Operational amplifiers operating in temperature range from 300 to 4.2 K

We present preamplifiers for frequencies from dc to few 10 MHz operating over temperature range from 300 to 4.2 K. Typical application of these circuits which use CMOS operational amplifiers is to match high impedance cryogenic sensors with low impedance cables to lead out a signal to room temperature electronics without bandwidth limiting while preserve signal to noise ratio and linearity. Temperature dependence of electrical characteristics is shown including dissipated power and input voltage noise density spectra.     

Specific heat and thermodynamic characteristics of the system Bi-Sr-Ca-Mg-Cu-O in the temperature range 4.2–300 K

Results are presented from an experimental study of specific heat of the superconductive metal oxide system Bi -Sr-Ca-Mg-Cu-O over the temperature range 4.2–300 K. Temperature-dependent components of entropy and enthalpy are calculated. A correlation is made between T_c and standard entropy and enthalpy values for high temperature superconductors of various classes.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 60, No. 6, pp. 974–979, June, 1991.     

Electrical properties of underformed and plastically deformed bismuth-thallium and bismuth-lead systems in the temperature range 4.2 to 300 K

Measurements of electrical conductivity and Hall coefficient have been made on undeformed and plastically deformed states of Bi-Tl (Bi + 3.92 at % Tl) and Bi-Pb (Bi + 4.00 at % Pb) single-crystal specimens, from 4.2 to 300 K. The carrier concentrationn and the Hall mobility obtained from these measurements show strong dependence on temperature. From the variation ofn with temperature, there is evidence for bend gaps of 40 meV obtained from observations between 100 and 300 K for Bi-Tl, and 18 meV between 70 and 300 K for Bi-Pb, in the undeformed states of the specimens. Theme band gaps increase due to plastic deformation. In the low-temperature region, the increase and the subsequent decrease inn have been explained on the basis of a thermal activation process and a phonon-induced electron-hole recombination process. The activation energies thus observed in the undeformed state of the specimens have been greatly reduced due to plastic deformation. These results show that the band structure of bismuth is greatly affected by doping, end that of the doped specimens of bismuth is further affected by plastic deformation. There is a correspondence between the increase inn and the decrease in and vice versa, over the entire range of temperature. The dependence of onT has been utilized to identify the scattering mechanisms.     

Debye temperature of metallic nanowires--an experimental determination from the resistance of metallic nanowires in the temperature range 4.2 K-300 K

We have studied the resistance of metallic nanowires (silver and copper) as a function of the wire diameter in the temperature range 4.2 K-300 K. The nanowires with an average diameter of 15 nm-200 nm and length 6 microm were electrochemically deposited using polycarbonate membranes as template from AgNO3 and CuSO4, respectively. The wires after growth were removed from the membranes by dissolving the polymer in dichloromethane and their crystalline nature confirmed by XRD and TEM studies. The TEM study establishes that the nanowires are single crystalline and can have twin in them. The resistivity data was fitted to Bloch-Gruneisen theorem with the values of Debye temperature and the electron-acoustic phonon coupling constant as the two fit variables. The value of the Debye temperature obtained for the Ag wires was seen to match well with that of the bulk while for Cu wires a significant reduction was observed. The observed increase in resistivity with a decrease in the wire diameter could be explained as due to diffuse surface scattering of the conduction electrons.     

Operation of the TVO temperature sensors in the range from 4.2 K up to 425 K

The report continues our investigations on cryogenic thermometers. To estimate the influence of warming the well known TVO temperature sensors [Proceedings of the ICEC17 (1998) 699, Cryogenics 41 (2001) 213, Advances in Cryogenic Engineering 45B (2000) 1817, Proceedings of the ICEC18 (2000) 627] up to 425 K on their calibration curve, a series of experiments have been carried out. The number of thermal cycles in the range from 425 K down to 77.3 K was 105. Comparison of readings of the sensors at 293, 77.3 and 4.2 K was performed with initial calibration curves for 100 cycles. Then several sensors were re-calibrated, and a new comparison was done during five additional thermal cycles at the same temperatures. The obtained results are discussed and they seem to be optimistic.     

An apparatus for measuring internal friction of films during the process of plastic deformation in the temperature range from 4.2 to 300 K

An apparatus is described in which internal friction (Q^?1) can be measured for specimens of dimensions 0.01 × 2 × 15 mm³ during the process of plastic deformation in the temperature range from 4.2 to 300 K and the frequency range 10² to 10⁴ Hz. The cryostat has three independent helium spaces, allowing Q^?1 to be measured in the magnetic field of a superconducting solenoid. The relative error in measuring Q^?1 during plastic deformation is ?5% at a deformation rate of 10^?3.     

Propagation of cracks in structural alloys at a temperature of 4.2 K

We study distinctive features of the process of crack propagation in structural materials under conditions of discontinuous yield and under the action of pulses of electric current at a temperature of 4.2 K. The kinetics of fracture processes in steel under the indicated conditions is studied by the method of stereofractographic analysis. We investigate the applicability of approaches to the evaluation of the characteristics of the crack-growth resistance of materials that take into account the effect of discontinuous yield and pulses of electric current on the process of formation of a plastic zone at a crack tip.     

Propagation of cracks in structural alloys at a temperature of 4.2 K

We study distinctive features of the process of crack propagation in structural materials under conditions of discontinuous yield and under the action of pulses of electric current at a temperature of 4.2 K. The kinetics of fracture processes in steel under the indicated conditions is studied by the method of stereofractographic analysis. We investigate the applicability of approaches to the evaluation of the characteristics of the crack-growth resistance of materials that take into account the effect of discontinuous yield and pulses of electric current on the process of formation of a plastic zone at a crack tip. Translated from Problemy Prochnosti, No. 6, pp. 36–40, November–December, 1997.     

Prediction of the temperature dependence of binary diffusion coefficients of gaseous systems from thermal diffusion factors and diffusion coefficients at 300 K

Data are presented which enable binary diffusion coefficients and their concentration dependences to be predicted from diffusion coefficients and thermal diffusion factors at 300 K. The results up to 2000 K are compared with corresponding values derived from the complication of Mason and Marrero. Paper dedicated to Professor Edward A. Mason.     

Stability of silicon diodes as temperature sensors in the range 4.2 – 273 K

Thermometric properties of TESLA — KA 136 silicon diodes as temperature sensors in the range 1.5 — 380 K are presented. Special attention is paid to the stability of these sensors which was examined for 30 diodes. This stability has been verified both dynamically using a method of cycling the diodes from room temperature to the temperature of liquid helium 100 times and statically using a method of storing the diodes at room temperature for 1 and 2 year periods. It has been found that moe than 90% of the diodes considered have a stability better than 0.4 K and 0.3 K at temperatures 4.2 K and 273 K, respectively, after 30 cycles and 12 months storage.