IPAC2012 - List of Authors (Lari, L.)

Paper	Title	Page
MOPPD077	Studies for an Alternative LHC Non-Linear Collimation System	544
	L. Lari, R.W. Assmann, V. Boccone, F. Cerutti, A. Mereghetti, R. Versaci, V. Vlachoudis CERN, Geneva, Switzerland A. Faus-Golfe, L. Lari, J. Resta-López IFIC, Valencia, Spain
	Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program. A LHC nonlinear Betatron cleaning collimation system would allow larger gap for the mechanical jaws, reducing as a consequence the collimator-induced impedance, which may limit the LHC beam intensity. In this paper, the performance of the proposed system is analyzed in terms of beam losses distribution around the LHC ring and cleaning efficiency in stable physics condition at 7TeV for Beam1. Moreover, the energy deposition distribution on the machine elements is compared to the present LHC Betatron cleaning collimation system in the Point 7 Insertion Region (IR).

MOPPD078	Accelerator Physics Study on the Effects from an Asynchronous Beam Dump in the LHC Experimental Region Collimators	547
	L. Lari, R.W. Assmann, V. Boccone, R. Bruce, F. Cerutti, A. Mereghetti, A. Rossi, V. Vlachoudis CERN, Geneva, Switzerland A. Faus-Golfe, L. Lari IFIC, Valencia, Spain
	Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program. Asynchronous beam aborts at the LHC are to be expected once per year. Accelerator physics studies of asynchronous dumps have been performed at different beam energies and beta-stars. The loss patterns are analyzed in order to identify the losses in particular on the Phase 1 Tertiary Collimators (TCT), since their Tungsten jaw insert has a low damage threshold with respect to the loss load expected. Settings for the tilt angle of the TCTs are discussed with the aim of reducing the thermal loads on the TCT themselves.

MOPPD080	Improved Robustness of the LHC Collimation System by Operating with a Jaw-beam Angle	553
	L. Lari, R.W. Assmann, A. Rossi CERN, Geneva, Switzerland M. Cauchi UoM, Msida, Malta A. Faus-Golfe, L. Lari IFIC, Valencia, Spain
	Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program. The robustness of the Phase I collimation system could be improved playing with the angular orientation of each single jaw. A preliminary study on the asymmetric misalignment of the collimator jaws, scanning through different jaw angles and varying beam sizes and energy, have been carried out, aiming at minimizing the energy deposited on metallic collimators, following an asynchronous dump.

MOPPD078	Accelerator Physics Study on the Effects from an Asynchronous Beam Dump in the LHC Experimental Region Collimators	547
	L. Lari, R.W. Assmann, V. Boccone, R. Bruce, F. Cerutti, A. Mereghetti, A. Rossi, V. Vlachoudis CERN, Geneva, Switzerland A. Faus-Golfe, L. Lari IFIC, Valencia, Spain
	Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program. Asynchronous beam aborts at the LHC are to be expected once per year. Accelerator physics studies of asynchronous dumps have been performed at different beam energies and beta-stars. The loss patterns are analyzed in order to identify the losses in particular on the Phase 1 Tertiary Collimators (TCT), since their Tungsten jaw insert has a low damage threshold with respect to the loss load expected. Settings for the tilt angle of the TCTs are discussed with the aim of reducing the thermal loads on the TCT themselves.

MOPPD079	Preliminary Thermo-Mechanical Analysis of Angular Beam Impact on LHC Collimators	550
	M. Cauchi, R.W. Assmann, A. Bertarelli, F. Carra, A. Dallocchio, D. Deboy, N. Mariani, A. Rossi CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain P. Mollicone UoM, Msida, Malta N.J. Sammut University of Malta, Faculty of Engineering, Msida, Malta
	Funding: This work is supported by EuCARD. The correct functioning of the LHC collimation system is crucial to attain the desired LHC luminosity performance. However, the requirements to handle high intensity beams can be demanding. In this respect, accident scenarios must be well studied in order to assess if the collimator design is robust against likely error scenarios. One of the catastrophic - though not very probable - accident scenarios identified is an asynchronous beam dump coupled with slight angular misalignment errors of the collimator jaw. Previous work presented a preliminary thermal evaluation of the extent of beam-induced damage for such scenarios, where it was shown that in some cases, a tilt of the jaw could actually serve to mitigate the effect of an asynchronous dump on the collimators. This paper will further analyze the response of tertiary collimators in presence of such angular jaw alignments, with the aim to identify optimal operational conditions.

MOPPD080	Improved Robustness of the LHC Collimation System by Operating with a Jaw-beam Angle	553
	L. Lari, R.W. Assmann, A. Rossi CERN, Geneva, Switzerland M. Cauchi UoM, Msida, Malta A. Faus-Golfe, L. Lari IFIC, Valencia, Spain
	Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program. The robustness of the Phase I collimation system could be improved playing with the angular orientation of each single jaw. A preliminary study on the asymmetric misalignment of the collimator jaws, scanning through different jaw angles and varying beam sizes and energy, have been carried out, aiming at minimizing the energy deposited on metallic collimators, following an asynchronous dump.

TUPPR097	Modeling and Simulation of LHC Beam-Based Collimator Setup	2059
	G. Valentino, N.J. Sammut University of Malta, Information and Communication Technology, Msida, Malta R.W. Assmann, F. Burkart, S. Redaelli, A. Rossi, D. Wollmann CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain
	In the 2011 Large Hadron Collider run, collimators were aligned for proton and heavy ion beams using a semi-automatic setup algorithm. The algorithm provided a reduction in the beam time required for setup, an elimination of beam dumps during setup and higher accuracy with respect to manual alignment. A collimator setup simulator was developed based on a Gaussian model of the beam distribution as well as a parametric model of the beam losses. A time-varying beam loss signal can be simulated for a given collimator movement into the beam. The simulation results and comparison to measurement data obtained during collimator setups and dedicated fills for beam halo scraping are presented. The simulator will then be used to develop a fully automatic collimator alignment algorithm.

TUPPR098	Comparison of LHC Collimator Beam-Based Alignment Centers to BPM-Interpolated Centers	2062
	G. Valentino, N.J. Sammut University of Malta, Information and Communication Technology, Msida, Malta R.W. Assmann, R. Bruce, G.J. Müller, S. Redaelli, A. Rossi, G. Valentino CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain
	The beam centers at the Large Hadron Collider collimators are determined by beam-based alignment, where both jaws of a collimator are moved in separately until a loss spike is detected on a Beam Loss Monitor downstream. Orbit drifts of more than a few hundred micrometers cannot be tolerated, as they would reduce the efficiency of the collimation system. Beam Position Monitors (BPMs) are installed at various locations around the LHC ring, and a linear interpolation of the orbit can be obtained at the collimator positions. In this paper, the results obtained from beam-based alignment are compared with the orbit interpolated from the BPM data throughout the 2011 LHC proton run. The stability of the orbit determined by collimator alignment during the run is evaluated.

Paper

Title

Page

Studies for an Alternative LHC Non-Linear Collimation System

544

L. Lari, R.W. Assmann, V. Boccone, F. Cerutti, A. Mereghetti, R. Versaci, V. Vlachoudis
CERN, Geneva, Switzerland
A. Faus-Golfe, L. Lari, J. Resta-López
IFIC, Valencia, Spain

Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program.
A LHC nonlinear Betatron cleaning collimation system would allow larger gap for the mechanical jaws, reducing as a consequence the collimator-induced impedance, which may limit the LHC beam intensity. In this paper, the performance of the proposed system is analyzed in terms of beam losses distribution around the LHC ring and cleaning efficiency in stable physics condition at 7TeV for Beam1. Moreover, the energy deposition distribution on the machine elements is compared to the present LHC Betatron cleaning collimation system in the Point 7 Insertion Region (IR).

MOPPD078

Accelerator Physics Study on the Effects from an Asynchronous Beam Dump in the LHC Experimental Region Collimators

547

L. Lari, R.W. Assmann, V. Boccone, R. Bruce, F. Cerutti, A. Mereghetti, A. Rossi, V. Vlachoudis
CERN, Geneva, Switzerland
A. Faus-Golfe, L. Lari
IFIC, Valencia, Spain

Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program.
Asynchronous beam aborts at the LHC are to be expected once per year. Accelerator physics studies of asynchronous dumps have been performed at different beam energies and beta-stars. The loss patterns are analyzed in order to identify the losses in particular on the Phase 1 Tertiary Collimators (TCT), since their Tungsten jaw insert has a low damage threshold with respect to the loss load expected. Settings for the tilt angle of the TCTs are discussed with the aim of reducing the thermal loads on the TCT themselves.

MOPPD080

Improved Robustness of the LHC Collimation System by Operating with a Jaw-beam Angle

553

L. Lari, R.W. Assmann, A. Rossi
CERN, Geneva, Switzerland
M. Cauchi
UoM, Msida, Malta
A. Faus-Golfe, L. Lari
IFIC, Valencia, Spain

Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program.
The robustness of the Phase I collimation system could be improved playing with the angular orientation of each single jaw. A preliminary study on the asymmetric misalignment of the collimator jaws, scanning through different jaw angles and varying beam sizes and energy, have been carried out, aiming at minimizing the energy deposited on metallic collimators, following an asynchronous dump.

MOPPD078

Accelerator Physics Study on the Effects from an Asynchronous Beam Dump in the LHC Experimental Region Collimators

547

L. Lari, R.W. Assmann, V. Boccone, R. Bruce, F. Cerutti, A. Mereghetti, A. Rossi, V. Vlachoudis
CERN, Geneva, Switzerland
A. Faus-Golfe, L. Lari
IFIC, Valencia, Spain

Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program.
Asynchronous beam aborts at the LHC are to be expected once per year. Accelerator physics studies of asynchronous dumps have been performed at different beam energies and beta-stars. The loss patterns are analyzed in order to identify the losses in particular on the Phase 1 Tertiary Collimators (TCT), since their Tungsten jaw insert has a low damage threshold with respect to the loss load expected. Settings for the tilt angle of the TCTs are discussed with the aim of reducing the thermal loads on the TCT themselves.

MOPPD079

Preliminary Thermo-Mechanical Analysis of Angular Beam Impact on LHC Collimators

550

M. Cauchi, R.W. Assmann, A. Bertarelli, F. Carra, A. Dallocchio, D. Deboy, N. Mariani, A. Rossi
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain
P. Mollicone
UoM, Msida, Malta
N.J. Sammut
University of Malta, Faculty of Engineering, Msida, Malta

Funding: This work is supported by EuCARD.
The correct functioning of the LHC collimation system is crucial to attain the desired LHC luminosity performance. However, the requirements to handle high intensity beams can be demanding. In this respect, accident scenarios must be well studied in order to assess if the collimator design is robust against likely error scenarios. One of the catastrophic - though not very probable - accident scenarios identified is an asynchronous beam dump coupled with slight angular misalignment errors of the collimator jaw. Previous work presented a preliminary thermal evaluation of the extent of beam-induced damage for such scenarios, where it was shown that in some cases, a tilt of the jaw could actually serve to mitigate the effect of an asynchronous dump on the collimators. This paper will further analyze the response of tertiary collimators in presence of such angular jaw alignments, with the aim to identify optimal operational conditions.

MOPPD080

Improved Robustness of the LHC Collimation System by Operating with a Jaw-beam Angle

553

L. Lari, R.W. Assmann, A. Rossi
CERN, Geneva, Switzerland
M. Cauchi
UoM, Msida, Malta
A. Faus-Golfe, L. Lari
IFIC, Valencia, Spain

Funding: This work has been carried out through of the European Coordination for Accelerator Research and Development (EuCARD), co-sponsored by EU 7th Framework Program.
The robustness of the Phase I collimation system could be improved playing with the angular orientation of each single jaw. A preliminary study on the asymmetric misalignment of the collimator jaws, scanning through different jaw angles and varying beam sizes and energy, have been carried out, aiming at minimizing the energy deposited on metallic collimators, following an asynchronous dump.

TUPPR097

Modeling and Simulation of LHC Beam-Based Collimator Setup

2059

G. Valentino, N.J. Sammut
University of Malta, Information and Communication Technology, Msida, Malta
R.W. Assmann, F. Burkart, S. Redaelli, A. Rossi, D. Wollmann
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain

In the 2011 Large Hadron Collider run, collimators were aligned for proton and heavy ion beams using a semi-automatic setup algorithm. The algorithm provided a reduction in the beam time required for setup, an elimination of beam dumps during setup and higher accuracy with respect to manual alignment. A collimator setup simulator was developed based on a Gaussian model of the beam distribution as well as a parametric model of the beam losses. A time-varying beam loss signal can be simulated for a given collimator movement into the beam. The simulation results and comparison to measurement data obtained during collimator setups and dedicated fills for beam halo scraping are presented. The simulator will then be used to develop a fully automatic collimator alignment algorithm.

TUPPR098

Comparison of LHC Collimator Beam-Based Alignment Centers to BPM-Interpolated Centers

2062

G. Valentino, N.J. Sammut
University of Malta, Information and Communication Technology, Msida, Malta
R.W. Assmann, R. Bruce, G.J. Müller, S. Redaelli, A. Rossi, G. Valentino
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain

The beam centers at the Large Hadron Collider collimators are determined by beam-based alignment, where both jaws of a collimator are moved in separately until a loss spike is detected on a Beam Loss Monitor downstream. Orbit drifts of more than a few hundred micrometers cannot be tolerated, as they would reduce the efficiency of the collimation system. Beam Position Monitors (BPMs) are installed at various locations around the LHC ring, and a linear interpolation of the orbit can be obtained at the collimator positions. In this paper, the results obtained from beam-based alignment are compared with the orbit interpolated from the BPM data throughout the 2011 LHC proton run. The stability of the orbit determined by collimator alignment during the run is evaluated.