Query: Microchannel plate ion feedback

title: The effect of high velocity dust particle impacts on microchannel plate (MCP) detectors
abstract: The detection efficiency and durability of a microchannel plate (MCP) detector to direct impacts of high velocity dust particles is investigated experimentally. A new type of in situ time of flight cosmic dust analyzer instrument has been developed, where the ion detector is exposed to occasional impacts of cosmic dust particles. The dust accelerator facility operated at the University of Colorado is used to directly measure the effect of dust impacts on a commercial, off the shelf microchannel plate (MCP) detector. The MCP is exposed to approx. 480 dust particle impacts from wide size and velocity ranges of 0.05 1.6 mm radii and 2 35 km/s, respectively. The dust impact events are registered with 96% efficiency. Of these, 57% of the output signals are single charge pulses, and 43% are more complex signals that suggest ion feedback mechanisms within the detector. For all dust detection events, the output charge pulse is significantly larger than those from the detection of single ions or photons. The gain of the MCP detector shows no apparent degradation after the bombardment. In the investigated size/velocity range, the dust particles do not pose a risk of damaging the MCP. Scanning electron microscope images show that the impact generated craters are small, on the order of the size of the impacting particles. The performed measurements and the extrapolation of the results to the worst case expected to occur for the duration of a spaceflight mission indicate that MCP detectors require protection from dust impacts in order to reduce the risk of detector damage for these types of dust analyzer instruments, and a mechanism for providing protection is described.

title: Study on the FOV quality test of the micro channel plate with anti ion feedback by ultraviolet photoelectric method
abstract: A new method of FOV quality test of the anti ion feedback microchannel plate was introduced, Ultraviolet Photoelectric Method, and the principle and the structure of the device were given. The test principle and device structure are given. The problems in the testing, including the mutual relationship between the UV transmittance and the quantum efficiency of the Au cathode, and the influence of the photoelectrons on the field of view caused by the UV excited MCP were discussed. The advantages of the UV photoelectron method in the field defect detection were compared. Which provided a basis for the application of Ultraviolet Photoelectric Method and proves the research direction.

title: A Microchannel Plate with Curved Channels: An Improvement in Gain, Relative Variance and Ion Noise for Channel Plate Tubes
abstract: Publisher Summary This chapter describes an improvement in gain, relative variance, and ion noise for channel plate tubes in an microchannel plate (MCP) with curved channels. MCPs have reached a rather high level of quality and they are used in second generation image tubes as well as in some sophisticated devices, such as high speed cathode ray tubes and photomultipliers. A means of limiting ion feedback has been devised. This involves curving all the channels of the MCP and has been made possible by the development of a new technology. The channel curvature overcomes ion feedback limitations and offers some distinct improvements over the straight MCP in electron gain, the statistical fluctuation of gain, the background noise level, and the lifetime of the tube. The very sharp resolution in gain is demonstrated by the multielectron distribution curves. These were obtained by exposing the photocathode to very faint light pulses. It is found that the background noise of the curved MCP has been measured for the experimental photomultiplier by removing the photocathode voltage.

title: Analysis and modeling on noise factor of microchannel plate
abstract: The Microchannel plate (MCP) is the main noise source of low level light (LLL) image intensifier. Material and the whole manufacturing process of MCP have great impact on the noises of MCP. In this paper, based on the physical mechanisms of MCP, noises of MCP are classified scientifically. By using the data obtained from the actual production and the process test, the regression equation of the noise figure of MCP is derived, and the theoretical model of MCP noise figure is established, including the background noise figure model caused by the dark current of the MCP primarily about the time of the alkali corrosion technic, the ion feedback induced noise figure model caused by the patterns of the MCP channel wall primarily about the time and temperature of the hydrogen reduction technic, and the electronic scattering noise figure model caused by the open area ratio of the MCP primarily about the time of the alkali corrosion technic. Guided by the theoretical model of noise figure, the methods of suppressing noises of MCP are obtained and the technics are optimized. Taking advantage of the new techniques, the noise figure of the third generation MCP has been reduced to below 1.8.

title: Microchannel plate photon counting detector in UV range
abstract: A Microchannel Plate(MCP) photon detector was developed to detect the 30.4 nm radiation in a plasma layer of the earth.By changing voltages,temperatures and other parameters,the variations of the dark noise and resolution for the MCP detector were compared.The results indicate that the dark noise of the detector comes from the ion feedback of residual gas and the thermal noises mainly.Therefore,to reduce the dark noise,the microchannel should be preprocessed by removing residual gases and the detector could not work at a high temperature state.After preprocessing at the room temperature,the dark noise counting rate of the detector has reduced to 0.34 count/s*cm2.Furthermore,the temperature has a little effect on the resolution of the detector,and the resolution dependents on the variances of voltage or counting rate obviously.With different resist pressure abilities for different MCPs,it demonstrates that the proper voltage or counting rate can provide a better resolution.

title: Fabrication of a bulk conductive glass microchannel plate
abstract: Extension of Microchannel Plate (MCP) to a bulk conductive substrate was considered to be an effective approach to eliminate ion feedback problem, and a vanadium iron lead phosphate glass had been identified can be tailored to have appropriate volume conductivity and suitable for MCP fabrication. In this paper, a new reformulated vanadium iron lead alumina phosphate glass was used to fabricate a bulk conductive glass MCP, the fabrication process is in the same way as the conventional lead silicate glass MCP fabrication, but in the absence of a hydrogen firing treatment, although it was succeed in fabricating some experimental samples of 25mm diameter full active area MCP with 10mm pore diameter and 40:1~60:1 length to diameter ratio, the experimental sample also demonstrated its bulk conductivity and certain secondary electron emission property, but its gain is very low, especially its mechanical strength is insufficient. The physical and chemical properties of this vanadium iron lead alumina phosphate glass, and the performance and behavior of this glass during the bulk conductive glass MCP fabrication process, as well as its experimental sample test results were detail described.

title: Ion feedback suppression using inclined MCP holes in a "single MCP+micromegas+pads" detector
abstract: We show that the ion backflow to photocathode can be completely suppressed if one uses inclined MCP holes in the presence of a magnetic field. The inclined hole angles are chosen to be aligned with the Lorentz electron angle allowing the electron transmission and amplification, while positive ions, traveling along a different angle, are caught on the MCP hole walls. The detector under investigation is a new gaseous detector structure based on a tandem of two parts, a single MCP (microchannel plate) a micromegas with pad readout. We are aiming to develop a gaseous photon detector with the Bialkali photocathode, however, one could use some ideas in the paper for other types of detectors.

title: Ion feedback suppression using inclined MCP holes in a "single MCP+Micromegas+pads" detector
abstract: We show that the ion backflow to photocathode can he completely suppressed if one uses inclined MCP holes in a presence of magnetic field. The inclined hole angles are chosen to be aligned with the Lorentz electron angle allowing the electron transmission and amplification, while positive ions, traveling along a different angle, are caught on the MCP hole walls. The detector under investigation is a new gaseous detector structure based on a tandem of two parts, the first one is a single MCP (microchannel) plate, and the second one is a Micromegas with pad readout. The paper compares relative merits of gaseous and vacuum based MCP detectors. We are aiming to develop a gaseous detector with the bialkali photocathode.

title: Innovative microchannel plate with reformulation of composition and modification of microstructure
abstract: The signal to noise ratio (SNR) and mean time to failure (MTTF) are two important attributes to describe the performance and operation life of an image intensifier. The presents of the ion barrier film (IBF) in Gen. III image intensifier, which used to suppress MCP's ion feedback, while dramatically improve the MTTF but significantly reduce the SNR, so more completely diminishing the ion poisoning source within the channels of MCP are crucial for improved Gen. III; image intensifier to thinned thickness IBF and achieving this two conflicting attributes promotion simultaneously. This research was originally initiated to develop a MCP with glass composition redesigned specially for GaAs photocathode image intensifier, proved which can be imposed an exceedingly intensive electron bombard degassing but without suffering a fatal gain degrade, and had achieved significantly improved SNR of Gen. III image intensifier but with a short distance to meet the lifetime success, so that our research work step forward to intent upon the restriction of ion poisoning source formation within the MCP substrate, we reformulated the MCP glass composition, and modified the microstructure of this MCP glass substrate though a glass crystal phase transition during the MCP fabricate heating process, we present an innovative MCP based on a glass ceramic substrate, with reformulated composition and close linked network microstructure mix with many of nanometer size crystal grains, provide this MCP with sustainable high gain, lower ion feedback and less outgasing performance, this glass ceramic MCPs are assembled to Gen. III image intensifiers which results showing promoting both the MTTF and SNR of Gen. III image intensifier.

title: Performance of Microchannel Plates with Al2O3 Ion Barrier Film after High Temperature Degassing
abstract: The ion barrier film of microchannel plate (MCP) plays a most important role in the third generation low light level image intensifier to prevent the feedback of positive ions, protect the photocathode and prolong the operating life of image intensifier. In this paper, the influence of high temperature degassing on the performances of the ion barrier film and the MCP itself were investigated by the experiments. The high temperature degassing and the corresponding measurement system of MCP were shown, the detailed technology process was given, and the changes of the ion barrier film's morphology and the MCP's electrical performance after high temperature degassing were compared. For a MCP with an ion barrier film, it was found that the electron gain decreased, the bulk resistance increased, the grain size of the ion barrier film increased and the dead voltage decreased after high temperature degassing.