Cryogenic Facility Research Articles

Outsourcing strategy and tendering methodology for the operation and maintenance of CERN’s cryogenic facilities

CERN operates and maintains the world largest cryogenic infrastructure ranging from ageing but well maintained installations feeding detectors, test facilities and general services, to the state-of-the-art cryogenic system serving the flagship LHC machine complex. A study was conducted and a methodology proposed to outsource to industry the operation and maintenance of the whole cryogenic infrastructure. The cryogenic installations coupled to non LHC-detectors, test facilities and general services infrastructure have been fully outsourced for operation and maintenance on the basis of performance obligations. The contractor is responsible for the operational performance of the installations based on a yearly operation schedule provided by CERN. The maintenance of the cryogenic system serving the LHC machine and its detectors has been outsourced on the basis of tasks oriented obligations, monitored by key performance indicators. CERN operation team, with the support of the contractor operation team, remains responsible for the operational strategy and performances. We report the analysis, strategy, definition of the requirements and technical specifications as well as the achieved technical and economic performances after one year of operation.

A high field and cryogenic test facility for neutron irradiated superconducting wire

A 15.5 T superconducting magnet and a variable temperature insert (VTI) system were installed at a radiation control area in Oarai center in Tohoku University to investigate the superconducting properties of activated superconducting materials by fast neutron. The superconductivity was measured at cryogenic temperature and high magnetic field. During these tests, some inconvenient problems were observed and the additional investigation was carried out. The variable temperature insert was designed and assembled to perform the superconducting property tests. without the liquid helium. To remove the heat induced by radiation and joule heating, high purity aluminum rod was used in VTI. The thermal contact was checked by FEM analysis and an additional support was added to confirm the decreasing the stress concentration and the good thermal contact. After the work for improvement, it was affirmed that the test system works well and all troubles were resolved. In this report, the improved technical solution is described and the first data set on the irradiation effect on Nb3Sn wire is presented.

Safety studies on vacuum insulated liquid helium cryostats

The loss of insulating vacuum is often considered as a reasonable foreseeable accident for the dimensioning of cryogenic safety relief devices (SRD). The cryogenic safety test facility PICARD was designed at KIT to investigate such events. In the course of first experiments, discharge instabilities of the spring loaded safety relief valve (SRV) occurred, the so-called chattering and pumping effects. These instabilities reduce the relief flow capacity, which leads to impermissible over-pressures in the system. The analysis of the process dynamics showed first indications for a smaller heat flux than the commonly assumed 4W/cm2. This results in an oversized discharge area for the reduced relief flow rate, which corresponds to the lower heat flux.This paper presents further experimental investigations on the venting of the insulating vacuum with atmospheric air under variation of the set pressure (pset) of the SRV. Based on dynamic process analysis, the results are discussed with focus on effective heat fluxes and operating characteristics of the spring-loaded SRV.

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

The magnets for the next steps in accelerator physics, such as the High Luminosity upgrade of the LHC (HL- LHC) 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.

Commissioning and Testing of a new 4.5K Cold Box for JLab Cryogenic Test Facility

A new 4.5K cold box at Jefferson Lab (JLab) Cryogenic Test Facility (CTF) was recently installed and commissioned to upgrade the existing 4.5 K refrigeration system and work in parallel with the existing 4.5 K cold box. This new 4.5 K cold box is equipped with two turbo-expanders and, at its maximum capacity condition, it is expected to support at least 6.6 g/s of helium liquefaction or 650 W of refrigeration at 4.5 K. It can also handle up to 10 g/s 30 K return flow for 2 K refrigeration recovery that supports cryo-module and superconducting cavity testing. Performances of the cold box at its maximum capacity conditions as well as several other operating modes were tested for acceptance. We will briefly review the new 4.5 K cold box design features and discuss the commissioning and performance testing results.

Use of PROFIBUS for cryogenic instrumentation at XFEL

The European X-ray Free Electron Laser (XFEL) is a research facility and since December 2016 under commissioning at DESY in Hamburg. The XFEL superconducting accelerator is 1.5 km long and contains 96 superconducting accelerator modules. The control system EPICS (Experimental Physics and Industrial Control System) is used to control and operate the XFEL cryogenic system consisting of the XFEL refrigerator, cryogenic distribution systems and the XFEL accelerator. The PROFIBUS fieldbus technology is the key technology of the cryogenic instrumentation and the link to the control system. More than 650 PROFIBUS nodes are implemented in the different parts of the XFEL cryogenic facilities. The presentation will give an overview of PROFIBUS installation in these facilities regarding engineering, possibilities of diagnostics, commissioning and the first operating experience.

Unseeded Velocity Measurements Around a Transonic Airfoil Using Femtosecond Laser Tagging

Femtosecond laser electronic excitation tagging velocimetry was used to study the flowfield around a symmetric, transonic airfoil in the NASA Langley Research Center’s 0.3 m transonic cryogenic tunnel facility. A nominal Mach number of 0.85 was investigated with a total pressure of 125 kPa and a total temperature of 280 K. Two components of velocity were measured along vertical profiles at different locations above, below, and aft of the airfoil at angles of attack of 0 and 7 deg. Velocity profiles within the wake showed sufficient accuracy, precision, and sensitivity to resolve both the mean and fluctuating velocities and general flow physics, such as shear-layer growth. Evidence of flow separation was found at high angles of attack. Velocity measurements were assessed for their accuracy, precision, dynamic range, spatial resolution, and overall measurement uncertainty as they relate to the present experiments. Measurement precisions as low as were observed, whereas the velocity dynamic range was found to be nearly a factor of 500. The spatial resolution of between 1 and 5 mm was found to be primarily limited by the femtosecond laser electronic excitation tagging spot size and advection of the flow. Overall measurement uncertainties ranged from 3 to 4%.

A New Cryogenic Test Facility for Large and Heavy Superconducting Magnets

A New Cryogenic Test Facility for Large and Heavy Superconducting Magnets

Development of an experimental variable temperature set-up for a temperature range from 2.2 K to 325 K for cost-effective temperature sensor calibration

A prototype of a variable temperature insert has been developed in-house as a cryogenic thermometer calibration facility. It was commissioned in fulfilment of the very stringent requirements of the temperature control of the cryogenic system. The calibration facility is designed for calibrating industrial cryogenic thermometers that include a temperature sensor and the wires heat-intercept in the 2.2 K–325 K temperature range. The isothermal section of the calibration block onto which the thermometers are mounted is weakly linked with the temperature control zone mounted with cooling capillary coil and cryogenic heater. The connecting wires of the thermometer are thermally anchored with the support of the temperature insert. The calibration procedure begins once the temperature of the support is stabilized. Homogeneity of the calibration block’s temperature is established both by simulation and by cross-comparison of two calibrated sensors. The absolute uncertainty present in temperature measurement is calculated and found comparable with the measured uncertainty at different temperature points. Measured data is presented in comparison to the standard thermometers at fixed points and it is possible to infer that the absolute accuracy achieved is better than ±0.5% of the reading in comparison to the fixed point temperature. The design and development of simpler, low cost equipment, and approach to analysis of the calibration results are discussed further in this paper, so that it can be easily devised by other researchers.

First experimental data of the cryogenic safety test facility PICARD

The test facility PICARD, which stands for Pressure Increase in Cryostats and Analysis of Relief Devices, has been designed and constructed for cryogenic safety experiments. With a cryogenic liquid volume of 100 L, a nominal design pressure of 16 bar(g) and the capacity of measuring helium mass flow rates through safety relief devices up to 4 kg/s, the test facility allows the systematic investigation of hazardous incidents in cryostats under realistic conditions. In the course of experiments, the insulating vacuum is vented with atmospheric air or gaseous nitrogen at ambient temperature under variation of the venting diameter, the thermal insulation, the cryogenic fluid, the liquid level and the set pressure in order to analyze the impact on the heat flux and hence on the process dynamics. A special focus will be on the occurrence and implications of two-phase flow during expansion and on measuring the flow coefficients of safety devices at cryogenic temperatures. This paper describes the commissioning and the general performance of the test facility at liquid helium temperatures. Furthermore, the results of first venting experiments are presented.

Experimental results of ITER cold circulators towards the performance demonstration

The cold circulators, the most challenging component of ITER cryo-distribution system, have been designed, manufactured and tested successfully at factory. The design point for the cold circulator has been specified as 2.21 kg/s at 4.3 K inlet temperature having 0.155 MPa pressure head, dedicated for the nominal operation of toroidal field (TF) superconducting magnet of ITER. The expected isentropic efficiency has been defined as 70 % or more suitable to cater the demands of the cryo-distribution system. Two cold circulators for TF superconducting magnet have been installed in the Test Auxiliary Cold Box (TACB) followed by the integration of TACB system with the 5.0 kW at 4.5 K class cryogenic test facility at Japan. Final cold acceptance test of the complete system has been performed in order to validate the design conditions of TACB and cold circulators. Qualification tests of two cold circulators have been executed at closed loop operating condition. The cool-down of cold circulators down to 4.6 K temperature level and normal operating results as well as the experimental validation of performance along with the obtained isentropic efficiencies at the operating conditions have been demonstrated meeting the system level requirements of ITER cryo-distribution.

Design and thermodynamic performance analysis of multichannel cryogenic transfer line for XFEL AMTF

The XATL1 cryogenic transfer line for XFEL/AMTF is dedicated for transferring cryogenic cooling power from helium refrigerators to a cryogenic test facility by means of the continuous flows of cold helium in supercritical and gaseous state. The external envelope of the transfer line contains 4 cold process lines and a common radiation shield, as well as the system of supports and thermal contraction compensators. The XATL1 was designed and manufactured within the Polish in-kind contribution to the XFEL project. The line has been under operation since year 2012. The paper presents a design, including supporting and thermal compensation systems, of the XATL1 line. The line performance analysis based on the Second Law of Thermodynamics has been done, and the output has been compared with the design assumptions.

Design of a 0-50 mbar pressure measurement channel compatible with the LHC tunnel radiation environment

The monitoring of cryogenic facilities often require the measurement of pressure in the sub 5’000 Pa range that are used for flow metering applications, for saturated superfluid helium, etc. The pressure measurement is based on the minute displacement of a sensing diaphragm often through contactless techniques by using capacitive or inductive methods. The LHC radiation environment forbid the use of standard commercial sensors because of the embedded electronics that are affected both by radiation induced drift and transient Single Event Effects (SEE). Passive pressure sensors from two manufacturers were investigated and a CERN designed radiation-tolerant electronics has been developed for measuring variable-reluctance sensors. During the last maintenance stop of the LHC accelerator, four absolute pressure sensors were installed in some of the low pressure bayonet heat exchangers and four differential pressure sensors on the venturi flowmeters that monitor the cooling flow of the 20.5 kA current leads of the ATLAS end-cap superconducting toroids. The pressure sensors operating range is about 1000 to 5000 Pa and the targeted uncertainty is +/- 50 Pa which would permit to measure the equivalent saturation temperature at 1.8 K within better than 0.01 K. This paper describes the radiation hard measuring head that is based on an inductive bridge, its associated radiation-tolerant electronics that is installed under the LHC superconducting magnets or the ATLAS detector cavern; and the first operational experience.

Boundary-Layer Detection at Cryogenic Conditions Using Temperature Sensitive Paint Coupled with a Carbon Nanotube Heating Layer.

Detection of flow transition on aircraft surfaces and models can be vital to the development of future vehicles and computational methods for evaluating vehicle concepts. In testing at ambient conditions, IR thermography is ideal for this measurement. However, for higher Reynolds number testing, cryogenic facilities are often used, in which IR thermography is difficult to employ. In these facilities, temperature sensitive paint is an alternative with a temperature step introduced to enhance the natural temperature change from transition. Traditional methods for inducing the temperature step by changing the liquid nitrogen injection rate often change the tunnel conditions. Recent work has shown that adding a layer consisting of carbon nanotubes to the surface can be used to impart a temperature step on the model surface with little change in the operating conditions. Unfortunately, this system physically degraded at 130 K and lost heating capability. This paper describes a modification of this technique enabling operation down to at least 77 K, well below the temperature reached in cryogenic facilities. This is possible because the CNT layer is in a polyurethane binder. This was tested on a Natural Laminar Flow model in a cryogenic facility and transition detection was successfully visualized at conditions from 200 K to 110 K. Results were also compared with the traditional temperature step method.

Performance of VUV-sensitive MPPC for liquid argon scintillation light

A new multi-pixel photon counter (MPPC) sensitive to vacuum ultra-violet (VUV) light (wavelength λ<150nm) has recently been developed and produced by Hamamatsu Photonics K.K. In this study, the basic properties of the new MPPC are measured at the cryogenic facility of the Waseda University using liquid nitrogen. The temperature dependence of the breakdown voltage, capacitance, and dark count rate of the MPPCs are also evaluated. Using an 241Am α-ray source, the absolute photon detection efficiency (PDE) of the liquid argon (LAr) scintillation light (λ=128nm) for the latest MPPC model is estimated to be 13%. Based on these basic measurements a possible application of the new MPPC to LAr detectors in dark matter search is suggested.

Modelization of the thermal coupling between the ITER TF coil conductor and the structure cooling circuit

The ITER Toroidal Field (TF) coils are required not to quench during the most demanding event: a plasma disruption followed by a fast discharge of the Central Solenoid (CS), the Poloidal Field (PF) coils and the Correction Coils (CC). This event creates large heat deposition in the ITER magnet stainless steel structures in addition to the conductor AC losses. In order to prevent quench occurring in the TF conductor, cooling channels, implemented in the TF coil structure (TFCS), have to remove a large fraction of the heat deposited. The first integrated TF and structure mock-up has been manufactured and then tested in the HELIOS cryogenic test facility (CEA Grenoble) to determine the thermal coupling between the TFCS and the TF conductor, both actively cooled by supercritical helium at 4.4K and 5bar. It consists in a stainless steel casing, a cooling pipe glued with resin in the casing groove, winding pack (WP) ground insulation, a radial plate and a copper dummy cable-in-conduit-conductor (CICC). Steady state as well as transient thermal characterizations have been completed in May 2015. Simulation results by thermal hydraulic codes (VENECIA/SuperMagnet) and some of the experimental data are presented and discussed. The thermal coupling between the helium in the cooling tube and the TF coil structure is then modelled as an equivalent heat transfer coefficient in order to simplify the thermal hydraulic (TH) models. Comparison between simplified coupling and detailed coupling is presented.

Iseult/INUMAC 11.7-T MRI Assembly Status

A new innovative whole-body 11.7-T MRI magnet is currently being manufactured at Alstom Belfort as part the Iseult/Inumac project, a French-German initiative focused on very high magnetic field molecular imaging. It will be installed at the end of year 2016 in a neuroscience research center with other very high field MRI equipment, operating in France at CEA Saclay since November 2006. The main coil constructed from a stack of 170 double pancakes of 2-m diameter, with a finished height of 4 m and 50 t in weight, has been completed within required tolerances. The two shielding coils, vacuum impregnated solenoids of 4 m in diameter and 10 t in weight, have been also completed within tolerances. A crack has been discovered inside the 2-m diameter mandrel of the cryogenic correction coils. A new mandrel has been manufactured, with delivery in July 2015. The main coil and the shielding coils have been integrated inside the helium vessel, and the assembly of thermal shield and vacuum vessel is due to start, with completion expected by the middle of 2016. The magnet will be serviced by a separate cryogenic and electrical facility; the installation of this external equipment will be completed by the end of 2015 when the first phase of the commissioning will start. Full tests and commissioning of the magnet at 1.8 K are expected at NeuroSpin at the beginning of 2017.

Direct Detection of Liquid Argon Scintillation with MPPC

A new type of the Multi-Pixel Photon Counter (MPPC), sensitive to Vacuum Ultra-Violet (VUV) light (wavelength < 150 nm), is recently developed and produced by Hamamatsu Photonics K.K.. We have successfully achieved direct detection of liquid argon (LAr) scintillation light (wavelength = 128 nm) using this device without any wavelength shifter. We first measured basic properties (temperature dependence of gain, cross-talk, after pulse, etc.) at cryogenic facility at Waseda university. We have also estimated the absolute photon detection efficiency (PDE) for LAr scintillation light emitted from 241Am α-ray (5.5 MeV) source. Finally, a possible application of the new MPPC to LAr detector for dark matter search is discussed.

Development of low noise amplifier and associated RF switching circuit for the penning ion trap

In this paper we describe the design and development of cryogenic electronic instrumentation required for VECC cryogenic Penning ion trap facility. As a part of the development of cryogenic electronic instrumentation, a low noise amplifier based on GaAs technology is designed and room temperature testing of the amplifier is successfully accomplished. The equivalent input voltage noise density of the amplifier measured at room temperature is found to be in the range of (1.8.2)nV Hz at the ion trap axial frequency of 63 MHz. Also a cryogenic switching and RC filtering circuit is developed in order to maintain proper switching of RF energy used to excite the motional amplitude of trapped electrons. These RC filtering circuits filter the noise in the DC supply lines. The performance of this circuit board has been tested successfully upto 90K.

Structural Design and Simulated Analysis of the Cryostat and Its Affiliated Parts of CFETR CSMC Cryogenic Test Facility

According to the CFETR CSMC properties test requirements, a large cryogenic test platform will be set up. The cryostat and its affiliated parts, as one of the important components of the platform, should be studied to make sure them could afford the much valued help for the basic test facilities. This paper focuses on the structural design and the finite element analysis of the cryostat and its affiliated parts. All of the work could not only provide necessary help for building CFETR CS model coil test platform, but also provide the important experience of the large cryogenic test platform in future.