摘要:

A solid state, linear array piezoelectric acoustic image converter is described which has been developed for realtime underwater viewing, especially in turbid and/or turbulent oceanic environments. Sensitivity and resolution of the acoustoelectric transducer are on the order of 10−11W/cm2and 1 mm, respectively, at a frequency of 2.5 MHz. Imaging range up to 10 m is possible in turbidity concentrations of suspended ocean sediment (average particle diameter from 1 to 10 &mgr;) of several thousand parts per million. Expected ranges are at least five times larger in clear water. Fabrication and performance of the transducer array are discussed. Image scanning mirror, internal and external electronic circuitry, and the image display, all associated with the hydroacoustic converter, are also delineated.

ISSN:0034-6748    

DOI:10.1063/1.1685344

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

An apparatus for high pressure microwave experiments has been developed which can be operated at pressures up to 2 kilobars at 4.2 K using helium as the pressure transmitting medium. The high pressure chamber contains a rutile microwave resonator oscillating at ∼35 GHz. Microwave radiation is coupled into the resonator via a self‐sealing conical dielectric waveguide. The apparatus has been used in preliminary measurements of the effect of pressure on cyclotron resonance in bismuth.

ISSN:0034-6748    

DOI:10.1063/1.1685345

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A form of digital servo with printed disk dc motor drive, incremental measurement, nonlinear feedback, and digital integrated circuit logic is found eminently suited to application in photogrammetric instruments. Complexity ranges from unity transfer through nonlinear transfer to use of a computer in the control loop. A steering circuit for drawing in a plane is also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1685346

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A new apparatus is described whose purpose is the study of ion‐atom excitation processes. A single photon emitted by the excited target atom is detected in coincidence with the ion scattered at a given angle. Preliminary results are given for the He+&sngbnd;He collision at 300 eV and scattering angle from 6 to 15° with excitation of the 33Pstate and emission of the 33P−23Sline (3889 Å).

ISSN:0034-6748    

DOI:10.1063/1.1685347

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A pulsed valve is described for regulation of gas flow in vacuum systems using phase sensitive detection techniques. Mechanical and electrical construction detail is given with throughput performance and other characteristics in a given system application.

ISSN:0034-6748    

DOI:10.1063/1.1685348

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The sensitivity of an end‐on detection technique used to monitor light emission behind reflected shock waves is described. Using this detection method, emission from a test gas heated by a reflected shock wave is monitored through an observation window mounted in the end wall of the shock tube. The geometric factor of the end‐on detection system which relates the emission intensity within the test gas to the actual monitored intensity is derived and is shown to be constant under a number of experimental configurations. For the case of an exponentially growing emission signal, the sensitivities of the end‐on and more conventional side‐on detection techniques can be directly compared. For typical conditions encountered in studying the exponential growth of emission occurring during the C2H2+O2induction period, the end‐on detection system is shown to be 100 times more sensitive than a side‐on apparatus for experiments in which a detector with a small surface area is used (e.g., a liquid nitrogen cooled InSb ir detector). For detectors with large surface areas (e.g., photomultipliers with end windows), the end‐on technique is over 500 times as sensitive as side‐on methods.

ISSN:0034-6748    

DOI:10.1063/1.1685349

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A simple compact window assembly for ultrahigh vacuum systems is described which uses Irtran 2 or Irtran 6 ir transmitting optical material. The assembly is made in a standard ultrahigh vacuum flange using commercially available components. The window is sealed in place with silicone resin. After curing, the assembly can be repeatedly heat cycled up to 200°C without failure.

ISSN:0034-6748    

DOI:10.1063/1.1685350

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A method is described for suppressing the long tails which appear when signals are transmitted through cables. The principles of tail suppression are presented in a general frame and may be applied to various pulse transmission systems. The determination of the passive compensating filters is obtained by approximating the system impulse response with a convolution product, one factor being completely invertible. The compensating networks are realized by cascading impedance matched (50–50 &OHgr;, for instance) bridged T type filters of easy construction. For a 105 m long RG‐8 cable the 10 to 90% risetime was reduced from 18 to 2.5 nsec using only two filters, with a total attenuation of factor 2. It is shown that, in favorable cases, once an optimal filter for a given cable is found, other filters may be deduced from it for similar cables of different length and diameter (RG‐8 and RG‐58 C, for example); the theory and the measurement technique of the corresponding scaling factors are described. Various other applications are shown, including the compensation of an air cable in the subnanosecond region.

ISSN:0034-6748    

DOI:10.1063/1.1685351

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A 50 kV square wave pulse generator and associated control circuitry for use in spectrophotometric dissociation field effect experiments has been constructed. The design differs from previous pulse generators in that cumbersome delay cables are not used. A 0.005 &mgr;F plastic capacitor is charged to a voltage adjustable from 30 to 52 kV. When the desired voltage is reached, a triggered spark gap is fired, connecting the capacitor to the chemical cell. At a preset delay time, continuously adjustable from 0 to 29 &mgr;sec, a second spark gap is fired, shorting the cell and causing the voltage remaining on the storage capacitor to be discharged through a 100 &OHgr; resistor. This apparatus produces an exceptionally clean pulse with a rise‐ and fall‐time of less than 22 nsec and does not produce the troublesome reflections associated with devices using delay cables. This high voltage pulse perturbs the equilibrium between reacting species in the chemical cell, and the return to equilibrium is observed spectrophotometrically. Chemical relaxation times faster than 30 nsec have been reliably measured with this device.

ISSN:0034-6748    

DOI:10.1063/1.1685352

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A pin on disk machine is described which is used to study the friction, wear, and electrical behavior of sliding electrical contacts at speeds to 145 m/sec. Some typical results for an electrographite brush on medium carbon steel are presented.

ISSN:0034-6748    

DOI:10.1063/1.1685353

出版商:AIP    

年代:1971

数据来源: AIP