Abstract
The far Detector of the Deep Underground Neutrino Experiment (DUNE) will be housed in several large volume (about 12.500 m
3
) liquid argon cryostats. The design principle of these large ...cryostats, and of the cryogenic system belonging to them, are investigated through the design, construction and operation of a series of prototype installations.
The Neutrino Platform 02 (NP02) and 04 (NP04) cryostats, placed at CERN, contain DUNE proto-type detectors, each of them housed in an about 600 m
3
liquid argon bath. These cryostats, based on the membrane cryostat principle, and their cryogenic systems have been designed according to the DUNE principle. Measurements performed in these test stands shall confirm the foreseen heat loads into the cryostat systems entering via its walls, via detector cabling and via the cold electronics, shall confirm the low temperature gradient over the active detector volume and shall certify the liquid argon purification principle.
This paper introduces the requirements for the NP02 and NP04 cryostats and their cryogenic systems, describes the design principle applied to these two systems and gives an overview of the different modes in which the two systems have been operating. The experimental results are presented and discussed, and “lessons learned” for future installations are dawn.
In the context of the Neutrino Platform, CERN has designed, constructed, and commissioned the proximity cryogenics systems that serve two CERN based large-scale prototypes of future neutrino ...detectors. Each of these prototypes features a high voltage time projection chamber placed inside a membrane cryostat being submerged in 600m3 of liquid argon at about 1.0 bar. A copper and molecular sieve based cryogenic purification system has to ensure that the argon in the cryostat has a contamination level below 100 ppt oxygen equivalent. The two proximity cryogenics systems provide the purging, cool-down, filling, normal operation and emptying modes for each cryostat. This paper reports on the design, construction and commissioning of the ProtoDUNE proximity cryogenics facilities.
The ITER superconducting (SC) magnet system, which consists of central solenoid coils, toroidal field (TF) coils, TF structures, and poloidal field and correction coils, is cooled by supercritical ...helium (SHe) circuits located in dedicated auxiliary cold boxes (ACBs) of the cryodistribution (CD). Due to the increase in the nuclear heat load during the deuterium-tritium plasma phase, the necessary cooling power to maintain the thermal stability of the magnet system can be beyond the presently designed and contracted specification of the cryoplant (LHe and liquid nitrogen plants). Increasing the cryoplant capacity or performance in turn will significantly increase the project cost apart from the impacts on the utility infrastructures (cooling water, electricity, civil works, etc.). In this paper, we will present arrangements within the CD for an efficient and flexible operation. Instead of a common control, which is the present design, by individually controlling the LHe bath temperature of the ACBs, the cooling power can be concentrated to the magnet system in need (reduction in the SHe circuit temperature). In addition to this, a proposal to minimize the heat of compression of the cold rotating machines in order to further allocate the cooling power to the SC magnet system will be introduced.
•Process analyses of ACB-ST under plasma operation.•Evaluation of Mitigation techniques as utilizing developed dynamic simulation model.•Assessment of ST functionality as a thermal ...buffer.•Feasibility of cold circulator operation under plasma disruption.
Process studies for Toroidal Field Structure (TF ST) system with a dedicated Auxiliary Cold Box (ACB-ST) have been conducted under 15 MA baseline, including plasma disruptions. ACB-ST consists of two heat exchangers immersed in the Liquid Helium (LHe) subcooler, which are placed at the inlet/outlet of a Supercritical Helium (SHe) cold circulator (centrifugal pump). Robustness of ACB-ST is a key to achieve the stability of TF coil operation since it provides the thermal barrier at the interface of the TF Winding Pack (WP) with ST. The paper discusses the control logic for the nominal plasma operating scenario and for Mitigation to regulate the dynamic heat loads on ST. In addition, the operation field of a cold circulator is described in the case of plasma disruptions. The required performance of heat exchangers in the ACB-ST is assessed based on the expected operating conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The Short-Baseline Neutrino (SBN) physics program at Fermilab and Neutrino Platform (NP) at CERN are part of the international Neutrino Program leading to the development of Long-Baseline Neutrino ...Facility/Deep Underground Neutrino Experiment (LBNF/DUNE) science project. The SBN program consisting of three Liquid Argon Time Projection Chamber (LAr-TPC) detectors positioned along the Booster Neutrino Beam (BNB) at Fermilab includes an existing detector known as MicroBooNE (170-ton LAr-TPC) plus two new experiments known as SBN's Near Detector (SBND, ∼260 tons) and SBN's Far Detector (SBN-FD, ∼760 tons). All three detectors have distinctly different design of their cryostats thus defining specific requirements for the cryogenic systems. Fermilab has already built two new facilities to house SBND and SBN-FD detectors. The cryogenic systems for these detectors are in various stages of design and construction with CERN and Fermilab being responsible for delivery of specific sub-systems. This contribution presents specific design requirements and typical implementation solutions for each sub-system of the SBND and SBN-FD cryogenic systems.
The pressure head necessary for the forced convection of supercritical helium (SHe) across the ITER superconducting (SC) magnet system is generated by centrifugal-compressor type cold circulators. ...From the viewpoint of the cryogenic system, simulation results indicate that the main challenge of the ITER Central Solenoid (CS) operation is the peaking pressure head of SHe across the cold circulator induced during the rapid ramping of electrical current on the coils. Excess variation in pressure head will push the operation point of the rotating machine beyond the surge line in the compressor map which can trip the circulator and in the worst case result in damages. Therefore, in order to avoid the occurrence of a surge, it has been proposed to open adaptively a cryogenic valve, installed in parallel with the CS cooling channels, during the high pressure head instances. Such an action creates an additional flow channel which consequently suppresses the pressure head peak. The proposed strategy has been numerically benchmarked and tests have been performed in existing cryogenic facilities. In this paper, we will present the test results of pressure head mitigation across the cold circulator dedicated to the KSTAR CS and Poloidal Field (PF) coil cooling circuit with the main purpose of demonstrating the safe operation of the ITER CS circulator as well as cooling circuit during plasma shots. The tests were performed by progressively increasing the coil by-pass valve opening during identical PF/CS current shots and monitoring the tendency of the maximum pressure head variation across the cold circulator. Also, preliminary results of pressure head mitigation during real plasma experiments will be introduced.
ITER cryolines (CLs) are complex network of vacuum-insulated multi and single process pipe lines, distributed in three different areas at ITER site. The CLs will support different operating loads ...during the machine life-time; either considered as nominal, occasional or exceptional. The major loads, which form the design basis are inertial, pressure, temperature, assembly, magnetic, snow, wind, enforced relative displacement and are put together in loads specification. Based on the defined load combinations, conceptual estimation of reaction loads have been carried out for the lines located inside the Tokamak building. Adequate numbers of embedded plates (EPs) per line have been defined and integrated in the building design. The finalization of building EPs to support the lines, before the detailed design, is one of the major design challenges as the usual logic of the design may alter. At the ITER project level, it was important to finalize EPs to allow adequate design and timely availability of the Tokamak building. The paper describes the single loads, load combinations considered in load specification and the approach for conceptual load estimation and selection of EPs for Toroidal Field (TF) Cryoline as an example by converting the load combinations in two main load categories; pressure and seismic.
System of Cryoline and Cryo-distribution for ITER has matured to a stage of preliminary design with the advent of industrial associates. Starting from the cold power source, the system of Cryoline ...and Cryo-distribution transfers the controlled cold power through a large network to the superconducting magnets and cryopumps. The functional responsibility also includes very high reliability and availability with respect to the operation of the ITER machine. Following the completion of conceptual design, it was necessary to perform a detailed engineering study of the complete network of distribution system in totality, before entering in to the industrial phase. This is to ensure the functional responsibility of the system. Value engineering in the area of distribution boxes including interfacing Cryolines has been performed in order to access the integrated reliable performance with respect to the overall cryogenic system, reducing the risk transferred to the industrial partners. These include technical risk assessment, analysis, mitigation plan and implementation with the industrial partners. The paper describes the methodology of technical risk management, value engineering performed to ensure fulfilment of licensing and regulatory obligations, functional reliability, testing and manufacturability by standard industrial processes, so that highly reliable integrated distribution system is delivered for the project.
In a few weeks the Large Hadron Collider which is built at CERN will deliver its first beam. ATLAS (A Toroïdal Large hadron collider ApparatuS 1) is one of the four experiments whose aim is to ...analyze the products of the collisions. As many of these particle detectors, ATLAS is designed with four concentric layers which are, from inside to outside: the inner detector to measure the charged particles tracks, the electromagnetic calorimeter to measure the energy deposited by both electrons and photons, then the hadronic calorimeter and finally the muon detector. The active part of the electromagnetic calorimeter is a bath of liquid argon 2 whose large volume (78 m3) has to be maintained precisely at its operating temperature (about 88 K) by the means of nitrogen circulation. In this paper we will describe how with industry-like control systems an application has been built for the command and the monitoring of the whole cryogenics equipment.
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