Showing papers in "Advances in electronics and electron physics in 1972"
TL;DR: In this paper, the detection and timing of a single photoelectron released by light from a photosensitive surface of a photomultiplier, channel multiplier, avalanche multiplier photodiode, or other photodevice are discussed.
Abstract: Single photon detection and timing means essentially the detection and timing of a single photoelectron released by light from a photosensitive surface of a photomultiplier, channel multiplier, avalanche multiplier photodiode, or other photodevice. Necessary photodevice gain and detection circuits, mechanisms and statistics of photodevice gain, photodevice and background noise and their reduction, and practical photodevice techniques and photon detection performance tests are discussed. Fast timing with single photons, and single photon detection with moderate timing requirements are considered.
37 citations
TL;DR: In this article, the authors presented the classification of electron-optical device modulation transfer functions (MTFs) and compared the MTF responses of similar devices with different manufacturers.
Abstract: Publisher Summary This chapter presents the classification of electron-optical device modulation transfer functions (MTFs). MTFs of most electron-optical devices satisfy the general equation. Examples of the MTFs of a wide variety of devices produced by many manufacturers are given, and the responses of similar devices are compared. MTF data obtained from image intensifiers employing microchannel plates with channels packed in a close spaced hexagonal array, in which the principal factor of the device limiting the overall MTF is the microchannel plate itself, suggests that the frequency constant is given by the ratio (270/ d ), where d is the center-to-center spacing of adjacent channels in microns. The discrepancy between the predicted and measured MTFs is smaller than the discrepancy that would result by assuming Gaussian MTFs, and it probably results from MTF deterioration at the element interfaces. The chapter suggests that the overall point-spread functions of most electron-optical devices is broader than what would be predicted by assuming a Gaussian form.
21 citations
TL;DR: In this paper, an image photon counting system for optical astronomy is presented, where the photoelectron events exhibited by a high-gain cascade image intensifier are detected by means of a continuously scanning television camera, acting both as a sensor and buffer store, which is put on-line to a small computer.
Abstract: Publisher Summary This chapter presents an image photon counting system for optical astronomy. The information contained in an optical image can be expressed as the spatial and temporal variation in the number of photons. The problem of detecting and recording such an image is then essentially of counting the number of photons in each image element. The photoelectron events exhibited by a high-gain cascade image intensifier are detected by means of a continuously scanning television camera, acting both as a sensor and buffer store, which is put on-line to a small computer. The framing period of the television camera is set to ensure that the probability of superimposing two or more events in consecutive frames is small. The camera operates with a digital frame scan and an analog line scan. Clock pulses cause a 10-bit counter to accumulate during the scan of each frame. One counter drives a digital-to-analog converter, which in turn provides the reference signal for the frame-scan coil driver. It is observed that the observed modulation is of the level expected for the combination of the photographic resolution pattern and the input lens for the intensifier and does not represent the limitation of the detecting system itself.
16 citations
TL;DR: In this paper, the photoemitter-membrane, light-modulator image transducer is described and integrated exposure, image storage, adjustable sensitometry during the storage period, and compatibility with coherent optical read-out systems.
Abstract: Publisher Summary This chapter provides an overview of the photoemitter-membrane, light-modulator image transducer. The term transducer is used to convey the concept of input-image transformation from a two-dimensional irradiance distribution into a two-dimensional optical-phase modulation. This is accomplished by deflection of a membrane mirror with electrostatic forces, the deflection being in some way proportional to the local irradiance. When the read-out phosphor of a conventional multiplier-channel-plate (m.c.p.)-image intensifier is replaced by an array of flexible dielectric elements (that is a membrane array), a new class of image transducer is realized. This transducer is characterized by (l) integrated exposure; (2) image storage; (3) adjustable sensitometry during the storage period; and (4) compatibility with coherent optical–read-out systems. Compatibility with coherent optical systems is the motivation for and the significance of this image transducer because it makes possible the application of coherent optical–information-processing techniques to the output image. In this chapter, the design and operation of an image transducer suitable for coherent optical-image processing is described.
14 citations
TL;DR: In this article, a camera system based on the extraction-electrode image tube has been employed to measure the durations and background energy content of mode-locked dye laser pulse train.
Abstract: Publisher Summary This chapter elaborates the various aspects of the picosecond chronography with image tubes. The interaction of light with matter on a picosecond time scale can be investigated by means of ultrashort pulses from mode-locked neodymium and ruby solid-state, and organic dye-liquid lasers. A camera system based on the extraction-electrode image tube has been employed to measure the durations and background energy content of mode-locked dye laser pulse train. The train of picosecond pulses from the mode-locked rhodamine 6G dye laser, tuned to operate at 605 nm with an intracavity Fabry–Perot interferometer filter, was employed with beam splitters for recording the two-photon fluorescence profile in a triangular configuration using a saturated solution of dimethyl POPOP in benzene, anti for triggering a fast co-axial photodiode. This result, which is in agreement with the achievement of a spatial resolution of 8 lp/ mm with the four-stage intensifier image-tube, when gated under picosecond illumination, indicates that there is an intensity dependent transit-time spread, probably arising from space charge near the photocathode.
12 citations
TL;DR: In this article, the counting image tube photoelectrons with semiconductor diodes was investigated and it was found that 80% of the incident photo-electrons should be counted with negligible electronics background noise.
Abstract: Publisher Summary This chapter elaborates the counting image tube photoelectrons with semiconductor diodes. The most effective means of detection of the information contained in a very weak photon image is by digital counting techniques. The microcircuit technology has made it possible to construct arrays of small p–n diodes and electronics on a single chip of silicon. The combination of the advances allows the construction of an image tube capable of simultaneous detection of photoelectrons at many different locations. Multidiode element structures are formed by integrated circuit techniques from a single chip of silicon. It is found that by placing the discriminator level at approximately 10 keV, 80% of the incident photoelectrons should be counted with negligible electronics background noise. To prove the practicability of the diode image tube and at the same time construct a useful instrument for low light-level astronomy, a 38-diode element system was made and tested. The dark current is mainly thermionic, resulting in 0.01 count/sec per diode element and the detective quantum efficiency is 4.1% at 400 nm.
11 citations
TL;DR: In this article, various properties of Al 2 O 3 -Al-CsI film for the transmission-type secondary-emission dynode were studied experimentally, and a compromise between the measured electron transmission and the mechanical strength requirement for the Al2O3 substrate film resulted in a thickness of 60 nm.
Abstract: Publisher Summary This chapter discusses cesium–activated, CsI transmission-type secondary-emission dynode. In this study, various properties of Al 2 O 3 –Al–CsI film for the transmission-type secondary-emission dynode were studied experimentally. A compromise between the measured electron transmission and the mechanical strength requirement for the Al2O3 substrate film resulted in a thickness of 60 nm. The electron-transmission experiment also showed that a 20-nm-thick Al-conducting layer did not reduce the transmission of the electrons through the film. Thickness of the CsI layer was found to be optimum when it was equal to or slightly larger than the range of the electrons in the layer. This gave a value of 40 to 60 nm for practical primary beam voltages. The result is a layer structure of A1 2 O 3 , 60 nm; Al, 20 nm; and CsI, 40 to 60 nm for the TSE dynode application. A comparison of KCl–TSE dynode with the conventional KC1–TSE dynode in terms of the secondary-electron yield and the ratio of secondary to transmitted primary electrons showed that the former was definitely superior. It was also found that the degree of degeneration when exposed to humid air was considerably smaller for CsI than for KCl.
9 citations
TL;DR: In this paper, an infrared pick-up tube with electronic scanning and uncooled target is described, and the tube is comprised of a glass envelope with a germanium window, indium sealed, having a transparency of 45% for wavelengths between 2 and 14 μm; a TGS target, with a back electrode formed by a semitransparent deposit of gold on the side facing the window; a mesh electrode and a vidicon gun; and outside the envelope, conventional focusing and deflecting coils.
Abstract: Publisher Summary This chapter provides an overview of an infrared pick-up tube with electronic scanning and uncooled target. The tube is comprised of the following: a glass envelope with a germanium window, indium sealed, having a transparency of 45% for wavelengths between 2 and 14 μm; a TGS target, with a back electrode formed by a semitransparent deposit of gold on the side facing the window; a mesh electrode and a vidicon gun; and outside the envelope, conventional focusing and deflecting coils. The cathode potential stabilization (CPS) mode is chosen for read out to avoid electron redistribution. In this mode, electrons land on the target and read out is destructive. The electron beam scans the target continuously with a standard television raster of 25 frames/s and 625 lines per frame. When a small area of the target is suddenly heated by the thermal flux, the spontaneous polarization decreases, and the corresponding bound positive charges are freed and neutralized by slow electrons giving a video signal across the signal-electrode load resistor. Both the thermal and electrical properties of the device have been theoretically computed and the results are in rather good agreement with experiment.
9 citations
TL;DR: In this paper, the authors investigated the uniform-layer heterojunction targets for television camera tubes, which were formed by evaporation of amorphous Sb 2 S 3 on to an n-type silicon wafer.
Abstract: Publisher Summary This chapter investigates the uniform-layer heterojunction targets for television camera tubes. In this experimental study, holes generated by optical absorption in a thin n-type silicon wafer diffuse to a surface on which a 1-μm-thick layer of antimony trisulfide has been deposited by evaporation. This layer is scanned by a low-energy electron beam, as it is in a vidicon, and biased by connecting the silicon wafer through a load resistor to a source a few volts to tens of volts more positive than the electron-gun cathode. A typical spectral-response curve for a target structure is shown. The experimental data shows that heterojunction structures formed by evaporation of amorphous Sb 2 S 3 on to an n-type silicon wafer can function as a camera tube target, having low dark current, a nearly linear transfer characteristic, and the spectral response of silicon. On the negative side, the best collection efficiency measured so far is only 1 to 2% as compared to the 60 to 70% measured for a diode target, and considerable variability in characteristics between targets underlines the need for a far better understanding of the physics of the interface.
8 citations
TL;DR: In this article, an overview of the electronic camera used in a reflection mode is presented, which has the advantage of extending the spectral range in the ultraviolet and infrared parts of the spectrum when compared with classical transmission-mode image tubes.
Abstract: Publisher Summary This chapter provides an overview of the electronic camera used in a reflection mode. This mode of operation has the advantage of extending the spectral range in the ultraviolet and infrared parts of the spectrum when compared with classical transmission-mode image tubes. In the design of a “reflection-mode camera,” it is essential to prevent the screening of the photon flux by the electron receptor. As electrons are confined by magnetic lines of force, one possibility is to incline the accelerating electric field at an angle to the focusing magnetic field in an electromagnetically focused image tube. A model has been built to test the image quality of a reflection-mode camera. This model is operated in the transmission mode knowing that image quality is independent of the mode used. The results obtained with this model are very promising. Several plates have been taken showing a resolution of 40 lp/mm over almost the entire field and a maximum resolution of 90 lp/mm. It seems that the best resolution can be obtained in a direction perpendicular to the plane defined by the electric and magnetic fields.
8 citations
TL;DR: In this paper, the authors describe thermal imaging with pyroelectric television tubes, where the incident thermal radiation is modulated by a chopper and gives rise to a variation of the target temperature, which is sensed by the scanning electron beam, which provides the video-signal current.
Abstract: Publisher Summary This chapter describes thermal imaging with pyroelectric television tubes. In operation of the pyroelectric vidicon tube, the incident thermal radiation is modulated by a chopper and gives rise to a variation of the target temperature, which is transformed by the pyroelectric effect into an electric-charge signal. This is sensed by the scanning electron beam, which thus provides the video-signal current. Unlike the photonsensitive and other bolometric detectors of infrared radiation, which give signals proportional to the scene temperature, the pyroelectric target produces a charge signal that is proportional to its change of temperature between scans, and this is proportional to the small-scene temperature increments (∆T) at ambient temperature. The signal-to-noise ratio is enhanced or correspondingly, the noise-equivalent temperature is reduced, by the use of te low bandwidth. The fall off in performance with the increasing spatial frequency is described by the overall modulation-transfer function. This chapter relates detailed calculations on the possible modes of operation to the choice of pyroelectric material. The performance recently achieved in such tubes is also reported.
TL;DR: In this article, the authors analyzed the direct current operation of channel electron multipliers and deduced the multiplication processes and resulting gains by calculating only the electron trajectories within the channel space and ignoring end effects, and verified that the increasing magnitude of the electron current along the channel can be represented by exp (Gξ), where G is gain factor and ξ is normalized length.
Abstract: Publisher Summary This chapter analyzes the direct current operation of channel electron multipliers. In most cases, electron; multiplication processes and resulting gains are deduced by calculating only the electron trajectories within the channel space and ignoring end effects, In this chapter, end effects are taken into account and the multiplication process inside the channel is analyzed. It is verified that in general, the increasing magnitude of the electron current along the channel can be represented by exp (Gξ), where G is gain factor and ξ is normalized length. The gain factor G is related to the electric field, properties of secondary electron emission of the channel wall, and channel configuration. Assuming that the direction of secondary electron emission is normal to the channel wall, G is calculated by computer for a straight channel with an inclined electric field, and also for a curved channel. Calculation of the gain factor has been carried out for the cases of a channel with an inclined applied field and for a curved channel. In the former case, the gain can be larger than for the parallel field case, depending on the angle of the applied field, and gain saturation disappears at an angle of around 62°. In the extremely curved channel, the gain is high and gain saturation tends to disappear.
TL;DR: In this paper, the authors examined the current saturation mechanism in junction field effect transistors (JFETs) and showed that space-charge-limited current is physically realizable in very short JFET structures that produce triode-like characteristics.
Abstract: Publisher Summary This chapter examines the current saturation mechanisms in junction field-effect transistors (JFET). A JFET is an active semiconductor triode in which the current is primarily carried by the majority carriers. An n -channel JFET consists of a lightly doped n -type channel sandwiched between two heavily doped p -type gate layers. The drain current flows parallel to the metallurgical gate junctions that are reversely biased. The reverse bias across the p-n junctions depletes free carriers from the channel and produces space-charge regions extending into the channel. Under the current saturation condition, the electric field along the channel near the drain is comparable to the field normal to the channel. This two-dimensional field distribution violates the gradual channel approximation that assumes negligible electric field along the direction of the channel. The finite channel model provides a path for current flow after saturation that avoids the difficulty in the depleted channel model. The chapter also states that space-charge-limited current is physically realizable in very short JFET structures that produce triode-like characteristics.
TL;DR: In this article, the magnetically focused electronographic cameras utilize a front-surface, alkali-halide photocathode mounted at the focus of an optical system which is partially contained within the imaging device.
Abstract: Publisher Summary This chapter presents the developments of magnetically focused, internal-optic image converters. The magnetically focused electronographic cameras utilize a front-surface, alkali-halide photocathode mounted at the focus of an optical system which is partially contained within the imaging device. The high quantum yields, which can be obtained in the far-ultraviolet, with front-surface alkali-halide photo- cathodes are described in the chapter. It is found that when used with all-reflecting optics, the front-surface photocathodes allow operation at much shorter wavelengths than is possible with semitransparent photocathodes. The front-surface photocathodes are considerably easier to prepare than the semitransparent types, as thickness of the photocathode is not critical. For work in the infrared, cooling of the photocathode is facilitated by the fact that a solid metal substrate can be used, and by the central location of the photocathode in vacuum. In the case of the negative affinity photocathode materials, it is possible that the substrate could be made from a ground and polished single crystal of the parent semiconductor material, which is then cesiated in vacuum.
TL;DR: In this article, the use of channel plate intensifiers in the field-ion microscope is described. But although the brightness gain is sufficient, an acceptable signal-to-noise ratio is only preserved in the case of a helium-ion image.
Abstract: Publisher Summary This chapter describes the use of channel-plate intensifiers in the field-ion microscope. The specimen is in the form of a very sharp point, having a radius of the order of 100 nm, to which a high positive voltage is applied. The electric field is sufficiently high to cause ionization of the residual inert gas at the specimen, and the image is formed by the impingement of the resulting positive ions on a phosphor screen. Details of the specimen are revealed by a spatial modulation of the ion current density. A single image point is produced typically by an ion flux of some 10 14 particles/s. The number of ions per second per image point is independent of the image gas, and if it were possible to record each of these ions directly, an acceptable signal-to-noise ratio could be obtained within a few milliseconds. Coupling a high-gain image intensifier to the microscope is not the best way of achieving this. It is found that although the brightness gain is sufficient, an acceptable signal-to-noise ratio is only preserved in the case of a helium-ion image. It is found that images using any gas may be recorded in times that are limited only by the noise in the primary ion signal.
TL;DR: In this paper, the authors discuss electronographic image tube development at the Royal Greenwich Observatory and the solution that was adopted in this research was to incorporate a mica window but to protect it from atmospheric pressure by a vacuum lock.
Abstract: Publisher Summary This chapter discusses electronographic image tube development at the Royal Greenwich Observatory. The Image Tube Department at the Royal Greenwich Observatory was set up for the development of electronographic image tubes, both for stellar field photometry and for the recording of spectra. Of the existing tubes, those because of Lallemand and Kron have reasonably large image areas, but they are not easy to operate because the electronographic plate is introduced into the same vacuum environment as the photocathode. An observatory using these tubes should have a high-vacuum laboratory for the preparation of the tubes (including photocathode processing). The Spectracon, on the other hand, is simple to operate because of its mica window, which enables the electronographic film to be exposed externally to the tube. The image size is limited to about 30 × 15 mm 2 because the mica window, which is only 4 μm thick, has to withstand atmospheric pressure. The solution that was adopted in this research was to incorporate a mica window but to protect it from atmospheric pressure by a vacuum lock. This overcomes the limitation on window size set by strength considerations and minimizes the possibility of mica breakage.
TL;DR: In this article, a combination of deflection and focusing in the same space with the same electrodes is discussed, and the work described in this chapter also demonstrates that electrostatic focusing and deflection with superposed deflections and focusing fields is possible.
Abstract: Publisher Summary This chapter explains concepts related to combined electrostatic focusing and deflection. The idea of combined electrostatic focusing and deflection is, in principle, very attractive for the construction of short TV camera tubes or of tubes in which small deflection angles are needed to give a high linearity of scanning. Instead of using two sets of deflection plates in succession, the line and field deflection is accomplished in the same space. This has been achieved with “deflectron” and using an octupole deflector. However, in both applications, which are all electrostatic, the beam is first focused before it is deflected. The next step is the combination of deflection and focusing in the same space with the same electrodes, and this problem is discussed in this chapter. Although this step looks very logical from a geometrical point of view, it is rather unattractive electron optically because most electrostatic lenses are constructed for one purpose only, the imaging of a point source (such as a crossover) on the axis. The work described in this chapter also demonstrates that electrostatic deflection and focusing with superposed deflection and focusing fields is possible.
TL;DR: In this paper, a cascade image intensifier with three photocathodes of the S-11-type (Sb-Cs[Mn-O]), which remain separate from the accelerating region of the intensifier to prevent cesium contamination of the internal surfaces, is described.
Abstract: Publisher Summary This chapter elaborates research on the Imperial College cascade image intensifier. For this intensifier, the diameter of the working field is 40 mm. The three photocathodes, which are of the S-11-type (Sb–Cs[Mn–O]), are activated simultaneously in the processing compartment, which remains separate from the accelerating region of the intensifier to prevent cesium contamination of the internal surfaces. Subsequent to seal off, the primary photocathode and the dynodes are moved to their operating positions where they are locked by means of magnetically operated catches. The phosphor screens are made of fine-grain P·11 phosphor powder, EM1-type MA 214, which is electrophoretically deposited. The accelerating electrodes are made of molybdenum and are spring mounted in slots cut in the inner wall of the Pyrex envelope. The conversion efficiency of the phosphor screens is about 12% for 13 keV electrons. The photoelectron recording efficiency is about 70%. This departure from the ideal is mainly because of the loss of photoelectrons by backscattering from the first phosphor screen. The equivalent quantum efficiency at zero spatial frequency can be estimated, using the r.m.s. deviation of the pulse heights and the recording efficiency, and is found to be ∼61% of the quantum efficiency of the primary photocathode.
TL;DR: This chapter describes a system for human cine-angiography in which the illumination of the retina of the patient is tolerable and an image intensifier is used to increase the brightness of the fundus image to a level suitable forcine-photography.
Abstract: Publisher Summary This chapter examines the various aspects of the image intensifier cine-angiography. The chapter describes a system for human cine-angiography in which the illumination of the retina of the patient is tolerable and an image intensifier is used to increase the brightness of the fundus image to a level suitable for cine-photography The intensifier is a three-stage cascade image intensifier of the type developed in the Applied Physics Department of Imperial College. The pupil of the eye of the patient is maximally dilated and the patient is asked to direct the gaze of his other eye at a fixation light. The latter is moved to bring the required retinal area in the center of the field. The light source is imaged in the center of the pupil by an aspherical lens to provide optimum and uniform illumination of the retina. The success of this technique depends partially on the correct choice of the two optical filters. Measurements of the limiting resolution of the entire system, using an artificial eye with a 100% modulated resolution pattern, indicated that about 60 lp/ mm can be resolved in the plane of the retina.
TL;DR: In this article, the physicochemical aspects of the synthesis of antimonide photocathodes are discussed, and the most usual process of synthesis occurs when a thin antimony film absorbs alkali-metal vapor.
Abstract: Publisher Summary This chapter focuses on some physicochemical aspects of the synthesis of antimonide photocathodes. For the preparation of antimonide photocathodes, four alkali metals: Na, K, Rb, and Cs are used. Lithium compounds have very low sensitivity and cannot be handled with the usual experimental techniques. Antimonides of the type A 3 Sb (A=alkali metal), in which the elements are in their normal valence state, have optimal photoemissive properties. The A 3 Sb compounds crystallize either in hexagonal or cubic form, but only the cubic compounds have a high photoelectric quantum efficiency. In the state of maximum photoelectric sensitivity, they have a slight stoichiometric excess of antimony and are p-type semiconductor. Antimonide photocathodes are synthesized by direct reaction between the elements. The affinity between alkali metals and antimony is quite strong, and therefore, the reactions are highly exothermic. The most usual process of synthesis occurs when a thin antimony film absorbs alkali-metal vapor. By monitoring a quasi-reversible synthesis, it can be learnt which intermediate products are instrumental in forming the photoemissive material. Homogeneous bialkali antimonide films cannot be obtained either by synthesis by substitution or by addition because the surface layers are richer in the last-added alkali metal.
TL;DR: In this paper, a CdSe layer was prepared by vapor deposition on to a faceplate previously coated with conducting transparent SnO 2 (NESA) film and by subsequent heat treatment.
Abstract: Publisher Summary This chapter discusses characteristics of a new camera tube with a CdSe photoconductive target. It presents results of an examination of the materials for the scanned surface layer and the characteristics of the resulting new CdSe vidicons including both 25 mm and 18 mm tubes. In this study, a CdSe layer was prepared by vapor deposition on to a faceplate previously coated with a conducting transparent SnO 2 (NESA) film and by subsequent heat treatment. Then, the surface of the CdSe layer was converted to CdSeO 3 (cadmium selenite) by moderate oxidation. Both the CdSe layer and the CdSeO 3 layer are referred to as the first layer in vapor-deposition procedure. Next, the second layer was deposited by evaporation to form the double layer. The results obtained in this study show that by using the double-layer target, it has been possible to improve the characteristics of the CdSe vidicon without degrading the high sensitivity of the CdSe photoconductive layer. The target is completely different from the conventional type, because of the n-type CdSe photoconductive underlayer and the heterojunction-type multilayer structure.
TL;DR: In this article, the pulse-height distribution of an array of channel multipliers, which was subjected to sequential, single-electron input events, was investigated and the presence of ionic feedback was found to be very prominent.
Abstract: Publisher Summary This chapter focuses on ion-feedback noise in channel multipliers. Experimental measurements were made of the pulse-height distribution of an array of channel multipliers, which was subjected to sequential, single-electron input events. The presence of ionic feedback was found to be very prominent. The output pulse-height distribution of the channel multiplier array is shown for two different electric-field conditions in the input region in front of the array. The lower curve was obtained when an electron-retarding field was established between the electrode adjacent to the array and the input surface of the array so that ions emanating from the input surface of the array impacted upon this adjacent electrode. However, the resulting low-energy secondary electrons were unable to enter the array, so that the output was small. Based on preliminary results, it is felt that ionic feedback is a major factor affecting the average gain, the noise, and the operating lifetime of channel multipliers. Imaging devices using channel plates should preferably be constructed using the concentric, spherical electron optics in the input region. Additional electrodes may improve focusing and trap or deflect the hydrogen ions emanating from the channel plate.
TL;DR: In this paper, the properties of commercial electron-sensitive plates for astronomical electronography were investigated, under an appropriate range of variables, including image size, accelerating voltage, and type of plate.
Abstract: Publisher Summary This chapter elaborates the properties of commercial electron-sensitive plates for astronomical electronography. The advantages of electronography over classical photography are well known, especially the higher quantum efficiency, almost zero threshold density, and greater information storage capacity. Although several successful electronographic cameras are in routine use, relatively little information has been available to help in the choice of design and operating parameters, such as image size, accelerating voltage, and type of plate. Accordingly, this study was undertaken to investigate the characteristic curves and detective quantum efficiency of plates useful for astronomical electronography, under an appropriate range of variables. After a preliminary investigation, this study was restricted to four types of emulsion used in astronomical work—namely, Kodak NTB 2, Ilford G5, K5, and L4, all 10 μm thick. This study forms two separate parts: (a) the determination of the characteristic curves and absolute sensitivities for which fairly consistent results have been obtained, and (b) the measurement of noise and resolution, the difficulties of which are pointed out and some significant results are given.
TL;DR: In this article, the effects of small variations from the ideal fields and derives general expressions for the displacement of a point in the image from its correct position were derived, and the way in which the displacements vary with distance from the center of an axially symmetric system was deduced and characteristics of focusing fields that will yield images having little distortion were described.
Abstract: Publisher Summary This chapter explains distortion of electron images focused by almost uniform electric and magnetic fields. Electron images free from distortion are produced if electrons are accelerated in uniform parallel electric and magnetic fields. The fields that can be produced in any practical device will depart from the ideal and will result in geometrical distortion of the image. This chapter considers the effects of small variations from the ideal fields and derives general expressions for the displacement of a point in the image from its correct position. The way in which the displacements vary with distance from the center of an axially symmetric system is deduced and characteristics of focusing fields that will yield images having little distortion are described. These analytic results are supported by computations of electron trajectories through simple nonuniform fields. The computations confirm the theory, indicate the limits of its applicability, and give some insight into the nature of focusing in such fields. Formulae are derived that relate the displacement of image points to small variations of the focusing fields from their ideal forms. Forms of field variation that are especially undesirable are shown.
TL;DR: In this article, a fiber-optic face-plate at the tube entrance was used to improve the image quality of X-ray image intensifiers, and a number of tangential and sagittal trajectories were calculated and weighted in accordance with reasonable assumptions as to the distribution of initial direction and energy of the photoelectrons.
Abstract: Publisher Summary This chapter elaborates the image quality and possibilities for enhancement for x-ray image intensifiers. X-ray image intensifiers have greatly changed and improved the diagnostic methods of the radiologist. In order to achieve improved image quality in X-ray image intensifiers, three techniques were investigated. The tube wall was replaced by a fiber-optic face-plate at the tube entrance. X-ray screens with increased quantum absorption and improved transfer characteristic were used and the electron-optical image surface at the output was made as flat as possible. The background due to scattered X-rays is much lower than in tubes with a conventional face-plate. There is only a small probability that X-rays scattered in the fiber-optic plate reach the screen and excite background light. For several object points on the photocathode, a number of tangential and sagittal electron trajectories were calculated and weighted in accordance with reasonable assumptions as to the distribution of initial direction and energy of the photoelectrons. It is suggested that it is possible to build X-ray image intensifiers of correspondingly improved image quality, provided that the viewing screen and the electron-optics are sufficiently good.
TL;DR: In this paper, a microchannel image intensifier designed for recording fast luminous events was presented, with double proximity focusing and the use of a fiber-optics output window.
Abstract: Publisher Summary This chapter focuses on a microchannel image intensifier designed for recording fast luminous events. This tube with a large useful area has been specially designed for being easily used in physics laboratories, chiefly for widening the range of use of recording equipment for fast events, such as high-speed cameras, high writing-speed oscilloscopes, high-speed spectrographs, etc. The design of this tube was based on two main features: double proximity focusing and the use of a fiber-optics output window. The microchannel plate, with a useful area of 45 × 65 mm 2 is located at a few tenths of a millimeter behind the photocathode window. An example of the capabilities of the tube is the fact that it has been possible to record with its aid a single sweep trace having a writing speed of 0.5 cm/ns on a 519 Tektronix oscilloscope. Under the same conditions, without the tube, it was necessary to superimpose 70 sweeps to reach the same density on the photographic film. This clearly demonstrates one of the possible applications of such a microchannel intensifier.
TL;DR: In this paper, the electron-bombarded-silicon (EBS)-target camera tubes in which the diode array senses, amplifies, and stores information from a photoemissive surface were discussed.
Abstract: Publisher Summary This chapter deals with electron-bombarded-silicon (EBS)-target camera tubes in which the diode array senses, amplifies, and stores information from a photoemissive surface. In the EBS mode, the diode array uses electron–hole pair generation as the mechanism to provide high target gain, of the order of 2500 for 10 keV photoelectrons. This high gain makes EBS tubes the most sensitive camera tubes known. They also resist burns from high lights and perform well under difficult environmental conditions. An EBS tube works in the following manner: light is imaged on the fiber-optic input surface and is transmitted to the photoemissive surface through the fiber bundles. The emitted photoelectrons are accelerated to and focused on the target by the electrostatic image section. The electrons strike the target with energies of up to 12 keV and create a charge pattern corresponding to the image on the fiber-optic input. EBS camera tubes offer extremely high sensitivity. Resolution performance has been limited, however, by the 16-mm target. Higher resolution has now been realized by the development of tubes with 25 mm EBS targets. Performance of the tubes has been shown to be excellent and not significantly reduced by lag, dark current, or low mesh-voltage effects.
TL;DR: The Imacon is normally synchronized to the event by the application of a trigger pulse that starts the sinusoidal oscillation from its peak level, which maintains the camera shuttering in the closed condition until the arrival of the trigger pulse.
Abstract: Publisher Summary This chapter describes the developments in image tube high-speed framing cameras. In the development of high-speed cameras for the investigation of fast-moving phenomena, the demand for increased time resolution is usually met, in the first instance, by recourse to streak photography. The Imacon is normally synchronized to the event by the application of a trigger pulse that starts the sinusoidal oscillation from its peak level. This maintains the camera shuttering in the closed condition until the arrival of the trigger pulse, but introduces a delay, of one-half of the interval between frames, between the receipt of the trigger pulse and the first frame. The system obtains the necessary beam deflections without the generation of a staircase waveform as such. The rate of rise of the linear part of the saw-tooth waveform is adjusted to be identical to the rate of fall of the linear ramp, so that, the two waveforms, when added, give a staircase, the plateaux of which are formed by the cancellation of the rise of one waveform by the fall of the other.
TL;DR: In this article, an inverting electrostatic lens is used to focus the electron image from the primary photocathode to the input of the channel plate, and proximity focusing between the output and the fluorescent screen.
Abstract: Publisher Summary This chapter discusses some design aspects of a small high-contrast channel image intensifier. This channel image intensifier uses an inverting electrostatic lens to focus the electron image from the primary photocathode to the input of the channel plate, and proximity focusing between the channel plate output and the fluorescent screen. The major electron optical-design problem occurs in the inverting section in meeting the principal design requirements of: (1) a flat image plane to match the planar channel-plate input; (2) a resolution performance such that the major effect on the overall modulation transfer is that of the proximity-focused channel plate to screen section, and (3) a diode construction to obviate the need for preset stabilized focusing voltages. The operating voltages required for the tube are 5 kV between the photocathode and input to the channel plate, and a further 5 kV between the channel-plate output and the fluorescent screen. Results demonstrate that a small, high-contrast image intensifier can be manufactured using the channel multiplication principle, which has a performance equal to or better than other types of intensifiers at all but extremely low light levels.
TL;DR: An overview of the proximity-focused diode image intensifier can be found in this paper, where the authors provide an overview of an image intensification tube with a photocathode parallel to, and closely spaced from, the phosphor screen.
Abstract: Publisher Summary This chapter provides an overview of the proximity-focused-diode image intensifier A proximity-focused diode is an image intensifier tube with a plane photocathode parallel to, and closely spaced from, the phosphor screen The photoelectrons are not focused in the normal sense, but lateral motion is restricted by a strong, uniform electric field created when a potential of the order of l0 kV is applied; therefore, maintaining image definition Work on proximity tubes has involved the use of cathode “transfer’’ techniques The old “internal transfer” technique of first forming the cathode on a substrate spaced some distance from the screen and then moving it within the tube to its final position close to the screen, eliminates the possibility of making a thin compact tube In a modern variant of this technique, a cathode is formed on a substrate, which is then transferred to the tube body, and the final seal is then made The tube is processed in a bakeable vacuum chamber incorporating the sealing equipment Although high-quality cathodes in extremely compact tubes are made in this way, it is difficult to achieve long life