Martin K. Carter

Transputer-based image photon-counting detector

A prototype microprocessor-based electronic processing system is described which performs the on-line data processing in an image photon-counting detector. The detector head consists of a microchannel-plate intersifier optically coupled to a CCD with rapid-scanned readout. The digitized data are passed to a group of transputers which separate out the events, calculate the event centers to subpixel accuracy and accumulate the results in an image buffer. In the prototype, all processing is done in software for evaluation purposes. This paper discusses the basic design of the system, the centroiding algorithm and fixed patterning correction, and the implications of the results for future systems.

New techniques in photon counting detectors

Abstract We describe a centroiding image photon counting detector intended for photon counting applications in both ground-based and space astronomy. The detector uses a 40 mm diameter proximity focussed microchannel place intensifier and a rapid-scanned CCD readout system with a transputer based electronic processing system for the on-line data processing. An interesting result has been that this system resolves the pore structure in the front microchannel plate of the intensifier, showing that the system can work to the maximum possible resolution using the MCP intensifiers.

Uses of microchannel plate intensified detectors for imaging applications in the X-ray, EUV and visible wavelength regions

Abstract The Rutherford Appleton Laboratory Photon Counting Detector (RALPCD) has been refined to meet project requirements for a flexible imaging arrangement with applications at X-ray, EUV and visible wavelengths. The basic detector design comprises commercially available high gain microchannel plate intensifiers fibre optically coupled to CID or CCD cameras, to form a modular detector arrangement with the appropriate RAL detection and centroiding software. Frames of data from the cameras are detected and centroided in a Transputer or C40 parallel processor array where correction algorithms use look up tables to produce pattern free images at high resolution. Data from completed applications are used to illustrate the performance and future advances are discussed.

The implementation and performance of a connected regions centroiding algorithm for imaging photon counting

Abstract Many different types of imaging photon counting detectors use a centroiding algorithm to recover spatial resolution from a limited number of spatial sampling points. Typically, these use a fixed window about each photon event resulting in fixed patterning errors in the accumulated image due to neglecting the signal outside the window. We discuss a novel approach to the centroiding process using the connected region around each photon event. We describe the implementation and performance of this connected regions centroiding algorithm in an intensified CCD Photon Counting System (RALPCD).

Versatile high-resolution imaging detector system for use in x-ray, EUV, and visible wavelength regions

The Rutherford Appleton Laboratory Photon Counting Detector (RALPCD) is a highly adaptable intensified imaging system with applications in the x-ray, EUV and visible wavelength regions. The detector comprises commercially available high gain microchannel plate intensifiers fiber optically coupled to CID or CCD cameras, to form a modular detector arrangement. Frames of data from the cameras are detected and centroided in a transputer parallel processor array where correction algorithms using look up tables are used to produce pattern free images at high resolution. Data from the applications are used to illustrate the performance and future advances are discussed.

High-resolution image photon counting system (Poster Paper)

Many space applications of photon counting detectors (PCDs) are particularly challenging due to the requirements for high local and global count rates and for sensitivity down to the soft x ray region. The count rates per pixel required may be as high as several hundred counts/second and overall count rates as high as 1,000,000 counts/second. At the Rutherford Appleton Laboratory (RAL) we have been developing a range of modular detector systems in the visible and UV which are built specifically with solar UV observing in mind. The high resolution/high count rate imaging performed pushes the technology to the limit and shows up, in some detail, problems in intensifier and microchannel plate (MCP) manufacture. Close cooperation with the manufacturers of the intensifiers used, Photok Ltd., has led to improvements in the intensifier design. In the following paper the performance of these detectors is discussed in detail along with plans for their future development.

Imaging photon counting system for the extreme ultraviolet(EUV)

We describe an imaging photon counting system for the EUV and its application to the measurement of the imaging quality of CDS EUV telescope for SOHO. The detector system uses an open window micro-channel plate intensifier coupled to a CCD with a fiber-optic taper. The digitized data are processed using a transputer based processing system which resolves the channel pores in the front micro-channel plate. The pores are used to register the EUV image. Dithering of the detector is used to enhance the resolution.

Large-format photon-counting x-ray and gamma-ray imagers

Photoemissive photon counting tubes of 40 mm diameter are routinely made, and 75 mm tubes are in development. When these tubes are coupled to a suitable scintillator, substantial quantum efficiency can be achieved from soft rays through to gamma energies. Available scintillators and their performance are described in this paper. The advent of fast PC compatible computers has enabled the electronics readout to be improved, simplified, and reduced in cost. The new electronic readout system is described, and the image processing capability outlined. The pulse height distribution is available to the user, and to a limited extent, this allows the user to measure the energy of the input photons to the system. Systems of this type are used for x-ray crystallography, and could find wider applications in nuclear medicine and gamma ray photography.

Ultrahigh-resolution photon-counting system

The requirement for ever improved resolution at lower and lower photon levels has lead researchers to a number of various possible systems. Since we make image tubes on a custom basis, we have made several different photon counting tubes with different readout systems for a variety of laboratories. These readout systems are reviewed in our paper, and we attempt to analyze the state of the art with these different readout systems. Since all these systems use micro channel plate electron amplification, the fundamental properties of the channel plate effects them all to some degree. Advanced micro channel plates are being assessed, and the progress made is reviewed. Advanced electronic readout systems based upon the latest components, including transputers, promises increased resolution and count rates in systems optimized for X-ray and UV applications.