Abstract: A thermal imaging device comprises a layer 11 of pyroelectric material, an array of interconnected electrodes 13, and an array of discrete electrodes 15 supported from a substrate 27 by pillars 23 of thermally insulating material. Heaters 17 and associated control electrodes 19 are also provided to reduce the temperature difference between the discrete electrodes 15 and the pillars 23 and substrate 27. Control circuits 25 are provided to control energisation of the heaters 17.In a preferred embodiment the heaters may be provided on the substrate 27 for heating the discrete electrodes 13, the control current to the heaters providing an indication of the temperature of the source of radiation.

Abstract: A vacuum package for electron devices operating at cryogenic temperatures provides a silicon-metal multilayer heatpath with lowest thermal impedance between electron device and cryogen, has a solid body for heat transfer to the external heat sink and a silicon carrier board as mounting cold station for electron device assemblies with high multifunction and integration complexity. For heat transfer component is joined to the package wall by a silicon-glass seal. The multilayer heatpath construction uses standard silicon technology and materials which are compatible with requirements for high vacuum integrity performance. A modular package construction flow chart results in high design flexibility, low cost and mass production capability.

Abstract: The invention relates to a housing for opto-electronic components having an integrated Joule-Thomson cooler, the housing including a lower section, a center section and an upper section intended for radiation intake. The invention provides for the housing lower section and the housing center section, which enclose a heat exchanger pipe of the Joule-Thomson cooler, to be made of a material with low heat conductivity, and for the heat exchanger pipe to be arranged in coil form in one plane.

Abstract: An infrared detection system is disclosed in which a re-imaging optical system produces a non-axisymmetric aperture stop image at an exit pupil point in or near the cold shield entrance aperture. To achieve high cold shield efficiency notwithstanding the asymmetry of the aperture stop image and the resulting astigmatism in such image, two exit pupil stop members disposed in non-coplanar relation are provided adjacent the exit pupil point. The stop aperture in one such member has its radially extending edges congruent with the corresponding edges of the aperture stop image and is disposed in the plane of best exit pupil formation for those edges; the aperture in the other exit pupil stop member is correspondingly configured and oriented with respect to the circumferential edges of the aperture stop image.

Abstract: In a cryostat with a refrigerator containing a superconductive magnet, in which a material to be cooled and a low temperature end of the refrigerator for cooling the to-be-cooled material are disposed within a heat-insulating tank, the refrigerator is connected in unison with a part of a structural member other than the heat-insulating tank by a rigid coupling member. Accordingly, a heat portion of the refrigerator is tightly coupled to a magnetic shield member having a large mass and is connected to a vacuum container through bellows. The end portion of the refrigerator is formed in unison with heat shield sleeves and/or the heat shield tank through heat-conductive material having elasticity. Also, in order to prevent the leakage of the sound or noise from the heat portion, a sound-insulating cover is provided also for passages connecting to the head portion and is fixed to the magnetic shield member.

Abstract: In order to measure the temperature of a body (3) extensively independently of interference radiation (.theta..sub.U1), a sensor (1) is provided wherein the radiation (.theta..sub.3) of the body (3) is chopped by means of a chopper (5) between the sensor (1) and the body (3). Since extraneous radiation originates predominantly from losses at the sensor (1) as well as from frictional heat of the chopper (5) in case a mechanical chopper (5) is provided, the housing temperature of the sensor (1) is detected for correction purposes on the side of the chopper (5) facing the sensor (1) by means of an additional sensor (13). Around and in the zone of the travel path of the mechanical chopper (5), by means of a third sensor (15), the ambient temperature of the chopper is detected, again for correction purposes.

Abstract: A cryostat is provided which comprises a vacuum vessel; a target disposed within the vacuum vessel; a heat sink disposed within the vacuum vesssel for absorbing heat from the detector; a cooling mechanism for cooling the heat sink; a cryoabsorption mechanism for cryoabsorbing residual gas within the vacuum vessel; and a heater for maintaining the target above a temperature at which the residual gas is cryoabsorbed in the course of cryoabsorption of the residual gas by the cryoabsorption mechanism.

Abstract: An infrared detector assembly (12) of the type used in munitions and night vision systems having an improved focal plane platform (10). The focal plane platform (10) includes an end-cap (32) made from tungsten. Adhesively bonded to end-cap (32) is a ceramic mounting board (34). Ceramic mounting board (34) further comprises gold trace pattern (50) for conducting electrical signals generated by hybrid detector (26) to external control electronics. The improved focal plane platform (10) provides a relatively distortion free, thermally stable mounting platform upon which detector (26) is secured. Premature thermal fatigue failure of the hybrid detector is thereby inhibited.

Abstract: In a cryogenic refrigerator having a precooling refrigerating circuit including a cryostat for cooling and maintaining a cryogenic working apparatus which is operated at a very low temperature level, expander for expanding refrigerant gas, such as helium gas, and a J-T circuit for generating cold by Joule-Thomson expanding refrigerant gas precooled by the precooling refrigerating circuit, the present invention prevents the working vibration of the expander from unduly effecting the cryogenic working apparatus and to maintain the cryogenic working apparatus at a very low temperature level for many hours, even while the precooling refrigerating circuit is stopped, thereby enabling a stabilized operation of the cryogenic working apparatus to be performed.

Abstract: An infrared detector assembly (10) of the type used in munitions and night vision systems having an improved coldfinger assembly (42). Such detector assemblies (10) include a tubular coldfinger (22) which is surrounded by a vacuum and an end-cap (28) mounted to the coldfinger tube (22) to define a cold end (24) which supports the infrared detector array (30) and related components. In accordance with this invention, the coldfinger tube (22) is a thin-walled titanium cylinder and the end-cap (28) is made of tungsten. The components are metallurgically bonded at the cold end (24) by an active brazing alloy deposited during vacuum furnace brazing. The titanium coldfinger (22) provides the necessary bending stiffness to support cold end components. The tungsten end-cap (28) provides a low distortion, thermally stable focal-plane. The metallurgical bond (46) provides for a hermetic seal which inhibits structural distortion during brazing, and during cyclical cooling of the detector assembly (10).

Abstract: An infrared gas analyzer using a pyroelectric infrared sensor, which includes a heating unit for heating the infrared sensor, a heating sensor for detecting its heating temperature and a temperature sensor for detecting the ambient temperature of the infrared sensor, and controls the heating unit so as to retain the ambient temperature of the infrared sensor at a constant so that the output error is small irrespective of the change in ambient temperature.

Abstract: A non-evacuated dewar 10 advantageously employs a molecular sieve 30 that serves to adsorb gasses in the dewar when cooled during operation of the detector 24 thereby preventing liquid formation onto the detector. The effects of outgassing and permeation during storage are substantially eliminated because the dewar package is in partial pressure equilibrium with its environment since the interior of the dewar is backfilled with the same inert gas as is in the surrounding outside environment. A second molecular sieve 40 may be used to adsorb moisture which may permeate into the housing.

Abstract: A method and apparatus for scientific analysis of a sample under low temperature vacuum conditions uses a vacuum chamber with a conveyor belt disposed therein. One end of the conveyor belt is a cool end in thermal contact with the cold stage of a refrigerator, whereas the other end of the conveyor belt is a warm end spaced from the refrigerator. A septum allows injection of a sample into the vacuum chamber on top of the conveyor belt for spectroscopic or other analysis. The sample freezes on the conveyor belt at the cold end. One or more windows in the vacuum chamber housing allow spectroscopic analysis of the sample. Following the spectroscopic analysis, the conveyor belt may be moved such that the sample moves toward the warm end of the conveyor belt where upon it evaporates, thereby cleaning the conveyor belt.

Abstract: The evacuated and cooled Dewar 1 of an infrared detector has a window end in the shape of an elliptical spheroid, and an IR detection element 3 is mounted within the focal circle of the spheroid. The construction minimizes the sensing of spurious IR rays by the detection element, as well as the heat load for the coolant and the cool down time.

Abstract: Demountable cryocoller cold heads must make reliable contacts having low thermal resistance at cryogenic temperatures for cooling such devices as radiation shields used in superconducting magnets. Cryostat vacuum and a bellows is utilized in order to engage the cold head second stage interface, while the first stage interface is independently engaged by means of a bolted flange and a bellows. A soft metal such as indium is employed at the contact surfaces of the heat stations.

Abstract: A counter-countermeasure provided within a thermal imgaging device (TID) rein an enemy black hole, or cold spot, radiometer (BHR) is prevented from detecting the presence of cryogenic detectors within the TID. The thermal imager counter-countermeasure comprises a beam splitter placed in the primary optical path of the TID and a projection heater positioned to one side of the primary optical path and at, or close to, the same point as the array of cryogenic detectors.

Abstract: A superconductive magnet coolable with a two stage cryocooler is provided. The superconductive magnet includes a cryostat containing a magnet winding, a thermal radiation shield surrounding the magnet winding and spaced away therefrom. The cryostat defines an aperture in which a cryocooler cold head interface receptacle is situated. The interface receptacle has a first and second heat station for connecting in a heat flow relationship with the first and second heat stations of the crycooler, respectively. A precooler has first and second stage heat exchangers connected in a heat flow relationship with the first and second heat stations of said interface, respectively. The interface has an inlet and outlet port for supplying and removing cryogens. Piping means fabricated from heat insulating material connect the first and second heat exchangers in a series flow relationship between the inlet and outlet ports.

Abstract: A system for measuring electromagnetic radiation originating from the hemhere corresponding to a solid angle of 2.pi. is provided wherein a highly sensitive low-inertia detector is disposed below a transmissive dome and wherein the chopped light detection method is utilized. There are provided above the transmissive dome two similarly or differently designed modulators which are in the shape of dome segments and which are fitted into each other. At least one of the modulators rotates about their common vertical axis or the modulators may both rotate about the common vertical axis, either at the same or a different speed in the same direction or in opposite directions.

Abstract: Consolidation of active and passive detectors (26, 28, 34) on a single coldfinger (20) in a dewar (10) is made possible by interposing between the detectors (26, 28, 34) an electromagnetic interference shield (64, 68) which acts as a waveguide filter blocking any interfering frequencies. The waveguide is formed by a pair of spaced interleaved shields (64, 68), one of which (64) is associated with the dewar envelope and is externally grounded, and the other of which is associated with the coldfinger (20). Photons which penetrate through the waveguide (64, 68) are deflected to the outside of the dewar (10) by a flanged narcissus shield (40) surrounding the passive detector (34).

Abstract: An infrared detector assembly (10) of the type used in munitions and night vision systems having improved coldfinger dewar tube (22). Such detectors include a tubular coldfinger which is surrounded by a vacuum and has a cold end (24) which supports the infrared detector array (30) and related components, and an opposite warm end (26). In accordance with this invention, the coldfinger tube is a two-material composite structure having plastic (44) and metal (42) layers. The plastic layer provides the necessary bending stiffness to support the cold end components while minimizing heat transfer rate between the warm and cold ends of the tube. The metal film layer provides a gas seal to preserve the integrity of the dewar vacuum, but is sufficiently thin to provide a minimal increase in thermal conductivity. The compositie coldfinger tube in accordance with this invention features lower overall heat conductivity thus minimizing cryogenic cooling requirements while providing the necessary bending stiffness.

Abstract: An arrangement for ensuring the stability of the set point for a gas analyzer is disclosed. The set point control circuit utilizes an amplifier which is alternately switched between a reference voltage and a sensor signal to provide a signal to a processor representing the reference signal and the sensor signal. The processor compares the two signals and adjusts the heater associated with the sensor to provide a stable set point for the gas analyzer. The arrangement eliminates the need for precision resistors within the set point control circuit and therefore significantly reduces the cost of the circuitry.

Abstract: The present invention is directed to an integrated detector dewar cryoengine (10). The integrated detector dewar cryoengine (10) includes a detector (12) for detecting received electromagnetic radiation. The integrated detector dewar cryoengine (10) further comprises expander end cap (18) for removing thermal energy from said detector (12) which is in mechanical communication with said detector (12).

Abstract: In a radiation image detecting apparatus having its image receiving means constituted of a two-dimensional array of composite radiation detecting units each of which includes a radiation sensor and a signal processing circuit, the composite radiation detecting units are provided with circuit cooling means for suppressing heat generation at the above signal processing circuits. The circuit cooling means consists only of piping in thermal contact with the composite radiation detecting units, or consists both of the the piping or the duct-and-coolant intakes combination and of porous-walled gas piping stretched through the clearances left between two adjacent composite radiation detecting units constituting the two-dimensional or the one-dimensional composite radiation detecting unit array. The piping and the duct-and-coolant intakes combination are supplied with a liquid coolant, while the porous-walled gas piping supplied with a gaseous coolant.

Abstract: A shield for limiting the radiation received by an array of detectors along the length of the detector array of an electromagnetic radiation detection system to radiation provided to the detectors by the optics of the system. The shield comprises a pair of glass rods mounted in a parallel relationship to each other and to the linear direction of the array and forming an aperture along the length of the array so as to shield the elements of the array from electromagnetic radiation generated outside the field-of-view of the detectors.

Abstract: Gas analyzers of the non-dispersive infrared radiation type which are designed to measure the concentration of one gas in a mixture of gases containing that gas. An infrared radiation emitter is employed to emit energy at a frequency of 40-100 Hz with a system which includes a source driver and a timer; and a detector is used to intercept the attenuated beam after it has passed through the mixture being analyzed and output a signal indicative of the concentration of the selected gas. Also, a second detector is preferably provided so that a ratioed, error eliminating output signal can be supplied to the failsafe, signal processing circuitry of the analyzer. The detectors are electrically biased by way of flyback transformer based circuitry to improve the signal-to-noise ratio, and the signal processing circuitry can be adjusted to compensate for drift. The detectors are mounted on a thermally conductive substrate along with appropriate filters, a filter frame, and a cover.

Abstract: An apparatus for testing infrared detector response to ionizing radiation within an infrared shielded environment includes a cryostat having an aperture which is positioned adjacent to a scanning electron microscope (SEM). The SEM generates an electron beam which propagates through the aperture and is absorbed by a foil positioned adjacent the detector. The interaction of the electron beam with the foil produces X-rays which irradiate the detector. Instruments electrically coupled to the detector record and display the detector response.

Abstract: An improved prism cold shield for use in an infrared detection system which includes a detector array comprised of a plurality of detectors sensitive to a radiation of interest in a predetermined wavelength band. The prism comprises a substrate having a top surface partially coated with a first coating layer arranged to define a plurality of bow-like stripes alternating with top surface openings which are covered by a second coating layer. The substrate has a bottom surface partially coated with a third coating layer in a pattern to define a line of windows on the bottom surface which are aligned with the top surface openings so as to define a field of view for the plurality of detectors. The first and third coating layers ae comprised of high absorption, low reflectivity coatings in the wavelength band of the radiation of interest and the second coating layer is an anti-reflective coating.

Abstract: A broadband photon detector device which operates using a superconducting material is biased at the temperature where the material changes from a superconducting to a non-superconducting state. Photons which strike said material cause a temperature rise and a measurable increase in resistivity of the material. Measuring the increase in resistivity allows the detection of the incident photons.

Abstract: A method and apparatus for measuring a temperature of a body extensively independently of an interference radiation. The apparatus comprising a sensor wherein a radiation of the body is chopped or interrupted by a chopper disposed between the sensor and a body. In order to sense extraneous radiation which originates predominately from losses at the sensor as well as from frictional heat of the chopper, the housing temperature of the sensor is detected for correction purposes on a side of the chopper facing the sensor by an additional sensor. Around and in the zone of the travel path of the chopper, an additional sensor is provided for sensing an ambient temperature of the chopper.

Abstract: A non-evacuated dewar 10 advantageously employs a molecular sieve 30 that serves to adsorb gasses in the dewar when cooled during operation of the detector 24 thereby preventing liquid formation onto the detector. The effects of outgassing and permeation during storage are substantially eliminated because the dewar package is in partial pressure equilibrium with its environment since the interior of the dewar is backfilled with the same inert gas as is in the surrounding outside environment. A desiccant 40 made of a barium oxide/RTV silicone rubber composite may be used to adsorb moisture which may permeate into the housing.

Abstract: Two broad blackbody sources (24, 26) having a constantly maintained temperature differential therebetween are alternately directed via a chopper (40) onto a detector array (12) for testing same.

Abstract: Disclosed are a radiation detector and a method of manufacturing the same. The radiation detector includes a radiation screening member for cutting off radiation incident upon the marginal portions of the radiation incident surface of a semiconductor radiation sensor or a semiconductor radiation sensor array for outputting pulses in correspondence with radiation photons, as well as upon the boundary portions between adjacent sensors. In order to manufacture such a radiation detector, leads are provided by the wire bonding, soldering or bump contacting on the radiation screening member, and at least part of the radiation screening member is then fitted to the semiconductor radiation sensor or the semiconductor radiation sensor array so as to make it electrically connected to the electrodes of the semiconductor radiation sensor or the semiconductor radiation sensor array.

Abstract: An infrared ray detector includes, an infrared ray detection element farbicated in a water which is produced by growing a semiconductor responsive to infrared ray on a high resistance substrate, a metal submount provided with two lead terminals insulated from each other, to which submount the infrared ray detection element is mechanically fixed, an adiabatic vacuum vessel for containing and cooling the infrared ray detection element, to which vessel the metal submount is mechanically fixed, the infrared ray detection element and the metal submount. The metal submount and the adiabatic vacuum vessel are respectively adhered to each other by solder.

Abstract: A refrigerated environment for multiple laser sources and/or sensors which provides the same thermal conditions in a single cold-cycle refrigerator for the sensors and sources. A mounting structure which comprises a cold-head assembly accomodating plural sensors or sources and positions them for radiation transfer with the ambient while they are held at consistent temperature relationships for efficient operation.

Abstract: An improved open-cycle cooling apparatus in which a cooling chamber holding a device to be cooled is coupled with a cold fluid delivery system and, in which the cold fluid delivery system includes a delivery tube which directs a stream of cold fluid to strike the device and a return which vents the expended cold fluid from the cooling chamber. The improvement comprises a rigid enclosure formed within the chamber and configured to adaptively engage one end of the cold fluid delivery tube. The device to be cooled is disposed within the enclosure. The enclosure also includes a return to remove expended cold fluid from the cooling chamber to the return of the cold fluid delivery stystem. The improvement further comprises an alignment guide disposed within the enclosure between the device to be cooled and the one end of the cold fluid delivery tube engaged to the enclosure.

Abstract: The invention relates to a multiple channel readout circuit optimized for a cryogenically operated IR sensor head. The circuit is applicable to the individual channel preamplifiers of a charge injection device (CID) IR sensor. Since the thermal leakage must be minimized, the voltages on the principal current supply path to the individual preamplifiers will vary when a strong signal is present on any channel. Crosstalk is avoided by using a four transistor cascode preamplifier circuit having a source follower output, in which the gate of the transistor, which acts as a load to the two cascoded transistors, is isolated from the drain of the load transistor, connected to a gate load node common to the other channels, and the node connected via a single connection of high thermal impedance to a terminal external to the cryogenic environment, at which filtering may be provided as needed.

Abstract: An improved thermal imaging device is provided herein, which includes an internally-mirrored autocollimating mirror, a multi-element detector and a diaphragm in the mirror for limiting the aperture of the multi-element detector. In the improved device the multi-element detector is offset from the optical axis. At a symmetrical point on the other side of the optical axis, at which the autocollimating mirror forms an image of the multi-element detector, a mirror is disposed. Such mirror project the image of the multi-element detector back to the autocollimating mirror. Such image is then reflected once more right way up and laterally unreversed onto the multi-element detector in such a way that each individual detector element receives its own image.

Abstract: In a photon detector system, such as a cryogenic gamma radiation detector cooled by a dewar, a vacuum-jacketed radiation detector is provided in a cryostat assembly. The detector can be used with any one of a plurality of cryostats without breaking the vacuum seal therearound when transferring from one cryostat or dewar to another. The detector is vacuum-jacketed and mechanically and thermally connected to an axially projecting conducting member, which member is received in a thermally conducting transition member contained in the cryostat. The transition member is thermally and mechanically coupled to the dewar and may include a fluid path completing a vacuum jacket in the dewar.

Abstract: The present invention pertains to an apparatus that is capable of correcting for inaccuracies caused by molecular collision broadening in analyzers. The apparatus includes an analyzer for analyzing a fluid. The analyzer is capable of producing an output signal corresponding to the fluid in the analyzer. The apparatus also includes a device for detecting molecular collision broadening in the fluid. The detecting device produces an output signal proportional to the molecular collision broadening. There is also a device for correcting inaccuracies in the analyzer output signal caused by molecular collision broadening. The correcting device is disposed to receive the analyzer output signal and the detecting device output signal, and is capable of producing an output signal corresponding thereto. Preferably, the detecting device includes a thermal conductivity cell and the correcting device is either a voltage control gain operational amplifier or a computer.

Abstract: In a cryogenic refrigerator having a precooling refrigerating circuit including a cryostat for cooling and maintaining a cryogenic working apparatus which is operated at a very low temperature level, an expander for expanding refrigerant gas, such as helium gas, and a J-T circuit for generating cold by Joule-Thomson expanding refrigerant gas precooled by the precooling refrigerating circuit, the present invention prevents the working vibration of the expander from unduly effecting the cryogenic working apparatus and to maintain the cryogenic working apparatus at a very low temperature level for many hours, even while the precooling refrigerating circuit is stopped thereby enabling a stabilized operation of the cryogenic working apparatus to be performed.

Abstract: Consolidation of active and passive detectors (26, 28, 34) on a single coldfinger (20) in a dewar (10) is made possible by interposing between the detectors (26, 28, 34) an electromagnetic interference shield (64, 68) which acts as a waveguide filter blocking any interfering frequencies. The waveguide is formed by a pair of spaced interleaved shields (64, 68) one of which (64) is associated with the dewar envelope and is externally grounded, and the other of which is associated with the coldfinger (20). Photons which penetrate through the waveguide (64, 68) are deflected to the outside of the dewar (10) by a flanged narcissus shield (40) surrounding the passive detector (34).

Abstract: A non-dispersive infrared gas analyzer is disclosed that accurately measures the concentration levels of a plurality of gases within a gas mixture. The analyzer includes first and second sample cells and is utilized advantageously for the measurement of NO.sub.x and hydrocarbon gas present in the exhaust of an automobile engine. The gas mixture of the exhaust is chilled before entering the first sample cell to remove a substantial amount of the water vapor from that sample cell to facilitate measurement of the NO.sub.x gas. The second sample cell receives the gas mixtue in an unchilled state to allow for accurate measurement of the hydrocarbon gas. The analyzer includes processors which are utilized to further correct the NO.sub.x measurement and which also interact with each other to provide an output data stream that is representative of the concentration levels of the gases that are being analyzed.

Abstract: An infrared imager includes an array of imager elements. Infrared radiation is focussed onto the array by a lens assembly including a plurality of lens elements. The imager array and the lens are within a cold box which includes an infrared-transparent window. For low noise, a spectrum-limiting filter is also located within the cold box, between the lens assembly and the window, at or within the pupil relief distance of the lens assembly. The pupil relief distance is extended by the use of at least one aspheric surface for one of the lens elements of the lens assembly. The mounting structure of the filter is the aperture stop for the infrared imager. The field of view may be reduced, if desired, without significant effect on the noise performance by use of a telescope including a second lens assembly optically identical to the first lens assembly, operated in conjunction with a confocal large-diameter lens assembly.

Abstract: As a means for connecting a gas chromatograph and an IR-spectrometer, devices are used which include a cooled carrier which allows to condensate the substances supplied by the gas chromatograph on its surface where they may be examined by spectroscopy. The examination of a new sample makes necessary the evaporation of the substances condensated on this surface before. Up to now, the heating and the cooling of the carrier which was necessary to this end, took a rather long time. Further, the heating of the carrier was limited to a temperature at which not all substances could be completely eliminated from the surface of the carrier. Now, the invention provides for a thermal decoupling of the carrier from the cooling device. Such decoupling allows to heat the carrier to higher tempreatures and to reduce the time needed for performing a measuring cycle, since as a result of the decoupling the cooling device is not heated but the heating is limited to the small mass of the carrier.

Abstract: A warmshield reflector for a cryogenically cooled radiation detector has a reflective surface of toroidal shape. The surface has geometric properties which cause a ray emanating from the detector to be reflected such that a ray is imaged as a defocused ring outside of and surrounding the active detector area. Several such segments are located in front of a small, cryogenically cooled detector shield, to provide an overall detector shielding effect similar to that of a larger, cryogenically cooled shield.

Abstract: In a cryostatic device for cooling an infrared detector, based on the Joule-Thomson effect, a countercurrent heat exchanger is located with a forward flow conduit in a Dewar vessel. The forward flow conduit ends in an expansion nozzle. The infrared detector is located on the front side of the inner wall of the Dewar vessel. To reduce the heat load, a heat insulating layer is arranged between the Dewar vessel and a base. To improve the cooling power of the Joule-Thomson process achievable with a predetermined pressurized gas mass flow, an inlet end of the forward flow conduit is cooled by Peltier elements. Thus the required pressurized gas flow is reduced.

Abstract: A cold shield for an array of detectors of predetermined shape comprising a first cover of radiation blocking material formed with parallel rows of apertures and lying a first distance away from the detectors and a second cover of radiation blocking material formed with a plurality of apertures of generally the predetermined shape therethrough and lying a second distance, smaller than the first distance, away from the detectors so as to minimize background radiation from reaching the detectors while permitting desired radiation approaching the array from any of a plurality of angles to reach the detectors.

Abstract: A prism cold shield adaptable to an infrared detector system comprising a prism-shaped substrate having an upper portion partially coated with opaque material and a lower portion partially coated with opaque material wherein windows formed by the upper and lower coatings defined the field of view for a plurality of infrared detectors thereby cold shielding the detectors in the linear direction of the detector array.

Abstract: A sharp edged aperture for use with radiation sensing apparatus to permit radiation to pass through a relatively thick layer of radiation absorbing material with a minimum of reflection off the edges of the opening by utilizing a thin layer of radiation blocking material overlaying the layer of radiation absorbing material.

Abstract: Coolant gas pumped into the inner flask (3) of a cryostat dewar (2) causes an unwanted electrostatic charge on the inner surface (34) of the inner flask (3). This electrostatic charge can put an unwanted noise into the electrical output from an electromagnetic detector (16) cooled by the cryostat (2). The invention comprises a foraminous metallic screen (7) interposed between coolant coils (5) of the cryostat (2) and said inner surface (34). The screen (7) siphons off unwanted electrostatic charge from said surface (34) while allowing coolant to contact said surface (34) and thus allow cooling of the detector (16).