摘要:

A system was developed for obtaining &ggr;‐ray spectra with high resolution at high input rates. For rates up to 100 000 &ggr;‐ray events/sec in a 3.5 cm3(13 mm thick) Ge(Li) detector, the FWHM at 1.33 MeV is 2–3½ keV and the spectral shift is no more than 0.1%. The amplifying chain, consisting of a cooled FET preamplifier and a simple main amplifier, is pole‐zero compensated throughout. The amplifier produces unipolar pulses shaped with equal integrating and differentiating time constants of 1.2 &mgr;sec. The amplifier is followed by a two‐diode baseline restorer, a pileup rejector, a linear gate, and an analog to digital converter. The salient features of the system are described and performance data are presented and discussed.

ISSN:0034-6748    

DOI:10.1063/1.1720876

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A magnetic amplifier used at 4.2°K to measure small dc voltages is described. A sensitivity of 5×10−3&mgr;V was obtained without any precaution other than second harmonic detection for eliminating ac noise. Suggestions for increased sensitivity and comparisons with other techniques are given.

ISSN:0034-6748    

DOI:10.1063/1.1720877

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Techniques are described for the evaporation of homogeneous alloy films from a single source. InTl, a substance whose components have very different vapor pressures, and PbBi, whose components have more similar vapor pressures, were successfully deposited as thin films by these techniques. Comparisons of superconducting transition temperatures with published data confirm that the films are indeed homogeneous.

ISSN:0034-6748    

DOI:10.1063/1.1720878

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A transmission apparatus for the x‐ray diffraction of liquids is described. Its main advantages are: (1) precise determination of the intensity in the range of scattering angle 0°<2&thgr;<30°, (2) easy adaptability of commercially available equipment for its construction, and (3) simple temperature control from room temperature up to 250°C. Results obtained with the apparatus are presented, and in a short appendix possible sources of error in the use of a conventional pulse height analyzer for monochromatization are briefly discussed, illustrating the necessity of crystal monochromatization.

ISSN:0034-6748    

DOI:10.1063/1.1720879

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A piezoelectric pressure transducer has been designed, using readily available, inexpensive materials, which is capable of measuring sidewall pressures over a wide frequency range without serious distortion of the signal due to spurious elastic waves in the sensing element. The rise time is limited primarily by the transit time across the surface of the sensing element. The response of the gauge to a Mach 3.2 shock, gaseous detonations at pressure levels of 11 and 34 atm, respectively, is presented.

ISSN:0034-6748    

DOI:10.1063/1.1720880

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Rasmussen [Rev. Sci. Instr.33, 38 (1962)] has analyzed thermistor bead flow meters, treating constant current and constant temperature modes of operation, and summarizing the velocity dependence of the dissipation constant by means of a single curve. This paper treats a third mode of operation in which neither the bead current nor its temperature is kept constant: the bead's resistance is one leg of a dc Wheatstone bridge, and the bridge unbalance voltage is a measure of the flow velocity. Three results are reported. (i) The dissipation constant possesses two regimes of behavior, one being that noted by Rasmussen, but the other characterized by a velocity dependence featuring a nonmonotonic slope when the bead's temperature approaches that of the medium; (ii) the Wheatstone bridge unbalance voltage, initially, is almost linearly dependent on the velocity; and (iii) the ratio of velocity to bridge unbalance voltage achieves a plateau on which this ratio is nearly independent of thermistor power.

ISSN:0034-6748    

DOI:10.1063/1.1720881

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A duoplasmatron has been constructed specifically to produce negative ion beams of less than 5 keV energy. Design parameters are given for construction and operation of the source. Ion beam energy analyses indicate an energy full width at half maximum of less than 10 eV, and when the ion beam energy is extrapolated to zero, a full width at half maximum of 3 eV is observed. Ion beams of H−, O−, OH−, F−, CN−, and NO2−were produced at 2 keV with beam intensities between 3×10−7and 10×10−7A, measured behind a 0.63 cm diam aperture 140 cm downstream from the source.

ISSN:0034-6748    

DOI:10.1063/1.1720882

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A special purpose analog computer based upon an arbitrary number of zones annular approximation for Abel's integral equation has been designed and built. The computer inverts axial data to radial data economically in terms of time and effort. The resulting radial contours have been compared with both analytical and experimental (numerical inversion) contours representative of spectral intensity distributions found in axisymmetric plasmas. The computer is as accurate as the complex numerical inversion techniques and considerably more accurate than the anticipated measurements of spectral intensities.

ISSN:0034-6748    

DOI:10.1063/1.1720883

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Two programmed digital data‐collection systems have been developed and used with static‐field mass spectrometers to improve the precision of isotopic analyses of solid samples and to reduce the time required for collection and reduction of data. A large high‐sensitivity spectrometer using ion pulse counting detection has been equipped with a programmer and multiscaler so that up to four masses can be sequentially scanned and the resulting counts stored in different groups of the core memory. The simpler scheme of adding a programmed integrating digital voltmeter to sample the detector output of an analytical spectrometer is used where high sensitivity is not required. Both instruments use voltage switching between masses and magnetic sweeping of the mass peaks. Mass programming is done simply, but precisely and directly, by the use of operational amplifier techniques in voltage supplies.

ISSN:0034-6748    

DOI:10.1063/1.1720884

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A method for determining the change in elastic constants as a function of some parameter such as temperature or pressure is described. The method is a modification of the pulsed radio frequency sound technique, in which the echoes are mixed with a signal from a free‐ringing quartz crystal in order to extract small phase changes in the echoes. Conventional ultrasonic attenuation equipment, which ordinarily is too imprecise for such work, is utilized. The precision is shown to be about 2 parts in 105.

ISSN:0034-6748    

DOI:10.1063/1.1720885

出版商:AIP    

年代:1967

数据来源: AIP