Cryogenic Gas Research Articles

Collisional cooling of ultracold molecules.

Since the original work on Bose-Einstein condensation1,2, the use of quantum degenerate gases of atoms has enabled the quantum emulation of important systems in condensed matter and nuclear physics, as well as the study of many-body states that have no analogue in other fields of physics3. Ultracold molecules in the micro- and nanokelvin regimes are expected to bring powerful capabilities to quantum emulation4 and quantum computing5, owing to their rich internal degrees of freedom compared to atoms, and to facilitate precision measurement and the study of quantum chemistry6. Quantum gases of ultracoldatoms can be created using collision-based cooling schemes such as evaporative cooling, but thermalization and collisional cooling have not yet been realized for ultracold molecules. Other techniques, such as the use of supersonic jets and cryogenic buffer gases, have reached temperatures limited to above 10 millikelvin7,8. Here we show cooling of NaLi molecules to micro- and nanokelvin temperatures through collisions with ultracold Na atoms, with both molecules and atoms prepared in their stretched hyperfine spin states. We find a lower bound on the ratio of elastic to inelastic molecule-atom collisions that is greater than 50-large enough to support sustained collisional cooling. By employing two stages of evaporation, we increase the phase-space density of the molecules by a factor of 20, achieving temperatures as low as 220 nanokelvin. The favourable collisional properties of the Na-NaLi system could enable the creation of deeply quantum degenerate dipolar molecules and raises the possibility of using stretched spin states in the cooling of other molecules.

Numerical analysis of the heat flux density of the whole-body cryotherapy (WBC) object coming from the skin

In technologies of cryotherapeutic effects, the main attention is paid to the choice of temperature of cryogenic gas. At the same time, along with the gas temperature, other process parameters are also essential: the gas velocity, the dimensions and spatial orientation of the biological cooling object, the humidity and gas velocity, etc. To develop the technique and technology of general cryotherapy, generalizing research is needed that can form the theoretical basis for the production and design of cryotherapy equipment. The most general results can be obtained by studying the effect that cooling has on a biological object with different intensities of heat removal along the length of the biological object. The work will conduct a chilled analysis of heat flux losses from the surface of the skin of a biological object with a slight change in the geometry of cryosauna during the whole-body cryotherapy process (WBC). To implement these tasks, a software package using the finite element method will be used. To describe the biological object with internal heat release, these biological heat equations were solved using the Penns approximation. The results of this work will help to give recommendations to cryosauna manufacturers to optimize the design of the cryotherapy unit, which in turn will help to increase the effectiveness of cryotherapy.

The study of thermal processes of the skin of the object of the whole-body cryotherapy (WBC) using numerical analysis

The work investigated the thermophysical processes occurring in the cryosauna during cryotherapeutic effects on the human body. Experimental studies in the field of the whole-body cryotherapy (WBC) are complex, since studies are necessary in such a wide range of environmental parameters as phase state, temperature, heat flux density, gas flow velocity in the cryosauna. One of the solutions to this problem is the development of computer models of the processes of heat transfer of a biological object in a cryosauna, allowing a wide range of studies to be carried out without human experiments. In this paper, we analyze a modification of the design of a cryochamber with a biological object. In this work, several types of computer models will be created, the models of which vary depending on the geometry of the wall of the cryosauna chamber from 90 to 85 degrees. The paper will show how much it is necessary to pay attention to the geometry of the cryosauna and work on the modification of the geometry. This work shows that when the geometry of the wall of the cryosauna was changed, it turned out that it smoothed the temperature distribution along the length of the object, which, in turn, will positively affect further research in this area. The results can be applied to optimize the supply of cryogenic gas in saunas, further geometry modernization, as well as to increase the efficiency and safety of the WBC process.

Experimental influence of twist angle and cryogenic gas on quality of drilled hole in carbon fiber reinforced plastic composites

The considerable body of literature on the effect of moisture on the mechanical properties of composites has shown that there is a disinclination to use coolant fluids within the composite industry. Tool geometry and cryogenic liquid cooling also have a significant impact on carbon fiber–reinforced plastic machining capabilities. In this paper, the two issues mentioned are improving the drilled hole quality and reducing the amount of CO2 released into the air to protect the environment. The experimental characteristics using a carbide drill with three levels of twist angle of flute and a gas mixture of CO2–N2 were investigated. To verify hole quality, the diameter, the delamination, the uncut fiber area, and the surface roughness were analyzed. With the goal of reducing the amount of CO2 released into the atmosphere, a list of experiments was proceeded in the dry, the air, gas CO2, and a gas mixture of CO2–N2. The thrust force and the temperature were observed. Based on the experiment results, the high helix tool was more advantageous than the triple tool and low helix tool. The difference in the effect of CO2 and CO2–N2 was not significant with the triple tool and the low helix tool; however, the performance of the CO2–N2 gas mixture showed a positive effect on the high helix tool.

Multireference study of ionic/covalent electronic states of MF (M=Be, Mg and Ca).

Ultracold environments composed by atoms or molecules offer an opportunity to study chemical reactions at the quantum-state level, for simulation of solid-state systems, as qubits in quantum computing, and for test fundamental symmetries. Those ultracold conditions formed by molecules can be obtained from cryogenic buffer gas, via supersonic expansion, followed by deceleration or from the laser cooling process. Diatomic alkaline earth monofluoride molecules have been shown as great candidates for the laser cooling process. In this sense, the present work focuses on the characterization of the low-lying doublet electronic states correlated to the first dissociation channel of the alkaline earth monofluorides diatomic molecules MF (M=Be, Mg and Ca). The developed state-of-the-art methodology was based on a qualitative analysis of the diatomic electronic structure, employing a hypothetical potential energy curve or by a simple molecular orbital diagram combined with bond order analysis. The potential energy curves, excitation and dissociation energies, and various sets of spectroscopic parameters were calculated by the MRCI/cc-pV5Z methodology. Transition probabilities for emission and radiative lifetimes among the characterized electronic states were also calculated for the (A)2Π⟶(X)2Σ+ electronic transition. Comparing the spectroscopy properties, we were able to indicate the CaF molecule as the best candidate molecule for laser cooling devices among the studied molecules.

Cryogenic Performance Test Platform for the Gas Bearings of Helium Turbine Expanders

The turbo-expander is the core part of the helium refrigerator, and the gas bearing is the critical component influences the stability of the machine. There is 300 K operating temperature difference between the turbine wheel and the gas bearing regions in the helium turbo-expander. Therefore, it is necessary to consider the heat transfer between the bearing surfaces, nominally at room temperature, and the rest of the machine when studying bearing dynamic stability. This paper describes a cryogenic test platform that is being developed to analyze the dynamic performance of gas bearings with cryogenic gas supply. The system flow loop has been designed for bearing and small turbine testing at 80 K and above. The experimental method has been determined. All of the components are ready for the cold box assembly. The commissioning of the platform will be carried out in the near future.

Pollution Characteristics and Ozone Formation Potential of Ambient Volatile Organic Compounds(VOCs)in Summer and Autumn in Different Functional Zones of Lianyungang, China

Atmospheric volatile organic compounds (VOCs) were collected from different functional zones of Lianyungang during the summer and autumn of 2018. One-hundred-seven VOCs species were measured by cryogenic pre-concentration and gas chromatography-mass spectrometry (GC/MS). The ozone generation potential (OFP) of VOCs was estimated by maximum incremental reactivity (MIR). Results showed that the average volume fraction of VOCs was (22.1±13.1)×10-9. Alkanes and alkenes from C2-C4 as well as acetone and ethyl acetate were the predominant species, accounting for 59.8%-75.8% of TVOCs. The mean volume fraction in the industrial zone was the largest[(28.4±13.5)×10-9], followed by the scenic zone[(21.7±4.4)×10-9] and the traffic and residential mixed zone[(20.8±7.2)×10-9]. The concentration of VOCs in autumn was significantly higher than that in summer. The industrial zone was the site with the highest volume fraction in autumn (35.4×10-9), while the scenic zone had the highest volume fraction in summer (21.5×10-9). Alkane, sulfur, or oxygen containing compounds and halogenated hydrocarbons were the predominant components of VOCs, accounting for 35.3%, 26.9%, and 15.6% of the total amount, respectively. Due to industrial emissions, the content of sulfur or oxygen containing compounds in the industrial zone was significantly higher than that in scenic zone and the traffic and residential mixed zone. The average ratio of T/B (toluene/benzene) indicated that vehicle and solvent use were the main sources of VOCs in the urban area. The highest OFP was found in the industrial zone, followed by the traffic and residential mixed zone and the scenic zone. Alkenes and aromatics were the largest contributors to OFP.

Enhanced molecular yield from a cryogenic buffer gas beam source via excited state chemistry

We use narrow-band laser excitation of Yb atoms to substantially enhance the brightness of a cold beam of YbOH, a polyatomic molecule with high sensitivity to physics beyond the standard model (BSM). By exciting atomic Yb to the metastable 3P1 state in a cryogenic environment, we significantly increase the chemical reaction cross-section for collisions of Yb with reactants. We characterize the dependence of the enhancement on the properties of the laser light, and study the final state distribution of the YbOH products. The resulting bright, cold YbOH beam can be used to increase the statistical sensitivity in searches for new physics utilizing YbOH, such as electron electric dipole moment and nuclear magnetic quadrupole moment experiments. We also perform new quantum chemical calculations that confirm the enhanced reactivity observed in our experiment and compare reaction pathways of Yb(3P) with the reactants H2O and H2O2. More generally, our work presents a broad approach for improving experiments that use cryogenic molecular beams for laser cooling and precision measurement searches of BSM physics.

Towards the determination of an equivalent standard column set between cryogenic and flow-modulated comprehensive two-dimensional gas chromatography

This preliminary research is focused on the task of defining an equivalent standard column set between cryogenic and flow-modulation comprehensive two-dimensional gas chromatography (GC × GC) combined with mass spectrometry (MS). Cryogenic modulation (CM) was carried out by using a loop-type device, while the flow modulator used was a seven-port wafer chip, equipped with an external accumulation loop.Initially, a common low-polarity + mid-polarity CM GC × GC column set was selected (30 m × 0.25 mm ID × 0.25 μm df + 1.5 m × 0.25 mm ID × 0.25 μm df), a method was developed, and a GC × GC-MS fingerprint was attained (on a sample of bio-oil derived from coconut fibers). After, a column set with the same stationary phases was selected for the flow modulation GC × GC-MS method (20 m × 0.18 mm ID × 0.18 μm df + 5 m × 0.32 mm ID × 0.25 μm df), with the capability to provide a-similar-as-possible separation. A side-by-side measurement of several chromatography parameters (efficiency, peak capacity, resolution, peak widths, retention factors, elution temperatures) was made.

Pushing the boundaries of diode-pumped solid-state lasers for high-energy applications

We report on the successful demonstration of a 150 J nanosecond pulsed cryogenic gas cooled, diode-pumped multi-slab Yb:YAG laser operating at 1 Hz. To the best of our knowledge, this is the highest energy ever recorded for a diode-pumped laser system.

Comparison of thermodynamic efficiency of cryogenic gas and solid-state magnetocaloric cycles

Comparison of thermodynamic efficiency of cryogenic gas and solid-state magnetocaloric cycles

The study of temperature fields of the WBC object in three-dimensional formulation using numerical methods

In this paper, we reviewed the temperature fields and heat flux emanating from the target tissues of the object. The influence of low temperatures on the integumentary tissues of the object with cryotherapy treatment on the given object or the whole-body cryotherapy (WBC) procedure was analysed. WBC is a method connected with the use of cryogenic gas for the treatment and prevention of certain diseases. The results that are shown in this article are derived using a mathematical model of heat exchange between the flow of a gaseous medium (liquid nitrogen vapor) and a biological object (an object of WBC impact) in a three-dimensional non-stationary formulation. The study and construction of the model was carried out using the finite element method. The computer model allows you to calculate the dynamics of the thermal field in the skin of the patient’s body during and after the WBC. Computer simulations in the future could increase both safety and comfort of cryotherapy.

The ELI-NP IGISOL radioactive ion beam facility

The Extreme Light Infrastructure – Nuclear Physics (ELI-NP) laboratory in Bucharest, Romania, will host an IGISOL-type facility which will study exotic neutron-rich ion beams produced via photo-fission in actinide targets placed at the center of a cryogenic gas cell. Using a complex radio frequency quadrupole for radioactive ion beam formation, a powerful multiple-reflection time-of-flight mass spectrometer for selecting the refractory isotopes of interest, and several measurement stations, this facility will be an exciting new tool for nuclear scientists. The two mechanisms of ion transport inside the gas cell, namely drift by electric fields and drag by supersonic gas jets, are studied. A program to test the individual components of the stopping cell is discussed.

Effects of eco-friendly cooling strategy on machining performance in micro-scale diamond turning of Ti–6Al–4V

Abstract Titanium alloys are difficult-to-cut materials due to their low elastic modulus and poor thermal conductivity. To deepen the understanding of the cutting performance for Ti–6Al–4V under various eco-friendly cooling conditions, surface integrity, cutting forces, and tool wear were comprehensively investigated through cutting experiments implementing three cooling methods, namely, cryogenic gas (CG), minimum quantity lubrication (MQL), and a combination of CG and MQL (CG + MQL), respectively. The results show that the lowest surface roughness ( S a = 76.71 nm) was achieved at a low spindle speed under the CG + MQL cooling conditions. This suggests that of the three cooling methods, the CG + MQL hybrid cooling method achieved the highest cooling efficiency. Compared with the MQL cooling method, the CG + MQL cooling method led to more pronounced tool wear and material adhesion due to reduced oil-based lubricity caused by low temperatures. Under the MQL cooling conditions, the elastic recovery of Ti–6Al–4V accelerated the formation of micro-cleavages on the clearance face of the diamond tool. Additionally, the depth of cut was also comparable to the tool edge radius in the micro-scale diamond turning. Compared with the conventional turning of Ti–6Al–4V, this round-edge effect, combined with the adhesion and built-up edge, led to a relatively stronger friction effect, evidenced by an increase in the coefficient of friction from 1.027 to 3.532, and higher specific cutting energy under all the cooling conditions in micro-scale diamond turning.

Comparison between Dry, MQL, and Cryogenic Cooling Technique on Surface Integrity of Burnished Surface

Environmental concerns has contributed towards higher demands for green products. Therefore, various machining conditions, such as dry and near dry machining have been introduced to resolve the cutting fluid problem. However, the application of cryogenic cooling still not well understood especially for burnishing process. It is essential to initiate a study on the effect of cryogenic cooling technique to substitute other techniques to improvement burnishing process. Carbon dioxide is used as the cryogenic gas under supercritical state, and compare with dry and minimal quantity lubricant. Solid carbide burnishing tool is used with a diameter and corner radius of 16 mm and 1 mm, respectively. The result shows that burnishing process under cryogenic condition recorded less burn mark and better tool wear than dry and MQL conditions. In addition, cryogenic condition exhibits significant grain refinement and surface hardness. In conclusion, the performance of carbon dioxide gas under supercritical state outperformed other coolant conditions.

A generic concept for Helium purification and liquefaction plant

This study describes and evaluates the performance of producing a pure Helium fraction from Helium extraction facility designed for cryogenic natural gas plants. A generic concept for obtaining a Helium pure fraction, which has relatively lower capital and operating costs should be provided. In order to achieve this objective, a new concept for obtaining a Helium pure fraction from a crude Helium fraction, is proposed based on simulations run under diverse process conditions regarding crude Helium gas’ temperature, pressure and composition. This concept is characterized by; reducing the plant safety requirements due to the extensive separation of combustible components, and compact layout of Helium extraction plant. Further re-purification is included in the subsequent Helium liquefaction step through selective adsorption, hence then increasing the purity of the Helium product and reducing the plant energy consumption required for liquefying Helium-rich fraction and the valuable Helium boil-off routed from the storage facility. The Nitrogen-rich fraction is routed to Nitrogen liquefaction installation. Liquid Nitrogen is generated within Helium recovery facility for liquid Helium shielding and container cooling. Surplus gaseous Nitrogen either can be liquefied and used within cryogenic natural gas plant as process coolant or be vented to atmosphere.

Understanding Surface Flashover Strength in Cryogenic Helium Gas for Superconducting Devices

One of the limitations when developing GHe cooled HTS devices for power applications is determining suitable insulation designs. There would be significant reductions in cost, time, and effort if insulation designs could be accurately measured and characterized at room temperature instead of cryogenic temperatures. Our previous research on the intrinsic breakdown strength of GHe demonstrated that it is independent of temperature, and it is solely based on the mass density of the gas. However, the insulation of HTS power devices contains solid insulation materials, and it is necessary to confirm that the interaction between the solid insulation and GHe is also independent of temperature. This paper contains the development and fabrication of a surface flashover experiment setup which can be used at both room and cryogenic temperatures to characterize surface flashover in a GHe environment.

Cold, dense, atomic ion clouds produced by cryogenic buffer-gas cooling

We produce cold and dense clouds of atomic ions (Ca$^+$, Dy$^+$) by laser ablation of metal targets and cryogenic buffer gas cooling of the resulting plasma. We measure the temperature and density of the ion clouds using laser absorption spectroscopy. We find that large ion densities can be obtained at temperatures as low as 6 K. Our method opens up new ways to study cold neutral plasmas, and to perform survey spectroscopy of ions that cannot be laser-cooled easily.

A new multi-reflection time-of-flight mass spectrograph for the SLOWRI facility

A new multi-reflection time-of-flight mass spectrograph for nuclear mass measurements with high precision has been constructed at the SLOWRI facility at RIKEN-RIBF. We aim to couple this new device to a cryogenic gas cell operated at the BigRIPS facility of RIBF. It is part of the SLOWRI project for slowing down and stopping intense radioactive ion beams provided downstream of RIKEN’s superconducting ring cyclotron accelerator. In particular, this device is dedicated to be located at the end of the BigRIPS beam line to access ions that are presently guided to beam dumps during in-beam experiments. In this article the apparatus is described in detail.

Carbon chain extension processes in cryogenic environments: UV-assisted growth of polyynic nitriles in solidified rare gases

As demonstrated in recent years, polyynic nitriles may photochemically arise from smaller unsaturated chain species in an apparently rigid environment of a cryogenic rare gas matrix. Here I summarize the highlights of respective research that has advanced the spectroscopic description of R–(C≡C)n–C≡N molecules (R = H, CN or CH3).