The Off-Axis Channel Macroplate

The technique of atomic layer deposition (ALD) has enabled the development of alternative glass microchannel plates (MCPs) with independently tunable resistive and emissive layers, resulting in excellent thickness uniformity across the large area (20 × 20 cm), high aspect ratio (60:1 L/d) glass substrates. Furthermore, the use of ALD to deposit functional layers allows the optimal substrate material to be selected, such as borosilicate glass, which has many benefits compared to the lead-oxide glass used in conventional MCPs, including increased stability and lifetime, low background noise, mechanical robustness, and larger area (at present up to 400 cm2). Resistively stable, high gain MCPs are demonstrated due to the deposition of uniform ALD resistive and emissive layers on alternative glass microcapillary substrates. The MCP performance characteristics reported include increased stability and lifetime, low background noise (0.04 events cm−2 s−1), and low gain variation (±5%).

Current Generation II Gallium Arsenide (GaAs) image intensifier tube technology requires that the tube microchannel plate (MCP) component have a thin dielectric coating on the side facing the tube's photocathode component. This protective coating substantially reduces the release from the MCP of ions and neutral species, particularly when the image intensifier is operated. The prevention of MCP outgassing is necessary in order ot prevent the poisoning of the Cs:O surface on the GaAs photocathode. Many authors have experimented with omitting the MCP coating. Such experiments have consistently led to an intensifier with a significantly reduced lifetime, due to contamination of the Cs:O layer on the photocathode. Unfortunately the MCP film acts as a scattering cneter to electron transport within the intensifier and effectively reduces the photoelectron detection efficiency. Substantial enhancement of the image intensifier operating parameters is the motivation for the removal of the MCP film. Removal of the MCP film promises to simplify MCP fabrication and enhance the intensifier parameters related to Electro-Optical performance and image quality. This paper presents results showing for the first time that it is possible to fabricate a long lifetime image intensifier with a single unfilmed MCP and achieve improved imaging and performance characteristics.

The microchannel plate (MCP) is a semiconducting glass plate containing an array of open channels that can provide photo-electron amplification for imaging applications. Conventional MCP channel geometries are designed to inhibit ion-feedback that occurs in straight channel plates at high applied potentials. Ion-feedback must be reduced as much as possible since its presence degrades the performance of the plate by adding noise to the plate's output. The performance characteristics of a new geometrical design for a high-gain MCP, that employs channels that spiral downward in a helical fashion to inhibit ion-feedback, have been evaluated in the laboratory. A Multi-Anode Microchannel Array (MAMA) detector was used to test the new MCP. The "helical-channel" MCPs tested to date have channel diameters of 50 microns and have demonstrated stable operation at gains above 106 electrons/pulse. The goal of the program is to develop "helical-channel" MCPs with channel diameters as small as 12 microns within two years. Detailed performance data including the dynamic range, pulse-height distribution, and gain characteristics of this new MCP will be presented.

We have developed a novel microchannel plate (MCP) by introducing new materials and process technologies. The key features of our MCP are summarized as follows: (i) bulk alumina as a substrate, (ii) the channel location defined by a programmed-hole puncher, (iii) thin film deposition by electroless plating and/or sol–gel process, and (iv) an easy fabrication process suitable for mass production and a large-sized MCP. The characteristics of the resulting MCP have been evaluated with a high input current source such as a continuous electron beam from an electron gun and Spindt-type field emitters to obtain information on electron multiplication. In the case of a 0.28 μA incident beam, the output current enhances ∼170 times, which is equal to 1% of the total bias current of the MCP at a given bias voltage of 2600 V. When we insert a MCP between the cathode and the anode of a field emission display panel, the brightness of luminescent light increases 3–4 times by multiplying the emitted electrons through pore arrays of a MCP.

We describe the design and report on the experimental results of a novel thermal and cold neutron imaging detector utilizing neutron sensitive (10B-doped) microchannel plates (MCPs). In this detector, the incoming neutron interaction products produce secondary electrons at the pores adjacent to the absorption point within the MCP glass. This electron signal is then multiplied by a stack of conventional MCPs within those adjacent pores limiting the spread of the signal to less than two pore diameters (currently 6-10 mum pores on 8-12 mum centers). The event position then can be encoded by a number of readout techniques already developed for photon/charged particle counting applications. This paper presents the results of experimental evaluation of neutron sensing MCP detector with Medipix2 readout allowing operation at high counting rate mode (>100 MHz level) at a spatial resolution limited by the 55 mum pixel size of the Medipix2 readout. Other attractive features of MCP neutron detectors are their high detection efficiency (approaching 50% levels) for thermal and cold neutrons and the absence of readout noise.

ALD-GCA-MCPs are a technology advancement that affords microchannel plates (MCPs) with significant performance benefits compared to conventional MCP technology. Incom now routinely produces ALD-GCA-MCPs with dimensions up to 20 cm x 20 cm. Notable advancements and benefits over conventional lead-oxide based MCPs are larger size and higher mechanical stability, high and stable gain (>1e4for single MCP @ 1000 V, stable gain to ≥ 1 C/cm2 extracted charge), low dark counts (≤ 0.05 cts/sec/cm2), ~3x lower gamma-ray sensitivity, and the unique ability to individually customize and control the MCP resistance and secondary electron emission (SEE) amplification characteristics. ALD-GCA-MCPs find application in a variety of photon and charged particle counting applications and are particularly suited for applications that require fast timing, high spatial resolution, radiation hardness, and long detector life times, such as Ion-TOF, electron spectroscopies, and a variety of other analytical instruments. They can also be incorporated into low-power, low-background photodetectors suitable for applications in extreme environments such as remote sensing applications in rugged environments, in space flight instrumentation, as well as in high-energy physics and nuclear physics experiments. In this paper we will provide a brief ALD-GCA-MCP technology overview highlighting recent developments that focused on improving the glass capillary array (GCA) substrate, and their implications for large-area photodetectors and spectrometers used in nuclear and high energy physics, space science, and other sensing applications.

Sealed tube MCP detectors have provided a valuable platform for high spatial resolution photon counting detectors. Specifically, electronic readout microchannel plate (MCP) based sensors have been used as photon counting, imaging, event time tagging detectors for astronomy, time resolved biological imaging, imaging LIDAR, Cherenkov (RICH), scintillation detection, and neutron imaging [1]–[10]. For future applications we have been developing novel atomic layer deposited MCPs, UV optimized photocathodes and high resolution cross strip readouts for sealed tube detectors. The Photonis Planacon is a useful sealed detector format (~50 mm square active area) to employ and demonstrate these novel technologies. The Planacon standard geometry has been used, but the standard anode pad array is replaced with a cross strip anode that demonstrates ~20 µm FWHM spatial resolution for single photon events at electron gains of the order 106. Atomic layer deposited MCPs with 10µm pores have been used in place of conventional MCPs, providing tight pulse amplitude distributions, enhanced gain stability and reduced gamma ray sensitivity. The entrance window (Sapphire or MgF2) permits the high UV sensitivity of bialkali photocathodes (>30% @180nm) to be utilized. Event encoding electronics implemented in surface mount components also provides high resolution imaging at event rates of up to 5 MHz. ASIC versions of the encoding electronics are in the prototype phase and show considerable promise for enhanced performance with lower power and smaller footprints.

This chapter describes the development of the continuous-dynode electron multiplier and its evolution into the microchannel plate (MCP). The fabrication procedures for MCPs are described and the performance characteristics of MCPs and MCP stacks are enumerated. The configurations and performances of imaging MCP electronic readout systems currently in use in space instruments are described in detail. The unique capabilities of MCP electronic systems for fast timing and for time-tag imaging are listed. Finally, the prospects for the development of the next generation of MCPs are briefly outlined.

Amorphous silicon-based microchannel plates

A sandwich plate is a novel type of high-gain electron multiplier formed by bonding, in permanent contact, three standard (channel length-to-diameter ratio L/D=40:1) image-intensifier multichannel plates. This geometry has the advantage of mechanical and electrical simplicity when compared with conventional multiplate stacks. An evaluation of sandwich plates for X-ray photon counting is presented. Sandwich plate gain, gain uniformity, pulse height FWHM, dark noise, high-count-rate operation, and X-ray quantum efficiency are compared with previous measurements made with conventional two-stage MCP (microchannel plate) multipliers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The characteristics and performance of several kinds of high-gain micro-channel plate photomultipliers have been investigated. Special attention was directed towards i) lifetime studies, ii) performance in the magnetic field, and iii) timing properties. Lifetime studies include separate investigations of the photocathode quentum efficiency degradation caused by ion feedback, and the deterioration of the micro-channel plate gain. The dependence of the micro-channel plate photomultiplier gain on the intensity and the direction of the magnetic field (up to 7 kGauss) is reported.

Electric field inside high gain microchannel plate multipliers was studied. The calculations were based directly on the solution of the Maxwell equations applied to the microchannel plate (MCP) rather than on the conventional lumped RC model. The results are important to explain the performance of MCP's, i) under a pulsed bias tension and, ii) at high rate conditions. The results were tested experimentally and a new method of MCP operation free from the positive ion feedback was demonstrated.

A pulsed ion deflection system for background reduction in 252Cf-plasma desorption mass spectrometry

Effect of pilot injection strategy on the methanol-mineral diesel fueled reactivity controlled compression ignition combustion engine

A flexible and versatile method combining sputtering and electrospinning techniques was used to shape different palladium morphological structures with nanoscale features. The samples were prepared by dc-magnetron sputtering onto thermally degradable polymer templates. The sputtering parameters were chosen to deposit the metal under low adatom-mobility conditions. After deposition, the template was removed by heat treatment, thereby forming different palladium morphologies with shapes resembling ribbons and half tubes, amongst others. X-ray diffraction studies demonstrated that they are composed of crystalline palladium or palladium oxide, depending on the heat treatment. The cylindrical walls are composed of 30 nm or smaller crystallites, as measured from transmission electron microscopy images. A mathematical simulation demonstrate that the morphological structures obtained are a consequence of the sputtering line-of-sight deposition process. This fabrication process can be varied to modify three types of structures at the nanoscale level: the external shape, the columnar shape of the walls, and the nano-crystallinity. The external shape can be modified by controlling the deposition time and the fiber template diameter. The columnar shape of the walls and the nano-crystallinity can be modified by changes in the sputtering process parameters. The nanoscale morphologies created have potential uses in sensing and photonic applications.