An electron tube includes a housing having a window having an electromagnetic wave transmitting property, an electron emission plate disposed inside the housing, the electron emission plate emitting electrons, and a holding member disposed inside the housing and configured to hold the electron emission plate and to apply a voltage to the electron emission plate. The electron emission plate has a first main surface and a second main surface facing each other. The holding member has a base portion being in contact with the first main surface, and a plurality of electron emission plate biasing portions which are in contact with an edge of the second main surface and are configured to elastically bias the electron emission plate to the base portion. The holding member is electrically connected to the second main surface through the plurality of electron emission plate biasing portions.

An electron tube includes a housing having a window having an electromagnetic wave transmitting property, an electron emission plate disposed inside the housing, the electron emission plate emitting electrons, and a holding member disposed inside the housing and configured to hold the electron emission plate and to apply a voltage to the electron emission plate. The electron emission plate has a first main surface and a second main surface facing each other. The holding member has a base portion being in contact with the first main surface, and a plurality of electron emission plate biasing portions which are in contact with an edge of the second main surface and are configured to elastically bias the electron emission plate to the base portion. The holding member is electrically connected to the second main surface through the plurality of electron emission plate biasing portions.

A magnetic photomultiplier tube (PMT) system, including a PMT. The PMT including a photocathode for converting an impinging photon to a photoelectron, an anode, and at least two or a series of oppositely facing pairs of dynodes, wherein each pair is spaced apart from an adjacent pair, a first electric field being generated intermediate at least one pair of oppositely facing dynodes and a second electric field generated intermediate at least one adjacent pairs of dynodes. The PMT system includes a magnetic field generated by a magnetic system, the PMT being positioned within the magnetic field.

A magnetic photomultiplier tube (PMT) system, including a PMT. The PMT including a photocathode for converting an impinging photon to a photoelectron, an anode, and at least two or a series of oppositely facing pairs of dynodes, wherein each pair is spaced apart from an adjacent pair, a first electric field being generated intermediate at least one pair of oppositely facing dynodes and a second electric field generated intermediate at least one adjacent pairs of dynodes. The PMT system includes a magnetic field generated by a magnetic system, the PMT being positioned within the magnetic field.

A dual polarity ion detector comprises: an entrance electrode disposed to receive ions and maintained at a reference voltage, V.sub.0; a first dynode maintained at a voltage, V.sub.1, that is negative relative to V.sub.0; a second dynode maintained at a voltage, V.sub.2, that is positive relative to V.sub.0; a shielding electrode disposed between the first and second dynodes and maintained at a voltage, V.sub.3; and an ion detector comprising an entrance aperture configured to receive first secondary particles from the first dynode and second secondary particles from the second dynode, the entrance aperture maintained at a voltage, V.sub.aperture; that is intermediate between the voltage, V.sub.1, and the voltage, V.sub.2. In some instances, the voltage, V.sub.3, may be equal to or approximately equal to the voltage, V.sub.0.

A dual polarity ion detector comprises: an entrance electrode disposed to receive ions and maintained at a reference voltage, V.sub.0; a first dynode maintained at a voltage, V.sub.1, that is negative relative to V.sub.0; a second dynode maintained at a voltage, V.sub.2, that is positive relative to V.sub.0; a shielding electrode disposed between the first and second dynodes and maintained at a voltage, V.sub.3; and an ion detector comprising an entrance aperture configured to receive first secondary particles from the first dynode and second secondary particles from the second dynode, the entrance aperture maintained at a voltage, V.sub.aperture; that is intermediate between the voltage, V.sub.1, and the voltage, V.sub.2. In some instances, the voltage, V.sub.3, may be equal to or approximately equal to the voltage, V.sub.0.

A photocathode including a substrate, a photoelectric conversion layer provided on the substrate and generating photoelectrons in response to incidence of light, and an underlayer provided between the substrate and the photoelectric conversion layer and containing beryllium, in which the underlayer has a first underlayer containing a nitride of beryllium.

A photocathode including a substrate, a photoelectric conversion layer provided on the substrate and generating photoelectrons in response to incidence of light, and an underlayer provided between the substrate and the photoelectric conversion layer and containing beryllium, in which the underlayer has a first underlayer containing a nitride of beryllium.

Certain embodiments described herein are directed to detectors and systems using them. In some examples, the detector can include a plurality of dynodes, in which one or more of the dynodes are coupled to an electrometer. In some instances, an analog signal from a non-saturated dynode is measured and cross-calibrated with a pulse count signal to extend the dynamic range of the detector.

Certain embodiments described herein are directed to detectors and systems using them. In some examples, the detector can include a plurality of dynodes, in which one or more of the dynodes are coupled to an electrometer. In some instances, an analog signal from a non-saturated dynode is measured and cross-calibrated with a pulse count signal to extend the dynamic range of the detector.