Accelerated testing of soft soldered, small-diameter, thin-walled CuNi pipes subjected to cyclic internal pressure loading

Small-diameter, thin-walled pipes have applications in a wide range of industries including high-energy physics, heat transfer, nuclear, medical and communications. However, there are currently no standards that exist for permanently joining these components either via welding (melting the base material) or soldering. As such it is difficult to determine the likely performance of a thin-walled pipe connection. Porosity is largely inevitable in soldered joints and is a determining factor in the performance of a connection. This study focused on characterisation of failure initiation and propagation within soft soldered CuNi thin-walled pipe joints under cyclic internal pressure loading. A step-stress accelerated life testing regime (SSALT) was developed to simulate the loads the joints would experience over their operational lifetime, in a shorter timescale. 10 soldered joints were studied in total, with varying levels of porosity within the soldered joints prior to testing. Pressurised Nitrogen gas was used to internally pressurise the samples, with cyclic loading between atmospheric conditions and a prescribed maximum pressure value. The results of the SSALT showed that the soldered samples experienced early failure through crack initiation and propagation through the solder. Cracks, or failures, were seen to initiate from existing voids, or porosity, within the soft-soldered joints. From this work, it can be concluded that the performance of soft-soldered joints under cyclic, internal pressure loading is strongly influenced by the presence of voids that are created during the manufacture of such soldered connections

Manufacturing technologies and joining methods of metallic thin-walled pipes for use in high pressure cooling systems

Small diameter thin-walled pipes, typically with a diameter less than 20 mm and a ratio of outer diameter to wall thickness is 20 or above, have increasingly become a key value adding factor for a number of industries including medical applications, electronics and chemical industries. In high-energy physics experiments, thin-walled pipes are needed in tracking detector cooling systems where the mass of all components needs to be minimised for physics measurement reasons. The pipework must reliably withstand the cooling fluid operation pressures (of up to 100 bar), but must also be able to be reliably and easily joined within the cooling system. Suitable standard and/or commercial solutions combining the needed low mass and reliable high-pressure operation are poorly available. The following review of literature compares the various techniques that exist for the manufacture and joining of thin-walled pipes, both well-established techniques and novel methods which have potential to increase the use of thin-walled pipes within industrial cooling systems. Gaps in knowledge have been identified, along with further research directions. Operational challenges and key considerations which have to be identified when designing a system which uses thin-walled pipes are also discussed

Mechanical and Microstructural Characterisation of Cooling Pipes for the Compact Muon Solenoid Experiment at CERN

The Compact Muon Solenoid (CMS) is a particle physics experiment situated on the Large Hadron Collider (LHC) at CERN, Switzerland. The CMS upgrade (planned for 2025) involves installing a new advanced sensor system within the CMS tracker, the centre of the detector closest to the particle collisions. The increased heat load associated with these sensors has required the design of an enhanced cooling system that exploits the latent heat of 40 bar CO2. In order to minimise interaction with the incident radiation and improve the detector performance, the cooling pipes within this system need to be thin-walled (~100 μm) and strong enough to withstand these pressures. The purpose of this paper is to analyse the microstructure and mechanical properties of thin-walled cooling pipes currently in use in existing detectors to assess their potential for the tracker upgrade. In total, 22 different pipes were examined, which were composed of CuNi, SS316L, and Ti and were coated with Ni, Cu, and Au. The samples were characterised using computer tomography for 3D structural assessment, focused ion beam ring-core milling for microscale residual stress analysis, optical profilometry for surface roughness, optical microscopy for grain size analysis, and energy dispersive X-ray spectroscopy for elemental analysis. Overall, this examination demonstrated that the Ni- and Cu-coated SS316L tubing was optimal due to a combination of low residual stress (20 MPa axial and 5 MPa hoop absolute), low coating roughness (0.4 μm Ra), minimal elemental diffusion, and a small void fraction (1.4%). This result offers a crucial starting point for the ongoing thin-walled pipe selection, development, and pipe-joining research required for the CMS tracker upgrade, as well as the widespread use of CO2 cooling systems in general

CO2_2 evaporative cooling: The future for tracking detector thermal management

\begin{abstract} In the last few years, CO$_2$ evaporative cooling has been one of the favourite technologies chosen for the thermal management of tracking detectors at LHC. ATLAS Insertable B-Layer and CMS Pixel phase 1 upgrade have adopted it and their systems are now operational or under commissioning. The CERN PH-DT team is now merging the lessons learnt on these two systems in order to prepare the design and construction of the cooling systems for the new Upstream Tracker and the Velo upgrade in LHCb, due by 2018. Meanwhile, the preliminary design of the ATLAS and CMS full tracker upgrades is started, and both concepts heavily rely on CO$_2$ evaporative cooling. This paper highlights the performances of the systems now in operation and the challenges to overcome in order to scale them up to the requirements of the future generations of trackers. In particular, it focuses on the conceptual design of a new cooling system suited for the large phase 2 upgrade programmes, which will be validated with the construction of a common prototype in the next years. \end{abstract

A semi-empirical model for preheater design to trigger CO2_2 boiling for detector cooling

The fluid properties of CO$_2$ make it an ideal medium for the cooling of tracking detectors in experiments at particle accelerators. Detectors such as the Compact Muon Solenoid Outer Tracker at CERN will be cooled to a nominal temperature of -35$^{\circ}$C with CO$_2$ cooling to ensure the longevity of the silicon sensors. In theory, two-phase CO$_2$ cooling results in a very low temperature change along the detector tube, dependent only on pressure drop. Experimentally, however, superheating - the existence of a fluid in the liquid form above its boiling temperature - has been observed to occur frequently. This results in higher fluid temperatures and a poor heat transfer coefficient over the first section of the detector tube, disrupting the cooling performance of the detector and possibly leading to deterioration of the silicon sensors. In order to prevent superheating, a preheater is proposed to trigger nucleate boiling in the Compact Muon Solenoid Outer Tracker detector cooling tube just upstream of the sensors. A theoretical - semi-empirical - model for the preheater design is presented, starting from experimental data points. With this model, the triggering of nucleation can be characterised for tubes made of the same material as that tested and with the same surface cavity size. The model validation is promising, closely matching the trends from experimental results, and giving preheater specific powers significantly lower than those derived from spinodal theory

Development, commissioning and operation of the large scale CO2_2 detector cooling systems for CMS pixel phase I upgrade

During the 2017 Year-end Technical Stop of the Large Hadron Collider at CERN, the CMS experiment has successfully installed a new pixel detector in the frame of Phase I upgrade. This new detector will operate using evaporative CO$_{2}$ technology as its cooling system. Carbon Dioxide, as state of the art technology for current and future tracking detectors, allows for significant material budget saving that is critical for the tracking performance. The road towards operation of the final CO$_{2}$ cooling system in the experiment passed through intensive prototype phase at the CMS Tracker Integration Facility (TIF) for both cooling process hardware and its control system. This paper briefly describes the general design of both the CMS and TIF CO$_{2}$ detector cooling systems, and focuses on control system architecture, operation and safety philosophy, commissioning results and operation experience. Additionally, experience in using the Ethernet IP industrial fieldbus as distributed IO is presented. Various pros and cons of using this technology are discussed, based on the solutions developed for Schneider Premium PLCs, WAGO and FESTO IOs using the UNICOS CPC 6 framework of CERN

First Steps in Automated Software Development Approach for LHC Phase II Upgrades CO₂ Detector Cooling Systems

With refrigerating power of the order of 1.5 kW at -35 °C and full compatibility with Detector Control System standards, Light Use Cooling Appliance for Surface Zones (LUCASZ) is the first movable medium size evaporative CO₂ detector cooling system. By 2018 a series of 4 LUCASZ units has been fully deployed by the EP-DT group at CERN. LUCASZ is capable to provide CO₂ cooling for various needs of detector development and testing required for Phase Iⅈ upgrades of LHC experiments. This paper describes selected software and controls hardware ideas used to develop the LUCASZ control system as baseline solutions for CO₂ cooling systems for Phase II upgrade of ATLAS and CMS trackers. The main challenges for future control system development will come from the number of cooling plants, the modularity, operation, and the implementation of backup philosophy. The introduction of automated software generation for both PLC and SCADA is expected to bring major improvement on the efficiency of control system implementation. In this respect, a unification step between experiments is highly required without neglecting specific needs of ATLAS and CMS

IL-7 receptor influences anti-TNF responsiveness and T cell gut homing in inflammatory bowel disease

International audienceIt remains unknown what causes inflammatory bowel disease (IBD), including signaling networks perpetuating chronic gastrointestinal inflammation in Crohn’s disease (CD) and ulcerative colitis (UC), in humans. According to an analysis of up to 500 patients with IBD and 100 controls, we report that key transcripts of the IL-7 receptor (IL-7R) pathway are accumulated in inflamed colon tissues of severe CD and UC patients not responding to either immunosuppressive/corticosteroid, anti-TNF, or anti-α4β7 therapies. High expression of both IL7R and IL-7R signaling signature in the colon before treatment is strongly associated with nonresponsiveness to anti-TNF therapy. While in mice IL-7 is known to play a role in systemic inflammation, we found that in humans IL-7 also controlled α4β7 integrin expression and imprinted gut-homing specificity on T cells. IL-7R blockade reduced human T cell homing to the gut and colonic inflammation in vivo in humanized mouse models, and altered effector T cells in colon explants from UC patients grown ex vivo. Our findings show that failure of current treatments for CD and UC is strongly associated with an overexpressed IL-7R signaling pathway and point to IL-7R as a relevant therapeutic target and potential biomarker to fill an unmet need in clinical IBD detection and treatment