IPAC2011 - List of Authors (Schmidt, R.)

Paper	Title	Page
TUPS070	An Experiment at HiRadMat: Irradiation of High-Z Materials	1698
	J. Blanco, C. Maglioni, R. Schmidt CERN, Geneva, Switzerland N.A. Tahir GSI, Darmstadt, Germany
	Calculations of the impact of dense high intensity proton beams at SPS and LHC into material have been presented in several papers,,*. This paper presents the plans for an experiment to validate the theoretical results with experimental data. The experiment will be performed at the High Radiation to Materials (HiRadMat) facility at the CERN-SPS. The HiRadMat facility is dedicated to shock beam impact experiments. It allows testing of accelerator components with respect to the impact of high-intensity pulsed beams. It will provide a 440 GeV proton beam with a focal size down to 0.1 mm, thus providing very dense beam (energy/cross section). The transversal profile of the beam is considered to be Gaussian with a tunable σ from 0.1 mm to 2 mm. This facility will allow to study “high energy density” physics as the energy density will be high enough to create strong coupled plasma in the core of high-Z materials (copper, tungsten) and to produce strong enough shock waves to create a density depletion channel along the beam axis (tunneling effect). The paper introduces the layout of the experiment and the monitoring system to detect tunneling of protons through the target. N.A.Tahir et al. HB2010 Proc., Morschach, Switzerland. N.A.Tahir et al. NIMA 606(1-2) 2009 186. * N.A.Tahir et al. 11th EPAC, Genoa, Italy, 2008, WEPP073.

TUPS071	Performance of the Protection System for Superconducting Circuits during LHC Operation	1701
	R. Denz, Z. Charifoulline, K. Dahlerup-Petersen, R. Schmidt, A.P. Siemko, J. Steckert CERN, Geneva, Switzerland
	The protection system for superconducting magnets and bus-bars is an essential part of the LHC machine protection and ensures the integrity of substantial elements of the accelerator. Due to the large amount of hardwired and software interlock channels the dependability of the system is a critical parameter for the successful exploitation of the LHC. The paper will report on observed failure modes, present fault statistics and discuss the overall performance of the protection system during LHC operation in 2010 and 2011. Foreseen measures for further improvements and operational results obtained with already implemented system upgrades will be described.

WEPC174	A Failure Catalogue for the LHC	2394
	S. Wagner, R. Schmidt, B. Todd, J.A. Uythoven, M. Zerlauth CERN, Geneva, Switzerland
	The LHC, with a stored energy of more than 360 MJ per beam, requires a complex machine protection system to prevent equipment damage. The system was designed based on a large number of possible failures in the subsystems and operational phases of the LHC. This led to a mixed system with active and passive protection. The active part monitors many thousand parameters (such as beam losses, temperatures in superconducting magnets, power converter currents, etc.) and triggers a beam dump in case a failure is detected. The passive part includes protection elements like collimators and beam absorbers to ensure the prevention of damage in case of single turn beam losses (e.g. during beam transfer and injection). So far, the knowledge of the possible failures is distributed over the different teams involved in the design, construction and operation of the LHC. A newly started project aims at bringing together this knowledge in a common failure catalogue. The chosen approach in addition is expected to allow for the identification of failures that might not have been considered yet or that require further measures. This paper introduces the approach and presents the first experience.

WEPC175	FLUKA Studies of the Asynchronous Beam Dump Effects on LHC Point 6	2397
	R. Versaci, V. Boccone, B. Goddard, A. Mereghetti, R. Schmidt, V. Vlachoudis CERN, Geneva, Switzerland
	The LHC is a record-breaking machine for beam energy and intensity. An intense effort has therefore been deployed in simulating critical operational scenarios of energy deposition. FLUKA is the most widely used code for this kind of simulations at CERN because of the high reliability of its results and the ease to custom detailed simulations all along hundreds of meters of beam line. We have investigated the effects of an asynchronous beam dump on the LHC Point 6 where, beams with a stored energy of 360 MJ, can instantaneously release up to a few J cm^-3 in the cryogenic magnets which have a quench limit of the order of the mJ cm^-3. In the present paper we will briefly introduce FLUKA, describe the simulation approach, and discuss the evaluated maximum energy release onto the superconducting magnets during an asynchronous beam dump. We will then analyse the shielding provided by collimators installed in the area and discuss safety limits for the operation of the LHC.

TUPC136	Analysis of Fast Losses in the LHC with the BLM System	1344
	E. Nebot Del Busto, T. Baer, B. Dehning, E. Effinger, J. Emery, E.B. Holzer, A. Marsili, A. Nordt, M. Sapinski, R. Schmidt, B. Velghe, J. Wenninger, C. Zamantzas, F. Zimmermann CERN, Geneva, Switzerland N. Fuster Valencia University, Atomic Molecular and Nuclear Physics Department, Valencia, Spain Z. Yang EPFL, Lausanne, Switzerland
	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 us 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. During the 2010 run, a limiting factor in the machine availability were sudden losses appearing around the ring on the ms time scale and detected exclusively by the BLM system. It is believed that such losses originate from dust particles falling into the beam, or being attracted by its strong electromagnetic field. This document describes some of the properties of these "Unidentified Falling Objects" (UFOs) putting special emphasis on their dependence on beam parameters (energy, intensity, etc). The subsequent modification of the BLM beam abort thresholds for the 2011 run that were made to avoid unnecessary beam dumps caused by these UFO losses are also discussed.

THPS088	LHC Beam Impact on Materials Considering the Time Structure of the Beam	3639
	N.A. Tahir GSI, Darmstadt, Germany J. Blanco, R. Schmidt CERN, Geneva, Switzerland R. Piriz Universidad de Castilla-La Mancha, Ciudad Real, Spain A. Shutov IPCP, Chernogolovka, Moscow region, Russia
	The LHC is the world's largest and highest energy accelerator. Two counter-rotating beams can be accelerated up to 7 TeV and kept colliding for several hours. The energy stored in each beam is up to 362MJ, enough to melt 500 kg of copper. A fast loss of a small fraction of the beam can cause damage to a superconducting coil in a magnet. Primary beam collimators, one of the most robust parts of the machine protection, can be damaged with about 5% of the beam. An accident involving the entire beam is very unlikely but cannot be fully excluded. Understanding the consequences of such accidents is fundamental for the machine protection. Detailed numerical simulations have been carried out to assess the damage caused by full LHC beam impact on solid Cu and C cylinders. The energy loss of the protons is calculated with the FLUKA code and this data is used as input to a 2D hydrodynamic code BIG2, to study the thermodynamic and hydrodynamic response of the material. Since the target parameters change substantially during the time of impact, a new approach of running the two codes iteratively, has been developed. In this paper the results are presented and compared with the previous studies.

Paper

Title

Page

An Experiment at HiRadMat: Irradiation of High-Z Materials

1698

J. Blanco, C. Maglioni, R. Schmidt
CERN, Geneva, Switzerland
N.A. Tahir
GSI, Darmstadt, Germany

Calculations of the impact of dense high intensity proton beams at SPS and LHC into material have been presented in several papers*,**,***. This paper presents the plans for an experiment to validate the theoretical results with experimental data. The experiment will be performed at the High Radiation to Materials (HiRadMat) facility at the CERN-SPS. The HiRadMat facility is dedicated to shock beam impact experiments. It allows testing of accelerator components with respect to the impact of high-intensity pulsed beams. It will provide a 440 GeV proton beam with a focal size down to 0.1 mm, thus providing very dense beam (energy/cross section). The transversal profile of the beam is considered to be Gaussian with a tunable σ from 0.1 mm to 2 mm. This facility will allow to study “high energy density” physics as the energy density will be high enough to create strong coupled plasma in the core of high-Z materials (copper, tungsten) and to produce strong enough shock waves to create a density depletion channel along the beam axis (tunneling effect). The paper introduces the layout of the experiment and the monitoring system to detect tunneling of protons through the target.
* N.A.Tahir et al. HB2010 Proc., Morschach, Switzerland.
** N.A.Tahir et al. NIMA 606(1-2) 2009 186.
*** N.A.Tahir et al. 11th EPAC, Genoa, Italy, 2008, WEPP073.

TUPS071

Performance of the Protection System for Superconducting Circuits during LHC Operation

1701

R. Denz, Z. Charifoulline, K. Dahlerup-Petersen, R. Schmidt, A.P. Siemko, J. Steckert
CERN, Geneva, Switzerland

The protection system for superconducting magnets and bus-bars is an essential part of the LHC machine protection and ensures the integrity of substantial elements of the accelerator. Due to the large amount of hardwired and software interlock channels the dependability of the system is a critical parameter for the successful exploitation of the LHC. The paper will report on observed failure modes, present fault statistics and discuss the overall performance of the protection system during LHC operation in 2010 and 2011. Foreseen measures for further improvements and operational results obtained with already implemented system upgrades will be described.

WEPC174

A Failure Catalogue for the LHC

2394

S. Wagner, R. Schmidt, B. Todd, J.A. Uythoven, M. Zerlauth
CERN, Geneva, Switzerland

The LHC, with a stored energy of more than 360 MJ per beam, requires a complex machine protection system to prevent equipment damage. The system was designed based on a large number of possible failures in the subsystems and operational phases of the LHC. This led to a mixed system with active and passive protection. The active part monitors many thousand parameters (such as beam losses, temperatures in superconducting magnets, power converter currents, etc.) and triggers a beam dump in case a failure is detected. The passive part includes protection elements like collimators and beam absorbers to ensure the prevention of damage in case of single turn beam losses (e.g. during beam transfer and injection). So far, the knowledge of the possible failures is distributed over the different teams involved in the design, construction and operation of the LHC. A newly started project aims at bringing together this knowledge in a common failure catalogue. The chosen approach in addition is expected to allow for the identification of failures that might not have been considered yet or that require further measures. This paper introduces the approach and presents the first experience.

WEPC175

FLUKA Studies of the Asynchronous Beam Dump Effects on LHC Point 6

2397

R. Versaci, V. Boccone, B. Goddard, A. Mereghetti, R. Schmidt, V. Vlachoudis
CERN, Geneva, Switzerland

The LHC is a record-breaking machine for beam energy and intensity. An intense effort has therefore been deployed in simulating critical operational scenarios of energy deposition. FLUKA is the most widely used code for this kind of simulations at CERN because of the high reliability of its results and the ease to custom detailed simulations all along hundreds of meters of beam line. We have investigated the effects of an asynchronous beam dump on the LHC Point 6 where, beams with a stored energy of 360 MJ, can instantaneously release up to a few J cm^-3 in the cryogenic magnets which have a quench limit of the order of the mJ cm^-3. In the present paper we will briefly introduce FLUKA, describe the simulation approach, and discuss the evaluated maximum energy release onto the superconducting magnets during an asynchronous beam dump. We will then analyse the shielding provided by collimators installed in the area and discuss safety limits for the operation of the LHC.

TUPC136

Analysis of Fast Losses in the LHC with the BLM System

1344

E. Nebot Del Busto, T. Baer, B. Dehning, E. Effinger, J. Emery, E.B. Holzer, A. Marsili, A. Nordt, M. Sapinski, R. Schmidt, B. Velghe, J. Wenninger, C. Zamantzas, F. Zimmermann
CERN, Geneva, Switzerland
N. Fuster
Valencia University, Atomic Molecular and Nuclear Physics Department, Valencia, Spain
Z. Yang
EPFL, Lausanne, Switzerland

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 us 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. During the 2010 run, a limiting factor in the machine availability were sudden losses appearing around the ring on the ms time scale and detected exclusively by the BLM system. It is believed that such losses originate from dust particles falling into the beam, or being attracted by its strong electromagnetic field. This document describes some of the properties of these "Unidentified Falling Objects" (UFOs) putting special emphasis on their dependence on beam parameters (energy, intensity, etc). The subsequent modification of the BLM beam abort thresholds for the 2011 run that were made to avoid unnecessary beam dumps caused by these UFO losses are also discussed.

THPS088

LHC Beam Impact on Materials Considering the Time Structure of the Beam

3639

N.A. Tahir
GSI, Darmstadt, Germany
J. Blanco, R. Schmidt
CERN, Geneva, Switzerland
R. Piriz
Universidad de Castilla-La Mancha, Ciudad Real, Spain
A. Shutov
IPCP, Chernogolovka, Moscow region, Russia

The LHC is the world's largest and highest energy accelerator. Two counter-rotating beams can be accelerated up to 7 TeV and kept colliding for several hours. The energy stored in each beam is up to 362MJ, enough to melt 500 kg of copper. A fast loss of a small fraction of the beam can cause damage to a superconducting coil in a magnet. Primary beam collimators, one of the most robust parts of the machine protection, can be damaged with about 5% of the beam. An accident involving the entire beam is very unlikely but cannot be fully excluded. Understanding the consequences of such accidents is fundamental for the machine protection. Detailed numerical simulations have been carried out to assess the damage caused by full LHC beam impact on solid Cu and C cylinders. The energy loss of the protons is calculated with the FLUKA code and this data is used as input to a 2D hydrodynamic code BIG2, to study the thermodynamic and hydrodynamic response of the material. Since the target parameters change substantially during the time of impact, a new approach of running the two codes iteratively, has been developed. In this paper the results are presented and compared with the previous studies.