A downhole seismic signal source (vibrational or impulsive) capable of producing a signal of sufficiently high energy to permit the tool to be used in a deep wellbore (exceeding 4000 feet). A piston rod having two pistons reciprocates in an elongated cylindrical housing. An electrohydraulic valve controls the flow of hydraulic fluid to opposite sides of a first piston to control the piston rod's vertical movement. The second piston is positioned between a fluidic spring which balances the pressu...

A radioactive light source consists of a vacuum tight envelope filled with a mixture of a radioactive gas such as tritium with one or more other gases which luminesce when excited by the emission from the radioactive gas without the aid or requirement of any externally applied energy source, such as electrical power. This luminescence may be viewed through the wall of the chamber which may be transparent. Alternatively, all or a part of the luminescence may be converted to a different region of ...

A uniform source of nuclear radiation is produced by converting a convertible surface portion of a body. The conversion can be by chemical combination or reaction, neutron bombardment, ion exchange of an element present in the convertible material with a solution of radio-active ions of the element or by permitting the radio active particles to be embodied into the surface portion. A preferred embodiment utilises conventional photographic film in which the silver halide grains are treated chemic...

First and second monitoring channel apparatus detect the level of the normal output and load current, respectively, supplied by a principal energy source to a variable load network. Source output varies from normal to low level and load current from low to high level as load network varies between relatively no load and heavy load conditions. The monitor channel detection signals are checked through a logic circuit so that if at least one exceeds a predetermined level indicating the operable con...

An arrangement which enables the presence in an observed field of a light source whose radiation spectrum is known to be detected with a high signal to noise ratio. It includes an acousto-optical tunable filter controlled to scan through the expected spectrum of the source periodically and preferably linearly. The photo-detected signals are processed by a high-pass filter which removes the D.C. component due to ambient interference radiation and provides a periodic signal which correspond to the...

A light source comprises a semiconductor laser and a gas laser. The semiconductor laser is injection locked using the highly coherent output from the gas laser. The output from the semiconductor laser has a narrow linewidth and a high stability. The invention has a major application in optical fibre communications systems.

A source for the provision of ions or charged droplets of a liquid metal, consisting of a needle having an emitting tip, a reservoir for a liquid metal, ions or charged droplets of which are to be emitted by the source, and a sheath surrounding the needle and from which the needle projects. The sheath serves to convey liquid metal to the emitting tip of the needle at a controlled rate. There is provided a device for withdrawing the emitting tip of the needle into the sheath so as to enable the e...

A system for identifying an object, and in particular a vehicle, by analyzing the noise spectrum emitted thereby to determine the basic noise characteristic thereof and then comparing the basic noise spectrum signal with known basic noise spectra. The noise from the object, which includes both the basic noise characteristic and other superimposed noise, is detected and converted to an electrical analog signal which is then sampled. The sampled electrical signal, preferably after passing through ...

A radiation sensor improved to increase the signal-to-noise ratio in the presence of a luminous background of high light intensity and to reduce the danger of direct detection of solar radiation. The sensor comprises optoelectric shutter means associated with the transparent slits of the optical mask in order to pass substantially only the radiation emitted by the source to be located and received by the associated detector. The shutter can be provided from a plate of ferroelectric ceramic mater...

A radiation sensor for determining the angular location of a light source and locating a direction defined by a plurality of sources fastened to a movable structure such as a helmet-mounted sight visor. The sensor comprises a housing with an optical mask which is provided with transparent zones of circular shape, with the result that the omnidirectional radiation transmitted by a point source is confined within a cone. Radiation-detecting means constituted by linear arrays of photosensitive elem...