Intensifier Tube Research Articles

Development of the EXITE Detector: A New Imaging Detector for 20 - 300 keV Astronomy

We report on the development and testing of a detector to be used in the Energetic X-ray Imaging Telescope Experiment (EXITE). It consists of a 34 cm diameter NaI(Tl) cyrstal coupled directly to a single large image intensifier tube with associated silicon PIN diode readout. The measured spatial and energy resolutions at 122 keV are 6mm (FWHM) and 9% (FWHM), respectively. This energy resolution is ~50% better than that of any previously flown hard x-ray experiment. These resolutions decrease with the square root of the energy of the incident x-ray, indicating that they are determined by the number of photons emitted in the NaI(Tl) scintillator light flash.

OH airglow observation by image intensifier combined with solid-state image sensor.

A new observation system of OH airglow was developed for balloon-borne experiments to obtain a better resolution in space and time than with a usual scanning photometer. The system consists of a camera lens, a two-dimensional solid state image sensor combined with an image intensifier tube and a microcomputer. The performance of the system was tested by ground based observation and it was proven to be satisfactory. Intensity variations in a few minutes were observed by using this system.

Simple inexpensive high-voltage rectangular pulse generator

In this paper, we describe a simple high-voltage rectangular pulse generator for the gating of an image intensifier tube (type EMI 9912). This device, which uses a krytron, is able to furnish 4-kV pseudo-rectangular pulses with variable widths from 30 to 100 ns or more. The possible repetition rate is about 30 pps, the rise and fall time 5 ns, the total delay 100 ns, and the jitter less than 5 ns. The image intensifier tube is used for the study of luminous samples using the Raman effect.

A multistep avalanche chamber with optical readout for use as a 2-dimensional VUV photon or particle track detector

Abstract A multistep avalance chamber with optical readout has been built and tested as a position sensitive VUV photon detector for use in Cherenkov ring imaging and as a particle track detector. Readout of the chamber, which has a uniform field geometry, is achieved by exploitation of the secondary light emission that occurs during gaseous multiplication. This light is focused onto, and detected by, an image intensifier tube which is itself viewed by an electronic image sensor array affording a genuinely 2-dimensional readout of the position of the avalanche initiated by an incident VUV photon or particle track. Efficient detection of single VUV photons has been achieved with a positional resolution of 260 μm in both dimensions. Given a more suitable image intensifier tube, this could be reduced to 100 μm or less for both VUV photons or particle tracks.

Microcomputer programs for the design of image intensifier tubes

Details of some transportable microcomputer programs developed for the non-iterative computation of electron trajectories in image intensifier tubes are presented. For the computation of the cylindrically symmetric electrostatic field, the integral equation method and a new version of the dynamic programming method for rotationally symmetric systems are used. The program for electron trajectories eliminates the numerical integration errors associated with classical integration techniques. The computational efficiency of the programs on microcomputers supported by the UCSD p-system is discussed. Improvement of the efficiency and generalization to general electromagnetic systems are briefly indicated.

Sonoluminescence produced by ‘‘stable’’ cavitation

This article reports on a phenomenological study of sonoluminescence produced by acoustic cavitation in which a sensitive, high-gain image intensifier tube (EMI type 9912) was used to view the cavitation. We discovered that large amounts of light were being emitted from regions near pressure antinodes in the standing wave field where the pressure amplitude was approximately 0.17±0.03 MPa. Visual observation of these areas indicated activity resembling ‘‘stable’’ cavitation rather than ‘‘transient’’ cavitation.

Multichordal charge exchange recombination spectroscopy on Doublet III (abstract)

Single shot, multipoint ion temperature and plasma rotation profiles have been routinely obtained on the Doublet III tokamak for 32 consecutive time slices with 20-ms resolution. A six-chord tangentially viewing spectroscopic diagnostic has been built to look at radiation emitted by fully stripped low-Z impurity ions (He, C, O) that have undergone charge exchange recombination with hydrogen atoms from a 3-MW heating beam. The main components of the instrument are a single monochromator for wavelength dispersion, a single image intensifier tube for photon gain, and a pair of 1024-element linear photodiode arrays for detection. A special arrangement of fiber optics allows simultaneous data acquisition from all chords without the use of scanning mirrors or other moving parts. Ion temperature profiles taken under a variety of plasma conditions will be presented.

Evaluation of a photon-counting detector for Doppler ion temperature measurements (abstract)

A photon-counting detector for determination of the ion temperature in magnetically confined plasmas has been developed.1 The detector is based around an image intensifier tube which is fiber optically coupled to a self-scanning linear photodiode array. The image intensifier incorporates three high strip current (∼280 μA) microchannel plates in a ‘‘Z’’ configuration. Frame times of 10 μs are possible through the use of pixel selection, resulting in a time resolution on the order of 5 ms. The detector system will be mounted on a 1-M Ebert–Fastie spectrometer and used to study the Alcator C plasma. Laboratory evaluation of the detector and associated electronics has been completed. The results of this evaluation, and progress toward integration of the detector and spectrometer systems, will be presented. This work, and additional information, will be published in greater detail in the near future.

Design of a high energy x-ray imaging system for the Tandem Mirror Experiment-Upgrade (abstract)

We want to image the hot, mirror-confined electrons produced by electron cyclotron resonant heating in the end cells of the Tandem Mirror Experiment-Upgrade. Preliminary spectroscopic measurements with NaI(Tl) detectors indicate tail electron temperatures in the range of 100–300 keV. Our goal is to image x-rays in the energy range 10–200 keV, for plasma densities as low as 1011 cm−3. A spatial resolution of one part in forty at framing rates of 200 Hz should be achieved. The imaging system will consist of an x-ray converter (phosphor or scintillator) and image intensifier (diode or microchannel plate), followed by a video readout (silicon intensifier tube). We will outline the steps we are taking to implement this system.

Persistence of phosphor glow in microchannel plate image intensifiers

Image intensifier tubes using microchannel plate amplification stages and phosphor output stages are being increasingly used in various detection applications. In this paper, measurements of the decay times of what are attributed to be the P20 phosphors in various image intensifiers are reported. It is found that the long tail on the decay curve of the phosphor following illumination can be a limitation for certain observations. In addition, the background level of phosphor glow (which is seen by the subsequent detection system as a light signal) continues to build with continuing illumination.

Reduction of Background Luminance Generated in the Output Screen of X-Ray Image Intensifier Tubes

Background luminance of several origins introduced into an X-ray image intensifier tube deteriorates the contrast of its output image. The output screen, which consists of a phosphor layer usually prepared on a transparent substrate, generates influential background luminance in the X-ray image intensifier tube. A theoretical and experimental study on how reduce the background luminance of the output screen by increasing the thickness of the substrate is presented. In evaluating the effect of the background luminance, we calculated and measured the contrast ratio usually used as a characteristic index of the image intensifier tube. The theory and results from the experimental image intensifier tubes show good agreement. This method of background luminance reduction is not only more economical but also superior to the other methods utilizing dark substrates or optical fiber plates.

Earth-to-geosynchronous satellite laser beam transmission

Some experimental results for detection of a ground-based laser beacon by a geosynchronous satellite are reported. A 50-cm diam telescope and silicon intensifier tube camera were used for optical observation of the satellite. The transmitted argon laser beam was detected by the visible channel of a radiometer on board the Japanese Geostationary Meteorological Satellite. Two activities, (1) orbit prediction correction using optical observation and (2) detection of the earth laser beacon by the radiometer, are described.

ASIT Gamma-Ray Camera : A New Camera Head Provided with an Array of Scintillation Intensifier Tubes

After a brief examination of the main physical and technological problems which determine the limits of performance of various kinds of scintillation cameras, a new gamma camera is suggested in this paper. The detection head is composed of an array of scintillation intensifier tubes (ASIT), the bialkali photocathodes of which are closely coupled to a large NaI (Tl) scintillator plate. The output phosphor (P 47) screens of the intensifiers emit blue light pulses collected by a conventional event localizer which includes an array of photomultiplier tubes and an electronic calculator. A description of the basic operation of an ASIT gamma camera indicates that the event coordinates result from a barycentric estimation of the spatial distribution of detected light photons emitted from the scintillation. A computer simulation made to estimate the performance parameters of ASIT cameras shows that high intrinsic spatial and spectral resolutions can be reached. For a particular camera head design, 2.3 mm and 11.3 KeV FWHM at 122 KeV are obtained.

Activities in vacuum science and technology in the USSR and Eastern Europe

This chapter provides an overview of the transmission secondary emission image intensifier tube. Electrons from a tri-alkali photocathode are accelerated and focused on to a series of dynodes where multiplication takes place by transmission secondary emission. The electrons from the final dynode are then focused on to the output phosphor. The body is formed from a number of equally spaced metal rings joined together by short glass cylinders. Some of the rings serve as supports for the multiplying dynodes, whilst, the intermediate electrodes are attached to others. Focusing is achieved by superimposed uniform electric and magnetic fields, and a field of 260 G is required with an overall potential of 34 kV. Each multiplying dynode consists of layers of aluminum and potassium chloride on a thin supporting film of aluminum oxide. From a single film an electron gain of about 6 at an accelerating potential of 4.2 kV is typical. The phosphor used at present is silver-activated zinc sulfide P.11, however there should be little difficulty in replacing this with the faster P.16 if required. Resolutions of 23 lp/mm have been obtained in experimental tubes with photocathodes and output phosphors 45 mm in diameter.

Laser excited fluorescence of hematoporphyrin derivative for diagnosis of cancer

Hematoporphyrin derivative (HPD) is selectively retained in malignant tumors for several days after intravenous injection. It fluoresces in the red (600-720 nm) when excited by shorter wavelengths, especially violet (near 400 nm). While fluorescence efficiency is not high, it can be detected at parts per million concentrations when excited by a low-background source such as a krypton ion laser (413 nm), and the fluorescence detected by an image intensifier or photomultiplier tube. We have developed an intensifier based fluorescence imaging system for localization of carcinoma in situ of the lung, aided by digital background subtraction in a video system. A ratio fluorometer and spectrum analyzer have been added for research and for quantitative, noncontact measurements of fluorescence intensity and spectrum of HPD fluorescence and autofluorescence of tissue. Research is continuing to determine the optimum time after injection for best contrast, and the maximum allowable dosage of HPD, limited by the induced temporary photosensitivity of the skin. In diagnosis of epithelial or superficial tumors, the monochromatic radiation and suitability for coupling through fiberoptics, as well as reasonable power (typically 15 mW violet is used) are the principal advantages of the laser.

Experience with a 36 cm image intensifier system in neuroradiological examinations.

A large-sized image intensifier-TV-fluorographic system in combination with 100 mm sheet-film camera was evaluated for use in neuroradiologic practice. The image intensifier tube had new features such as a large input screen diameter, metal input screen cover and fiber optics on the output screen. The system was evaluated both technically and clinically. With some modifications, the tested system can be recommended for use in neuroangiography provided that it is supplemented by facilities for full-size or magnification technique.

A photodiode array x-ray imaging system for digital angiography.

A line scanning imaging system that can be used to make low-noise x-ray images to detect low-contrast structure is described. The system makes use of a 1024-element, self-scanning, photodiode array (Reticon RL 1024S) optically coupled to an x-ray image intensifier tube. Low-noise images are obtained by imaging only small areas of interest at a time to reduce the noise resulting from the detection of scattered radiation, and by making use of the very large dynamic range (8000:1) solid-state photodetector. Some performance characteristics of the diode array system are discussed. It was found that while sensitivities of individual elements differed by up to +/- 15% from the average, they could be corrected with a precision of 0.02% to 0.04% of the maximum signal. The limiting spatial resolution of the system in the direction of the diode array was 2.0 cycles/mm, limited by the image intensifier. The system linearity was studied by measuring the attenuation of a monoenergetic x-ray beam by Plexiglas. The measured attenuation agreed with the expected exponential decrease over a range of approximately 1000 to within experimental error. The imaging capabilities of the system were demonstrated by imaging an angiographic phantom consisting of an iodine-filled tube with an asymmetric 20% stenosis. The stenosis was oriented on the tube surface furthermost from the detector resulting in an image with a 2% radiographic contrast change but no decrease of the tube width. The stenosis was clearly imaged using a temporal subtraction technique.

Kinetics of the main phase transition of hydrated lecithin monitored by real-time X-ray diffraction

A method is described for observing and recording in real-time x-ray diffraction from an unoriented hydrated membrane lipid, dipalmitoylphosphatidylcholine (DPPC), through its thermotropic gel/liquid crystal phase transition. Synchrotron radiation from the Cornell High Energy Synchrotron Source (Ithaca, New York) was used as an x-ray source of extremely high brilliance and the dynamic display of the diffraction image was effected using a three-stage image intensifier tube coupled to an external fluorescent screen. The image on the output phosphor was sufficiently intense to be recorded cinematographically and to be displayed on a television monitor using a vidicon camera at 30 frames X s1. These measurements set an upper limit of 2 s on the DPPC gel----liquid crystal phase transition and indicate that the transition is a two-state process. The real-time method couples the power of x-ray diffraction as a structural probe with the ability to follow kinetics of structural changes. The method does not require an exogenous probe, is relatively nonperturbing, and can be used with membranes in a variety of physical states and with unstable samples. The method has the additional advantage over its static measurement counterpart in that it is more likely to detect transiently stable intermediates if present.

A Diode Intensifier Tube Designed for Scintillation Detection

An input and output faceplates diode intensifier tube having a large ratio (.8) useful-external diameters has been designed with a view to reach very good performance in scintillation detection. The photoelectrons emitted by the bialkali photocathode are accelerated up to about 10 kV and collected on a fast blue phosphor screen (P 47). The design is described and the main technological problems which has to be solved are reported, in particular the one allowing to overcome wall charge effects. The experimental results on image distortions, electron and photon gains, single electron resolution, dark noise, as well as on the phosphor screen characteristics are given. An assembly of this tube working as a high photon gain (?30 at 10 kV) light pre-amplifier, optically coupled to a fast photomultiplier could allow to obtain significant improvements of the FWHM energy resolution in scintillation detection by using a rather large NaI(T1) scintillator block (e.g. 9.4 % at 122 KeV instead of 10.5 % obtained with the fast PMT used alone).

Fast Imaging Applications in the Nuclear Test Program

Applications of fast imaging employ both streak cameras and fast framing techniques. Image intensifier tubes are gated to provide fast two-dimensional shutters of 2-3 ns duration with shatter ratios of greater than 106 and resolution greater than 104 pixels. Shutters of less than 1 ns have been achieved with experimental tubes. Characterization data demonstrate the importance of tube and pulser design. Streak cameras are used to simultaneously record temporal and intensity information from up to 200 spatial points. Streak cameras are combined with remote readout for downhole uses and are coupled to fiber optic cables for uphole uses. Optical wavelength multiplexing is being studied as a means of compressing additional image data onto optical fibers. Performance data demonstrate trade-offs between image resolution and system sensitivity.