HB2012 - List of Authors (Schmidt, R.)

Paper

Title

Page

LHC - Challenges in Handling Beams Exceeding 100 MJ

1

R. Schmidt
CERN, Geneva, Switzerland

The Large Hadron Collider (LHC) at CERN operates at 4 TeV with high intensity beams, with bunch intensities exceeding the nominal value by several 10 %. The energy stored in each beams is beyond 130 MJ, less than a factor of three from the nominal value at 7 TeV. With these parameters, operation entered into a regime where various effects due to high intensity bunches are observed (instabilities, beam-beam effects, e-cloud effects). The highly efficient collimation system limits beam losses that threaten to quench superconducting magnets. The correct functioning of the machine protection systems is vital during the different operational phases, where already a small fraction of the stored energy is sufficient to damage accelerator equipment or experiments in case of uncontrolled beam loss. Safe operation in presence of such high intensity proton beams is guaranteed by the interplay of many different systems: beam dumping system, beam interlocks, beam instrumentation, equipment monitoring, collimators and absorbers. The experience gained with the key systems of LHC machine protection and collimation will be discussed.

Slides MOI1A01 [31.116 MB]

MOP203

Bunch-by-Bunch Beam Loss Diagnostics with Diamond Detectors at the LHC

41

M. Hempel
BTU, Cottbus, Germany
T. Baer
University of Hamburg, Hamburg, Germany
S. Bart Pedersen, B. Dehning, E. Effinger, E. Griesmayer, A. Lechner, R. Schmidt
CERN, Geneva, Switzerland
W. Lohmann
DESY, Hamburg, Germany

A main challenge in the operation with high intensity beams is managing beam losses that imply the risk of quenching superconducting magnets or even damage equipment. There are various sources of beam losses, such as losses related to injection, to beam instabilities and to UFOs (Unidentified Falling Objects). Mostly surprising in the first years of LHC operation was the observation of UFOs. They are believed to be dust particles with a typical size of 1-100 um, which lead to beam losses with a duration of about ten revolutions when they fall into the beam. 3600 BLMs (Beam Loss Monitors) are installed around the LHC ring, allowing to determinate the accurate location of UFOs. The time resolution of the BLMs is 40 us (half a turn revolution). A measurement of the beam losses with a time resolution better than the bunch spacing of 50 ns is crucial to understand loss mechanisms. Diamond sensors are able to provide such diagnostics and perform particle counting with ns time resolution. In this paper, we present measurements of various types of beam losses with diamond detectors. We also compare measurements of UFO induced beam losses around the LHC ring with results from MadX simulations.

MOP241

An Experiment on Hydrodynamic Tunnelling of the SPS High Intensity Proton Beam at the HiRadMat Facility

141

J. Blanco, F. Burkart, N. Charitonidis, I. Efthymiopoulos, D. Grenier, C. Maglioni, R. Schmidt, C. Theis, D. Wollmann
CERN, Geneva, Switzerland
E. Griesmayer
CIVIDEC Instrumentation, Wien, Austria
N.A. Tahir
GSI, Darmstadt, Germany

The LHC will collide proton beams with an energy stored in each beam of 362 MJ. To predict damage for a catastrophic failure of the protections systems, simulation studies of the impact of an LHC beam on copper targets were performed. Firstly, the energy deposition of the first bunches in a target with FLUKA is calculated. The effect of the energy deposition on the target is then calculated with a hydrodynamic code, BIG2. The impact of only a few bunches leads to a change of target density. The calculations are done iteratively in several steps and show that such beam can tunnel up to 30-35 m into a target. Similar simulations for the SPS beam also predict hydrodynamic tunnelling. An experiment at the HiRadMat (High Radiation Materials) at CERN using the proton beam from the Super Proton Synchrotron (SPS) is performed to validate the simulations. The particle energy in the SPS beam is 440 GeV and has up to 288 bunches. Significant hydrodynamic tunnelling due to hydrodynamic effects are expected. First experiments are planned for July 2012. Simulation results, the experimental setup and the outcome of the tests will be reported at this workshop.

MOP245

Quench Tests at the Large Hadron Collider with Collimation Losses at 3.5 Z TeV

157

S. Redaelli, R.W. Aßmann, G. Bellodi, K. Brodzinski, R. Bruce, F. Burkart, M. Cauchi, D. Deboy, B. Dehning, E.B. Holzer, J.M. Jowett, E. Nebot Del Busto, M. Pojer, A. Priebe, A. Rossi, M. Sapinski, M. Schaumann, R. Schmidt, M. Solfaroli Camillocci, G. Valentino, R. Versteegen, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain

The Large Hadron Collider (LHC) has been operating since 2010 at 3.5 TeV and 4.0 TeV without experiencing quenches induced by losses from circulating beams. This situation might change at 7 TeV where the reduced margins in the superconducting magnets. The critical locations are the dispersion suppressors (DSs) at either side of the cleaning and experimental insertions, where dispersive losses are maximum. It is therefore crucial to understand in detail the quench limits with beam loss distributions alike those occurring in standard operation. In order to address this aspect, quench tests were performed by inducing large beam losses on the primary collimators of the betatron cleaning insertion, for proton and lead ion beams of 3.5 Z TeV, to probe the quench limits of the DS magnets. Losses up to 500 kW were achieved without quenches. The measurement technique and the results obtained are presented, including observations of heat loads in the cryogenics system.

TUO1C04

Detection of Unidentified Falling Objects at LHC

305

E. Nebot Del Busto, T. Baer, F.V. Day, B. Dehning, E.B. Holzer, A. Lechner, R. Schmidt, J. Wenninger, C. Zamantzas, M. Zerlauth, F. Zimmermann
CERN, Geneva, Switzerland
M. Hempel
BTU, Cottbus, Germany

About 3600 Ionization Chambers are located around the LHC ring to detect beam losses that could damage the equipment or quench superconducting magnets. The BLMs integrate the losses in 12 different time intervals (from 40 μs to 83.8 s) allowing for different abort thresholds depending on the duration of the loss and the beam energy. The signals are also recorded in a database at 1 Hz for offline analysis. Since the 2010 run, a limiting factor in the machine availability occurred due to unforeseen sudden losses appearing around the ring on the ms time scale. Those were detected exclusively by the BLM system and they are the result of the interaction of macro-particles, of sizes estimated to be 1-100 microns, with the proton beams. In this document we describe the techniques employed to identify such events as well as the mitigations implemented in the BLM system to avoid unnecessary LHC downtime.

Slides TUO1C04 [6.812 MB]

FRO1B01

Summary of the Working Group on Commissioning and Operation

620

R. Schmidt
CERN, Geneva, Switzerland
M.A. Plum
ORNL, Oak Ridge, Tennessee, USA
Y. Sato
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

The Working Group D summary report focussed on answering the following issues:

observation of beam losses (e.g. time structure, other parameters,…),
reducing beam losses with operational parameters away from the design set points,
reducing beam losses (or concentrating beam losses at a few locations) using collimators,
minimizing beam losses due to beam transfer from one accelerator to the following accelerator - what parameters are important?

The issue of reducing beam losses with operational parameters away from the design set points is especially valuable as it is rarely discussed.

Slides FRO1B01 [0.426 MB]

Paper	Title	Page
MOI1A01	LHC - Challenges in Handling Beams Exceeding 100 MJ	1
	R. Schmidt CERN, Geneva, Switzerland
	The Large Hadron Collider (LHC) at CERN operates at 4 TeV with high intensity beams, with bunch intensities exceeding the nominal value by several 10 %. The energy stored in each beams is beyond 130 MJ, less than a factor of three from the nominal value at 7 TeV. With these parameters, operation entered into a regime where various effects due to high intensity bunches are observed (instabilities, beam-beam effects, e-cloud effects). The highly efficient collimation system limits beam losses that threaten to quench superconducting magnets. The correct functioning of the machine protection systems is vital during the different operational phases, where already a small fraction of the stored energy is sufficient to damage accelerator equipment or experiments in case of uncontrolled beam loss. Safe operation in presence of such high intensity proton beams is guaranteed by the interplay of many different systems: beam dumping system, beam interlocks, beam instrumentation, equipment monitoring, collimators and absorbers. The experience gained with the key systems of LHC machine protection and collimation will be discussed.
	Slides MOI1A01 [31.116 MB]

MOP203	Bunch-by-Bunch Beam Loss Diagnostics with Diamond Detectors at the LHC	41
	M. Hempel BTU, Cottbus, Germany T. Baer University of Hamburg, Hamburg, Germany S. Bart Pedersen, B. Dehning, E. Effinger, E. Griesmayer, A. Lechner, R. Schmidt CERN, Geneva, Switzerland W. Lohmann DESY, Hamburg, Germany
	A main challenge in the operation with high intensity beams is managing beam losses that imply the risk of quenching superconducting magnets or even damage equipment. There are various sources of beam losses, such as losses related to injection, to beam instabilities and to UFOs (Unidentified Falling Objects). Mostly surprising in the first years of LHC operation was the observation of UFOs. They are believed to be dust particles with a typical size of 1-100 um, which lead to beam losses with a duration of about ten revolutions when they fall into the beam. 3600 BLMs (Beam Loss Monitors) are installed around the LHC ring, allowing to determinate the accurate location of UFOs. The time resolution of the BLMs is 40 us (half a turn revolution). A measurement of the beam losses with a time resolution better than the bunch spacing of 50 ns is crucial to understand loss mechanisms. Diamond sensors are able to provide such diagnostics and perform particle counting with ns time resolution. In this paper, we present measurements of various types of beam losses with diamond detectors. We also compare measurements of UFO induced beam losses around the LHC ring with results from MadX simulations.

MOP241	An Experiment on Hydrodynamic Tunnelling of the SPS High Intensity Proton Beam at the HiRadMat Facility	141
	J. Blanco, F. Burkart, N. Charitonidis, I. Efthymiopoulos, D. Grenier, C. Maglioni, R. Schmidt, C. Theis, D. Wollmann CERN, Geneva, Switzerland E. Griesmayer CIVIDEC Instrumentation, Wien, Austria N.A. Tahir GSI, Darmstadt, Germany
	The LHC will collide proton beams with an energy stored in each beam of 362 MJ. To predict damage for a catastrophic failure of the protections systems, simulation studies of the impact of an LHC beam on copper targets were performed. Firstly, the energy deposition of the first bunches in a target with FLUKA is calculated. The effect of the energy deposition on the target is then calculated with a hydrodynamic code, BIG2. The impact of only a few bunches leads to a change of target density. The calculations are done iteratively in several steps and show that such beam can tunnel up to 30-35 m into a target. Similar simulations for the SPS beam also predict hydrodynamic tunnelling. An experiment at the HiRadMat (High Radiation Materials) at CERN using the proton beam from the Super Proton Synchrotron (SPS) is performed to validate the simulations. The particle energy in the SPS beam is 440 GeV and has up to 288 bunches. Significant hydrodynamic tunnelling due to hydrodynamic effects are expected. First experiments are planned for July 2012. Simulation results, the experimental setup and the outcome of the tests will be reported at this workshop.

MOP245	Quench Tests at the Large Hadron Collider with Collimation Losses at 3.5 Z TeV	157
	S. Redaelli, R.W. Aßmann, G. Bellodi, K. Brodzinski, R. Bruce, F. Burkart, M. Cauchi, D. Deboy, B. Dehning, E.B. Holzer, J.M. Jowett, E. Nebot Del Busto, M. Pojer, A. Priebe, A. Rossi, M. Sapinski, M. Schaumann, R. Schmidt, M. Solfaroli Camillocci, G. Valentino, R. Versteegen, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain
	The Large Hadron Collider (LHC) has been operating since 2010 at 3.5 TeV and 4.0 TeV without experiencing quenches induced by losses from circulating beams. This situation might change at 7 TeV where the reduced margins in the superconducting magnets. The critical locations are the dispersion suppressors (DSs) at either side of the cleaning and experimental insertions, where dispersive losses are maximum. It is therefore crucial to understand in detail the quench limits with beam loss distributions alike those occurring in standard operation. In order to address this aspect, quench tests were performed by inducing large beam losses on the primary collimators of the betatron cleaning insertion, for proton and lead ion beams of 3.5 Z TeV, to probe the quench limits of the DS magnets. Losses up to 500 kW were achieved without quenches. The measurement technique and the results obtained are presented, including observations of heat loads in the cryogenics system.

TUO1C04	Detection of Unidentified Falling Objects at LHC	305
	E. Nebot Del Busto, T. Baer, F.V. Day, B. Dehning, E.B. Holzer, A. Lechner, R. Schmidt, J. Wenninger, C. Zamantzas, M. Zerlauth, F. Zimmermann CERN, Geneva, Switzerland M. Hempel BTU, Cottbus, Germany
	About 3600 Ionization Chambers are located around the LHC ring to detect beam losses that could damage the equipment or quench superconducting magnets. The BLMs integrate the losses in 12 different time intervals (from 40 μs to 83.8 s) allowing for different abort thresholds depending on the duration of the loss and the beam energy. The signals are also recorded in a database at 1 Hz for offline analysis. Since the 2010 run, a limiting factor in the machine availability occurred due to unforeseen sudden losses appearing around the ring on the ms time scale. Those were detected exclusively by the BLM system and they are the result of the interaction of macro-particles, of sizes estimated to be 1-100 microns, with the proton beams. In this document we describe the techniques employed to identify such events as well as the mitigations implemented in the BLM system to avoid unnecessary LHC downtime.
	Slides TUO1C04 [6.812 MB]

FRO1B01	Summary of the Working Group on Commissioning and Operation	620
	R. Schmidt CERN, Geneva, Switzerland M.A. Plum ORNL, Oak Ridge, Tennessee, USA Y. Sato J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	The Working Group D summary report focussed on answering the following issues: observation of beam losses (e.g. time structure, other parameters,…), reducing beam losses with operational parameters away from the design set points, reducing beam losses (or concentrating beam losses at a few locations) using collimators, minimizing beam losses due to beam transfer from one accelerator to the following accelerator - what parameters are important? The issue of reducing beam losses with operational parameters away from the design set points is especially valuable as it is rarely discussed.
	Slides FRO1B01 [0.426 MB]