摘要:

A pulsed laser illumination system for streak camera recording of impact‐induced shock wave transit times (∼1 &mgr;s) during impact experiments is described. Laser illumination of centimeter‐sized subjects offers many advantages over diffuse illumination techniques for streak photography. Source‐to‐sample and sample‐to‐camera distances of ∼100to 102m can be employed. Light filtering, and simultaneous recording of both the impact event and the camera streak rate calibration, can be carried out easily. For use in such a system we describe a Pockels cell controller in which the reference 10‐MHz oscillator signal is synchronously divided down to 38 Hz to provide a trigger signal for laser and streak camera testing.

ISSN:0034-6748    

DOI:10.1063/1.1137947

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The principles, construction, and operation of a versatile, orientable x‐ray diffractometer system having a position‐sensitive detector are described. The system precisely and rapidly measures Bragg scattering from very weak scatterers such as quantum crystals of helium and hydrogen held in fixed orientation at precisely controlled extreme temperatures and pressures inside fixed bulky apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1137956

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

An x‐ray acoustic detector was found to be sensitive to extremely soft x‐ray flashes (5 eV–10 keV,T≤1 &mgr;s). The total dose of the flash is measured by the x‐ray acoustic effect. The absorbed energy induces an acoustical pulse that is registered with a microphone. The microphone signal only depends on the absorbed energy. It is independent of the wavelength of the x‐rays. The dynamic range is limited only by the linearity of thermal properties of the x‐ray absorber and by the noise of the preamplifier. The measuring of continuous x radiation is possible using a chopper and lock‐in techniques.

ISSN:0034-6748    

DOI:10.1063/1.1137957

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A method has been developed, to modify the way power is applied to the test plate of a guarded hot plate, which enables continuous and accurate measurement of the power consumption of the test plate. It is very simple to produce and offers significant advantages in cost and flexibility over methods used in existing systems. The output of the temperature controller is converted into bursts of precisely regulated pulses of power, and these are counted against a time base. This enables digital manipulation of the power consumption data and interfacing of the guarded hot plate to a data processor.

ISSN:0034-6748    

DOI:10.1063/1.1137958

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A pressure regulator has been constructed that automatically nulls a sensitive differential pressure indicator of the type used in high‐quality PVT experiments, thus permitting at least partial automation of such experiments. Distinguishing features are: high resolution, sufficient rigidity for operation in a pressure range up to 100 MPa, and a control logic that permits nulling of the pressure transducer, even if the initial state is very far from balance.

ISSN:0034-6748    

DOI:10.1063/1.1137959

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

In the presence of electrostatic or electromagnetic fields, the viscometric thermometer is one of the few possible and feasible methods of temperature measurement. The device can be operated in a constant pressure or a constant flow mode. The former system is simpler and easier to build and operate but it requires a relatively long reading time of 1 to 2 min and, consequently, can be used only in ‘‘steady‐state’’ flows where the variations in temperature are much slower than the reading time required. Different configurations and measurement procedures are described. In particular, a viscometric thermometer was designed and built for the constant pressure mode which enabled us to obtain the temperature distribution inside the channel of an electrohydrodynamic pump.

ISSN:0034-6748    

DOI:10.1063/1.1137960

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The control unit and rf head of the SHE model 330X rf SQUID system are shown to be sensitive to ambient ac magnetic fields below 1 Hz, which cause the appearance of false signals corresponding to a magnetometer signal of 10−6&fgr;0per gauss of field applied. The control unit shows a sensitivity that is linear with frequency, suggesting that the signal is generated by Faraday induction. In contrast, the rf head response is independent of frequency and shows a strong second‐harmonic conversion. This response may be due to the magnetic field sensitivity of the ferrite core inductor in the tuned amplifier of the rf head. These signals induced by ambient fields are a potential source of error in Stanford’s Relativity Gyroscope experiment, which uses SQUID’s on board a rolling satellite as part of the gyroscope readout system. The extent of the magnetic field sensitivity in these components necessitates the use of additional magnetic shielding aboard the satellite.

ISSN:0034-6748    

DOI:10.1063/1.1137961

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

It is shown that an electric field uniform to fourth order can be formed by using two charged rings of equal radii separated by &sqrt;6 times the ring radius. Calculations of the field distribution and the deviation from uniformity are made. The axial and radial electric fields are calculated using an expansion valid near the origin of coordinates and, more generally, by evaluation of elliptic integrals.

ISSN:0034-6748    

DOI:10.1063/1.1137962

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

In some cesium frequency standards and clocks, the uniform, static magnetic field (C field) is generated by an assembly consisting of four conducting rods carrying equal currents and symmetrically placed at the corners of a rectangle inside concentric cylindrical magnetic shields. The spacing of the rods and their location within the shield to give minimum variation of the magnetic field within an area of rectangular cross section close to the axis of symmetry are calculated for the case of the National Research Council cesium clocks CsV and CsVI.

ISSN:0034-6748    

DOI:10.1063/1.1137963

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Superconducting heat switches consisting of tin and indium wires pressed between machined silver rods and oriented parallel to the operating magnetic field are described. Their advantages are simplicity of design and physical smallness. Thermal conductivities of such switches in the normal and in the superconducting state are reported.

ISSN:0034-6748    

DOI:10.1063/1.1137964

出版商:AIP    

年代:1984

数据来源: AIP