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[EN] The present invention relates to a cryocooler suitable for gas liquefaction applications, that comprises a coldhead (1) with one or more refrigeration stages (2, 3); further comprising: a refrigerator compressor (4) for distributing compressed gas-phase cryogen inside the coldhead (1); a heat exchanging coil (9) arranged at least partially around the external region of the coldhead (1); at least one extraction orifice (8) communicating a gas circulation circuit (5) inside the coldhead (1) with the heat exchanging coil (9); acting said extraction orifice/s (8) as pass-through port/s which allow the gas inside the coldhead (1) to flow through the inside of the heat exchanger coil (9) for exchanging heat with the exterior thereof, and wherein the heat exchanging coil (9) is adapted to connect and redirect the gas to one return port (8') connected to the gas circulation circuit (5). Another object of the invention relates to a cryogen-gas liquefaction system (11) and a method for liquefaction of gases that comprises said system (11), [FR] La présente invention concerne un refroidisseur cryogénique conçu pour des applications de liquéfaction de gaz, qui comprend une tête froide (1) dotée d'un ou de plusieurs étages de réfrigération (2, 3) ; comprenant en outre : un compresseur de réfrigérateur (4) pour distribuer un cryogène en phase gazeuse comprimé à l'intérieur de la tête froide (1) ; une bobine d'échangeur de chaleur (9) disposée au moins partiellement autour de la région externe de la tête froide (1) ; au moins un orifice d'extraction (8) communiquant un circuit de circulation de gaz (5) à l'intérieur de la tête froide (1) avec la bobine d'échange de chaleur (9) ; faire fonctionner ledit ou lesdits orifices d'extraction (8) en tant qu'orifices de passage qui permettent au gaz à l'intérieur de la culasse (1) de s'écouler à travers l'intérieur de la bobine d'échangeur de chaleur (9) pour échanger de la chaleur avec l'extérieur de celui-ci, et la bobine d'échangeur de chaleur (9) étant conçue pour connecter et rediriger le gaz vers un orifice de retour (8') raccordé au circuit de circulation de gaz (5). Un autre objet de l'invention concerne un système de liquéfaction de gaz cryogénique (11) et un procédé de liquéfaction de gaz qui comprend ledit système (11), Universidad de Zaragoza, Consejo Superior de Investigaciones Científicas (España), A3 Informe de búsqueda internacional

Resumen del trabajo presentado a la XXXVII Reunión Bienal de la Real Sociedad Española de Física celebrada en Zaragoza del 15 al 19 de julio de 2019., The presence of Hydrogen (H2) traces in LHe has disastrous consequences for some laboratory equipment such as evaporation cryostats, PPMS and MPMS. The working principle of those equipment to achieve temperatures below 4.2 K consists in pumping LHe through a capillary tube. If LHe contains H2 traces, that capillary will get blocked after some time. In order to unblock it, it is needed to heat the equipment at room temperature (RT) with the loss of liquid He and time. With the aim to solve this problem, the University of Zaragoza in collaboration with Quantum Design company developed a method to produce H2 free LHe. In this work, we present a study to determine what is the minimum H2 concentration in He gas that can generate blockages when the He gas is liquified. To carry out this proposal, we have developed an experimental setup to produce LHe contaminated with H2 in a controller manner. This setup can be divided in two stages (see figure): the first one consists in mixing the He gas (at RT and pressure larger than atmospheric) with a known H2 concentration to then be liquified (at 4.2 K and atmospheric pressure), whereas the second one consists in the detection of H2 traces present in the liquified He-H2 gas mixture by using a H2 detector developed by us, whose effectiveness has been proved in other labs around the world. This device consists of a flow microimpedance assembled to a stainless steel thin tube. The microimpedance is immersed in LHe while the other end of the tube is connected to a vacuum pump and a pressure sensor. If the tested LHe contains H2 traces (with an enough concentration to produce blockages), the pressure reading will decrease (in a few minutes) to the baseline of the vacuum pump.

Trabajo presentado al 8º Foro Europeo para la Ciencia, Tecnología e Innovación (TRANSFIERE), celebrado en Zaragoza (España) del 13 al 14 de febrero de 2019.

Trabajo presentado al ATL user workshop, celebrado en Zaragoza del 23 al 24 de octubre de 2018.

Trabajo presentado al ATL user workshop, celebrado en Zaragoza del 23 al 24 de octubre de 2018.

Trabajo presentado al X Meeting de GEFES (División de Física de la Materia Condensada de la Real Sociedad Española de Física), celebrado en Valencia del 24 al 26 de enero de 2018., Measurement systems for low temperature research in material science commonly use 4He evaporation cooling techniques based on impedances made with capillary tubes. These techniques use isenthalpic gas expansion to extend the temperature range achievable from 4,2 K, the liquid helium normal boiling point temperature, down to 1 K. However, they have a worldwide reported issue: the occasional blockage of the impedance that generates nuisances and a waste of helium and financial resources. We have recently shown that the mechanism of capillary blockage is the freeze of molecular hydrogen traces present in the liquid helium bath when the liquid helium is not sufficiently clean. Here we present a simple device based on a pumping system with a micro impedance to test the cleanliness of the liquid helium. We used a Focused Ion Beam (FIB) to drill the impedance hole in a copper foil with a thickness of 35 μm. This device makes possible to test the liquid helium quality in a few minutes before transferring the liquid into a blockage sensitive apparatus., The authors greatly acknowledge the financial support from the Spanish Ministry of economy and Competitiveness through the Project Nº MAT2015-64083-R, in addition to European Union FEDER funds.

Trabajo presentado al II Congreso del Instituto de Ciencia de Materiales de Aragón: “Materiales para los retos de la sociedad", celebrado en Jaca (Huesca) del 2 al 3 de febrero de 2017.

Five-coordinate oxo-derivatives [NBu 4 ][MO(C 6 F 5 ) 4 ] (1) have been prepared for the heavier Group 6 elements: 1-Mo and 1-W. The magnetic properties of that salts have been studied by a combination of Electron paramagnetic resonance (EPR), calorimetric and magnetochemical techniques, pointing out the existence of weak ferromagnetic interactions. These have been correlated with the arrangement of the magnetic units in the crystal.

[ES] Se describe una planta de recuperación de helio sin pérdidas y que permite el suministro continuo de helio en equipos que requieran dicho elemento para refrigeración, o para almacenarlo cuando no sea necesaria su distribución., [EN] The present invention relates to a helium-recovery plant that does not generate losses and that allows the continuous supply ofhelium in equipment requiring said element for refrigeration, or for the storage thereofwhen the distribution thereof is mmecessary., Consejo Superior de Investigaciones Científicas (España), Universidad de Zaragoza, A1 Solicitud de patente con informe sobre el estado de la técnica

Planta de recuperación de helio.Se describe una planta de recuperación de helio sin pérdidas y que permite el suministro continuo de helio en equipos que requieran dicho elemento para refrigeración, o para almacenarlo cuando no sea necesaria su distribución., Consejo Superior de Investigaciones Científicas (España), Universidad de Zaragoza, B1 Patente sin examen previo

Low-temperature research laboratories with typical liquid-helium consumption of the order of tens of liters per day have greatly benefited from the recent development of small-scale liquefiers. In general, these liquefiers are based on Gifford-McMahon or pulse-tube closed-cycle refrigerators with a nominal cooling power ranging from 1 to 1.5Wat 4.2 K. The liquefaction rate for these cryocooler-based liquefiers depends on the pressure at which the helium is liquefied, although the final user conditions of the produced liquid helium are always atmospheric pressure and boiling temperature (e.g., 4.2 K at 100 kPa). Here, we show a systematic study on this effect, in which an enhancement in excess of 70% in liquefaction rate is found experimentally for pressures near and above the critical point of helium (220 kPa). We propose that the underlying mechanism for the liquefaction enhancement is based on the increase in cryocooler cooling power with temperature and the decrease of the helium enthalpy with pressure.

Trabajo presentado al 19th International Cryocooler Conference, celebrada en San Diego, California (US) del 20 al 23 de junio de 2016., A cryocooler based helium recovery plant designed to store, compress and purify helium gas collected from one or more helium-using instruments, as well as to liquefy and redistribute the purified gas within a closed system, is presented. The recovery plant is composed to match the purification and liquefaction rate of the system with the consumption rate of the coupled instruments in an attempt to achieve zero loss. In addition, extreme purity helium (gas and liquid) is obtained by the combination of cryo-condensation of impurities and further chemical adsorption by a getter. Problems like clogging of low temperature impedances by impurities normally present in helium have been definitely solved using this plant concept., The authors express their gratitude for the financial support from the Spanish Ministry of Economy and Competitiveness through project MAT2015-64083-R.

[EN] The present invention relates to a method and a system for cooling liquid helium, that allows working without losses at temperatures under 2.5 K and at atmospheric pressure. The invention is preferably applicable to liquid helium baths for use in an NMR instrument, MRI instrument or instrument for measuring physical properties, and comprises: a cryostat (1) housing the cryogenic liquid which comprises inside thereof a superconducting device belonging to said instrument; a cryocooler (3) thermally connected to the cryostat; and an inlet source for cryogenic gas connected to the cryostat. Advantageously, the invention additionally comprises a subsystem (5) for regulating the pressure in the cryostat, operated by means for controlling the inlet of cryogenic gas into said cryostat., [ES] La presente invención se refiere a un método y un sistema para enfriar helio líquido, que permite trabajar sin pérdidas a temperaturas inferiores a 2,5 K y a presión atmosférica. La invención es preferiblemente aplicable a baños de helio líquido para uso en un instrumento de RMN, instrumento de IRM o instrumento para medir propiedades físicas, y comprende: un criostato (1) que aloja el líquido criogénico que comprende dentro de los mismos un dispositivo superconductor que pertenece a dicho instrumento; un refrigerador criogénico (3) conectado térmicamente al criostato; y una fuente de entrada para gas criogénico conectado al criostato. Ventajosamente, la invención comprende adicionalmente un subsistema (5) para regular la presión en el criostato, operado por medios para controlar la entrada de gas criogénico en dicho criostato., Universidad de Zaragoza, Consejo Superior de Investigaciones Científicas (España), A1 Solicitud de patente con informe sobre el estado de la técnica

Resumen del trabajo presentado a la 20th International Conference on Solid Compounds of Transition Elements, celebrada del 11 al 15 de abril de 2016 en Zaragoza (España)., Five-coordinate oxo compounds with formula [MOX4]- and open-shell electron configuration (d1) are known for all Group 6 metals. This kind of model compounds have attracted a great deal of attention over the years mainly because of two reasons: 1) they have played a key role in the proper understanding of the chemical bond between the oxo ligand and the metal center, and 2) because of their relevance to various Mo-containing enzymatic systems operating as oxotransferases and hydroxylases. In any case, the X ligands under consideration have always been typical (σ+π)-donors, such as halogens or thiolates, which should have a distinct effect on the precise ordering of the molecular orbitals. The properties of homologous compounds with the MO3+ unit being located in a coordination framework of s-only ligands are virtually unknown. Here we report on the synthesis and characterization of open-shell, five-coordinate [MOR4]- oxo-derivatives for the heavier Group 6 metals (M = Mo, W), with R being the bulky perfluorophenyl group C6F5, which acts mainly as a σ-donor ligand. The metal centers in the [NBu4][MO(C6F5)4] salts are located in regular square-pyramidal coordination environments as established by single-crystal X-ray diffraction. Thus, the paramagnetic (d1) MO3+ units are placed within an organic framework of near tetragonal symmetry defined by the four basal C-donor atoms. The C6F5 groups are hard ligands of mainly σ-donor character. This fact greatly simplifies the detailed description of the electronic structure of the [MOX4]− unit, which we consider best portrayed as containing a M≡O triple bond. Crystals of the [NBu4][MO(C6F5)4] salts of the heavier Group 6 metals Mo and W are isomorphic and isostructural with those of the lighter metal, Cr. In all cases, the crystal lattice is formed by alternating layers of cations and anions. The square-pyramidal [MO(C6F5)4]- anions show weak intermolecular contacts between meta- and para-C atoms of neighboring and roughly parallel perfluorophenyl rings (interplanar angle ~10°), as shown in Figure 1 for M = W. We consider these weak π-π interactions as the most likely path to explain the interactions between the individual magnetic centers that become noticeable at very low temperatures. The magnetic properties of these open-shell derivatives have been studied by a combination of spectroscopic (EPR), calorimetric and magnetochemical techniques. At higher temperatures, a simple paramagnetic behavior is observed both in solution and in the solid state, corresponding to separate single-spin (d1) magnetic entities.

A system and a method for liquefaction of gases which are utilized in their liquid state as refrigerants in applications that require low temperatures, throughout various pressure ranges, from slightly above atmospheric pressures to pressures near the critical point. The system and method are based on closed-cycle cryocoolers and utilize the thermodynamic properties of the gas to achieve optimal liquefaction rates., Consejo Superior de Investigaciones Científicas (España), Universidad de Zaragoza, GWR Instruments, Inc., B1 Patente sin examen previo

A system and a method for liquefaction of gases which are utilized in their liquid state as refrigerants in applications that require low temperatures, throughout various pressure ranges, from slightly aboye atmospheric pressures to pressures near the critical point. The system and method are based on closed-cycle cryocoolers and utilize the thermodynamic properties of the gas to achieve optimalliquefaction rates., Consejo Superior de Investigaciones Científicas (España), Universidad de Zaragoza, GWR Instrument INC, A2 Solicitud de patentes sin informe sobre el estado de la técnica

A system and a method for liquefaction of gases which are utilized in their liquid state as refrigerants in applications that require low temperatures, throughout various pressure ranges, from slightly above atmospheric pressures to pressures near the critical point. The system and method are based on closed-cycle cryocoolers and utilize the thermodynamic properties of the gas to achieve optimal liquefaction rates., Consejo Superior de Investigaciones Científicas (España), Universidad de Zaragoza, GWR Instruments, Inc., A2 Solicitud de patente sin informe sobre el estado de la técnica

The magnetic susceptibility studies and its application to the fabric studies depend on the mineralogical susceptibility sources. The mineralogical characterization of ferromagnetic phases has been developed parallel to the paleomagnetism techniques. While the ferromagnetic or paramagnetic particles cannot change along a cross-section of an orogen, because they are related with the same source area, similar diagenetic processes and fluid compositions. The different weight of them to the susceptibility can change in a significant manner in the same lithological unit or even at outcrop scale. The general assumption that clay rich levels can represent a higher paramagnetic contribution to the susceptibility is true in some cases, while in others the expected paramagnetic contribution can differ significantly respect the expected values: high paramagnetic contribution in detrital continental deposits or low values in clay rich levels as the elevels of the Bouma sequence. With independence of the studied lithological unit, higher values of paramagnetic contribution to the susceptibility show more oblate fabrics or prolate fabrics and lower values of the degree of anisotropy in the most ferromagnetic samples. The relation between Km and the paramagnetic contribution to the susceptibility shows that only in a Km range this relation is direct. These results show that a special attention in the analysis of the paramagnetic contribution to the susceptibility must be made in the AMS studies. The utilization of magnetic parameters, as T or P´, as an indicator of intensity of deformation (clustering of particles) only can be used in sectors without changes in the paramagnetic contribution to the susceptibility, even when the external lithological aspect can be very similar and the samples comes from the same structural position

The magnetic susceptibility studies and its application to the fabric studies depend on the mineralogical susceptibility sources. The mineralogical characterization of ferromagnetic phases has been developed parallel to the paleomagnetism techniques. While the ferromagnetic or paramagnetic particles cannot change along a cross-section of an orogen, because they are related with the same source area, similar diagenetic processes and fluid compositions. The different weight of them to the susceptibility can change in a significant manner in the same lithological unit or even at outcrop scale. The general assumption that clay rich levels can represent a higher paramagnetic contribution to the susceptibility is true in some cases, while in others the expected paramagnetic contribution can differ significantly respect the expected values: high paramagnetic contribution in detrital continental deposits or low values in clay rich levels as the elevels of the Bouma sequence. With independence of the studied lithological unit, higher values of paramagnetic contribution to the susceptibility show more oblate fabrics or prolate fabrics and lower values of the degree of anisotropy in the most ferromagnetic samples. The relation between Km and the paramagnetic contribution to the susceptibility shows that only in a Km range this relation is direct. These results show that a special attention in the analysis of the paramagnetic contribution to the susceptibility must be made in the AMS studies. The utilization of magnetic parameters, as T or P´, as an indicator of intensity of deformation (clustering of particles) only can be used in sectors without changes in the paramagnetic contribution to the susceptibility, even when the external lithological aspect can be very similar and the samples comes from the same structural position