Simulations and measurements of cleaning with 100 MJ beams in the LHC

The CERN Large Hadron Collider is routinely storing proton beam intensities of more than 100 MJ, which puts extraordinary demands on the control of beam losses to avoid quenches of the superconducting magnets. Therefore, a detailed understanding of the LHC beam cleaning is required. We present tracking and shower simulations of the LHC's multi-stage collimation system and compare with measured beam losses, which allow us to conclude on the predictive power of the simulations.Asian Committee for Future Accelerators (ACFA),American Physical Society Division of Physics of Beams (APS-DPB),Chinese Academy of Sciences (CAS),European Physical Society Accelerator Group (EPS-AG)peer-reviewe

Simulations and measurements of beam loss patterns at the CERN Large Hadron Collider

The CERN Large Hadron Collider (LHC) is designed to collide proton beams of unprecedented energy, in order to extend the frontiers of high-energy particle physics. During the first very successful running period in 2010-2013, the LHC was routinely storing protons at 3.5-4 TeV with a total beam energy of up to 146 MJ, and even higher stored energies are foreseen in the future. This puts extraordinary demands on the control of beam losses. An uncontrolled loss of even a tiny fraction of the beam could cause a superconducting magnet to undergo a transition into a normal-conducting state, or in the worst case cause material damage. Hence a multistage collimation system has been installed in order to safely intercept high-amplitude beam protons before they are lost elsewhere. To guarantee adequate protection from the collimators, a detailed theoretical understanding is needed. This article presents results of numerical simulations of the distribution of beam losses around the LHC that have leaked out of the collimation system. The studies include tracking of protons through the fields of more than 5000 magnets in the 27 km LHC ring over hundreds of revolutions, and Monte Carlo simulations of particle-matter interactions both in collimators and machine elements being hit by escaping particles. The simulation results agree typically within a factor 2 with measurements of beam loss distributions from the previous LHC run. Considering the complex simulation, which must account for a very large number of unknown imperfections, and in view of the total losses around the ring spanning over 7 orders of magnitude, we consider this an excellent agreement. Our results give confidence in the simulation tools, which are used also for the design of future accelerators.peer-reviewe

Collimation for the LHC high intensity beams

The unprecedented design intensities of the LHC require several important advances in beam collimation. With its more than 100 collimators, acting on various planes and beams, the LHC collimation system is the biggest and most performing such system ever designed and constructed. The solution for LHC collimation is explained, the technical components are introduced and the initial performance is presented. Residual beam leakage from the system is analysed. Measurements and simulations are presented which show that collimation efficiencies of better than 99.97 % have been measured with the 3.5 TeV proton beams of the LHC, in excellent agreement with expectations.peer-reviewe

Misura delle caratteristiche del rivelatore a Cathode Strip Chambers per l’esperimento Totem

The aim of my thesis was to characterize the Cathode Strip Chamber (CSC) detector of the T1 inelastic detector of the TOTEM experiment. In the first two chapters I briefly introduce the TOTEM physics and the TOTEM experiment. In the third chapter I describe the basic principles of the ionizing detectors relevant to the TOTEM CSCs. Here I show also the results of few simulations done to determine the construction and operating parameters of the detector. The last two chapter are dedicated to the description of the experimental apparatus I build and the discussion of the TOTEM test beam results

A LS-DYNA/FLUKA COUPLING FOR THE NUMERICAL SIMULATION OF HIGH ENERGY PARTICLE BEAM INTERACTION WITH MATTER

The interaction between intense high-energy particle beams and materials provokes a sudden non-uniform temperature increase. This induces a dynamic response of the structure entailing the generation of shock-waves, which start to travel in the component producing a strong reduction in density in the impacted zone. FLUKA is a numerical tool for the calculation of the energy delivered in matter based on the Monte-Carlo method. LSDYNA is a non-linear FE explicit code, which can use as input for the thermo-mechanical analysis the results from FLUKA code. In this work a soft-coupling method between the two codes is developed and applied for the numerical simulation of an accidental impact of a multi-bunch 7 TeV proton beam of LHC on a metallic collimator insert. The FLUKA model was obtained using a voxel structure approach, while the FEM simulation was a 3D Lagrangian analysis. The FLUKA energy distribution, calculated on the initial geometry, is updated in accordance with the density modification during the simulation. As a matter of fact, the next bunches will impact against a lower mass target and can penetrate more in depth in the material. These effects were evaluated with an iterative soft-coupling of the two codes, performed in Matlab. The number of the primary protons that need to be simulated determines the precision of the FLUKA results. The first FLUKA simulation, performed with an unmodified material, is followed by the first FEM mechanical analysis. At this point, at each step, the algorithm: takes as input the density map resulting from the FEM calculations, re-defines the regions with different density in the target material, using the voxel structure and then runs a new FLUKA calculation which will be used as input for the next step FEM analysis (and so on). The first results confirm that the density reduction in the maximum deposition area provokes a reduction in the particle beam/matter interaction with a reduction of deposited energy and a sort of tunnelling effect. In more details, the peak of the energy deposition moves into the component along the direction of the beam. The comparison with the uncoupled case shows that also the pressure is affected: the maximum value decreases since the shockwave penetrates more into the material. The results also show that to be able to appreciate the difference between coupled and uncoupled analysis, it is necessary to obtain a quite significant density reduction: this occurs when the shockwaves has the time to travel radially away from the hit zone producing a significant rarefactio

Shockwaves simulation of accidental particle beam impacts in LHC metal structures

The unprecedented energy intensities of modern hadron accelerators yield special problems with the materials that are placed close to or into the high intensity beams. The energy stored in a single beam of LHC particle accelerator is equivalent to about 80 kg of TNT explosive, stored in a transverse beam area with a typical value of 0.2 mm×0.2 mm. The materials placed close to the beam are used at, or even beyond, their damage limits. However, it is very difficult to predict structural efficiency and robustness accurately: beam-induced damage for high energy and high intensity occurs in a regime where practical experience does not exist. The interaction between high energy particle beams and metals induces a sudden non uniform temperature increase. This provokes a dynamic response of the structure entailing thermal stress waves and thermally induced vibrations or even the failure of the component. This study is performed in order to estimate the damage on metal components due to the impact with a proton beam generated by LHC. The solved problems represent some accidental cases consequent to an abnormal release of the beam: the energy delivered on the components is calculated using the FLUKA code and then used as input in the numerical simulations, that are carried out via the FEM code LS-DYNA

Effects of High-Energy Intense Multi-Bunches Proton Beam on Materials

The prediction of material response in case of interaction with successive high energy proton bunches requires new tools and multidisciplinary approaches. The impact leads the propagation of shock-waves, which travels through the hit component causing a substantial density reduction and the appearance of tunneling effect along the beam direction. For taking into account this effect, an automatic procedure, consisting in coupling FLUKA Monte-Carlo and FE LS-DYNA codes, is developed. The case study consists of the accidental loss of 60 bunches of one of the 7 TeV proton beams of the Large Hadron Collider (CERN) on a tungsten collimator

Shockwaves simulation of accidental particle beam impacts in LHC metal structures

The unprecedented energy intensities of modern hadron accelerators yield special problems with the materials that are placed close to or into the high intensity beams. The energy stored in a single beam of LHC particle accelerator is equivalent to about 80 kg of TNT explosive, stored in a transverse beam area with a typical value of 0.2 mm×0.2 mm. The materials placed close to the beam are used at, or even beyond, their damage limits. However, it is very difficult to predict structural efficiency and robustness accurately: beam-induced damage for high energy and high intensity occurs in a regime where practical experience does not exist. The interaction between high energy particle beams and metals induces a sudden non uniform temperature increase. This provokes a dynamic response of the structure entailing thermal stress waves and thermally induced vibrations or even the failure of the component. This study is performed in order to estimate the damage on metal components due to the impact with a proton beam generated by LHC. The solved problems represent some accidental cases consequent to an abnormal release of the beam: the energy delivered on the components is calculated using the FLUKA code and then used as input in the numerical simulations, that are carried out via the FEM code LS-DYNA

Design and operation of FACT – the first G-APD Cherenkov telescope

The First G-APD Cherenkov Telescope (FACT) is designed to detect cosmic gamma-rays with energies from several hundred GeV up to about 10 TeV using the Imaging Atmospheric Cherenkov Technique. In contrast to former or existing telescopes, the camera of the FACT telescope is comprised of solid-state Geiger-mode Avalanche Photodiodes (G-APD) instead of photomultiplier tubes for photo detection. It is the first full-scale device of its kind employing this new technology. The telescope is operated at the Observatorio del Roque de los Muchachos (La Palma, Canary Islands, Spain) since fall 2011. This paper describes in detail the design, construction and operation of the system, including hardware and software aspects. Technical experiences gained after one year of operation are discussed and conclusions with regard to future projects are drawn

Design, optimization and characterization of the light concentrators of the single-mirror small size telescopes of the Cherenkov Telescope Array

The focal-plane cameras of γ-ray telescopes frequently use light concentrators in front of the light sensors. The purpose of these concentrators is to increase the effective area of the camera as well as to reduce the stray light coming at large incident angles. These light concentrators are usually based on the Winston cone design. In this contribution we present the design of a hexagonal hollow light concentrator with a lateral profile optimized using a cubic Bézier function to achieve a higher collection efficiency in the angular region of interest. The design presented here is optimized for a Davies-Cotton telescope with a primary mirror of about 4 m in diameter and a focal length of 5.6 m. The described concentrators are part of an innovative camera made up of silicon-photomultiplier sensors, although a similar approach can be used for other sizes of single-mirror telescopes with different camera sensors, including photomultipliers. The challenge of our approach is to achieve a cost-effective design suitable for standard industrial production of both the plastic concentrator substrate and the reflective coating. At the same time we maximize the optical performance. In this paper we also describe the optical set-up to measure the absolute collection efficiency of the light concentrators and demonstrate our good understanding of the measured data using a professional ray-tracing simulation. © 2014 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe