Хранение инкапсулированных сфероидов, состоящих из клеток печени, при –80°С после хранения при температуре жидкого азота

The stochastic beam cooling amplifier front end consists of 180° hybrids, cables, directional couplers, power dividers/combiners and low noise preamplifiers. Most front ends will be operating at near liquid nitrogen (LN) temperature. Components used in the front ends should be able to operate at this temperature satisfactorily. Since the noise performance of the front end is of utmost importance to the beam cooling process, the insertion losses of cables, 180° hybrids, directional couplers and power combiners have been measured at room temperature and near liquid nitrogen temperature. The purpose of this report is to describe and present some measurements and data on the components mentioned, with the exception of the 1-2 and 2-4 GHz preamplifiers, which have been described elsewhere. 1,2

Silicon Photomultiplier (SiPM) is a sensor that can detect low-light signals lower than the single-photon level. In order to study the properties of neutrinos at a low detection threshold and low radioactivity experimental background, a low-temperature CsI neutrino coherent scattering detector is designed to be read by the SiPM sensor. Less thermal noise of SiPM and more light yield of CsI crystals can be obtained at the working temperature of liquid nitrogen. The breakdown voltage (Vbd) and dark count rate (DCR) of SiPM at liquid nitrogen temperature are two key parameters for coherent scattering detection. In this paper, a low-temperature test is conducted on the mass-produced ON Semiconductor J-Series SiPM. We design a cryogenic system for cooling SiPM at liquid nitrogen temperature and the changes of operating voltage and dark noise from room to liquid nitrogen temperature are measured in detail. The results show that SiPM works at the liquid nitrogen temperature, and the dark count rate drops by six orders of magnitude from room temperature (120 kHz/mm2) to liquid nitrogen temperature (0.1 Hz/mm2).

The hypothesis that at low homologous temperature, the pressure effect on the yielding of metals is closely related to the effect of pressure on the elastic constants was tested. An apparatus in which tension tests can be made at liquid nitrogen temperature and high hydrostatic pressure was designed and constructed. Tension tests for potassium and lead were carried out at liquid nitrogen temperature and as a function of pressure up to 5.15 kbars. The results show that the effect of hydrostatic pressure was to raise the stress strain curves of both potassium and lead at liquid nitrogen temperature.

Evaluation of loss of current leads for HTS power apparatuses

Ce14Fe78Co2B6 nanopowders with hard-magnetic properties have been successfully prepared by ball milling at low temperatures in liquid nitrogen. The morphology, structure, and magnetic properties of Ce14Fe78Co2B6 powders have been investigated using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. It was found that powder ball milling at low temperature in liquid nitrogen, has the advantage that the oxidation of powders is inhibited and the particles rapidly reach nanometric dimensions. In comparison to the Ce14Fe78Co2B6 powders prepared by ball milling at room temperature, the powders milled at low temperature present a more uniform particle size and no rare-earth oxides, which leads thus to remarkable magnetic properties. The nanocrystalline Ce14Fe78Co2B6 powders with optimum characteristics, prepared at low temperature, have the size of 153 nm or less, present a coercivity of 5.1 kOe, and a saturation magnetization of 113 emu/g after milling for 6 h at low temperature. Low temperature milling may become a promising technique for the fabrication of high performance powders used for permanent magnets preparation.

Extraordinary strength and ductility of cold-rolled 304L stainless steel at cryogenic temperature

We examined a portable cryostat utilizing liquid nitrogen with temperature control function for operation of high-temperature superconducting quantum interference devices (HTS-SQUIDs) to have a higher slew rate. To operate a non-destructive evaluation system with HTS-SQUID in city areas with serious environmental electromagnetic noise, we often need a higher slew rate. A glass Dewar is installed in an outer case made of aluminum, which is sealed hermetically. The temperature of liquid nitrogen is controlled by using a vacuum pump connected to a feedback circuit, which monitors the temperature of liquid nitrogen. The temperature of liquid nitrogen could be controlled in the range between 73 and 77.2 K with a 0.1 K step. For example, the temperature was kept at 75 K with precision of ±0.05 K for 9 hs and SQUID was operated stably for this period. The ΔV and the slew rate of a test SQUID were increased from 22 μV and 3.2 mT/s at 77.2 K to 37 μV and 5.9 mT/s at 73 K, respectively. The white noise was also improved from 48 fT/√Hz at 77.2 K to 32 fT/√Hz at 74 K. We believe that this technology is useful to extend application of HTS-SQUIDs in the fields.

MOV has been widely utilized in the power industry due to its high degree of nonlinearity and excellent capability to carry heavy electrical current. And the superconducting technology is a new development in the area of the electrical power supply, but one of difficulties for high temperature superconducting industry coming into our life is over-voltage protection, therefore, it is necessary to study characteristics of MOV at liquid nitrogen temperature for supplying in superconducting industry. An experiment about MOV has been done, and some data are gotten. Based on the MSV and VCC, this paper analyzes these data, and gets the leakage current wave, resistance current wave and capacitive current wave under different voltages. Also characteristics of MOV in low current region at liquid nitrogen temperature and in normal temperature are analyzed correspondingly. The conclusion is that the basic characteristics of MOV at liquid nitrogen temperature are better than normal temperature in low current region

Performance of a CMOS Schmitt trigger at liquid nitrogen temperature

Intrinsic ductility of Ni 3Al with and without boron at 77K

Highly crystallized graphite films were prepared by heat treatment of carbonized polyimide films (Kapton) at temperatures of 2700 and 3050° C. Interlayer spacing d002 at room temperature, and electrical resistivity, magnetoresistance and Hall coefficient at room and liquid nitrogen temperatures were measured. All of these data indicate high crystallinity of the graphitized Kapton films obtained. For the graphite films heat treated at 3050° C mean-square mobilities were estimated from the magnetoresistance data at 1 T to be 0.91 m2 V−1 sec−1 at room temperature and 2.3 m2 V−1 sec−1 at liquid nitrogen temperature; the value at liquid nitrogen temperature corresponds to that for a pyrolytic graphite heat treated at 3200° C for 1 h (PG 3200). Magnetic field dependence of Hall coefficient at liquid nitrogen temperature for this sample also agrees well with that for PG 3200. Scanning electron micrographs on the surfaces show that the present graphite films consist of grains of large crystallites, and grain size increases as the crystallinity of the material improves.

A two-dimensional device simulator was used to examine the various profile design strategies for silicon bipolar transistors operating at liquid-nitrogen temperatures. Special emphasis was placed on the scaling tradeoffs of these design approaches. It is concluded that a relaxed scaling technique based on the maintenance of constant base Gummel number with a slight decrease in emitter doping level probably offers the best overall low-temperature design strategy for scaled double-polysilicon devices. To verify these calculations, devices with 0.8- mu m lithography were fabricated using this design scheme. Transistors were found to be reasonably ideal at low temperatures and had adequate current gain for most digital applications. Unloaded ECL ring oscillators operated at sub-100-ps speeds at liquid-nitrogen temperatures. Simulations based on measured data indicate that sub-150-ps loaded ECL delays are achievable at about 4-mW power at 87 K if the circuit logic swing is reduced to 300 mV. These data suggest that conventionally designed silicon bipolar transistors are attractive candidates for very-high-performance applications in the low-temperature environment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Superconducting thick films of YBCO have been prepared successfully on MgOsingle-crystal substrate by a screen-printing method. A prototype magnetic field sensor hasbeen made from these thick films and characterized using x-ray diffraction, scanningelectron microscopy, and a magnetoresistance method. The microstructure of the YBCOthick film sensor was prepared in such a way so as to retain a small resistanceR(B = 0) at liquid nitrogen temperature and at zero magnetic field. TheR–T curves of the sensor revealed that the value of the resistanceR(T) ishighly sensitive to the relatively high applied magnetic fields in the temperature range from 75 to 85 K.The R–B curves were plotted at liquid nitrogen temperature. At relatively low applied magneticfields (up to 100 G), the value of the normalized resistance was well fitted to the relationR(B)/R(B = 0) = 1+αB2,where α is a constant. However, at higher values of the applied magnetic fields, the normalizedresistance exhibited an almost linear dependence with the applied field. The characteristicsof the sensors showed considerable hysteresis at high ranges of magnetic field (from 100 to500 G) with no significant hysteresis at low magnetic field (less than 100 G). TheI–V curves at liquid nitrogen temperature were also measured after several thermalcycles for various values of applied magnetic fields. It was demonstrated that theI–V curves were independent on the number of thermal cycles and exhibited nosignificant change at relatively low currents and magnetic fields. That is, theI–V curves are reproducible under the above conditions. This suggests that a betterperformance of the sensor in the presence of relatively weak magnetic field is needed to getthe ultimate sensitivity.

Impact of thin layers of HMX at room temperature and near liquid nitrogen temperature were performed. Polycrystalline powders of HMX irradiated with 7.5 megarad in evacuated tubes at liquid nitrogen temperature showed significant enhanced sensitivity. With 10‐megarad irradiations of HMX in evacuated tubes at liquid nitrogen temperature frequent spontaneous explosions in HMX have occurred. ESR measurements on impacted HMX and RDX powders at room temperature and near liquid nitrogen temperature at energies of less than 1 kg · m have not produced detectable mechanically generated free radicals. A significant increase in sensitivity of vacuum irradiated HMX was observed but efforts to correlate this with the dominant frozen‐in NO2 γ‐radical concentration were unsuccessful. It is suggested that the NO2 radical is a chain terminating radical in explosive systems.

The light yield and decay constant of BGO weremeasured at both dry ice and liquid nitrogen temperatures using two SiPMs directly coupled to a 6×6×6 cm2 cubic BGO crystal. With the measured light yield (5.2±0.3 PE/keV at dry ice temperature and 10.5±0.4 PE/keV at liquid nitrogen temperature) and decay constants, potential applications of BGO in ToF-PET and SPECT were discussed.