摘要:

Numerical calculations of the behavior of dilution refrigerator heat exchangers are discussed and some results for both discrete and continuous exchangers are presented. It is shown that thermal conductance along the stream is negligible for a typical continuous exchanger of the coaxial tube type, but becomes a dominant feature of a typical discrete exchanger operating below about 50 mK and degrades the performance considerably. A simple design change can be made that reduces the conductance along the liquid and improves the performance of such an exchanger. A simple means of determining whether conductivity is important in either continuous or discrete exchangers is given.

ISSN:0034-6748    

DOI:10.1063/1.1685324

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An apparatus is described in which solid samples of reactive materials are quenched following heating in a small drop‐away vacuum furnace chamber. The principal feature is that the furnace is supported by the differential pressure between the furnace chamber and its surroundings. Thus, when the quenching gas is injected over the sample in the furnace chamber the vacuum is instantly broken, causing the furnace to drop away from the sample. By using chilled helium gas, quenching rates up to 1.8×104°C/sec have been achieved with 0.25 mm thick samples. Higher cooling rates should be attainable by the use of thinner samples and higher gas velocities and possibly by improving the quench nozzle design. The simplicity of the unit and the small volume to be evacuated are attractive features.

ISSN:0034-6748    

DOI:10.1063/1.1685325

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The methods used to measure response and performances of an electrostatic spectrometer with an identical apparatus are studied in the case of the 127° cylindrical spectrometer by means of a method of calculation of the electron energy distribution. The distribution given by the monochromator is calculated and its analysis with the identical analyzer is simulated. The three usual methods of analysis are found to give inaccurate results not only for the widths of the energy distribution but also for its profile. It is shown that because of the inherent angular dispersion of the analyzer, it is necessary to carry out the analysis of the beam by narrow angular slices in order to recover the exact profile of the energy distribution yielded by the monochromator.

ISSN:0034-6748    

DOI:10.1063/1.1685326

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A pressure transducer, consisting of a peizojunction sensing element, has been developed for meauring both static and transient pressures. In the static mode of operation the calibration curve showed a ±1.5% FSO (full scale output) independent linearity, a 3% FSO hysteresis, and a repeatability of 0.5% FSO. Dynamically, the transducer exhibited a thermal sensitivity shift of 0.27% FSO/°C.

ISSN:0034-6748    

DOI:10.1063/1.1685327

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An acoustic emission test facility was designed and constructed to allow constant strain rate compressive deformation of samples up to an applied load of approximately 180 kg. Strain rates of from 1.6×10−3to 3.2×10−6sec−1were obtained with total system noise limited to less than 10 &mgr;V peak‐to‐peak referred to the input of the pre‐amplifier. Over‐all signal amplification was 9900±100 over a bandwidth of 200 Hz–200 kHz.

ISSN:0034-6748    

DOI:10.1063/1.1685328

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A technique is described for determining both the elastic surfce wave velocity and its temperature coefficient. The technique can be used on very small samples and is not restricted to any particular class of materials, such as piezoelectrics. It employs an adaptation of the old method of acoustic wave generation with a dc pulse rather than an rf signal applied to a piezoelectric transducer. The generator and receiver transducers are very small chips, approximating point sources, and at the receiver the vertical component of particle velocity is measured as a function of time enabling one to distinguish clearly between various types of surface modes, e.g., Rayleigh wave, pseudosurface wave, Lamb wave, etc. The technique yields absolute surface wave velocities accurate to 0.2% and is readily adaptable to the use of the sing‐around technique for measuring relative changes in the sound velocity as small as 1 ppm.

ISSN:0034-6748    

DOI:10.1063/1.1685329

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A magnetic suspension technique has been developed for use in making absolute density measurements on cryogenic fluids at low temperatures and elevated pressures. Adapting a method, previously used at room temperature, for PVT work in this region required several modifications. This apparatus can be used at any temperature below ambient and at pressures up to 340 atm. The density of saturated liquid nitrogen at 77.46 K has been determined in order to evaluate its performance.

ISSN:0034-6748    

DOI:10.1063/1.1685330

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An instrument is described which permits energy analysis, by electrostatic deflection, of any of six beams of scattered electrons. In the particular design discussed, the beams define scattering angles between 40 and 140°, in 20° intervals. Various parameters of electron trajectories, including effects of small magnetic fields, have been computed and design criteria for optimum angular and energy resolution are presented.

ISSN:0034-6748    

DOI:10.1063/1.1685331

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A cell volume sensing instrument has been built which employs the principle used in the Coulter counter in which a cell changes the impedance of a narrow orifice as it passes through the orifice. An improved transducer utilizes a coaxial flow of the cell suspension inside a sheath of cell‐free solution through the orifice, thereby avoiding some drawbacks of earlier systems. The instrument is described, and the procedure necessary to achieve acceptable operation is discussed. The output for normal human red blood cells is nearly symmetrical with a narrow peak. Abnormal blood samples show various departures from symmetry and narrowness of peak. The output of this instrument is compared with that from a commercially available instrument, and our data show a more accurate representation of the actual distribution of blood volumes. The resolution of this instrument is such that it could be of significant value in a clinical laboratory.

ISSN:0034-6748    

DOI:10.1063/1.1685332

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A silicon diffused transistor, connected in the transdiode mode, is utilized to generate the antilogarithm of the commercial Severinghaus type Pco2electrode. Operational amplifier requirements are discussed and a new single point calibrating procedure is introduced. A theoretical relationship for output errors is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1685333

出版商:AIP    

年代:1971

数据来源: AIP