Effect of local electric fields on microchannel plate detection of incident 20 keV protons

Abstract

Absolute detection efficiencies of a microchannel plate detector for 0.5-5 keV neutrals Rev. Sci. Instrum. 81, 063301 (2010); 10.1063/1.3442514Current response characteristics of microchannel plates xray detector using synchrotron radiation (0.6-2 keV and 5-20 keV) Rev. Sci. Instrum. 59, 252 (1988);Relative electron detection efficiency of microchannel plates from 0-3 keV Rev.We present data demonstrating the influence of an applied electric field E oriented normal to the input surface of a microchannel plate ͑MCP͒ detector on the critical operating parameters of the detector, including the quantum detection efficiency, the spatial resolution, and pulse height distribution. The MCP detector response is characterized using 20 keV protons as the primary radiation. An applied electric field EϽϪ4 V/mm, where a negative value of E corresponds to a nearby object that is biased positive relative to the input surface, results in a high spatial resolution and a quantum detection efficiency that is approximately equal to the open area ratio of the MCP. An electric field Ϫ1ϽEϽ5 V/mm results in low spatial resolution, in which up to 32% of the measured signal appears as a localized noise that extends several millimeters from the point of ion impact, and a maximum quantum detection efficiency of approximately 0.87. Furthermore, a separate peak in the pulse-height distribution arises from ions striking the web of the MCP detector and has a much lower pulse magnitude than that of ions striking channels. For EϾ5 V/mm, the spatial resolution increases, and the quantum detection efficiency slightly decreases from its maximum value with increasing E. The characteristics of each of these electric field configurations are analyzed in the context of the yield and transport of secondary electrons created at the web of the MCP detector, and the results can be scaled to other ions and energies according to the secondary electron yield of ions striking the web.

Characterization of Efficiency Enhancement in Microchannel Plate Detectors

“…It is interesting to note that the results of Deconihout et al on the variation of efficiency with grid voltage [4] differ from those reported here and by Funsten et al [5] in two respects: the voltage required to achieve maximum eficiency and the efficiency decrease at high voltages. Deconihout et al required 50V before reaching peak efficiency, whereas we find a voltage of 5V is sufficient, and Funsten et al suggest an even lower voltage.…”

“…If the open area ratio of the detector is taken to be 65%, then the use of a biassed grid has increased this detection efficiency to 81%, which is a significant improvement. This is less then the maximum detection efficiency quoted by Deconihout et al [4], though similar to that seen by Funsten et al [5]. Again, the higher saturation achieved by the curved-channel MCPs allows more of the secondary electrons to be detected, leading to a higher overall efficiency.…”

The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) NASA Mission-of-Opportunity

“…An electric field is applied at the entrance surface of the MCP detector using a 70 line-perinch suppression grid biased at -12V and a +100 V bias on the front of the MCP detector. This field increases both the detection efficiency of the MCP and the spatial imaging resolution (Funsten et al 1996). In addition, the -12 V on the grid rejects secondary electrons at thermal energies generated anywhere inside the sensors other than the carbon foils (which are accelerated by the -2 kV of bias voltage).…”

Absolute detection efficiency of space-based ion mass spectrometers and neutral atom imagers

“…11 All of these quantities also depend on the energy and mass of an ENA. 11 All of these quantities also depend on the energy and mass of an ENA.…”