Cedric Garion

CERN | CERN · Technology Department (TE)

Novel NiTi-based shape memory alloy (SMA) pipe couplers were designed and developed. They are suitable for room-temperature ultrahigh vacuum (UHV) systems and provide a quick and compact solution at reasonable cost. Their use is particularly interesting for restricted-access areas of particle accelerators as their installation/dismounting can be pe...

Recent studies on Shape Memory Alloy rings have been undertaken at the European Organization for Nuclear Research (CERN) to develop smart and leak-tight couplers for Ultra High Vacuum systems of particle accelerators. A special thermo-mechanical process (training) is needed to provide SMA rings with proper functional properties, that is to allow th...

Synchrotron radiation (SR) originated at superconducting bending magnets is known to be at the origin of several beam detrimental effects related to vacuum instabilities. One of the major challenges in the design of the vacuum beam pipes of high-energy hadron colliders is the SR coping strategy. In the case of the future circular hadron collider (F...

In the framework of the High-Luminosity LHC project, larger and shielded beam screens will be installed in the beam pipe of the superconducting magnets of the insertion next to the ATLAS and CMS detectors. The beam screen is a complex assembly that guarantees the vacuum requirements while shielding the magnet cold mass from the induced heat loads....

The general features of Shape Memory Alloys (SMAs) operating in constrained recovery mode were described. A particular focus was given to the fastening and connection systems of recent industrial and scientific interest such as the beam-pipe couplers for Ultra High Vacuum (UHV) systems of particle accelerators. Such bolt-free connectors find a vari...

All systems are expected to be designed to fulfil their functions over their requested lifetime. Nevertheless, failure of a system may occur, and this is unfortunately, true also for vacuum systems. From a mechanical point of view, buckling, leak by fatigue crack propagation, rupture of a fixed support under unbalanced vacuum force... may happen. T...

EuroCirCol is a conceptual design study of a post-LHC, Future Circular Hadron Collider (FCC-hh) which aims to expand the current energy and luminosity frontiers. The vacuum chamber of this 100 TeV, 100 km collider, will have to cope with unprecedented levels of synchrotron radiation linear power for proton colliders, 160 times higher than in the LH...

Vacuum chambers used in high-energy particle accelerator experiments are conventionally made of bulk beryllium, which shows significant drawbacks due to cost and toxicity. An alternative solution could be to develop cold sprayed Al-coated chamber. This requires that cold sprayed Al behaves as a perfect vacuum barrier. The study focuses on the relat...

Coping with synchrotron radiation (SR) that originated at superconducting bending magnets is one of the major challenges in the design of the vacuum beam pipes of hadron colliders. In the case of the Future Circular hadron Collider (FCC-hh), similarly as for the LHC, a beam screen, operating at higher temperatures than the cold mass, has been desig...

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km...

Porosity is a crucial property in cold sprayed coatings. If it can be beneficial for certain applications, e.g. lubricated contacts in tribology, it is generally detrimental for mechanical and anti-corrosion properties and for gas tightness of the coating. It is thus important to understand what are the process variables affecting coating porosity...

Electron multipacting and electron cloud have been identified as being the major limiting factors for the beam quality or for the cryogenic system of high-intensity positive particles accelerators. Among conditioning operational techniques and other surface structuration techniques used to decrease the Secondary Electron Yield (SEY) of surfaces, la...

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km...

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km...

We review the physics opportunities of the Future Circular Collider, covering its e+e-, pp, ep and heavy ion programmes. We describe the measurement capabilities of each FCC component, addressing the study of electroweak, Higgs and strong interactions, the top quark and flavour, as well as phenomena beyond the Standard Model. We highlight the syner...

In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in...

The one-way and two-way shape memory effects (SMEs) as well as the thermal hysteresis represent fundamental properties when dealing with the design of detachable and thermally-stable connection systems based on shape memory alloys (SMAs). Such properties can be induced and tuned by thermo-mechanical processes that include thermal treatments and sev...

In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in...

We review the physics opportunities of the Future Circular Collider, covering its e+e-, pp, ep and heavy ion programmes. We describe the measurement capabilities of each FCC component, addressing the study of electroweak, Higgs and strong interactions, the top quark and flavour, as well as phenomena beyond the Standard Model. We highlight the syner...

The LHC beams are producing significant dynamic heat loads on the LHC cryogenic system. These heat loads are deposited on beam screens, where they must be properly extracted with dedicated cooling loops between 4.6 K and 20 K. Since 2015, unexpected beam-induced heat loads are observed in specific locations of the machine and their origin is still...

The new beam screens for the inner triplets in the HL-LHC are designed to intercept heat loads of up to 25 Wm⁻¹ between 60 K and 80 K. The screens need to be mechanically supported by the beam tube at 1.9 K while limiting heat transfer to the same tube to less than 0.5 W m⁻¹. Measurements for the thermal validation of the beam screens were carried...

A new generation of shape memory alloy (SMA)-based coupling systems, for ultra-high vacuum (UHV) applications in particle in accelerators, is currently under investigation at the European organization for nuclear research (CERN). The use of such technology in some restricted-access radioactive areas within CERN accelerators could result in noticeab...

Magnetic fields used to control particle beams in accelerators are usually controlled by regulating the electrical current of the power converters. In order to minimize lifetime degradation and ultimately luminosity loss in circular colliders, current-noise is a highly critical figure of merit of power converters, in particular for magnets located...

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km...

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km...

In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCCee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in...

We review the physics opportunities of the Future Circular Collider, covering its e+e−, pp, ep and heavy ion programmes.We describe the measurement capabilities of each FCC component, addressing the study of electroweak, Higgs and strong interactions, the top quark and flavour, as well as phenomena beyond the Standard Model. We highlight the synerg...

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear e+e− collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and imp...

In the framework of the High-Luminosity Large Hadron Collider (HL-LHC) project, new beam screens will be installed by 2024 within the cold bore of the superconducting magnets. The beam screen is an octagonal shaped pipe that shields the 1.9 K magnet cryogenic system from the heat loads and damage to the magnet coils that would be otherwise induced...

The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) will increase the accelerator's luminosity by a factor 10 beyond its original design value, giving rise to more collisions and generating an intense flow of debris. A new beam screen has been designed for the inner triplets that incorporates tungsten alloy blocks to shield the superc...

Chapter 12 in High-Luminosity Large Hadron Collider (HL-LHC) : Preliminary Design Report. The Large Hadron Collider (LHC) is one of the largest scientific instruments ever built. Since opening up a new energy frontier for exploration in 2010, it has gathered a global user community of about 7,000 scientists working in fundamental particle physics a...

The ultrahigh-vacuum (UHV) coupling performance of NiTiNb shape memory alloy (SMA) rings was investigated by finite element (FE) simulations and experimental measurements. The contact pressure at the interface between the SMA ring and the vacuum pipe was measured and good agreements with the FE results were obtained. Furthermore, a design method wa...

Shape Memory Alloy (SMA) rings have been studied for possible applications as beam-pipe connectors in particle accelerators. The rings were analyzed by both experimental tests and finite element simulations. In particular, the tightening performance of NiTiNb rings, in terms of contact pressure and clamping/unclamping mechanisms, was studied for di...

The Compact Linear Collider (CLIC) is a multi-TeV high-luminosity linear e+e− collider under development. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in a staged approach with three centre-of-mass energy stages ranging from a few hundred GeV up to 3 TeV. The first stage will focus on precision Sta...

The High Luminosity LHC project (HL-LHC) aims at increasing the luminosity (rate of collisions) in the Large Hadron Collider (LHC) experiments by a factor of 10 beyond the original design value (from 300 to 3000 fb-1). It relies on new superconducting magnets, installed close to the interaction points, equipped with new beam screen. This component...

The first Large Hadron Collider (LHC) Long Shutdown (LS1) started in February 2013. It was triggered by the need to consolidate the 13 kA splices between the superconducting magnets to allow the LHC to reach safely its design energy of 14 TeV center of mass. The SMACC (Superconducting Magnets And Circuits Consolidation) project has principally cove...

A new beam screen is needed in the High-Luminosity LHC (HL-LHC) final focusing magnets. Such an essential vacuum component, while operating in the range 40-60 K, has to ensure the vacuum performance and to prevent the beam-induced heating from reaching the cold bore which is at 1.9 K. In addition, it has to shield the cold mass from physics debris...

The first LHC long shutdown (LS1) started in February 2013. It was triggered by the need to consolidate the 13 kA splices between the superconducting magnets to allow the LHC to reach safely its design energy of 14 TeV center of mass. The final design of the consolidated splices is recalled. 1695 interconnections containing 10 170 splices have to b...

Highly transparent vacuum chambers are increasingly required in high energy particle physics. In particular, vacuum chambers in the experiments should be as transparent as possible to minimize the background to the detectors, whilst also reducing the material activation. Beryllium is, so far, the most performant material for this application, but i...

An unexpected gas inrush in a vacuum chamber leads to the development of a fast pressure wave. It carries small particles that can compromise functionality of sensitive machine systems such as the RF cavities or kickers. In the LHC machine, it has been proposed to protect this sensitive equipment by the installation of fast vacuum valves. The main...

The accident in the LHC in September 2008 occurred in an interconnection between two magnets of the 13 kA dipole circuit. Successive measurements of the resistance of other interconnects revealed other defective joints, even though the SC cables were properly connected. These defective joints are characterized by a poor bonding between the SC cable...

The Compact LInear Collider, under study, is based on room temperature high gradient structures. The vacuum specificities of these cavities are low conductance, large surface areas and a non-baked system. The main issue is to reach UHV conditions (typically 10-7 Pa) in a system where the residual vacuum is driven by water outgassing. A finite eleme...

The paper addresses a fundamental problem of tightness of ultra-high vacuum systems (UHV) at cryogenic temperatures in the light of continuum damage mechanics (CDM). The problem of indentation of a rigid punch into an elastic–plastic half-space is investigated based on rate independent plasticity with mixed kinematic and isotropic hardening. The mi...

Following the analysis of the September 2008 LHC incident, the assembly process and the quality assurance of the main 13 kA interconnection splices were improved, with new measurement and diagnostics methods introduced. During the 2008-2009 shutdown ~5% of these 10 000 splices were newly assembled with these improvements implemented, but essentiall...

All-metal joints are widely used in the vacuum systems of particle accelerators. The most common ConFlat® design consists of a flat soft copper gasket captured between two stainless steel flanges with sharp edges (knives). The gasket is plastically deformed and a high contact pressure develops around knives to obtain leak tightness. For large accel...

Modern particle accelerators require UHV conditions during their operation. In the accelerating cavities, breakdowns can occur, releasing large amount of gas into the vacuum chamber. To determine the pressure profile along the cavity as a function of time, the time-dependent behaviour of the gas has to be simulated. To do that, it is useful to appl...

The low-beta triplets of the Large Hadron Collider were designed and constructed by a world-wide collaboration officially formed in 1998. Over the course of the following years the collaboration worked to produce the triplet components, including four 215 T/m, 70 mm aperture quadrupoles, a DFBX distribution feedbox, and at the low luminosity intera...

The Compact Linear Collider, under study, requires vacuum chambers with a very small aperture, of the order of 8 mm in diameter, and with a length up to around 2 m for the main beam quadrupoles. To keep the very tight geometrical tolerances on the quadrupoles, no bake out is allowed. The main issue is to reach UHV conditions (typically 10-9 mbar st...

This report summarizes the findings and recommendations of the AT department Task Force established to investigate the 19th September 2008 incident which occurred in sector 3-4 of the LHC. It includes a number of annexes where specific analyses are detailed.

To achieve maximum beam energy in the LHC the accumulated length of the interconnections between LHC main magnets has been limited to around 3% of the total magnetic length in the Arcs and Dispersion Suppressors. Such a low ratio leads to a very compact design of components located in the LHC interconnections. This implies development and evolutio...

The present paper is focused on constitutive modelling and identification of parameters of the relevant model of plastic strain-induced martensitic transformation in austenitic stainless steels at low temperatures. The model used to describe the FCC → BCC phase transformation in austenitic stainless steels is based on the assumption of linearizatio...

The corrector magnets and the main quadrupoles of the LHC dispersion suppressors are powered by a special superconducting line (called auxiliary bus-bars line N), external to the cold mass and housed in a 50 mm diameter stainless steel tube fixed to the cold mass. As the line is periodically connected to the cold mass, the same gaseous and liquid h...

A majority of the thin‐walled components subjected to intensive plastic straining at cryogenic temperatures are made of stainless steels. The examples of such components can be found in the interconnections of particle accelerators, containing the superconducting magnets, where the thermal contraction is absorbed by thin‐walled, axisymetric shells...

The quest for high particle energies of modern superconducting lepton and hadron storage rings assumes a strong minimisation of the non-magnetic interconnection zones when compared to the total magnetic length of the main quadrupoles and the dipoles. The ratio of non-magnetic to magnetic zones in the LHC is close to 3%. Such a low percentage leads...

Ductile materials (like stainless steel or copper) show at cryogenic temperatures three principal phenomena: serrated yielding (discontinuous in terms of dσ/dε), plastic strain-induced phase transformations and evolution of ductile damage. The present paper deals exclusively with the two latter cases. Thus, it is assumed that the plastic flow...

A simplified model of martensitic transformation in stainless steels at cryogenic temperatures is proposed. The constitutive modeling of plastic flow under cryogenic conditions is based on the assumption of small strains (≤0.2). The hardening law for the biphase material (α′ martensite platelets embedded in the γ austenite matrix) has been obtained...

The Fe-Cr-Ni stainless steels are well known for their ductile behaviour at cryogenic temperatures. This implies development and evolution of plastic strain fields in the stainless steel components subjected to thermo-mechanical loads at low temperatures. The evolution of plastic strain fields is usually associated with two phenomena: ductile damag...

Liquid and Gaseous Helium are supplied to the superconducting magnets of the Large Hadron Collider (LHC), presently being assembled at CERN, by a cryogenic distribution line (QRL). The cryogenic module of the twin-quadrupole Short Straight Section (SSS) is supplied with these cryogens through a jumper connection linking the service module of the QR...

The LHC has ventured into unchartered territory for Particle Physics accelerators. A dedicated consolidation program is required between 2013 and 2014 to ensure optimal physics performance. The experiments, ALICE, ATLAS, CMS, and LHCb, will utilise this shutdown, along with the gained experience of three years of physics running, to make optimisati...

The present thesis is dedicated to the behaviour of austenitic stainless steels at cryogenic temperatures. The plastic strain induced martensitic transformation and ductile damage are taken into account in an elastic-plastic material modelling. The kinetic law of →’ transformation and the evolution laws of kinematic/isotropic mixed hardening are...

To achieve the maximum beam energy in the LHC the accumulated length of spatial zones, dedicated to the interconnections between the main cryo-magnets, has been limited to 3 % of the total magnetic length in the Arcs and Dispersion Suppressors. Such a low ratio leads to a very compact design of systems and sub-systems situated in the LHC interconne...

The interconnections between the cryomagnets and cryogenic utilities in the LHC long Straight Sections constitute the last machine installation activity. They are ensuring continuity of the beam and insulation vacuum systems, cryogenic fluid and electrical circuits and thermal insulation. The assembly is carried out in a constraining tunnel environ...

In addition to the standard interconnections (IC) of the continuous cryostat of the Large Hadron Collider (LHC), there exists a variety of special ones related to specific components and assemblies, such as cryomagnets of the insertion regions, electrical feedboxes and superconducting links. Though they are less numerous, their specificities create...