHC performance. Long range beam-beam interactions dominate the adverse effects on the dynamics but can profit from an increased beam brightness, in particular from small emittances. We summarize the experimental results and compare with the theoretical expectations. This allows to optimize the performance for future operation and a definition of promising upgrade scenarios.

MOP252	Measurements of the LHC Longitudinal Resistive Impedance with Beam	183
	J.F. Esteban Müller, T. Argyropoulos, T. Bohl, T. Mastoridis, N. Mounet, G. Papotti, B. Salvant, E.N. Shaposhnikova, D. Valuch CERN, Geneva, Switzerland
	The resistive part of the longitudinal impedance contributes to the heat deposition on different elements in the LHC ring including the beam screens, where it has to be absorbed by the cryogenic system and can be a practical limitation for the maximum beam intensity. In this paper, we present the first measurements of the LHC longitudinal resistive impedance with beam, done through synchronous phase shift measurements during Machine Development sessions in 2012. Synchronous phase shift is measured for different bunch intensities and lengths using the high-precision LHC Beam Phase Module and then data are post-processed to further increase the accuracy. The dependence of the energy loss per particle on bunch length is then obtained and compared with the expected values found using the LHC impedance model.

WEO1C06	Measurement and Simulation of Luminosity Leveling in LHC via Beam Separation	451
	S. Paret, J. Qiang LBNL, Berkeley, California, USA R. Alemany-Fernandez, R. Calaga, R. Giachino, W. Herr, D. Jacquet, G. Papotti, T. Pieloni, L. Ponce, M. Schaumann CERN, Geneva, Switzerland R. Miyamoto ESS, Lund, Sweden
	Funding: This work supported by the US LHC Accelerator Research Program and the National Energy Research Scientific Computing Center of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Leveling of the luminosity in LHC by means of separating the beams colliding at an interaction point is examined. An experiment in which the separation of the beams was stepwise increased to up to 2.5 times the beam width is presented. The luminosity at all IPs and emittance of the beams were measured to detect possible side effects of the collision with an offset. Strong-strong simulations that closely follow the experimental setup are discussed and compared with the measurements. Finally, potential alternatives for luminosity leveling are briefly described.
	Slides WEO1C06 [1.031 MB]