Stability and Control of Supercritical Helium Flow in the LHC Circuits

Hatchadourian, Emmanuel

doi:10.1007/978-1-4615-4215-5_19

Cited by 4 publications

(3 citation statements)

References 2 publications

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“…However, the strongly varying properties of helium close to the critical point may nevertheless create thermohydraulic instabilities, while the large aspect ratio of the cooling channels induces long control delays. These problems have been investigated both theoretically and experimentally on a full-scale test loop [25], thus permitting to identify critical parameters and to validate the steady-state and transient performance of the proposed solution [26].…”

Section: Superfluid-helium Magnet Cooling Schemementioning

confidence: 99%

Cryogenics for the Large Hadron Collider

Lebrun

2000

IEEE Trans. Appl. Supercond.

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The Large Hadron Collider (LHC), a 26.7 km circumference superconducting accelerator equipped with high-field magnets operating in superfluid helium below 1.9 K, has now fully entered construction at CERN, the European Laboratory for Particle Physics. The heart of the LHC cryogenic system is the quasi-isothermal magnet cooling scheme, in which flowing two-phase saturated superfluid helium removes the heat load from the 36'000 ton cold mass, immersed in some 400 m3 static pressurised superfluid helium. The LHC also makes use of supercritical helium for non-isothermal cooling of the beam screens which intercept most of the dynamic heat loads at higher temperature. Although not used in normal operation, liquid nitrogen will provide the source of refrigeration for precooling the machine. Refrigeration for the LHC is produced in eight large refrigerators, each with an equivalent capacity of about 18 kW at 4.5 K, completed by 1.8 K refrigeration units making use of several stages of hydrodynamic cold compressors. The cryogenic fluids are distributed to the cryomagnet strings by a compound cryogenic distribution line circling the tunnel. Procurement contracts for the major components of the LHC cryogenic system have been adjudicated to industry, and their progress will be briefly reported. Besides construction proper, the study and development of cryogenics for the LHC has resulted in salient advances in several fields of cryogenic engineering, which we shall also review. 1 Abstract--The Large Hadron Collider (LHC), a 26.7 km circumference superconducting accelerator equipped with highfield magnets operating in superfluid helium below 1.9 K, has now fully entered construction at CERN, the European Laboratory for Particle Physics. The heart of the LHC cryogenic system is the quasi-isothermal magnet cooling scheme, in which flowing twophase saturated superfluid helium removes the heat load from the 36'000 ton cold mass, immersed in some 400 m 3 static pressurised superfluid helium. The LHC also makes use of supercritical helium for non-isothermal cooling of the beam screens which intercept most of the dynamic heat loads at higher temperature. Although not used in normal operation, liquid nitrogen will provide the source of refrigeration for precooling the machine. Refrigeration for the LHC is produced in eight large refrigerators, each with an equivalent capacity of about 18 kW at 4.5 K, completed by 1.8 K refrigeration units making use of several stages of hydrodynamic cold compressors. The cryogenic fluids are distributed to the cryomagnet strings by a compound cryogenic distribution line circling the tunnel. Procurement contracts for the major components of the LHC cryogenic system have been adjudicated to industry, and their progress will be briefly reported. Besides construction proper, the study and development of cryogenics for the LHC has resulted in salient advances in several fields of cryogenic engineering, which we shall also review.

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Section: Superfluid-helium Magnet Cooling Schemementioning

confidence: 99%

Cryogenics for the Large Hadron Collider

Lebrun

2000

IEEE Trans. Appl. Supercond.

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“…The power deposition issue is particularly critical for superconducting devices [10] where the cooling capacity on the beam chamber might be limited (see, e.g., refs. [11,12] for some highlights of LHC-related aspects).…”

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Numerical simulations of electron cloud build-up in circular accelerators in the presence of multimode distribution beams

Cui

Gilardoni

Giovannozzi

et al. 2020

EPL

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Electron cloud effects have become one of the main performance limitations for circular particle accelerators operating with positively-charged beams. Among other machines worldwide, the CERN Super Proton Synchrotron (SPS), as well as the Large Hadron Collider (LHC) are affected by these phenomena. Intense efforts have been devoted in recent years to improve the understanding of electron cloud (EC) generation with the aim of finding efficient mitigation measures. In a different domain of accelerator physics, non-linear resonances in the transverse phase space have been proposed as novel means of manipulating charged particle beams. While the original goal was to perform multi-turn extraction from the CERN Proton Synchrotron (PS), several other applications have been proposed. In this paper, the study of EC generation in the presence of charged particle beams with multimode horizontal distribution is presented. Such a peculiar distribution can be generated by different approaches, one of which consists in splitting the initial Gaussian beam distribution by crossing a non-linear resonance. In this paper, the outcome of detailed numerical simulations is presented and discussed.

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“…FIGURE 4 shows the regulation performances of the beam screen temperature regulation with nominal and ultimate loads. Despite the abrupt change of applied load -in the machine it will be smoothed over a 20 minutes period -the controller was able to take back the beam screen output temperature to the nominal value of 20 K. No density wave oscillations in supercritical helium [7] were detected in the introduced working modes. The inlet temperature was always slightly above 5 K without the use of the inlet heater.…”

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confidence: 99%

Experimental Validation and Operation of the LHC Test String 2 Cryogenic System

Blanco¹,

Calzas²,

Casas³

et al. 2004

AIP Conference Proceedings

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The LHC Test String 2 is a 107-m long superconducting magnet string representing a full-cell of the LHC machine. It was designed and commissioned at CERN in order to validate the final design choices and to investigate the collective behavior and operation modes of the LHC machine systems. It has been commissioned and operated since April 2001 and has accumulated more than 8000 hours at its nominal operating temperature of 1.9 K under machine-like conditions. We report on the experimental validation of the supercritical and superfluid helium cooling loops, quench propagation and recovery, heat loads, as well as on investigation of operational performances, advanced control techniques, process control, instrumentation and long term behavior under electrical and thermal cycling. ABSTRACTThe LHC Test String 2 is a 107-m long superconducting magnet string representing a full-cell of the LHC machine. It was designed and commissioned at CERN in order to validate the final design choices and to investigate the collective behavior and operation modes of the LHC machine systems. It has been commissioned and operated since April 2001 and has accumulated more than 8000 hours at its nominal operating temperature of 1.9 K under machine-like conditions. We report on the experimental validation of the supercritical and superfluid helium cooling loops, quench propagation and recovery, heat loads, as well as on investigation of operational performances, advanced control techniques, process control, instrumentation and long term behavior under electrical and thermal cycling.

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Stability and Control of Supercritical Helium Flow in the LHC Circuits

Cited by 4 publications

References 2 publications

Cryogenics for the Large Hadron Collider

Cryogenics for the Large Hadron Collider

Numerical simulations of electron cloud build-up in circular accelerators in the presence of multimode distribution beams

Experimental Validation and Operation of the LHC Test String 2 Cryogenic System

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