Absolute efficiency of a two-stage microchannel plate for electrons in the 30–900 eV energy range

Abstract

We report on an apparatus able to measure the absolute detection efficiency of a detector for electrons in the 30 - 900 eV range. In particular, we discuss the characterisation of a two-stage chevron microchannel plate (MCP). The measurements have been performed in the LASEC laboratory at Roma Tre University, whit a custom-made electron gun. The very good stability of the beam current in the fA range, together with the picoammeter nominal resolution of 0.01 fA, allowed the measurement of the MCP absolute efficiency ε. We found an ε = (0.489±0.003) with no evident energy dependence. We fully characterised the MCP pulse shape distribution, which is quasi-Gaussian with a well visible peak above the noise level. We measured a 68% variation of the average pulse height between 30 and 500 eV. Furthermore, with a deeper analysis of the pulse shape, and in particular of the correlation between pulse height, area and width, we found a method to discriminate single- and multi- electron events occurring within a 10 ns time window.

Transmission Through Graphene of Electrons in the 30 - 900 Ev Range

“…The source of electrons, for both the transmission and the EELS measurements, is a custom-made monochromatic electron gun with an energy resolution of 45 meV [28]. The electron energy can be tuned within the 30-900 eV range.…”

“…The size of the beam is ∼0.5 mm (full width at half maximum) within this energy range. Details about the method for the beam size evaluation can be found in [28,29]. Therefore, the graphene transparency is measured as an average on several TEM grid holes (6.5 μm nominal diameter).…”

“…The energy scan is repeated with the sample mounted in front of the FC, thus measuring the transmitted current through the grid holes with or without the graphene. This measurement is performed by choosing the beam position at each energy step in order to match the region in which the coverage is evaluated (similar positioning procedure can be found in [28,29]). Finally another scan on the FC is performed, where the direct beam current is measured again.…”

Heisenberg's uncertainty principle in the PTOLEMY project: a theory update

“…, is m ν < 0.8 eV at 90% C.L., as obtained by the KATRIN experiment using gaseous molecular tritium [13,14]. As far as the cosmic neutrino background is concerned, instead, one could in principle detect it via the process of neutrino capture [15][16][17][18][19][20][21][22][23]. In this case, if the process happens in vacuum, the energy of the emitted electron is expected to be larger than the endpoint by twice m ν .…”

Implementation and optimization of the PTOLEMY transverse drift electromagnetic filter

“…For the PTOLEMY experimental program, a reversed filter provides a new tool to study transverse drift filter operation without the complexities of interfacing with the RF. Developments have also been made on the readout side to allow for filter testing without the microcalorime- ters in place, such as by using a two-stage microchannel plate [25]. However, these do not replace the need to benchmark the filter performance with an isotropically emitted electron conversion line source, as is typical for tritium endpoint spectrometers [26].…”