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A compact low-cost cryocooling system has been designed, constructed, and tested at SLAC National Accelerator Laboratory. The cooling power is provided by natural convection and phase change of the liquid nitrogen. The initial application was to cool silicon crystal optics to the sub-100 K range. A silicon crystal of dimension (width × depth × height) 50 × 50 × 30 mm3 has been used with an electric heater on the top surface in this prototyping test. This system can effectively provide more than 80 W of cooling power to the optics with a consumption of liquid nitrogen less than 2.1 l/h. The vibration of the silicon crystal was monitored during the tests with added electric heater power on the crystal. The vibration of the silicon crystal due to liquid nitrogen boiling is negligible. [ABSTRACT FROM AUTHOR]

A liquid nitrogen assisted polycrystalline diamond compact (PDC) bit drilling method is expected to be suitable for hot dry rock (HDR) drilling because the huge thermal stress induced in the drilling process can help to break the rock and the low temperature liquid nitrogen can efficiently cool the drilling tools. However, there is no experimental research on liquid nitrogen assisted PDC bits breaking high temperature granite, and the rock breaking efficiency of this new drilling method is still unclear. To investigate the feasibility and efficiency of liquid nitrogen assisted PDC bit breaking HDR, a novel experimental setup was designed. This setup is composed of four units: the drilling fluid circulation system, drilling system, formation simulation system, and data acquisition and control system. It can also be used to research the effects of drilling parameters such as weight on bit, rotary speed, drilling fluid jet pressure, and feed speed on drilling efficiency. A series of drilling experiments using liquid nitrogen and water have been successfully carried out with this setup. The results indicate that liquid nitrogen assisted PDC bit drilling has excellent performance in breaking HDR, which can accelerate the application of this new technique in geothermal drilling. [ABSTRACT FROM AUTHOR]

Liquid nitrogen (LN2) is considered as one of the potential fracturing fluids for unconventional oil/gas and geothermal reservoirs. In order to study the feasibility of the LN2 jet in fracturing operation, an integration test system is put forward in this paper. The system contains five units: the power system, the pure LN2 jet system, the abrasive LN2 jet system, the heat transfer system, and the control and data acquisition system. A series of experiments about rock breaking and heat transfer with the LN2 jet can be conducted by using this test system. The experiments in this paper demonstrate the reliability of the system for LN2 jet experiments. The results can provide theoretical supports for LN2 jet fracturing technology. [ABSTRACT FROM AUTHOR]

Efficient thermal management is essential for low-temperature optoelectronic devices. Traditional liquid nitrogen (LN2) cooling presents challenges such as frequent replenishment needs and limited operational duration. This study introduces micromachined Joule–Thomson (MJT) cooling as a superior alternative for temperature regulation in optoelectronic devices. We evaluated the thermal and optical performance of MJT cooling for a CdSe/ZnS quantum dot (QD) sample within a temperature range of 120–300 K. Thermal analysis showed that with a single 50 l nitrogen refill, the MJT system can operate continuously for over one week, surpassing the LN2 system by 11 times. The temperature stability was affected little by laser irradiation, with a <0.2 K rise at 5 mW of laser power. In addition, the MJT cooling led to an average blueshift of 1–3 meV in the emission peak of QDs and 0.3–2.3 meV reduced spectral broadening compared to LN2, attributed to a smaller sample-to-cold-stage temperature gap of about 8–9 K in the MJT setup. The standard deviations of peak energy and FWHM are in the order of E − 1 meV magnitude, demonstrating a comparable thermal uniformity compared to LN2. The vibration spectra obtained for both vertical and horizontal directions reveal the superior low-vibration characteristics of MJT cooling. These findings validate MJT cooling as a superior and reliable strategy for the thermal management of optoelectronics, ensuring prolonged operational durations, reliable temperature stability, enhanced temperature precision, high thermal homogeneity, and low vibrations. [ABSTRACT FROM AUTHOR]

Due to the unique physical and chemical properties of liquid nitrogen (LN2), LN2 fracturing has been considered as a promising reservoir stimulation technique. In order to further investigate the feasibility of LN2 fracturing, a new device is designed to research the effect of LN2 fracturing under different conditions, such as different specimen sizes, temperatures, and confining pressures. The setup consists of three units: a high-pressure LN2 generating system, a true-triaxial loading and heating system, and a control and data acquisition system. Now, a series of experiments have been successfully carried out based on the setup. The results have proven the excellent fracturing effect of LN2 and the applications of this setup. The apparatus lays a foundation for the application of LN2 fracturing in both conventional and geothermal reservoirs. [ABSTRACT FROM AUTHOR]

Many infrared spectroscopy setups are in principle stable enough to run overnight or longer, but the detector's Dewar vessel must be refilled manually with liquid nitrogen (LN2) every couple of hours. Commercial automatic LN2 refilling systems work reliably only for large Dewars. Here, we present a refilling system which can non-invasively be applied to already installed small Dewars. The system reliably refills LN2 once it has dropped below an adjustable level, with quick refilling (<3 min) for a 0.6 l Dewar. Our design protects the setup and the detector from overflowing or running without LN2. [ABSTRACT FROM AUTHOR]

In this study, a novel reciprocating tribometer, in which the frictional pairs were immersed in liquid nitrogen directly, was developed to simulate the cryogenic fluid lubrication. To eliminate the negative influence of extremely low temperature on force sensors, a transfer structure of force-deformation, consisting of cantilever beams and measurement beams, was designed specially. It can transfer the structural deformations caused by the loading force and the friction force from the cryogenic zone to the room-temperature zone. The corresponding measurement principle was discussed in detail, and the linear relationship between the structural deformation and the applied force was verified theoretically. Through static calibration experiments, the fitting relationship between the deformations and the loading/friction force was acquired for the developed tribometer. In final, a preliminary investigation of graphite materials was conducted on the tribometer to compare the room-temperature and cryogenic tribological behaviors. [ABSTRACT FROM AUTHOR]

We fabricated several sapphire screw threads and performed a strength test on them at the liquid nitrogen temperature of 77 K. The screw threads were subjected to and withstood a 3000 N load. To the best of our knowledge, this is the first strength test of sapphire screw threads at a cryogenic temperature. The result suggests a new way of connecting sapphire components. Although sapphire is already used in many applications, the result may provide a new way to use the material as a structural element in even more applications. [ABSTRACT FROM AUTHOR]

The liquid nitrogen distribution at Variable Energy Cyclotron Centre, Kolkata, India K500 super-conducting cyclotron uses parallel branches to cool the thermal shield of helium vessel housing the superconducting coil and the cryopanels. Liquid nitrogen is supplied to the thermal shields from a pressurised liquid nitrogen dewar. Direct measurement of flow is quite difficult and seldom used in an operational cryogenic system. The total flow and heat load of the liquid nitrogen system was estimated indirectly by continuous measurement of level in the liquid nitrogen tanks. A mathematical model was developed to evaluate liquid nitrogen flow in the parallel branches. The model was used to generate flow distribution for different settings and the total flow was compared with measured data. [ABSTRACT FROM AUTHOR]

High-Reynolds-number flows are common both in nature and industrial applications, but are difficult to attain in laboratory settings using standard test fluids such as air and water. To extend the Reynolds number range, water and air have been replaced at times by low-viscosity fluids such as pressurized air, sulfur hexafluoride, and cryogenic nitrogen gas, as well as liquid and gaseous helium. With a few exceptions, liquid nitrogen has been neglected despite the fact that it has a kinematic viscosity of about a fifth of that of water at room temperature. We explore the use of liquid nitrogen here. In particular, we study the use of frozen particles for flow visualization and velocimetry in liquid nitrogen. We create particles in situ by injecting a gaseous mixture of room-temperature nitrogen and an additional seeding gas into the flow. We present a systematic study of potential seeding gases to determine which create particles with the best fidelity and optical properties. The technique has proven capable of producing sub-micrometer sized tracers that allow particle tracking and particle image velocimetry. We review possible high-Reynolds-number experiments using this technique, and discuss the merits and challenges of using liquid nitrogen as a test fluid. [ABSTRACT FROM AUTHOR]

We describe a liquid-nitrogen-jet laser-plasma source with sufficient brightness, uniformity, stability, and reliability to be suitable for compact water-window soft x-ray transmission microscopy. A cooled capillary nozzle arrangement allows long-term operation and avoids previously reported jet instabilities. The source is quantitatively characterized by calibrated slit-grating spectroscopy and zone-plate imaging. The absolute photon number in the major spectral lines (λ=2.48 nm and λ=2.88 nm) is 1.0×1012 photons/(pulse×sr×line). The source diameter is ∼20 μm (full width at half maximum) and the spatial stability is better than ±2 μm. Within an area with uniformity of 20%, the average source brightness is 4×108 photons/(pulse×sr×μm2×line), which allows operation of a compact soft x-ray transmission microscope with exposure times of a few minutes. [ABSTRACT FROM AUTHOR]

A technique to distinguish between materials that can and cannot shield microwaves in liquid nitrogen was developed. The samples are placed in a modified X-band waveguide, which operates by the same "insertion loss" principle as a coaxial device used to measure shielding effectiveness from 300 to 1000 MHz. Verification of the waveguide fixture was accomplished by measuring the shielding effectiveness of a good conductor, copper; a nonconductor, Teflon; and two intermediate conductors, steel and a carbon-filled elastomer. After verification, the waveguide fixture was used at liquid nitrogen temperatures to compare the shielding effectiveness of YBa[sub 2]Cu[sub 3]O[sub 7 - x], a high temperature superconductor, with copper, a known shielding material. [ABSTRACT FROM AUTHOR]

A proportional magnetic valve has been developed that permits continuous flow of cryogenic fluids and gases. The proportional valve (PV) may be electrically controlled in the manual mode (open loop current drive) or in the automatic mode (closed loop current drive). A complete control system for liquid-nitrogen (LN) flow control applications is described. The system includes alarm and automatic supply tank switching features. [ABSTRACT FROM AUTHOR]

A cryogenic cesium atomic fountain clock is a novel clock with the microwave cavity and atomic free flight region placed in liquid nitrogen. On the one hand, the blackbody radiation shift is reduced at cryogenic temperature. On the other hand, the vacuum in the atomic free flight region is optimized, and the background gas collision shift reduced. The microwave resonant cavity is the most important unit in a cryogenic cesium atomic fountain clock. Through theoretical and simulative investigation, this study designs the configuration and dimensions for an optimized microwave cavity. Concurrently, experiments reveal the effects of temperature, pressure, humidity, and other factors on the resonant frequency of the microwave cavity. Combining the theoretical and experimental study, we obtain the resonant frequency difference between the microwave cavity in a cryogenic vacuum and at room temperature and ambient pressure. By subtracting this frequency difference, we adjust the microwave cavity for room temperature and ambient pressure, then vacuumize and immerse it in liquid nitrogen for verification and fine tuning. Finally, we determine that the microwave cavity resonant frequency deviation from the clock transition frequency is 10 kHz with an unloaded quality factor of 25 000, which meets the application requirements of the cryogenic cesium atomic fountain clock. [ABSTRACT FROM AUTHOR]

In order to reduce the time and effort of the daily task of refilling Dewar vessels of Ge detectors with liquid nitrogen (LN2), we have developed an automatic LN2 filling system equipped with a LN2 plant. With this system, we were freed from the work of LN2 filling. Such an LN2 filling system is useful for moderate-scale Ge detector arrays consisting of fewer than 20 Ge detectors. [ABSTRACT FROM AUTHOR]

A versatile system has been developed for the measurement under LABVIEW™ control of junction temperatures in a light emitting diode (LED). Measurements are reported on a commercially available high-intensity InGaAlP LED immersed in liquid nitrogen and driven by currents in the range of 18.5–204 mA. The measured junction temperature has an expanded uncertainty of ±2 K at the 95% level of confidence for temperatures from 70 to 298 K. Using the measured junction temperatures, the junction-to-case thermal resistance of the LED was established as 440 K/W for devices with intact encapsulation and 307 K/W for partial encapsulation. [ABSTRACT FROM AUTHOR]

A high-pressure abrasive liquid nitrogen (L-N 2 ) jet is considered as an efficient rock-breaking technology due to its unique low-temperature characteristic. In order to experimentally investigate the impact of an abrasive L-N 2 jet on rock breakage, a new setup, which considers the low temperature and high expansibility of L-N 2 , is put forward in this note. The setup is composed of four units: the power system, nitrogen-gas pressurization system, particle mixing system, and impingement system. Both a pre-mixed abrasive L-N 2 jet and a post-mixed abrasive L-N 2 jet can be achieved by this equipment. Moreover, it can also be used to investigate the influences of injection parameters and particle parameters on rock breakage. A series of experiments have been carried out based on the setup. The results further promote the application of an abrasive L-N 2 jet.

We present the principle and implementation of a new type of fast response evaporative calorimeter designed to work at cryogenic temperatures and above-ambient pressures. It is capable of measuring input energy from an electric pulse and the thermal output energy by measuring the evaporation of liquid nitrogen through a mass flow meter. This system may be used to measure either the steady heat output from the system submersed under the cryogen or the heat output that results from a fast square-wave profile electrical pulse of duration from 10 µs or longer. The energy output of metal capillary-wire composite systems has been measured calorimetrically. A four-wire measurement was used to monitor the input electric energy with an uncertainty less than 5% for a typical pulse. Mass flow meters and pressure regulation systems were used to monitor the rate of evaporation of liquid nitrogen with a typical precision of 2 std.-ml/min. For a typical pulse, the integrated mass flow of nitrogen could be determined with an uncertainty less than 3%. The pressure controllers and ballast compliance volumes allow the system to return to a steady state of mass flow in less than 2 min following an electric pulse. The system is capable of housing and measuring four separate wire-capillary systems in a single Dewar. On average, a calibration resulted in 3.9 std. ml evaporated per joule of input energy. This corresponds to a 97% efficiency for this calorimeter. [ABSTRACT FROM AUTHOR]

We present the design and measured performance of a light emitting diode (LED) module for spatially mapping kinetic inductance detector (KID) arrays in the laboratory. Our novel approach uses a multiplexing scheme that only requires seven wires to control 480 red LEDs, and the number of LEDs can be scaled up without adding any additional wires. This multiplexing approach relies on active surface mount components that can operate at cryogenic temperatures down to 10 K. Cryogenic tests in liquid nitrogen and inside our cryostat demonstrate that the multiplexer circuit works at 77 and 10 K, respectively. The LED module presented here is tailored for our millimeter-wave detector modules, but the approach could be adapted for use with other KID-based detector systems. [ABSTRACT FROM AUTHOR]

A cryostat was constructed and installed in a MTS 810 servohydraulic testing machine for studying fatigue properties associated with pseudoelastic cycling of shape memory alloys down to liquid-nitrogen temperatures. Special attention was focused on eliminating temperature fluctuations during the fatigue experiments. In order to perform long time fatigue tests, an automatic controlled system which supplies the cryostat with liquid nitrogen was developed and described in detail. [ABSTRACT FROM AUTHOR]

A compact supersonic molecular beam source was developed that has a liquid nitrogen trap to cryogenically pump the gas and is small enough in size to install in conventional molecular beam epitaxy (MBE) systems. With the source, well-collimated molecular beams of N2O and NO2 whose flux densities are ∼1016 molecules cm-2 s-1 are generated. The effectiveness of the source was proved in the preparation of oxide superconducting thin films by MBE with an NO2 beam where as-grown superconducting films were obtained in high vacuum of ≤10-5 Pa. [ABSTRACT FROM AUTHOR]

The present work investigates the joined effects of temperature and static magnetic field on the electrical properties of a 64 MHz planar high-temperature superconducting (HTS) coil, in order to enhance the signal-to-noise ratio (SNR) in nuclear magnetic resonance (NMR) applications with a moderate decrease of the HTS coil temperature (THTS). Temperature control is provided with accuracy better than 0.1 K from 80 to 66 K by regulating the pressure of the liquid nitrogen bath of a dedicated cryostat. The actual temperature of the HTS coil is obtained using a straightforward wireless method that eliminates the risks of coupling electromagnetic interference to the HTS coil and of disturbing the static magnetic field by DC currents near the region of interest. The resonance frequency ( f0) and the quality factor (Q) of the HTS coil are measured as a function of temperature in the 0-4.7 T field range with parallel and orthogonal orientations relative to the coil plane. The intrinsic HTS coil sensitivity and the detuning effect are then analyzed from the Q and f0 data. In the presence of the static magnetic field, the initial value of f0 in Earth's field could be entirely recovered by decreasing THTS, except for the orthogonal orientation above 1 T. The improvement of Q by lowering THTS was substantial. From 80 to 66 K, Q was multiplied by a factor of 6 at 1.5 T in orthogonal orientation. In parallel orientation, the maximum measured improvement of Q from 80 K to 66 K was a factor of 2. From 80 to 66 K, the improvement of the RF sensitivity relative to the initial value at the Earth's field and ambient pressure was up to 4.4 dB in parallel orientation. It was even more important in orthogonal orientation and continued to increase, up to 8.4 dB, at the maximum explored field of 1.5 T. Assuming that the noise contributions from the RF receiver are negligible, the SNR improvement using enhanced HTS coil cooling in NMR experiments was extracted from Q measurements either with or without the presence of the sample. Notably, the additional cooling in the presence of conductive samples appears more beneficial at higher field strengths and with an orthogonal incidence than with parallel. The temperature range accessible here, involving a relatively straightforward cryogenic design, brings a gain in RF sensitivity that is of great significance to cutting-edge applications with very weakly conducting samples, small biological specimens, or small animals in vivo. This work also demonstrates a better tolerance to thin-film orientation misalignments relative to the magnetic field, and this could eventually play a role in designing effective non-planar HTS coils or coil arrays which include elements of various orientations. Finally, the data provided in this work may help understand some critical aspects in the design of HTS coils for NMR and MRI applications and accounts for the presence of the static magnetic field, particularly regarding the SNR loss due to a decreased quality factor and detuning issues. [ABSTRACT FROM AUTHOR]

The balloon-borne cryogenic telescope testbed is a stratospheric balloon payload intended to develop technology for a future cryogenic suborbital observatory. A series of flights are intended to establish ultra-light dewar performance and open-aperture observing techniques for large (3 m–5 m diameter) cryogenic telescopes at infrared wavelengths. An initial flight in 2019 demonstrated bulk transfer of liquid nitrogen and liquid helium at stratospheric altitudes. An 827 kg payload carried 14 l of liquid nitrogen (LN2) and 268 l of liquid helium (LHe) in pressurized storage dewars to an altitude of 39.7 km. Once at float altitude, liquid nitrogen transfer cooled a separate, unpressurized bucket dewar to a temperature of 65 K, followed by the transfer of 32 l of liquid helium from the storage dewar into the bucket dewar. Calorimetric tests measured the total heat leak to the LHe bath within the bucket dewar. A subsequent flight will replace the receiving bucket dewar with an ultra-light dewar of similar size to compare the performance of an ultra-light design dewar to that of conventional superinsulated dewars. [ABSTRACT FROM AUTHOR]

An up to 15 T pulsed magnetic field generator in a volume of a few cubic centimeters has been developed for experiments with magnetized laser plasma. The magnetic field is created by a pair of coils placed in a sealed reservoir with liquid nitrogen, installed in a vacuum chamber with a laser target. The bearing body provides the mechanical strength of the system both in the case of co-directional and oppositely connected coils. The configuration of the housing allows laser radiation to be introduced into the working area between the coils in a wide range of directions and focusing angles, places targets away from the symmetry axis of the magnetic system, and irradiates several targets simultaneously. [ABSTRACT FROM AUTHOR]

A new type of hydrothermal diamond-anvil cell (HDAC-VII) and its accompanied cooling system were designed. The design of HDAC-VII in which the three posts work simultaneously as guideposts and screw posts greatly shortened the horizontal size of HDAC compared with older types. It provides more open space and shorter distance to analyze and observe the sample chamber from side access. Moreover, four ports were used to connect the upper and lower spaces between windows and anvils, so mixed gas (Ar + H2) can pass through both of them. In the heating experiments, the mixed gas prevents diamond anvils and other parts from being oxidized as well as cooling the observing windows. Dry gas can be passed through those spaces during cooling, preventing condensation on the table faces of anvils and the observing windows. The cooling system can cool the sample chamber to −170 °C with an accuracy of ±0.5 °C by using a nitrogen stream cooled through a stainless steel coil immersed in a liquid nitrogen Dewar. The heating rates while reheating a frozen sample can be controlled to be 0.1 °C/min with a temperature fluctuation of 0.1 °C. These improvements extend the HDAC applications especially in low temperature conditions. For example, (1) we measured the salinities of NaCl–H2O loaded in the sample chamber, (2) we observed the ice I and VI-melting process and correspondingly calculated the density of water in the sample chamber, and (3) we performed lepidolite crystallization in an aqueous solution with 10 wt. % NaCl to simulate its natural forming conditions. [ABSTRACT FROM AUTHOR]

We fabricated several sapphire screw threads and performed a strength test on them at the liquid nitrogen temperature of 77 K. The screw threads were subjected to and withstood a 3000 N load. To the best of our knowledge, this is the first strength test of sapphire screw threads at a cryogenic temperature. The result suggests a new way of connecting sapphire components. Although sapphire is already used in many applications, the result may provide a new way to use the material as a structural element in even more applications.

An ultrahigh vacuum compatible compact helium cryostat with a 48 h hold time for a 2.5 l of liquid helium capacity has been realized. The design exploits the large enthalpy of the gas phase helium, by using two layers of vapor-cooled radiation shield in place of the conventional liquid nitrogen jacket. The mechanical rigidity, the absence of liquid nitrogen bubbling, and a low helium boil-off rate make this cryostat particularly suitable for applications that require a low vibration environment such as scanning probe microscopy. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A new recirculating liquid-microjet photoelectron spectrometer for multiphoton ultraviolet photoelectron spectroscopy is described. A recirculating system is essential for studying samples that are only available in relatively small quantities. The reduction in background pressure when using the recirculating system compared to a liquid-nitrogen cold-trap results in a significant improvement in the quality of the photoelectron spectra. Moreover, the recirculating system results in a negligible streaming potential. The instrument design, operation, and characterization are described in detail, and its performance is illustrated by comparing a photoelectron spectrum of aqueous phenol recorded using the recirculating system with one recorded using a liquid nitrogen cold-trap. [ABSTRACT FROM AUTHOR]

We have developed an apparatus to investigate transport critical current (I(c)) as a function of magnetic field and temperature using only liquid nitrogen. The apparatus consists of a (Bi,Pb)(2)Sr(2)Ca(2)Cu(3)O(10) (Bi-2223) superconducting magnet, an outer dewar, and a variable temperature insert (VTI). The magnet, which is operated in depressurized liquid nitrogen, generates magnetic field up to 1.26 T. The sample is also immersed in liquid nitrogen. The pressure in the VTI is controlled from 0.02 to 0.3 MPa, which corresponds to temperature ranging from 66 to 88 K. We have confirmed the long-term stable operation of the Bi-2223 magnet at 1 T. The temperature stability of the sample at high transport current was also demonstrated. The apparatus provides easy-operating I(c) measurement environment for a high-T(c) superconductor up to 500 A in magnetic fields up to 1 T and in temperatures ranging from 66 to 88 K.

A double-sided guarded hot plate apparatus (GHP) is specifically designed, fabricated, and constructed for the measurement of thermal conductivities of insulation specimens operated down to liquid nitrogen temperature (-196 °C), at different controlled pressures from 0.005 Pa to 0.105 MPa. The specimens placed in this apparatus are 300 mm in diameter at various thicknesses ranging from 4 mm to 40 mm. The apparatus is different from traditional GHP in terms of structure, supporting and heating method. The details of the design and construction of the hot plate, the cold plates, the suspensions, the clampings, and the vacuum chamber of the system are presented. The measurement methods of the temperatures, the input power, the meter area, and the thickness of the specimens are given. The apparatus is calibrated with teflon plates as sample and the maximum deviation from the published data is about 6% for thermal conductivity. The uncertainties for the measurement are also discussed in this paper.

A liquid nitrogen gas-flow cryostat is described which provides steady temperatures between 77 K and room temperature for variable temperature laser luminescence studies. The cryostat is constructed from common laboratory apparatus and requires no quartz glassware. Liquid nitrogen is consumed by the cryostat at a rate of 1 l per hour. [ABSTRACT FROM AUTHOR]

A self-pressurizing, two-level automatic liquid-nitrogen filler is described which utilizes the vapor from the natural evaporation of cryogen in both the research and supply Dewars to continuously pressurize the liquid-nitrogen reservoir. The system has greatly improved response time compared to other self-pressurizing systems while avoiding the disadvantages of using heating elements or external gas sources for pressurization. [ABSTRACT FROM AUTHOR]

An efficient loading technique has been developed for flammable, toxic, or explosive gases which can be condensed at liquid nitrogen temperature and ambient pressure in membrane diamond anvil cells (DACs). This cryogenic technique consists in a deposition of small quantities of the desired gas directly into the sample chamber. The deposition is performed using a capillary that reaches the space between the diamond anvils. The DAC is kept under inert gas overpressure during the whole process, in order to avoid contamination from atmospheric O2, CO2, and H2O. This technique provides significant advantages over standard cryo-loading and gas-loading when the condensation of dangerous samples at liquid nitrogen temperature raises safety concerns because it allows dealing with minimum quantities of condensed gases. The whole procedure is particularly fast and efficient. The “spray-loading” has been successfully used in our laboratory to load several samples including acetylene, ammonia, ethylene, and carbon dioxide/water or red phosphorus/NH3 mixtures. [ABSTRACT FROM AUTHOR]

Describes the principle of operation and construction of an inexpensive, reliable system for the automated dispensing of liquid nitrogen from a single supply Dewar to multiple cryogenic traps. Computer control; Programmed temperature cycles.