Peter D. Read

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).

Production And Testing Of Microchannel Plate Intensifier

As part of a collaborative project to develop a high gain microchannel plate (MCP) intensifier for large area photon counting detectors, a detailed study has been carried out on a prototype device. A calibrated absolute faint light source has been used for the DQE measurements, and direct comparison has been made with a number of photomultiplier tubes. As a result of this work it became apparent that an advanced production chamber would be required to make it possible to introduce modifications readily into the design, and to improve quality control during manufacture. Such a chamber has recently been commissioned. A proposal is discussed for a design of intensifier using a combination of curved and straight channelled MCPs.

Further investigations on the use of polycrystalline CVD diamond as a UV detector

Metal-semiconductor-metal planar structures were fabricated on free-standing diamond films. The devices were found to operate successfully as photodetectors for deep ultraviolet light with their response being dependent on the post-growth treatment. However, evidences of trapping were found both in the spectral photoresponse and temporal response to monochromatic light transients.

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.

Development of the MIC photon-counting detector for astronomical applications

The MIC, a 40-mm intensified microchannel-plate photo-counting detector being developed for the Anglo-Australian, Isaac Newton, and William Herschel telescopes, is described and illustrated with diagrams and sample spectra. The MIC is linked by optical fibers to a fast-scanning CCD detector, and an accurate centroiding technique is applied to yield an effective maximum of 3104 x 2304 10.6-micron pixels, for field-averaged resolution 27 microns FWHM. Applications include high-resolution spectroscopy, especially in the blue, and Fabry-Perot and speckle interferometry.

Properties of a 40-mm Microchannel Plate Intensifier

A 40mm, proximity-focussed, micro channel— plate intensifier using dual double-thickness plates has been developed for use in image photon counting applications. Some of the more important manufacturing techniques are described, along with the results of initial tests of the performance characteristics of the tube.