Cryogenic Laboratory Research Articles

Cold Moves: Cryogenics in Indo-German Research Networks.

By unravelling the complexities and dynamics of a collaboration between scientists in India and West Germany to establish a cryogenic network, this paper intends to contribute to our understanding of the transnational movement of research technologies during the Cold War. In 1971, a cryogenic laboratory including a helium and a nitrogen liquefier was set up at the physics department of the Indian Institute of Technology (IIT) Madras as part of the Indo-German partnership at IIT Madras between 1959 and 1974. As a generic research technology with many applications, cryogenics became crucial for a solid state research agenda for semiconductor development. After initial difficulties, Ramaswami Srinivasan at IIT Madras and Gustav Klipping of the Fritz Haber Institute in Berlin built a successful collaboration based on mutual trust and on Indian and German scientists travelling and working in each other's laboratories. If the initial motivation of the Indo-German partnership was informed by the logic of Cold War development policy, Klipping and Srinivasan developed their collaboration into a vibrant cryogenic research network around different actors, instruments, and skills moving between India and the Federal Republic of Germany.

Study on personal comfort heating system and human thermal comfort in extremely low-temperature building environments

Exposure to extremely low-temperature building environments around −20 °C causes various hazards to human health. However, few studies have studied human thermal comfort and physiological response in such environments, nor the personal comfort heating system. Thus, this study investigated the heating characteristics of personal comfort heating system and their effects on thermal responses and thermophysiological parameters in extremely low-temperature building environments. We conducted experimental tests and questionnaires in a cryogenic enthalpy difference laboratory with air temperature ranging from −21.2 to −15.6 °C and a relative humidity of 55 %. Eight experimental conditions were designed with several heating measures (heating mat, heating gloves, heating cushion and airwarmer). The heating parameters of the personal comfort heating systems as well as the subjective evaluations and skin temperature of the subjects were recorded and analyzed. The results showed that the airwarmer confinement box condition had a corrective power of up to 38.3 K. The overall thermal sensation vote and overall thermal comfort vote were maintained at 0.25 and −0.25. Further, we found that the face, hands, calves and feet got cold easier with the largest skin temperature difference of −4.9, −8.1, −6.7 and −7.6 °C, respectively. Besides, the relationships between thermal responses and between thermal responses and skin temperature were examined, as well as a thermal comfort assessment methodology was established for extremely low-temperature environments.

Phase and Morphology of Water-ice Grains Formed in a Cryogenic Laboratory Plasma

Grains of ice are formed spontaneously when water vapor is injected into a weakly ionized laboratory plasma in which the background gas has been cooled to cryogenic temperatures comparable to those of deep space. These ice grains are levitated indefinitely within the plasma so that their time evolution can be observed under free-floating conditions. Using microscope imaging, ice grains are shown to have a spindle-like fractal structure and grow over time. Both crystalline and amorphous phases of ice are observed using Fourier transform infrared spectroscopy. A mix of crystalline and amorphous grains coexists under certain thermal conditions, and a linear mixing model is used on the ice absorption band surrounding 3.2 μm to examine the ice phase composition and its temporal stability. The extinction spectrum is also affected by inelastic scattering as grains grow, and characteristic grain radii are obtained from Mie scattering theory and compared to size measurements from direct imaging. Observations are used to compare possible ice nucleation mechanisms, and it is concluded that nucleation is likely catalyzed by ions, as ice does not nucleate in the absence of plasma and impurities are not detected. Ice grain properties and infrared extinction spectra show similarity to observations of some astrophysical ices observed in protoplanetary disks, implying that the fractal morphology of the ice and observed processes of homogeneous ice nucleation could occur as well in such astrophysical environments with weakly ionized conditions.

Numerical analysis of a steady-state and transient performance using a tube-in-tube heat exchanger unit for cryogenic process simulator

Large scale Helium Refrigerators and Liquefiers (HRLs) are essential technologies in particle physics experiments and the nuclear energy sector. Most HRLs employ a modified version of the Collin's cycle, which involves a room temperature compressor, several counter-flow heat exchangers (HXs), expanders, and a J-T valve to produce liquid helium. The performance of HRLs is mainly governed by the efficacy of HXs and requires accurate process modeling and simulation. Although various platforms for process modeling and simulation of HXs are available, both commercial and open source, significant customization is required to use them in the cryogenic domain. Moreover, the transient simulation of a HX in two-phase has always been a concern. Therefore, there is a need to develop a numerical model of a HX to meet the requirements of the cryogenic domain specially in two-phase region.In present study, a HX is being modeled on the open source platform Python®. The developed numerical model is based on the distributed parameter approach to capture the impact of the variable fluid properties as well as their impact on the heat transfer coefficient. The model allows user to choose a suitable heat transfer correlation as per the requirement in different regime of the phases across the length of HX. The developed model may be suitable to simulate the HXs used as LN2 precooling, HXs of helium plant operating in mixed mode, and J-T heat exchangers where fluids undergoes phase changes along the flow length.The created models are initially tested against their design data, and results are then acquired under non-standard operating conditions. The outcomes are validated with experimental data from the ITER-India cryogenic Laboratory (IICL) after being first verified using the commercial process simulator Aspen HYSYS®.

Rapid qualification of fused filament fabrication thermoplastics for cryogenic applications

Thermoplastic additive manufacturing (AM) is an attractive process for fabricating cryogenic componentry, due to the potential for rapid, on-site parts replacement. However, using a process intended for low-feature prototypes in such a demanding application creates survivability concerns. AM further introduces significant material variability that complicates materials qualification. Herein, a highly-repeatable test procedure is developed to qualify as-manufactured samples. Fused Filament Fabrication (FFF) is used to produce both test samples and custom immersion equipment for cryogenic tensile testing, and data quality is improved by modifying the ASTM Type IV geometry. Tensile strength is measured directly, while elastic modulus is calculated using temperature measurements and thermomechanical model fitting. Via this methodology, cryogenic performance is characterized for Polylactic Acid (PLA), Acrylonitrile Butadiene Styrene (ABS), and Glycol-Modified Polyethylene Terephthalate (PETG). PLA notably demonstrates acceptable strain to failure of 2.6 % and a favorable increase in strength from 47 to 120 MPa when cooled. Testing of carbon fiber filled PLA (CF-PLA) finds a remarkable 250 % increase in strength, from 37 to 130 MPa. Both materials withstand 10 high-stress thermal cycles with mild strength gain, causing a loss of room temperature ductility in neat PLA but not CF-PLA. Dynamic Mechanical Analysis (DMA) indicates a β-transition at −20 to −40 °C, which correlates with the observed changes. These findings show AM thermoplastics are promising for use in cryogenic laboratory environments, and could be modified for use in production applications.

Design, Fabrication, and Test of a Prototype of Matrix Heat Exchanger for Cryogenic Distillation of Hydrogen Isotopes

The following properties are needed to increase the efficiency of refrigeration, liquefaction, and cryogenic separation cycles: Heat exchangers must have high effectiveness doubled by high compactness; small temperature differences between incoming and outgoing flows must be ensured to increase efficiency; there must be a large heat transfer surface, relative to the volume of the heat exchanger, to minimize heat loss; there must be a high heat transfer rate to reduce the transfer area; there must be a small pressure drop to reduce compression costs; and there must be high reliability with minimal maintenance. All these properties are entirely fulfilled by the designed matrix heat exchangers (MHEs). This paper presents the results of the research program developed by the team of the Cryogenic Laboratory from INC-DTCI ICSI Ramnicu Valcea, which included procedural stages of the realization and preliminary results of the characterization of the MHE-type heat exchanger in a narrow range of values to achieve a proper solution for a heat exchanger to be used for cryogenic purposes, such as cooling the gas mixture at the entrance of a distillation column of hydrogen isotopes and running at low pressure (typically regimes of 0.5 to 2.0 bars) and flows. Within several experimental campaigns, different assembly and testing techniques of the matrix heat exchanger (MHE) prototype were performed to achieve numerical data for the temperature and pressure drops along the heat exchanger and to verify ANSYS Fluent numerical simulation results. The results showed that for the designed and tested MHE prototype, a temperature drop of up to almost 230 K can be obtained at the established parameters correlated with pressure losses within a few millibars (the maximum recorded pressure drop is 80 mbars), small dimensions (64 mm high), and accessible weight (up to 2000 g).

New Achievements of H2-HD-D2 Isotopic Separation with the Cryogenic Distillation Experimental Stand from ICSI Cryogenic Laboratory

In the design process of a cryogenic distillation plant for the separation of hydrogen isotopes, two main objectives, often impossible to achieve simultaneously, are taken into account: a high separation factor for different mixtures and isotope concentrations and the reduction of design, manufacturing, and operating costs with increased efficiency and safety. All this should result from the use of a method for calculating the separation efficiency, a method that will generate a conceptual design that must form the basis of the final technical design. Unfortunately, most design methods treat these plants as chemical plants, although in the case of cryogenic plants, it is not possible to readjust the new process operating parameters quickly and with great precision so that the separation efficiency and performance are not affected. There are three causes affecting the separation performance of cryogenic distillation plants, namely, nonideality of the cryogenic process, imperfection of heat exchangers, and heat losses. This paper presents our proposed solutions for increasing the efficiency of the cryogenic distillation process and discusses solutions tested in experimental campaigns with the cryogenic distillation stand developed in the Cryogenic Laboratory at ICSI Rm. Vâlcea.

A versatile cryogenic system for liquid argon detectors

Detectors for direct dark matter search using noble gases in the liquid phase as a detection medium need to be coupled to liquefaction, purification and recirculation systems. A dedicated cryogenic system has been assembled and operated at the INFN-Naples cryogenic laboratory with the aim to liquefy and purify the argon used as an active target in liquid argon detectors to study the scintillation and ionization signals detected by large SiPM arrays. The cryogenic system is mainly composed of a double wall cryostat hosting the detector, a purification stage to reduce the impurities below one part per billion level, a condenser to liquefy the argon, and a recirculation gas panel connected to the cryostat equipped with a custom gas pump. The main features of the cryogenic system are reported as well as the performance, long term operation and stability in terms of the most relevant thermodynamic parameters.

Experimental Investigation of Uniaxial Compressive Strength of Distilled Water Ice at Different Growth Temperatures

The existence of ice in nature will threaten the safety of navigation and water operations in cold regions. In order to improve the knowledge system of ice strength, the uniaxial compressive strength of distilled water ice grown at different temperatures is studied in this paper. Distilled water ice samples grown at −5 °C, −10 °C, −15 °C, −20 °C, −25 °C, −30 °C and −35 °C are prepared in the cryogenic laboratory. The density and grain size are measured. The uniaxial compressive strength tests are carried out at −10 °C. The stress-strain curves and the mechanical properties and failure modes of ice are obtained by loading along the vertical direction in the strain rate range of 10−6 s−1 to 10−2 s−1. It is found that the uniaxial compressive strength of ice is a power function of strain rate and a linear relationship with the −1/2 power of grain size. Combined with the relationship between strength and grain size and the relationship between grain size and temperature, it is deduced that the peak compressive strength has a logarithmic relationship with the growth temperature. In addition, it shows that the growth temperature affects the strength of ice by controlling the grain size.

Application of the Frozen and Unfrozen Soil model to modelling effects of freeze-thaw on low-volume roads

Freezing and thawing of soils are of the utmost importance in the design of infrastructure in seasonally cold regions. Cycles of freezing-thawing can severely affect the performance of thinly paved low-volume roads, causing frost heave during the winter and thaw weakening in the spring. Thus, a designer must have an understanding of freezing effects on infrastructure and adequate design tools to deal with them. Freezing of soils entails several coupled processes, necessitating advanced analysis tools such as numerical modelling. This paper applies the Frozen and Unfrozen Soil material model for the finite element program Plaxis 2D into a case study of freezing and thawing induced deformation of a low-volume road on dry-crust clay subgrade in Vesilahti, Finland supported by a literature review and a laboratory study. The Vesilahti test site monitoring results of frost heave, temperature and groundwater level were used in this study to simulate the frost heave of a pavement with shallow structural layers. In addition, soil sampling and laboratory tests were performed to determine the Vesilahti dry-crust clay material properties at the Aalto University. These were combined to simulate the frost heave and thaw settlement measured on the site and to study the feasibility of the material model in replicating actual measured frost action. The road deformation at the measurement times was replicated qualitatively well and the model performed mostly according to expectations. However, the multitude of parameters, complexity of the coupled phenomena modelled and the black box nature of the model implementation in Plaxis make the evaluation of calculation errors tough and time-consuming. Further research on the model could include the implementation of various user-friendly improvements in Plaxis, development of cryogenic suction-and temperature-controlled laboratory testing for the model parameter determination and better utilization of the model’s predictive capabilities by studying continuous frost heave measurements.

Effect of magnetic field environment on the performance of 3/2 solenoid valve

• 3/2 solenoid valve functionality has been checked under external magnetic field environment. • External magnetic field limit has been defined below which 3/2 solenoid valve functions well. • Magnetic shielding of the 3/2 solenoid valve has been proposed. ITER, an experimental fusion reactor uses solenoid valves to close cryogenic control valves instantly in case of any incidental event in the ITER cryogenic system takes place. Many of these solenoid valves are functioning with the magnetic field environment of the order of ∼25 m T. Since a solenoid valves is an electrically activated valve, presence of the environment magnetic field can lead to partial or non-closing of the valve. In this paper, the effect of magnetic field environment on the performance of 3/2 solenoid valves through simulation and experiment is studied. The variable external magnetic field is generated by supplying variable power from Switched Mode Power Supply (SMPS) to the magnetic coil and magnetic field readings are recorded with a tesla meter. The validation of the magnetic field profile of the magnetic coil is done by comparing the E-mag analysis simulation performed on ANSYS® platform and the experimental results. An experiment setup, inside ITER-India cryogenic laboratory, has been assembled to see the functionality of the 3/2 solenoid valve in the presence of an external magnetic field. A 3/2 solenoid valve is placed in the external magnetic field which has been generated with the help of an air core inductor magnetic coil. The external magnetic field from the coil is varied from 10 m T to 35 m T with the help of a variable power supply and checked the functionality of the solenoid valve in different orientation and different external magnetic fields strengths. The outcome of the study shows that the 3/2 solenoid valve stopped functioning over the external magnetic field strength of 14.29 m T. The paper also concludes the requirement of the magnetic shielding and correct orientation of the solenoid valves to be installed in order to nullify the effect of external magnetic field on the functionality of the 3/2 solenoid valves.

Standoff Raman spectroscopy for future Europa Lander missions

AbstractNear Infrared Mapping Spectrograph data from the Galileo spacecraft and cryogenic laboratory reflectance measurements on hydrated compounds identified the presence of mixtures of hydrous magnesium sulfate, sulfuric acid, and hydrogen peroxide on the surface of Europa. Standoff Raman spectroscopy is ideally suited for exploring terrestrial Europa analog sites and Europa because of its ability to unambiguously identify minerals, organic compounds, and biomarkers inside ice. In the present work, we evaluated the performance of a standoff Raman system at various distances by measuring Raman spectra of hydrogen peroxide, sulfuric acid, and hydrous sulfate minerals, which are predicted to be present on Europa's surface. To simulate Europa's surface environment, Raman spectra of MgSO4·7H2O, FeSO4·7H2O, gypsum (CaSO4·2H2O), dry ice (CO2‐ice), and polycyclic aromatic hydrocarbons (PAHs) naphthalene and anthracene inside crushed H2O‐ice, shaved H2O‐ice, and a clear H2O‐ice block have also been measured. The PAHs were selected in this study because of their presence in the interstellar medium, comets, and meteorites. The results show that it will be possible to map out the non‐ice components on the surface and subsurface of Europa analog sites and Europa up to a distance of 120 m from a static lander and to a depth of ~10 cm inside ice.We have evaluated the performance of a standoff Raman system at various distances by measuring Raman spectra of hydrogen peroxide, sulfuric acid, and hydrous sulfate minerals, which are predicted to be present on Europas surface. To simulate Europas surface environment, Raman spectra of MgSO4·7H2O, FeSO4·7H2O, gypsum (CaSO4·2H2O), dry ice (CO2‐ice), and polycyclic aromatic hydrocarbons (PAHs) naphthalene and anthracene inside crushed H2O‐ice, shaved H2O‐ice, and H2O‐ice block have been measured.

Transient Heat Transfer in Superfluid Helium Cooled Nb<inline-formula> <tex-math notation="LaTeX">$_3$</tex-math> </inline-formula>Sn Superconducting Coil Samples

An experimental setup is operational at the Central Cryogenics Laboratory of the European Organization for Nuclear Research to measure the cooling mechanisms of superfluid 4 He (He II) from prepared Rutherford-type superconducting cable stacks to a stagnant He II bath. For novel magnets designed for the so-called high-luminosity large hadron collider upgrade, a segment of a fully impregnated Nb 3 Sn 11T dipole magnet was measured. A dataset on the thermal behavior is presented, with homogeneous heat inputs of up to approximately 4.8 mW cm -3 corresponding to an average steady-state temperature of 3.1 K for the inner layer and 4.0 K for the outer layer when cooled via a 1.9 K He II bath. We discuss the steady state as well as transient behavior observed.

Study on heat transfer between the High-Luminosity LHC beam screens and the He II-cooled beam tube

The new beam screens for the inner triplets in the HL-LHC are designed to intercept heat loads of up to 25 Wm−1 between 60 K and 80 K. The screens need to be mechanically supported by the beam tube at 1.9 K while limiting heat transfer to the same tube to less than 0.5 W m−1. Measurements for the thermal validation of the beam screens were carried out on a dedicated test stand at the Central Cryogenic Laboratory at CERN. This paper describes the first measurement campaign of a full-scale D1-type beam screen mock-up: several parameters such as base temperature and heating power were varied, and results include heat transfer mechanisms within the beam screen and more importantly to the 1.9 K beam tube that forms the physical boundary between beam screen and He II-cooled magnets.

Heat transfer at dielectric - metallic interfaces in the ultra-low temperature range

In the framework of the AEgIS project a series of steady state and dynamic heat transfer measurements at ultra-low temperatures was conducted in the Central Cryogenic Laboratory at CERN. Two sandwich setups, simulating the behaviour of ultra-cold AEgIS electrodes, were investigated and compared, namely: a sapphire — indium — copper and a sapphire — titanium — gold — indium — copper sandwich. The total thermal resistivity of both sandwich setups was evaluated as a function of the influence of normal and superconducting thin layers and multiple dielectric — metallic interfaces in terms of Kapitza resistance. The resulting limitations of the electrode’s design are presented.

Cryogenic distillation experimental stands for hydrogen isotopes separation

In cryogenic distillation columns complex phenomena appear, some of them are needed such as isotopic separations and others must be avoided, such as the non-uniform cooling of the distillation column or the impossibility of transfer of the cooling power to the gas’s mixture with major changes in the separation dynamics. The paper presents new solutions for the design of several components, parts of the new experimental cryogenic distillation stands developed in the Cryogenic Laboratory in order to expand the experimental base for ICSI Rm.Valcea “Experimental Pilot Plant for Tritium and Deuterium Separation” (PESTD). One stand will allow testing and characterization of new solutions for cryogenic distillation columns at laboratory scale and will be attached to hydrogen liquid liquefaction system while the second stand will allow testing of verified solutions at semi-industrial level and this will be attached to a Linde HRLS 11 refrigeration and liquefaction plant that has the capability to transfer in a closed loop helium gas at 16 K–20 K.

New Bridge Temperature Sensor for Superconducting Magnets and Other Cryogenic Applications

A few hundred temperature sensors are used to monitor the temperature behavior of the gigantic ATLAS toroid superconducting magnet system during cool down and normal operation. In order to guarantee good sensitivity of temperature measurements in the range from liquid helium to room temperature, two types of sensors are positioned at the same location: platinum resistance thermometers for the range 30–300 K and carbon composition resistors (Allen-Bradley) for the 4–30 K range. Both types are very well known for use in cryogenics and they have performed satisfactorily during 10 year of ATLAS operation. The sensors themselves are easily available and inexpensive and the main cost is for the many kilometers of cold and warm instrumentation cables, connectors, conditioners, and installation work. A reduction of the amount of measurement channels is an important issue and this motivated us to develop a new compact and robust sensor module covering the entire temperature range that would combine advantages of both platinum and carbon resistors. The solution is trivial, elegant, and simple. Two resistors with positive temperature derivative and two resistors with negative temperature derivative are connected in a full-bridge connection. We used two platinum and two carbon resistors. The output signal is a result of the subtraction of voltages across positive and negative temperature derivative resistors that makes this temperature bridge sensor very sensitive for the entire temperature range. Variable temperature characterization tests were performed in the helium gas environment in the CERN Cryogenic Laboratory. Our measurements have demonstrated that the bridge sensors have a full range sensitivity better than 0.1 mV/K at a supply current of 100 μ A. In the meantime, a few other superconducting detector magnets in experiments operating at CERN are equipped with these new, simple, and robust temperature sensors.

Cold Test and Performance Evaluation of Prototype Cryoline-X

The multi-process pipe vacuum jacketed cryolines for the ITER project are probably world’s most complex cryolines in terms of layout, load cases, quality, safety and regulatory requirements. As a risk mitigation plan, design, manufacturing and testing of prototype cryoline (PTCL) was planned before the approval of final design of ITER cryolines. The 29 meter long PTCL consist of 6 process pipes encased by thermal shield inside Outer Vacuum Jacket of DN 600 size and carries cold helium at 4.5 K and 80 K. The global heat load limit was defined as 1.2 W/m at 4.5 K and 4.5 W/m at 80 K. The PTCL-X (PTCL for Group-X cryolines) was specified in detail by ITER-India and designed as well as manufactured by Air Liquide. PTCL-X was installed and tested at cryogenic temperature at ITER-India Cryogenic Laboratory in 2016. The heat load at 4.5 K and 80 K, estimated using enthalpy difference method, was found to be approximately 0.8 W/m at 4.5 K, 4.2 W/m at 80 K, which is well within the defined limits. Thermal shield temperature profile was also found to be satisfactory. Paper summarizes the cold test results of PTCL-X

Reynolds number scaling in cryogenic turbulent Rayleigh–Bénard convection in a cylindrical aspect ratio one cell

We perform an experimental study of turbulent Rayleigh–Bénard convection up to very high Rayleigh number, $10^{8}<Ra<10^{14}$, in a cylindrical aspect ratio one cell, 30 cm in height, filled with cryogenic helium gas. We monitor temperature fluctuations in the convective flow with four small (0.2 mm) sensors positioned in pairs 1.5 cm from the sidewalls and 2.5 cm vertically apart and symmetrically around the mid-height of the cell. Based on one-point and two-point correlations of the temperature fluctuations, we determine different types of Reynolds numbers, $\mathit{Re}$, associated with the large-scale circulation (LSC). We observe a transition between two types of $\mathit{Re}(\mathit{Ra})$ scaling around $\mathit{Ra}=10^{10}{-}10^{11}$, which is accompanied by a scaling change of the skewness of the probability distribution functions (PDFs) of the temperature fluctuations. The $\mathit{Re}(\mathit{Ra})$ dependencies measured near the sidewall at Prandtl number $\mathit{Pr}\sim 1$ are consistent with the $\mathit{Ra}^{4/9}\mathit{Pr}^{-2/3}$ scaling above the transition, while for $\mathit{Ra}<10^{10}$, the $\mathit{Re}(\mathit{Ra})$ dependencies are steeper. It seems likely that this change in $\mathit{Re}(\mathit{Ra})$ scaling is linked to the previously reported change in the Nusselt number $\mathit{Nu}(\mathit{Ra})$ scaling. This behaviour is in agreement with independent cryogenic laboratory experiments with $\mathit{Pr}\sim 1$, but markedly different from the $\mathit{Re}$ scaling obtained in water experiments ($\mathit{Pr}\sim 3.3{-}5.6$). We discuss the results in comparison with different versions of the Grossmann–Lohse theory.

Acceptance tests and their results for 1st Pre-Series Cryoline (PTCL) of ITER

The Pre-Series Cryoline (PTCL) for ITER is a representative cryoline from the complicated network of all cryolines for the ITER project. It is ∼28 m in length with same cross-section (1:1) including main line (ML) and branch line (BL) as of ITER torus & cryostat cryoline. Geometrically; it has bends at different angles i.e. 90°, 120°, 135° & 160° comprising T-section & Z-section. The PTCL has been fabricated in 5 different elements based on the installation feasibility. The mechanical & instrumentation installation like sensors mounting, displacement sensors, etc. has been completed. The PTCL test has been performed after complete installation of PTCL and integration with the existing test facility at ITER-India cryogenics laboratory in order to verify the thermal performance and mechanical integrity. The primary objectives, which are evaluated during the PTCL test, are (i) Thermal performance of the PTCL (ii) Measurement of temperature profile on thermal shield of PTCL, (iii) Stress measurement at critical locations, (iv) Measurement of Outer Vacuum Jacket (OVJ) temperature during Break of Insulation Vacuum (BIV) test. The paper will summarize the methodology and observed results of PTCL.