IPAC2012 - List of Authors (Dehning, B.)

Paper

Title

Page

Study of the Response of Low Pressure Ionisation Chambers

888

E. Nebot Del Busto, B. Dehning, E. Effinger, V. Grishin, J.F. Herranz Alvarez
CERN, Geneva, Switzerland

The Beam Loss Monitoring System (BLM) of the Large Hadron Collider (LHC) is based on parallel plate Ionization Chambers (IC) with active volume ~1.5l and a nitrogen filling gas at 0.1 bar overpressure. At the largest loss locations, the ICs generate signals large enough to saturate the read-out electronics. A reduction of the active volume and filling pressure in the ICs would decrease the amount of charge collected in the electrodes, and so provide a higher saturation limit using the same electroncis. This makes Little Ionization Chambers (LIC) filled with both reduced pressure and active volume a good candidate for these high radiation areas. In this contribution we present measurements performed with several LIC monitors with reduced active volume and various filling pressures. These detectors were tested under various conditions with different beam setups, with standard LHC ICs used for calibration purposes.

TUOAB02

Investigation of the Use of Silicon, Diamond and Liquid Helium Detectors for Beam Loss Measurements at 2 Kelvin

1080

C. Kurfuerst, B. Dehning, W.T. Eisel, M. Sapinski
CERN, Geneva, Switzerland
V. Eremin
IOFFE, St. Petersburg, Russia
C. Fabjan
HEPHY, Wien, Austria

At the triplet magnets, close to the interaction regions of the LHC, the current Beam Loss Monitoring (BLM) system is very sensitive to the debris from the collisions. For future beams with higher energy and higher luminosity this will lead to a situation in which the BLM system can no longer distinguish between these interaction products and quench-provoking beam losses from the primary proton beams. The solution investigated is to locate the detectors as close as possible to the superconducting coil, i.e. the element to be protected. This means putting detectors inside the cold mass of the superconducting magnets at 1.9 K. As possible candidates for such loss monitors, diamond, silicon and a liquid helium chamber have been tested in a proton beam at liquid helium temperatures. The initial promising results from these tests will be presented and discussed in this contribution.

Slides TUOAB02 [3.412 MB]

THPPR036

Quench Limit Calculations for Steady State Heat Deposits in LHC Inner Triplet Magnets

4050

D. Bocian
IFJ-PAN, Kraków, Poland
F. Cerutti, B. Dehning, A.P. Siemko
CERN, Geneva, Switzerland

In hadron colliders such as the LHC, the energy deposited in the superconductors by the particles lost from the beams or coming from the collision debris may provoke quenches detrimental to the accelerator operation. A Network Model is used to simulate the thermodynamic behavior of the superconducting magnets. In previous papers the validations of network model with measurements performed in the CERN and Fermilab magnet test facilities were presented. This model was subsequently used for thermal analysis of the current LHC inner triplet quadrupole magnets for beam energy of 3.5 TeV and 7 TeV. The detailed study of helium cooling channels efficiency for energy deposits simulated with FLUKA is presented. Some conclusions are drawn on expected inner triplet magnets quench limit.

THPPR037

Estimation of Thresholds for the Signals of the BLMs around the LHC Final Focus Triplet Magnets

4053

M. Sapinski, F. Cerutti, B. Dehning, A. Ferrari, A. Lechner, M. Mauri, A. Mereghetti
CERN, Geneva, Switzerland
C. Hoa
CEA-CENG, Grenoble, France

The Interaction Points of the Large Hadron Collider are the regions where the two circulating beams collide. Hence, the magnets the closest to any Interaction Point are exposed to an elevated radiation field due to the collision debris. In this study the signal in the Beam Loss Monitors due to the debris is estimated and compared with the measurements. In addition, the energy density in the coils and the signal in the Beam Loss Monitors at quench are estimated for various beam loss scenarios. It is shown that the Beam Loss Monitors, as presently installed on the outside of the vacuum vessel of the magnets, cannot disentangle the signals due to a localised halo loss from that of the constant signal due to the collision debris.

THPPR040

First Operational Experience with the LHC Machine Protection System when Operating with Beam Energies Beyond the 100 MJ Range

4062

M. Zerlauth, R.W. Assmann, B. Dehning, M. Ferro-Luzzi, B. Goddard, M. Lamont, R. Schmidt, A.P. Siemko, J.A. Uythoven, J. Wenninger
CERN, Geneva, Switzerland

The LHC made a remarkable progress in luminosity production during 2011 operation. This was made possible by a progressive increase of beam intensities by more than 5 orders of magnitude, reaching stored beam energies beyond 100MJ at the end of the year. The correct functioning of the machine protection systems was vital during initial operation and even more when approaching nominal beam parameters, where an uncontrolled loss of a small fraction of the beam is already sufficient to damage accelerator equipment or the large experimental detectors The machine protection system depends on the interplay of many different elements: beam dumping system, beam interlocks, beam instrumentation, equipment monitoring, collimators and absorbers, etc. The strategy applied during 2011 to allow for an efficient but yet safe increase of the beam intensities is presented along with the associated risks and drawbacks of a too aggressive approach. The experience gained with the key systems will be discussed along with possibilities to further enhance machine availability whilst maintaining the current level of safety.

Paper	Title	Page
MOPPR047	Study of the Response of Low Pressure Ionisation Chambers	888
	E. Nebot Del Busto, B. Dehning, E. Effinger, V. Grishin, J.F. Herranz Alvarez CERN, Geneva, Switzerland
	The Beam Loss Monitoring System (BLM) of the Large Hadron Collider (LHC) is based on parallel plate Ionization Chambers (IC) with active volume ~1.5l and a nitrogen filling gas at 0.1 bar overpressure. At the largest loss locations, the ICs generate signals large enough to saturate the read-out electronics. A reduction of the active volume and filling pressure in the ICs would decrease the amount of charge collected in the electrodes, and so provide a higher saturation limit using the same electroncis. This makes Little Ionization Chambers (LIC) filled with both reduced pressure and active volume a good candidate for these high radiation areas. In this contribution we present measurements performed with several LIC monitors with reduced active volume and various filling pressures. These detectors were tested under various conditions with different beam setups, with standard LHC ICs used for calibration purposes.

TUOAB02	Investigation of the Use of Silicon, Diamond and Liquid Helium Detectors for Beam Loss Measurements at 2 Kelvin	1080
	C. Kurfuerst, B. Dehning, W.T. Eisel, M. Sapinski CERN, Geneva, Switzerland V. Eremin IOFFE, St. Petersburg, Russia C. Fabjan HEPHY, Wien, Austria
	At the triplet magnets, close to the interaction regions of the LHC, the current Beam Loss Monitoring (BLM) system is very sensitive to the debris from the collisions. For future beams with higher energy and higher luminosity this will lead to a situation in which the BLM system can no longer distinguish between these interaction products and quench-provoking beam losses from the primary proton beams. The solution investigated is to locate the detectors as close as possible to the superconducting coil, i.e. the element to be protected. This means putting detectors inside the cold mass of the superconducting magnets at 1.9 K. As possible candidates for such loss monitors, diamond, silicon and a liquid helium chamber have been tested in a proton beam at liquid helium temperatures. The initial promising results from these tests will be presented and discussed in this contribution.
	Slides TUOAB02 [3.412 MB]

THPPR036	Quench Limit Calculations for Steady State Heat Deposits in LHC Inner Triplet Magnets	4050
	D. Bocian IFJ-PAN, Kraków, Poland F. Cerutti, B. Dehning, A.P. Siemko CERN, Geneva, Switzerland
	In hadron colliders such as the LHC, the energy deposited in the superconductors by the particles lost from the beams or coming from the collision debris may provoke quenches detrimental to the accelerator operation. A Network Model is used to simulate the thermodynamic behavior of the superconducting magnets. In previous papers the validations of network model with measurements performed in the CERN and Fermilab magnet test facilities were presented. This model was subsequently used for thermal analysis of the current LHC inner triplet quadrupole magnets for beam energy of 3.5 TeV and 7 TeV. The detailed study of helium cooling channels efficiency for energy deposits simulated with FLUKA is presented. Some conclusions are drawn on expected inner triplet magnets quench limit.

THPPR037	Estimation of Thresholds for the Signals of the BLMs around the LHC Final Focus Triplet Magnets	4053
	M. Sapinski, F. Cerutti, B. Dehning, A. Ferrari, A. Lechner, M. Mauri, A. Mereghetti CERN, Geneva, Switzerland C. Hoa CEA-CENG, Grenoble, France
	The Interaction Points of the Large Hadron Collider are the regions where the two circulating beams collide. Hence, the magnets the closest to any Interaction Point are exposed to an elevated radiation field due to the collision debris. In this study the signal in the Beam Loss Monitors due to the debris is estimated and compared with the measurements. In addition, the energy density in the coils and the signal in the Beam Loss Monitors at quench are estimated for various beam loss scenarios. It is shown that the Beam Loss Monitors, as presently installed on the outside of the vacuum vessel of the magnets, cannot disentangle the signals due to a localised halo loss from that of the constant signal due to the collision debris.

THPPR040	First Operational Experience with the LHC Machine Protection System when Operating with Beam Energies Beyond the 100 MJ Range	4062
	M. Zerlauth, R.W. Assmann, B. Dehning, M. Ferro-Luzzi, B. Goddard, M. Lamont, R. Schmidt, A.P. Siemko, J.A. Uythoven, J. Wenninger CERN, Geneva, Switzerland
	The LHC made a remarkable progress in luminosity production during 2011 operation. This was made possible by a progressive increase of beam intensities by more than 5 orders of magnitude, reaching stored beam energies beyond 100MJ at the end of the year. The correct functioning of the machine protection systems was vital during initial operation and even more when approaching nominal beam parameters, where an uncontrolled loss of a small fraction of the beam is already sufficient to damage accelerator equipment or the large experimental detectors The machine protection system depends on the interplay of many different elements: beam dumping system, beam interlocks, beam instrumentation, equipment monitoring, collimators and absorbers, etc. The strategy applied during 2011 to allow for an efficient but yet safe increase of the beam intensities is presented along with the associated risks and drawbacks of a too aggressive approach. The experience gained with the key systems will be discussed along with possibilities to further enhance machine availability whilst maintaining the current level of safety.