In the framework of the High-Luminosity Large Hadron Collider, the installation of a new generation of quadrupole magnets is foreseen on each side of ATLAS and CMS experiments. The new magnets are based on Nb3Sn technology and shall be able to reach an ultimate current of 17.9 kA with a peak field of 12.3 T in the coil. In 2016 and 2017, the first two short models, called MQXFS3 and MQXFS5, have been tested at 4.2 and 1.9 K in the two new test benches at the European Organization for Nuclear Research. This paper presents the result of the quench performance of the two models; the first magnet reached nominal but failed to reach ultimate, showing detraining in one coil. MQXFS5 reached ultimate performance without any detraining phenomena, validating the PIT conductor used for the first time in this magnet program.

Test Result of the Short Models MQXFS3 and MQXFS5 for the HL-LHC Upgrade

Fermi National Accelerator Laboratory, together with Lawrence Berkeley National Laboratory, is building a new High Field Vertical Magnet Test Facility (HFVMTF) to be situated in the Magnet Test Facility at Fermilab. The HFVMTF is jointly funded by the US DOE Offices of Science, High Energy Physics, and Fusion Energy Sciences, and will serve as a superconducting cable test facility for both communities. The background magnetic field for test samples is 15 T and will be produced by a magnet provided by LBNL operating at 1.9 K in superfluid helium. The samples will be placed in the background magnetic field, cooled to between 4.5 K and a user-specified upper limit, and will be powered with a superconducting transformer at up to 100 kA. Additionally, this facility will be used to test high-field superconducting magnet models and demonstrators, including hybrid magnets, produced by the US Magnet Development Program. Currently, the various tasks of the project are at different stages of execution, from conceptual to ready-for-construction designs. This paper describes the parameters and design status of the pit construction, cryostat, heat exchanger, lambda plate, power system, and quench protection and monitoring systems of the facility.

Design and Construction of a High Field Cable Test Facility at Fermilab

The magnets for the next steps in accelerator physics, such as the High Luminosity upgrade of the LHC (HLLHC) and the Future Circular Collider (FCC), require the development of new technologies for manufacturing and monitoring. To meet the HL-LHC new requirements, a large upgrade of the CERN SM18 cryogenic test facilities is ongoing with the implementation of new cryostats and cryogenic instrumentation. The paper deals with the advances in the development and the calibration of fiber optic sensors in the range 300 4 K using a dedicated closed-cycle refrigerator system composed of a pulse tube and a cryogen-free cryostat. The calibrated fiber optic sensors (FOS) have been installed in three vertical cryostats used for testing superconducting magnets down to 1.9 K or 4.2 K and in the variable temperature test bench (100 4.2 K). Some examples of FOS measurements of cryostat temperature evolution are presented as well as measurements of strain performed on a subscale of High Temperature Superconducting magnet during its powering tests.

/pdf/cryogenic-test-facility-instrumentation-with-fiber-optic-and-3qhd3n5cup.pdf

Cryogenic test facility instrumentation with fiber optic and fiber optic sensors for testing superconducting accelerator magnets

/pdf/upgrade-of-the-cryogenic-infrastructure-of-sm18-cern-main-4ulvsqgtqe.pdf

Upgrade of the cryogenic infrastructure of SM18, CERN main test facility for superconducting magnets and RF cavities

https://cds.cern.ch/record/2103417/files/Physics Procedia - 66.pdf

Helium Inventory Management and Losses for LHC Cryogenics: Strategy and Results for Run 1

Cryogenic Design of the New High Field Magnet Test Facility at CERN

In the frame of the R&D program of the HL-LHC, the upgrade of the Large Hadron Collider (LHC), CERN augmented its test facility with two new large-scale vertical test stations for superconducting magnet testing. The cryostats composing the core of these test stations share design features but are of different dimensions: one allows testing magnets up to 1.5 m diameter, 2.5 m long for a maximum weight of 15 t, while the other can accommodate magnets up to 0.9 m diameter, and 5.5 m long for a maximum weight of 18 t. These test stations are designed to operate at 1.3 bar and at controlled temperatures in the range 1.9 – 4.5 K. They can provide for safe dissipation of stored energy in the magnet coils of up to 10 MJ. After a brief description of the cryostats, this paper describes the qualification measurements of heat loads at 4.5 K and 1.9 K of both cryostats, some design enhancements that were made and the performance improvements obtained.

/pdf/thermal-performance-of-the-new-superfluid-helium-vertical-3ljw4ro3h1.pdf

Thermal performance of the new superfluid helium vertical test cryostats for magnet tests at CERN

In the framework of the R&D program for new superconducting magnets for the Large Hadron Collider accelerator upgrades, CERN is building a new vertical test station to test high field superconducting magnets of unprecedented large size. This facility will allow testing of magnets by vertical insertion in a pressurized liquid helium bath, cooled to a controlled temperature between 4.2 K and 1.9 K. The dimensions of the cryostat will allow testing magnets of up to 2.5 m in length with a maximum diameter of 1.5 m and a mass of 15 tons. To allow for a faster insertion and removal of the magnets and reducing the risk of helium leaks, all cryogenics supply lines are foreseen to remain permanently connected to the cryostat. A specifically designed 100 W heat exchanger is integrated in the cryostat helium vessel for a controlled cooling of the magnet from 4.2 K down to 1.9 K in a 3 m3 helium bath. This paper describes the cryostat and its main functions, focusing on features specifically developed for this project. The status of the construction and the plans for assembly and installation at CERN are also presented.

New vertical cryostat for the high field superconducting magnet test station at CERN

The cryogenic system of the Large Hadron Collider (LHC) under operation at CERN has a total helium inventory of 140 t. Up to 50 t can be stored in gas storage tanks. The remaining inventory is stored in a liquid helium storage system consisting of six 15-t liquid helium tanks sited in 4 locations. The first phase with the commissioning of the two first liquid helium tanks including their infrastructure was already presented. In a second phase, four new tanks were commissioned at the end of 2010. The paper describes the modifications relating to these four tanks and presents the measurement of their thermal performance. Presented at ICEC 24 ICMC 2012 24 International Cryogenic Engineering Conference-International Cryogenic Materials Conference 2012 14-18 May 2012 – Fukoaka, Japan Upgrade of the liquid helium storage for the Large Hadron Collider Barth K., Benda V., Claudet S., Pezzetti M., Pirotte O., Vullierme B. Technology Department, CERN, Geneva, Switzerland The cryogenic system of the Large Hadron Collider (LHC) under operation at CERN has a total helium inventory of 140 t. Up to 50 t can be stored in gas storage tanks. The remaining inventory is stored in a liquid helium storage system consisting of six 15-t liquid helium tanks sited in 4 locations. The first phase with the commissioning of the two first liquid helium tanks including their infrastructure was already presented. In a second phase, four new tanks were commissioned at the end of 2010. The paper describes the modifications relating to these four tanks and presents the measurement of their thermal performance. INTRODUCTION During the annual shut down a big part of LHC helium inventory was sold and bought back again before each cool down. On the basis of a two-year experience this “virtual” storage appeared not flexible enough for the operation and the global management of the LHC helium inventory, as several weeks were required for logistic purposes. In order to store the whole LHC helium inventory at CERN, four new liquid helium tanks were necessary in addition to the two already operational at Point 1.8 [1]. The optimum was defined so as to install one tank at Point 4, two at Point 6 and one at Point 8, see Figure 1. At each point the storage system consists of liquid helium tank(s) connected to one of the refrigerators, a dedicated liquid nitrogen tank, helium and nitrogen cryogenic lines and related instrumentation. The whole architecture is similar as at Point 1.8. Figure 1, Helium storage distribution for LHC at CERN N°edms: 1174165 INFRASTRUCTURE DESCRIPTION Liquid helium tanks The required parameters of each horizontal tank are identical to [1]. The four additional tanks were produced by the two same manufacturers who supplied each one tank at Point 1.8. One tank was supplied by manufacturer A and three tanks by manufacturer B. Based on the experience with the two tanks at Point 1.8, the following improvements in comparison with the original specification were required. Both manufacturers were asked to improve reading of liquid helium level measurement and to install spinning rotor gauges for all vacuum spaces. In addition the manufacturer B was asked to modify the suspension system in order to simplify the cooling/warming procedure and to reduce the heat in-leak to liquid helium. Liquid nitrogen tanks A new tank of 10000 litres was purchased for the Point 6 while two tanks of 6000 litres from previous CERN installations were refurbished for Point 4 and 8. Based on the experience at Point 1.8 and the relatively low maximum working pressure required for the operation of tanks from manufacturer A, the pressurization system has been reviewed and adapted. Cryogenic lines As results of the call for tender to supply the necessary cryogenic transfer lines between the respective LHC refrigerators and the helium tanks, another manufacturer was selected to equip Points 4, 6 & 8. It proposed a different design with respect to the combined cryogenic transfer lines installed at Point 1.8 [1]. The line consists of a standard rigid shielded combined line. The process pipe to transfer the liquid helium from the refrigerator to the tank is shielded by an aluminium profile, cooled down by the process pipe transferring the cold helium gas return from the tank to the refrigerator. Basement and warm helium lines The basements and the warm helium lines are of the same type as in Point 1.8 [1]. The only exception concerns the LP gas return line to the suction of the compressor station (Figure 2). MODIFICATIONS Four major modifications were made with respect to the installation at Point 1.8 [1]. The updated flow scheme relative to reference [1] is presented in Figure 2. Supply connection The connections on the tank of the transfer lines of the liquid helium supply from the refrigerator and of the liquid helium connection with a truck have been separated in order to avoid hydraulic interferences during the transfers of liquid helium. LP gas return line The atmospheric heater and the standard warm helium pipe as installed in Point 1.8 have been replaced by a vacuum insulated transfer line in order to mix directly this cold return gas to the big helium mass flow (more than 1 kg/s) of the compressor stations of the LHC. It allows more flexibility for the operation. Slope The tanks from manufacturer B have been installed with a small slope towards the side of the process connection pipes. When emptying the tank it allows the remaining liquid to flow towards this side of the tank. Withdraw line The withdraw line (former supply at Point 1.8 [1]) has been connected with the LP gas return line and temperature sensors (T3 / T4) were installed to monitor the transition from liquid to gas. This brought two advantages with respect to the operations of cool down and emptying of the tanks : • For the cool down, the bypass valve in the distribution box is used to send cold helium at the top of the tank where it is distributed over the whole length and recuperated via the withdraw line to the LP. This provides a very smooth and homogenous cool down to 20 K in two weeks. • For the emptying operation warm gas (HP) is first injected via the supply line and the evaporated helium is recovered via the return line to the refrigerator. When the tank is almost empty, to recuperate the cold helium gas which represents about 2 tons at 4.5 K, warm gas is sent now via the return line and the helium is recuperated via the withdraw line to the LP. Figure 2, Simplified flow scheme of the storage system Control system and instrumentation The simplified Process and Instrumentation Diagram is shown in Figure 2. The control of the storage is handled by a system programmed and configured using the CERN/UNICOS framework [2]. The control system allows operating the liquid helium storage in automatic modes. A few hardwired safety interlocks have been adjusted in order to keep the installation operation at a high degree of flexibility. COMMISSIONING Cool down and warm up All four tanks were cooled down without any problem. The insulation vacua were monitored with the spinning rotor gauges. The tanks were fully filled and after a few weeks of stabilization, the thermal performance of each tank was measured. Satisfaction of new requirements All level meters of the new tanks showed 90% when full; this corresponds to reality and validates the improvements (70% for old tanks). The installation of spinning rotor gauges allows the monitoring of the vacuum residual pressures without opening the vacuum pumping valves. It eliminates also the leak risk. For the B-type tank the modified suspension system allowed to simplify the cool down/warm up procedure in comparison with the old tank at Point 1.8. At the same time the fragility of the suspension system was significantly reduced. Additional thermalizations (thermal shunts) in the design of the tanks B have appreciably improved the heat in-leak as it can be seen in Table 1. The above mentioned modifications were successfully approved during operation. Thermal performance measurement The heat in-leak of the tanks was measured by the boil-off method at a constant pressure. The mass of evaporated helium leaving the helium shield circuit was monitored by a flow-meter (F). The boiled-off helium was leaving the flow-meter directly into atmosphere in order to ensure a stable pressure not disturbed by a compressor pressure oscillation. The atmospheric pressure slowly fluctuated within an interval of ±5 mbar. The measured values were taken when the pressure and flow were stable. The comparison of the heat in-leak for all 6 tanks is shown in Table 1. A correction has been applied in order to take into account the decreasing helium level during the measurement. In order to ensure a correct comparison the heat in-leaks are presented in watts as pressures in the tanks were not the same. The two tanks already presented in [1] are also included for completeness. The residual pressure (cold condition) in the vacuum space of all type-B tanks was between 10 and 10 mbar, and for type A-new between 5x10 and 5x10 mbar. Table 1, Heat in-leak of liquid helium storage tanks Location/Manufacturer Heat in-leak [W] Liquid helium pressure [bar] Note Specification <10 Point 1.8/A 2.63 ± 0.3 ~ 1 Old [1] Point 1.8/B 7.4 ± 0.5 ~ 1 Old [1] Point 8/B 4.52 ± 0.5 1.470 New Point 6 #1/B 4.67 ± 0.5 1.106 New Point 6 #2/B 4,52 ± 0.5 1.088 New Point 4/A 2.1 ± 0.3 1.039 New A typical development of the heat in-leak measurement documenting a decrease of the liquid helium level while the pressure is almost stabilized is shown for the new A-type tank in Figure 3. Figure 3, Measurement chart for Point 4/A CONCLUSION The storage for about 90 t of liquid helium was erected at CERN for a majority of LHC helium inventory. The whole storage system was successfully commissioned and used end 2011. The heat in-leaks of the new type-B tanks were reduced by 40 % with respect to the old type-B but remain nearly two 

/pdf/upgrade-of-the-liquid-helium-storage-for-the-large-hadron-4mexujghnc.pdf

Upgrade of the Liquid Helium Storage for the Large Hadron Collider

First operational experience of the upgraded cryogenic infrastructure of the vertical magnet test facility in the SM18 hall, including HFM and cluster D test stations.

O. Pirotte

Papers

Cryogenic Design of the New High Field Magnet Test Facility at CERN

Thermal performance of the new superfluid helium vertical test cryostats for magnet tests at CERN

New vertical cryostat for the high field superconducting magnet test station at CERN

Upgrade of the Liquid Helium Storage for the Large Hadron Collider

First operational experience of the upgraded cryogenic infrastructure of the vertical magnet test facility in the SM18 hall, including HFM and cluster D test stations.