Abstract: A monitor that can detect at least one molecule. The monitor includes a housing with a passage that can receive a sample, and a photocathode that is located within the housing. The monitor also includes a first ultraviolet light source that can direct ultraviolet light onto the photocathode to create electrons that ionize molecules within the sample, and a detector that is coupled to the housing to detect at least one ionized molecule. The monitor enables electron ionization (EI) of a sample for chemical analysis without the disadvantages of current methods that use a hot filament or other thermal cathode devices.

Abstract: The present invention relates to a photomultiplier having a structure for making it possible to easily realize high detection accuracy and fine processing, and a method of manufacturing the same. The photomultiplier comprises an enclosure having an inside kept in a vacuum state, whereas a photocathode emitting electrons in response to incident light, an electron multiplier section multiplying in a cascading manner the electron emitted from the photocathode, and an anode for taking out a secondary electron generated in the electron multiplier section are arranged in the enclosure. A part of the enclosure is constructed by a glass substrate having a flat part, whereas each of the electron multiplier section and anode is two-dimensionally arranged on the flat part in the glass substrate.

Abstract: The present invention relates to a photomultiplier having a structure for making it possible to easily realize high detection accuracy and fine processing, and a method of manufacturing the same. The photomultiplier comprises an enclosure having an inside kept in a vacuum state, whereas a photocathode emitting electrons in response to incident light, an electron multiplier section multiplying in a cascading manner the electron emitted from the photocathode, and an anode for taking out a secondary electron generated in the electron multiplier section are arranged in the enclosure. A part of the enclosure is constructed by a glass substrate having a flat part, whereas each of the electron multiplier section and anode is two-dimensionally arranged on the flat part in the glass substrate.

Abstract: The present invention relates to a manufacturing method of obtaining a photoelectric converting device which can sufficiently maintain airtightness of a housing space for photocathode without degradation of the characteristics of the photocathode. In accordance with the manufacturing method, on the side wall end face of a lower frame and a bonding portion of an upper frame forming an envelope of the photoelectric converting device, a multilayered metal film of chromium and nickel is formed. In a vacuum space decompressed to a predetermined degree of vacuum and having a temperature not more than the melting point of indium, these upper and lower frames introduced therein are brought into close contact with each other with a predetermined pressure while sandwiching indium wire members, and accordingly, an envelope having a housing space whose airtightness is sufficiently maintained is obtained.

Abstract: The invention relates to a barrier layer provided on the electrode assembly of a discharge lamp comprising at least a layer of nanoclusters of a non-oxidizing material. Further, the invention relates to an electrode assembly for a discharge lamp comprising an electrode having a foil attached thereto to create an electrode assembly, the assembly being coated with a multi-layer coating comprising at least a layer of non-oxidizing material in the form of nanoclusters, and at least another layer of non-oxidizing material, such that the total coating thickness is up to 1500 nm.

Abstract: A multifunction module for an electron beam column comprises upper and lower electrodes, and a central ring electrode. The upper and lower electrodes have multipoles and are capable of deflecting, or correcting an aberration of, an electron beam passing through the electrodes. A voltage can be applied to the central ring electrode independently of the voltages applied to the upper and lower electrodes to focus the electron beam on a substrate.

Abstract: A photomultiplier tube 1 is an electron tube comprising an envelope 5 including a frame 3b having at least one end part formed with an opening and an upper substrate 2 airtightly joined to the opening, and a photocathode 6 contained within the envelope 5, the photocathode 6 emitting a photoelectron into the envelope 5 in response to light incident thereon from the outside; wherein multilayer metal films 10b, 10a each constituted by a metal film made of titanium, a metal film made of platinum, and a metal film made of gold laminated in this order are formed at the opening and the joint part between the upper substrate 2 and opening; and wherein the frame 3b and upper side substrate 2 are joined to each other by holding a joint layer 14 containing indium between the respective multilayer metal films 10b, 10a.

Abstract: An ion detector includes collision surfaces for converting both positively and negatively charged ions into emitted secondary electrons. Secondary electrons may be detected using an electron detector, than may, for example include an electron multiplier. Conveniently, secondary electrons (or electrons emitted by the multiplier) may be detected using an electron pulse counter.

Abstract: An envelope has a glass bulb body and a cylindrical glass bulb base. The glass bulb body includes an upper hemisphere and a lower hemisphere. The upper hemisphere is curved in a substantially spherical shape. The lower hemisphere is substantially curved in a spherical shape and connects the upper hemisphere and glass bulb base. A photocathode is formed on the inner surface of the glass bulb body. An avalanche photodiode is disposed on the glass bulb body side relative to an intersection between an imaginary extended curved surface of the lower hemisphere within the glass bulb base and an axis. When light enters the photocathode, electrons are emitted from the photocathode. The electrons are converged at the position above and in the vicinity of the APD by an electrical field in the electron tube, so that the electrons enter the APD in an efficient manner and are detected satisfactorily.

Abstract: A large area hybrid photomultiplier tube that includes a photocathode for emitting photoelectrons in correspondence with incident light, a semiconductor device having an electron incident surface for receiving photoelectrons from the photocathode, and a cone shaped container. The container has a first opening and a second opening. The photocathode is disposed at the first opening, and the semiconductor device is disposed at the second opening.

Abstract: The invention relates to a discharge lamp having and envelope and at least one pair of inner leads and at least one pair of outer leads corresponding thereto, at least one end of each lead disposed in the interior of the lamp, with a substantially planar foil between any one pair of inner and outer leads, and a connector provided between any one lead and the foil, the connector having at least one planar contact surface for connecting the lead to the foil and increasing the contact surface area and providing means for dissipating excess heat and energy that enters the lamp.

Abstract: A photocathode is capable of generating an electron beam from incident light. The photocathode comprises a light permeable support having a light receiving surface and an opposing surface. A Group III nitride layer is provided on the opposing surface of the support. The Group III nitride layer comprises at least one Group III element and nitrogen. An alkali halide layer is provided on the Group III nitride layer. The alkali halide can be a cesium halide, such as cesium bromide or iodide.

Abstract: An electron beam column comprises a thermal field emission electron source to generate an electron beam, an electron beam blanker, a beam shaping module, and electron beam optics comprising a plurality of electron beam lenses. In one version, the optical parameters of the electron beam blanker, beam shaping module, and electron beam optics are set to achieve an acceptance semi-angle ? of from about ¼ to about 3 mrads, where the acceptance semi-angle ? is half the angle subtended by the electron beam at the writing plane. The beam-shaping module can also operate as a single lens using upper and lower projection lenses. A multifunction module for an electron beam column is also described.

Abstract: An image display device is provided in which the overall brightness of an image can be varied without adversely affecting hue and contrast. The image display device includes emitters 16 connected to a cathode electrode 15, a gate electrode 13, an anode electrode 3, transistors Tr1 and Tr2, and a capacitor 12. A voltage applied to the capacitor 12 is varied to display an image. A constant voltage is applied to the gate electrode 13 to change a time ratio Du. Thus, the overall brightness of an image can be adjusted.

Abstract: In an electron tube, one end of an insulating tube is protruded toward the inside of an envelope, and an avalanche photodiode (APD) is provided on the one end of the insulating tube. Another end of the insulating tube is connected to an outer stem of the envelope. Alkali sources are provided inside the envelope. The alkali sources are disposed inside the envelope and generates alkali metal vapor to thereby form a photocathode on a predetermined part of the internal surface of the envelope. The alkali sources and insulating tube are isolated from each other by a separating member. When the electron tube is manufactured, the alkali metal vapor that is generated from the alkali sources is not deposited on the insulating tube due to existence of the separating member. This prevents voltage resistance between the envelope and APD from being decreased and the electrical field in the electron tube from being adversely affected, thereby preventing incident efficiency of electrons to the APD from being decreased.

Abstract: An electron beam lithography system has an electron gun including at least one laser that is operable in a first mode to generate electrons for lithography. The electron beam lithography system is operable in a second mode to regenerate the photocathode of the electron gun by application of the laser. The photocathode includes a layer of cesium telluride.

Abstract: A faceplate (F) for an image intensifier tube (10) for reducing veiling glare begins as a blank (36) of optical material of a desired glass composition having a shape that conforms substantially to a configuration of the faceplate (F) to be produced. An extraneous removable aperture step portion (54) is formed on the glass blank (36). The glass blank is blackened (41) and the aperture step portion (54) is removed creating a desired transmissive aperture (34) through the glass blank (36).

Abstract: A photomultiplier tube excellent in vibration resistance and having an anode with good pulse linearity characteristic. The photomultiplier tube has a mesh anode (A) composed of an anode frame (A11) and a mesh electrode (A12) supported and surrounded by the anode frame (A11). The central portion of one long side (A11B) of the anode frame (A11) serves as an electron converging part (F). The inner side of the anode frame (A11) swells toward the inner part of the anode (A), more from the middle of the long side (A11B) toward the corners of the anode frame (A11) along the long side (A11B), and therefore the thickness of the anode frame (A11) increases from the middle of the long side (A11) to the corners along the long side (A11B).

Abstract: An electron beam source has a photocathode with a photoemitter material having a work function, and with a beam receiving portion and an electron emitting portion. A first light source directs a first light beam onto the beam receiving portion of the photocathode to generate an electron beam from the electron emitting portion. The first light beam has a wavelength ?1 such that hc/?1 is at least about the work function of the photoemitter material, where ‘h’ is Planck's constant and ‘c’ is the speed of light. A second light source directs a second light beam onto the beam receiving portion of the photocathode, such as onto the beam receiving portion, to stabilize the electron beam. The second light beam having a wavelength ?2 such that hc/?2 is less than about the work function of the photoemitter material.

Abstract: A diamond transmission dynode and photocathode are described which include a thin layer of a crystalline semiconductive material. The semiconductive material is preferably textured with a (100) orientation. Metallic electrodes are formed on the input and output surfaces of the semiconductive material so that a bias potential can be applied to enhance electron transport through the semiconductive material. An imaging device and a photomultiplier utilizing the aforesaid transmission dynode and/or photocathode are also described.

Abstract: This invention discloses a thin-film-coated photocathode, including a photocathode formed of first material consisting of potassium cesiuin antimonide and a thin-film coating of a second material consisting of cesium bromide (CsBr).

Abstract: A housing for microelectronic devices requiring an internal vacuum for operation, e.g., an image detector, is formed by tape casting and incorporates leads between interior and exterior of said housing where said leads are disposed on a facing surface of green tape layers. Adjacent green tape layers having corresponding apertures therein are stacked on a first closure member to form a resulting cavity and increased electrical isolation or channel sub-structures are achievable by forming adjacent layers with aperture dimension which vary non-monotonically. After assembly of the device within the cavity, a second closure member is sealed against an open face of the package in a vacuum environment to produce a vacuum sealed device.

Abstract: In a radiographic image intensifier having an input window, and a method for its production, an intermediate layer is deposited on a substrate for a luminous layer, thereby smoothing the surface of the substrate. This intermediate layer serves to smooth the surface of the substrate and is thus a good base for a uniform growth of the crystal structure of the luminous layer.

Abstract: This invention relates to an electron tube having a structure for enabling a stable operation for a long time. In the electron tube, at least a confining mechanism is arranged between a photocathode and the electron incident surface of a semiconductor device, which are arranged to oppose each other. In the arrangement, the area of the opening of the confining mechanism is at least equal to or smaller than that of the electron incident surface, thereby confining the orbits of photoelectrons from the photocathode. This structure avoids bombardment of electrons arriving at portions other than the electron incident surface of the semiconductor device and prevents the semiconductor device from being unnecessarily charged.

Abstract: The present invention assures a satisfactory adhesiveness of an input screen 13 of an X-ray image intensifier, high resolution of an output image and brightness uniformity as required, by configuring an aluminum or aluminum alloy substrate 21 so to have a concave surface with minute irregularities of the substrate material removed by burnishing, excepting gentle irregularities 21c without directivity which are caused by pressing. The gentle irregularities 21c of the substrate 21 preferably have an average length L in a range of 50 &mgr;m to 300 &mgr;m between the neighboring bottoms and an average height H in a range of 0.3 &mgr;m to 4.0 &mgr;m from peaks to bottoms. The invention improves resolution with light on the substrate surface suppressed from being scattered, and decreases image noises which are caused by the minute irregularities.

Abstract: A photocathode device for use in an image intensifier of a night vision device, the device having a faceplate fabricated from an optically transparent material and a photoemissive semiconductor wafer bonded to the faceplate. The photoemissive wafer includes a first contact disposed on a peripheral surface thereof for electrically contacting the wafer and an annular-shaped second contact disposed on the emission surface of the wafer for enabing a potential difference to be applied across the wafer to facilitate the emission of photogenerated carriers from the emission surface.

Abstract: In the electron multiplier assembly 27, a dynode unit 10 is constructed from a plurality of dynodes 9 laminated one on another. Each dynode 9 is formed with multichannels 12 which are separated from one another by channel-separating portions 14. A focusing electrode plate 16 is formed with multichannels 18 which are separated from one another by channel-separating electrodes 20 which are located in correspondence with the channel-separating portions 14 of the first stage dynode 9a. A plurality of anodes 7 are provided for receiving electrons multiplied at the dynode unit 10 in their corresponding channels 18. Each channel-separating electrode 20 is formed with an opening 21, at a position confronting the channel-separating portion 14 of the first stage dynode 9a, for transmitting electrons therethrough.

Abstract: An electron source includes a negative electron affinity photocathode on a light-transmissive substrate and a light beam generator for directing a light beam through the substrate at the photocathode for exciting electrons into the conduction band. The photocathode has at least one active area for emission of electrons with dimensions of less than about two micrometers. The electron source further includes electron optics for forming the electrons into an electron beam and a vacuum enclosure for maintaining the photocathode at high vacuum. The photocathode is patterned to define emission areas. A patterned mask may be located on the emission surface of the active layer, may be buried within the active layer or may be located between the active layer and the substrate.

Abstract: An electron beam source includes a cathode having an electron emission surface including an active area for emission of electrons and a cathode shield assembly including a conductive shield disposed in proximity to the electron emission surface of the cathode. The shield has an opening aligned with the active area. The electron beam source further includes a device for stimulating emission of electrons from the active area of the cathode, electron optics for forming the electrons into an electron beam and a vacuum enclosure for maintaining the cathode at high vacuum. The cathode may be a negative electron affinity photocathode formed on a light-transmissive substrate. The shield protects non-emitting areas of the emission surface from contamination and inhibits cathode materials from contaminating components of the electron beam source. The cathode may be moved relative to the opening in the shield so as to align an new active area with the opening.

Abstract: In the photomultiplier tube 1, the focusing electrode plate 17 has the focusing portion 20 for focusing incident electrons and the frame 21 surrounding the focusing portion 20. The focusing portion 20 has a plurality of slit openings 18. The dynode unit 10 is constructed from a plurality of dynode plates 11 laminated one on another. Each dynode plate 11 has a plurality of electron through-holes 13 located in confrontation with the plurality of slit openings 18. A plurality of anodes 9 are provided for receiving electrons emitted from the respective through-holes 13 of the dynode unit 10. The frame 21 has dummy openings 22 at positions located in confrontation with edges 15 of the first stage dynode plate 11a in the dynode unit 10.

Abstract: This invention relates to an electron tube having a structure for enabling a stable operation for a long time. In the electron tube, at least a confining mechanism is arranged between a photocathode and the electron incident surface of a semiconductor device, which are arranged to oppose each other through a container. Particularly, the area of the opening of the confining mechanism is smaller than that of the electron incident surface, thereby confining the orbits of photoelectrons from the photocathode. This structure avoids bombardment of electrons arriving at portions other than the electron incident surface of the semiconductor device and prevents the semiconductor device from being unnecessarily charged.

Abstract: To eliminate a distortion of an output image detected by a semiconductor device serving as an anode in an electron tube, a faceplate is configured to a planar shape and a window provided on the semiconductor device has a pincushion outer profile in which points on the outer profile of the window that correspond to points on the outer profile of the faceplate are outwardly positioned farther than the corresponding points in the outer profile of the faceplate that are apart from the center of the faceplate. Further, the window is divided into a plurality of segments to define picture elements.

Abstract: In an X-ray image intensifier, an incident window on which X-rays are incident is fixed to a support frame fixed to a glass vessel. The incident window has a dome portion and a flat portion around the dome portion, and is fixed to the support frame through an annular brazing sheet. The brazing sheet has brazing material layers. The brazing material layers are melted, thereby welding the brazing sheet, the incident window, and the support frame with each other. A groove is formed in the brazing sheet to form a brazing material puddle, so the brazing material will not reach the input screen of the incident window during melting. In an alternate embodiment, an anti-wetting layer is disposed on the incident window to prevent brazing material from wetting the input screen. In a further embodiment, the thickness of the X-ray incident window has a thickness that increases gradually from the center toward a peripheral portion thereof.

Abstract: An electron source includes a negative electron affinity photocathode on a light-transmissive substrate and a light beam generator for directing a light beam through the substrate at the photocathode for exciting electrons into the conduction band. The photocathode has at least one active area for emission of electrons with dimensions of less than about two micrometers. The electron source further includes electron optics for forming the electrons into an electron beam and a vacuum enclosure for maintaining the photocathode at high vacuum. In one embodiment, the active emission area of the photocathode is defined by the light beam that is incident on the photocathode. In another embodiment, the active emission area of the photocathode is predefined by surface modification of the photocathode. The source provides very high brightness from an ultra-small active emission area of the photocathode.

Abstract: A transparent photocathode comprises a silver layer formed on a transparent substrate, comprising silver particles having an average diameter of 80 to 200 nm, and a silver oxide layer, potassium layer, and a cesium layer. As a result of the silver layer comprising silver particles having dispersive diameters, the transparent photocathode can selectively achieve high sensitivity to an infrared region of near 1.5 .mu.m wavelength.

Abstract: In order to increase the sensitivity of an image intensifier tube, the efficiency with which an electron image is formed from radiation of a first wavelength is increased. Radiation of the first wavelength is converted into radiation of a second wavelength by means of a conversion screen provided with a scintillation layer, and radiation of the second wavelength releases electrons from a photocathode which is sensitive to the second wavelength. Loss of radiation of a second wavelength, incurred because a part of this radiation does not reach the photocathode, is reduced. Radiation of the second wavelength which is not emitted in the direction of the photocathode is recaptured by providing the conversion screen with a metallic reflecting intermediate layer.

Abstract: A photomultiplier includes a cascade of microchannel plates which are physically and electrically connected to provide an electron multiplication through the microchannel cascade. One of the microchannel plates is a high-output microchannel plate providing a high level of electron multiplication. This high output microchannel plate is thermally conducted to ambient by a heat transfer path including outwardly disposed microchannel plates in the cascade. A unitary ceramic housing defines a vacuum envelope for the photomultiplier.

Abstract: There is provided a photomultiplier in which a transmittance of an incident light and a photosensitivity is high and a hysteresis characteristic is excellent. Therefore, in the present invention, a photocathode 16, dynodes 17a to 17c and an anode 18 are supported between insulating material substrates 12a and 12b provided in a glass bulb 11. A transparent conductive film 19 is formed on an inside wall surface of a light entrance portion 15. The transparent conductive film 19 electrically contacts with a pad 20 which is led through a terminal 14 to the outside. The same potential as the photocathode 12 is applied through the pad 20 to the transparent conductive film 19. The incident light directly impinges on the photocathode 16 through the glass bulb 11 and the transparent conductive film 19 at a place corresponding to the light entrance portion 15. As a result, the incident light reaches the photocathode 12 with not being interfered at all, and the transmittance of the incident light is improved.

Abstract: A photomultiplier has a focusing electrode plate for supporting focusing electrodes, provided between a photocathode and a dynode unit. Since the focusing electrode plate has holding springs which are integrally formed with the focusing electrode plate, resistance-welding becomes unnecessary to prevent field discharge. A concave portion is formed in a main surface of the focusing electrode plate to arrange an insulating member sandwiched between the focusing electrode plate and the photoelectron incidence side of the dynode unit and partially in contact with the concave portion. With this structure, discharge between the focusing electrode plate and the dynode unit can be prevented.

Abstract: An X-ray image intensifier has an input phosphor screen with a substrate in which a large number of small holes are formed, and a fluorescent material filled in the small holes. A ratio of a maximum inner diameter to a depth of each small hole is set to be 0.5 or less. Alternatively, the input phosphor screen of the X-ray image intensifier of the invention includes a substrate in which a large number of small holes are formed, a low-refractive-index material layer formed on the inner wall of each small hole, and a fluorescent material having a refractive index higher than the low-refractive-index material layer filling each small hole.

Abstract: A streak tube comprising a photocathode for converting an optical image into a photoelectron beam, accelerating means for accelerating the photoelectron beam, deflecting means for deflecting the accelerated photoelectron means, focusing means for focusing the deflected photoelectron beam and a phosphor screen for receiving the focused photoelectron beam and forming a streak image corresponding to the optical image. The photoelectron beam emitted from the photocathode is deflected immediately after accelerated by the accelerating means, and subsequently is focused on the phosphor screen, to thereby eliminate the spread of the photoelectron beam on the phosphor screen upon sweeping of the photoelectron beam.

Abstract: A method of manufacturing a photomultiplier tube (10) comprising a tube body (20), a photocathode (30) and an electron multiplier element (40) destined to be placed at a small distance from the photocathode (30). According to the invention the tube (10) is provided with sliding means (50) of the electron multiplier (40) parallel to the axis (22) of the tube body (20), means (50) provided with abutments (53) situated in the proximity of the said window (31).

Abstract: Photomultiplier tube 10 segmented into a plurality of elementary photomultipliers 11 comprising a photocathode 12 and a multiplier 13 of the type using sheets partitioned into a plurality of elementary multipliers 14. According to the invention the input space of the tube 10 located between the photocathode 12 and the multiplier 13 is partitioned into elementary input spaces 15 associated with the elementary photomultipliers and defining a plurality of elementary photocathodes 16, with each elementary input space 15 having a focussing electrode which causes the photo-electrons emitted by the associated elementary photocathode 16 to converge on the corresponding elementary multiplier 14.

Abstract: An imaging tube for amplifying and observing a diminished light image and a streaking tube for analyzing the light intensity distributions of light sources with elapsing of time. In order to avoid adhesion of alkali metal to the micro-channel-plate in fabrication of the imaging tube and to avoid adhesion of alkali metal to the deflection electrode in the streaking tube, a separation wall and a lid movable on the separation wall are used.

Abstract: A so-called "solar-blind" photomultiplier tube includes an envelope having a sidewall and an input faceplate formed from an ultraviolet transmitting filter. A photoemissive cathode is disposed within the envelope for providing photoelectrons in response to radiation incident thereon. The cathode has an intrinsic responsivity extending from the near-ultraviolet portion through the visible portion of the electromagnetic spectrum; however, the filter faceplate transmits only the ultraviolet portion of the spectrum to the photoemissive cathode. The combination of the filter faceplate and the photoemissive cathode therefore limits the tube to a responsivity within the wavelength range of about 300 to less than 400 nanometers.

Abstract: A faceplate assembly includes a faceplate flange, a faceplate member and a sealing material, such as a glass frit, for sealing the faceplate member to the faceplate flange. Three gauging members, integral with the flange, are in contact with the faceplate member to ensure that the faceplate member is sealed parallel to the faceplate flange and at a predetermined distance therefrom.

Abstract: A multi-layered photoconductive material which comprises first layers containing at least one VIb chalcogen element chosen from S, Se and Te and second layers containing at least one IIb element chosen from Zn, Cd and Hg and acting as electric potential barriers, said first layers and said second layers being alternatively arranged and the total number of said first layers and said second layers being not less than 5 and has a high response speed and an excellent sensitivity to long wavelength light with a great dark resistance.

Abstract: An improved electron discharge device comprises an evacuated envelope having at least one alumina ceramic insulator member. Within the device is a source of electrons, and an electron multiplier assembly including an anode. A high resistance material is diffused into the ceramic insulator to reduce luminescence within the insulator. The method of diffusion includes the steps of applying an opaque coating of a high resistance material to a surface of the ceramic insulator member and then firing the member in a reducing atmosphere at a temperature within the range of about 1500.degree. C. to 1550.degree. C. until the high resistance material diffuses into the surface of the member forming a diffusion region.

Abstract: The photocathode is of the type which comprises a photo-emissive layer consisting of at least an active layer of the P-type, a solid support for said semiconductor of a material which is transparent to radiation, a layer having a bonding glass for the photo-emissive layer on the support. The invention is characterized in that the support comprises two parts situated one on top of the other and which are bonded together, namely a thick second part (thickness for example 5 mm) of a type of glass having properties of thermal expansion which are substantially identical to those of the bonding glass and a part in the form of a disk-shaped first part (thickness for example 1 mm) of a material having softening and transition points which are much higher than those of the bonding glass and of the glass of the thick part.

Abstract: An electron tube having an evacuated envelope includes therein an insulating substrate with a photoemissive cathode thereon. The cathode comprises a plurality of discrete substantially isolated photoemissive regions. A plurality of spaced apart conductive strips are disposed on the substrate and interconnect each of the photoemissive regions.