摘要:

A new method for determining ultrasonic velocity (500 kHz) is described. Differential phase shift measurements are made with a three‐transducer cell to a precision of ± 0.2%. Calibration data are given for aqueous solutions of NaCl and with mixtures of water and tertiary butyl alcohol.

ISSN:0034-6748    

DOI:10.1063/1.1134408

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The calibration and in particular the linearity of a three‐plate capacitance displacement transducer of range 1 mm and sensitivity 0.1 nm is measured with reference to a He–Ne laser standard using a Fabry–Perot etalon. The magnitude of the nonlinearity over the operational range is compared with estimates obtained from calculations of fringing fields. The most important contribution to nonlinearity is found to be inaccuracy in machining the capacitor plates, but this can readily be restricted to less than 1 nm over a central range of 0.3 mm (i.e., 3 parts in 106).

ISSN:0034-6748    

DOI:10.1063/1.1134409

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The design and performance of a transverse flow subsonic chemical laser with a total power output of 40 W for HF and 16 W for DF are presented. Laser operation has been observed in the wavelength range 2.6–3.0 &mgr; for HF and 3.6–4.0 &mgr; for DF resulting fromv=2−1 and 1−0 transitions of the HF molecule and fromv=3−2, 2−1, and 1−0 transitions of DF. The range of the participating rotational states in the emission spectra can be controlled to some extent by a variation of the gas temperature in the optical cavity region. The observed total power levels correspond to an electrical efficiency of 1.3% for HF and 0.9% for DF.

ISSN:0034-6748    

DOI:10.1063/1.1134410

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A simple water‐jacketed electric birefringence cell is described which is suitable for use with a laser light source. The electrodes in the cell form an integral part of the cell walls, thus permitting a low internal volume (∼ 0.4 ml) to be achieved. This makes the cell particularly suitable for use in studying macromolecular materials, such as biopolymers, which may be available only in small quantities.

ISSN:0034-6748    

DOI:10.1063/1.1134411

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A new thermocouple pairing was formed by combining thermocouple elements from two existing commercially available thermocouples to form a new combination (Ir–40 Rh/Pt–40 Rh) thermocouple. The output of this new pairing is nearly linear with temperature, and approximately equal to the output of one of the originating pairs (Ir–40 Rh/Ir), and more than double that of the other pair (Pt–40 Rh/Pt–20 Rh). This new pairing was evolved during a search for a noble‐metal thermocouple combination which could operate above the temperature limit of a Pt–13 Rh/Pt thermocouple and have a higher oxidation resistance than an Ir–40 Rh/Ir thermocouple.

ISSN:0034-6748    

DOI:10.1063/1.1134413

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A ductile copper–germanium alloy shows a negative relative temperature coefficient of resistivity of a few parts in 106/K in the temperature range of 1.5–4.2 K. Resistors based on this material are studied for stability under thermal cycling.

ISSN:0034-6748    

DOI:10.1063/1.1134358

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A bridge circuit is described. It eliminates the influence of sample temperature fluctuations as well as of lead resistance.

ISSN:0034-6748    

DOI:10.1063/1.1134359

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An economical, high‐voltage, highly stable, current‐regulated power supply with less than 0.1% rms ripple is described. The dynamic capabilities of 0–30 kV and 0–30 mA provide a versatile instrument for use with many cw gas lasers.

ISSN:0034-6748    

DOI:10.1063/1.1134360

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A description of the instrumental modifications and additions required for the conversion of this class of field‐swept, field‐modulated 60‐MHz NMR spectrometers is given. The rf portions are straightforward adaptations of the single‐coil sample circuit to pulsed operation. The standard instrument achieves field‐frequency stabilization through use of a NMR sideband oscillator employing a separate sample. While such a configuration is adequate for the normal mode of operation, it does not provide sufficient absolute stability for the pulsed Fourier mode of operation. The requisite stability was achieved by phase locking the sideband oscillation frequency to an external reference by forcing the radio frequency to change in accordance with the phase‐lock error signal. Both analytical and control channels are driven by this common rf source, as is the reference signal to the analytical channel synchronous detector.

ISSN:0034-6748    

DOI:10.1063/1.1134361

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

We have designed and built a simple and inexpensive analog gate which, when used in combination with an electrometer and a high gain photomultiplier, has a sensitivity of better than 1 photoelectron/sec and a linearity of better than 10% over a dynamic range of 1000.

ISSN:0034-6748    

DOI:10.1063/1.1134362

出版商:AIP    

年代:1975

数据来源: AIP