Showing papers on "Microchannel published in 1987"
15 Nov 1987
TL;DR: In this article, the influence of exposure to a humid atmosphere on the efficiency of the CsI-photocathode has been studied in great detail, particularly for wavelengths longer than 140 nm.
Abstract: Quantum efficiency measurements are presented for CsI-coated microchannel plates in the waveband 25–200 nm. The influence of exposure to a humid atmosphere on the efficiency of the CsI-photocathode has been studied in great detail. Due to the very high susceptibility of CsI to humidity, particularly for wavelengths longer than 140 nm, the best quantum efficiencies have been obtained for a CsI-coated channelplate continuously stored in vacuum. The results are interpreted on the basis of photoelectron emission theory.
37 citations
Patent•
15 Sep 1987
TL;DR: In this article, a large cross-section molecular beam source for the controlled delivery of a reactant species to provide deposition or etching over a generally large crosssectional surface area of a substrate is described.
Abstract: A large cross-section molecular beam source for the controlled delivery of a reactant species to provide deposition or etching over a generally large cross-sectional surface area of a substrate is described. The apparatus includes a source (40, 40') of the reactant species, typically as a gaseous material, a microchannel array (30) for providing a directionalized, low divergence molecular beam (38) of the reactant species having a cross-sectional dimension directly comparable to that of the substrate (22). The apparatus further includes a substrate mount (20) that maintains the substrate so (22) as to allow the direct impingement of the columnarized molecular beam (38) on the wide area surface of the substrate (22). The reactant species source, microchannel array and substrate mount are housed within a vacuum chamber (12) adapted to maintain a vacuum sufficient to enable the formation of the directionalized molecular beam of the reactant species upon its passing through the microchannel array.
26 citations
TL;DR: In this paper, a model for the critical current and the critical temperature in a single circular cylindrical channel with a circular cross-section is presented. But the model is based on the Ginzburg-Landau formulation, and the measured reductions of these quantities are in reasonable agreement with the predictions of the model.
Abstract: We report on an investigation into confined geometry effects and critical currents of superfluid3He in a single circular cylindrical channel The diameter of the channel, 07 µm, is of the order of the (temperature-dependent) coherence length and its aspect ratio is ∼10 The reduction of the critical temperature demonstrates diffuse scattering on the solid walls of the microchannel Using the Ginzburg-Landau formulation, we derive a model for the critical current and the critical temperature in a small, infinitely long, cylindrical channel with a circular cross section The measured reductions of these quantities are in reasonable agreement with the predictions of the model
20 citations
TL;DR: A detector employing a curved channel microchannel plate in front of an optimised, thin substrate wedge and strip anode (WSA) imaging readout is described, obtaining a position resolution better than 20¿m FWHM allowing the images of individual MCP pores to be distinguished.
Abstract: We describe a detector employing a curved channel microchannel plate (MCP) in front of an optimised, thin substrate wedge and strip anode (WSA) imaging readout. We obtain a position resolution better than 20?m FWHM allowing the images of individual MCP pores to be distinguished. The collimation provided by a single pore is used to probe the fundamental limitations in resolution of the WSA. Finally, having experimentally verified the limitations imposed by electronic and partition noise, we describe a detector which will produce 20?m FWHM resolution over a 50mm diameter imaging area.
15 citations
01 May 1987
TL;DR: In this article, the soft X-ray detection efficiencies of CsI- and CsBr-coated microchannel plates are compared, and it is shown that CsB is the more efficient photocathode material for Xray wavelengths ∼ 20-100 A.
Abstract: The soft X-ray detection efficiencies of CsI- and CsBr-coated microchannel plates are compared. CsBr is the more efficient photocathode material for X-ray wavelengths ∼ 20–100 A .
11 citations
TL;DR: In this paper, an improved streak camera using a micro-channel plate electron multiplier was proposed, which achieved high temporal resolution and low energy x-ray detection without attenuation inside the cathode.
Abstract: An improved streak camera in which a microchannel plate electron multiplier is used in place of or in combination with the photocathode used in prior streak cameras. The improved streak camera is far more sensitive to photons (UV to gamma-rays) than the conventional x-ray streak camera which uses a photocathode. The improved streak camera offers gamma-ray detection with high temporal resolution. It also offers low-energy x-ray detection without attenuation inside the cathode. Using the microchannel plate in the improved camera has resulted in a time resolution of about 150 ps, and has provided a sensitivity sufficient for 1000 KeV x-rays.
10 citations
TL;DR: There still remains a factor of at least 3 quantum efficiency advantage in the separate opaque CsI photocathode configuration in the far- UV (below 2000-A) wavelength range.
Abstract: Measurements and comparisons have been made of the quantum efficiencies of microchannel plate (MCP) detectors in the far-UV (below 2000-A) wavelength range using CsI photocathodes (a) deposited on the front surfaces of microchannel plates and (b) deposited on solid substrates as opaque photocathodes with the resulting photoelectrons input to microchannel plates. The efficiences were measured in both pulse-counting and photodiode modes of operation. Typical efficiencies are about 15 percent at 1216 A for a CsI-coated MCP compared with 65 percent for an opaque CsI photocathode MCP detector. Special processing has yielded an efficiency as high as 20 percent for a CsI-coated MCP. This may possibly be further improved by optimization of the tilt angle of the MCP channels relative to the front face of the MCP and incident radiation. However, at present there still remains a factor of at least 3 quantum efficiency advantage in the separate opaque CsI photocathode configuration.
6 citations
TL;DR: In this paper, the detection quantum efficiency (DQE) of microchannel plates for electrons in the energy range from 5 to 50 keV was measured with enough spatial resolution to resolve the single channels using a scanning electron microscope.
Abstract: The detection quantum efficiency (DQE) of microchannel plates for electrons in the energy range from 5 to 50 keV was measured with enough spatial resolution to resolve the single channels using a scanning electron microscope. Between 10 and 50 keV the DQE is found to decrease with increasing energy from 0.4 to 0.2. Microchannel plates for image intensification in electron microscopy have been found inferior to photographic recording and well designed image pickup devises using phosphor screens on fibre plates. Nevertheless their DQE is sufficient for observing low intensity electron images at a high brightness level if some additional noise can be tolerated.
6 citations
01 Jun 1987
TL;DR: In this article, a large-area neutron detector design based on microchannel plates (MCPs) was proposed, which can have a very fast rise time and count at a high rate.
Abstract: We propose a large-area neutron detector design based on microchannel plates (MCPs). Two characteristics of the MCP make it ideal as a high-rate neutron detector: (1) its signals can have a very fast rise time, and (2) it can count at a high rate. The MCP-based detector could use both the high-voltage power supplies and the readout electronics designed for a neutron detector based on the multiwire proportional chamber (MWPC).
5 citations
TL;DR: In this paper, the authors describe the design and development of a large format 40mm active diameter imaging photon detector, which comprises an S20 semitransparent photocathode proximity focused onto a stack of two microchannel plates clamped back to back having channel length to diameter ratios of 80:1.
Abstract: We describe the design and development of a large format 40‐mm active diameter imaging photon detector. The design comprises an S20 semitransparent photocathode proximity focused onto a stack of two microchannel plates clamped back to back having channel length to diameter ratios of 80:1. Event readout is facilitated by a circular arc terminated resistive anode. The theoretical performance of the design is discussed with reference to gain measurements of the microchannel plates. Experimental results give an optimum position resolution of 100 μm which is spatially nonuniform and degrades towards the edge of the imaging field. We discuss the role of signal processing in this nonuniformity and describe design modifications which would achieve optimum imaging performance.
5 citations
15 Nov 1987-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, a position-sensitive event-counting microchannel plate detector with a quadrant anode readout system that combines the advantages of several centroid-finding readout techniques is described.
Abstract: We describe a position-sensitive event-counting microchannel plate detector with a quadrant anode readout system that combines the advantages of several centroid-finding readout techniques. The relative amount of charge collected by each quadrant of the anode mounted behind the output side of the microchannel plate is used to localize each event. The position-sensitive area is about 80% of the active microchannel plate surface. By changing a single voltage a remote-controlled image magnification can be achieved. Due to a correction function that minimizes image distortions the imaging characteristics of this low-cost readout system are similar to those of expensive resistive anodes.
TL;DR: In this paper, the color characteristics of a microchannel spatial light modulator (MSLM) under white-light read out illumination are examined, and a system for performing color optical processing operations using an electro-optic crystal plate along with the MSLM is presented.
15 Oct 1987-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, several properties that affect the physical growth and reproducibility of PVD CsI photocathode material particularly used as a coating for microchannel plates (MCPs) to improve soft X-ray sensitivity were investigated.
Abstract: We have investigated several properties that affect the physical growth and reproducibility of PVD CsI photocathode material particularly used as a coating for microchannel plates (MCPs) to improve soft X-ray sensitivity. We have measured the quantum efficiency of the CsI-coated microchannel plates in response to X-rays from 0.7 to 4.5 keV.
01 Apr 1987
TL;DR: In this article, the characteristics of a herringbone assembly of microchannel plates with gaps of 5 and 15 µm between them are studied, and a critical load of approx. 0.1/channel/sec is determined.
Abstract: The characteristics of a herringbone assembly of microchannel plates with gaps of 5 and 15 ..mu..m between them are studied. Gain K less than or equal to 3 x 10/sup 7/ with amplitude resolution R greater than or equal to 30% is achieved in registration of ultraviolet photons and energetic neutral particles; a critical load of approx. 0.1/channel/sec is determined. The assembly can be effectively used when microchannel plates with curved channels are required.
TL;DR: Applications to real-time optical processing operations which include the intensity color encoding analog hard clipping in colors are provided.
Abstract: A microchannel spatial light modulator-based white-light optical processor is presented. The basic principle of the system performance is studied. The operating characteristics of the spectral and contrast responses are measured. Applications to real-time optical processing operations which include the intensity color encoding analog hard clipping in colors are provided.
Journal Article•
TL;DR: In this paper, a compact, high-efficiency time detector, employing microchannel plates, is presented, in particular as regards the time resolution and the efficiency in time-of-flight measurements.
Abstract: A compact, high-efficiency time detector, employing microchannel plates, is presented. Its characteristics, in particular as regards the time resolution and the efficiency in time-of-flight measurements, are discussed.
21 Aug 1987
TL;DR: In this article, the color characteristics of a microchannel spatial light modulator (MSLM) under white-light read out illumination are examined, and a system for performing color optical processing operations using an electro-optic crystal plate along with the MSLM is presented.
Abstract: The color characteristics of a microchannel spatial light modulator (MSLM) under white-light read out illumination is examined, and a system for performing color optical processing operations using an electro-optic crystal plate along with the MSLM is presented. Experimental results for edge enhancement and image subtraction operations are demonstrated.