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Register a new userAbsolute ion detection efficiencies of microchannel plates and funnel microchannel plates for multi-coincidence detection
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Modern momentum imaging techniques allow for the investigation of complex molecules in the gas phase by detection of several fragment ions in coincidence. For these studies, it is of great importance that the single-particle detection efficiency e is as high as possible, as the overall efficiency scales with e over n, i.e. the power of the number of detected particles. Here we present measured absolute detection efficiencies for protons of several micro-channel plates (MCPs), including efficiency enhanced funnel MCPs. Furthermore, the relative detection efficiency for two-, three-, four-, and five-body fragmentation of CHBrClF has been examined. The funnel MCPs exhibit an efficiency of approx. 90 percent, gaining a factor of 24 (as compared to normal MCPs) in case of a five-fold ion coincidence detection.
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A system of two microchannel-plate detectors has been successfully implemented for tracking projectile-fragmentation beams. The detectors provide interaction positions, angles, and arrival times of ions at the reaction target. The current design is an adaptation of an assembly used for low-energy beams ($sim$1.4 MeV/nucleon). In order to improve resolution in tracking high-energy heavy-ion beams, the magnetic field strength between the secondary-electron accelerating foil and the microchannel plate had to be increased substantially. Results from an experiment using a 37-MeV/nucleon ${}^{56}$Ni beam show that the tracking system can achieve sub-nanosecond timing resolution and a position resolution of $sim$1 mm for beam intensities up to $5times10^{5}$ pps.
We report on the response of microchannel plates (MCPs) to single relativistic particles and to electromagnetic showers. Particle detection by means of secondary emission of electrons at the MCP surface has long been proposed and is used extensively in ion time-of-flight mass spectrometers. What has not been investigated in depth is their use to detect the ionizing component of showers. The time resolution of MCPs exceeds anything that has been previously used in calorimeters and, if exploited effectively, could aid in the event reconstruction at high luminosity colliders. Several prototypes of photodetectors with the amplification stage based on MCPs were exposed to cosmic rays and to 491 MeV electrons at the INFN-LNF Beam-Test Facility. The time resolution and the efficiency of the MCPs are measured as a function of the particle multiplicity, and the results used to model the response to high-energy showers.
In this paper, the detection efficiency of a large area neutron sensitive microchannel plate detector has been evaluated. A 6LiF/ZnS detector was employed as the benchmark detector, the TOF spectra of these two detectors were simultaneously measured and the energy spectra were then deduced to calculate the detection efficiency curve of the nMCP detector. Tests show the detection [email protected] meV thermal neutron is 34% for this nMCP detector.
A beam imaging detector was developed by coupling a multi-strip anode with delay line readout to an E$times$B microchannel plate (MCP) detector. This detector is capable of measuring the incident position of the beam particles in one-dimension. To assess the spatial resolution, the detector was illuminated by an $alpha$-source with an intervening mask that consists of a series of precisely-machined slits. The measured spatial resolution was 520$mu$m FWHM, which was improved to 413$mu$m FWHM by performing an FFT of the signals, rejecting spurious signals on the delay line, and requiring a minimum signal amplitude. This measured spatial resolution of 413$mu$m FWHM corresponds to an intrinsic resolution of 334$mu$m FWHM when the effect of the finite slit width is de-convoluted. To understand the measured resolution, the performance of the detector is simulated with the ion-trajectory code SIMION.
This paper first reviews non-traditional heat exchanger geometry, laser welding, practical issues with microchannel heat exchangers, and high effectiveness heat exchangers. Existing microchannel heat exchangers have low material costs, but high manufacturing costs. This paper presents a new expanded microchannel heat exchanger design and accompanying continuous manufacturing technique for potential low-cost production. Polymer heat exchangers have the potential for high effectiveness. The paper discusses one possible joining method - a new type of laser welding named forward conduction welding, used to fabricate the prototype. The expanded heat exchanger has the potential to have counter-flow, cross-flow, or parallel-flow configurations, be used for all types of fluids, and be made of polymers, metals, or polymer-ceramic precursors. The cost and ineffectiveness reduction may be an order of magnitude or more, saving a large fraction of primary energy. The measured effectiveness of the prototype with 28 micron thick black low density polyethylene walls and counterflow, water-to-water heat transfer in 2 mm channels was 72%, but multiple low-cost stages could realize the potential of higher effectiveness.
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