SEM-6M-1 Channel Type Secondary Electron Multiplier with Extended Dynamic Range

SEM-6 channel multiplier is intended for operation in pulse counting mode, however most advanced channel SEMs shall operate as a part of mass spectrometers and in analogue mode which requires a larger output current to extend the linearity range.

The output current in channel-type SEMs maintains linearity up to a value equal to about 10% of the strip current value. This constraint is due to the fact that the strip current supplies the electrons needed to compensate for the positive charge generated after the electron avalanches leave the output of the channeltron, providing the secondary emission process. In turn, the strip current is determined by the channel resistance and increases with decreasing resistance.

The task of extending the dynamic range has been solved by developing the technology of thermal hydrogen reduction of channeltron glass to a lower resistance level and optimizing the channel length-to-diameter ratio.



Basic performance

Parameter Normal value
Gain at supply voltage Usupply ≤ 2500 V1×107,  min
Gain at supply voltage Usupply ≤ 3000 V1×108,  min
Dark count rate, counts/s1, max
Channel strip current at Usupply  = 3000 V, µA90, min
Linear output current, µA10% of strip current, min
Pulse height resolution at count rate of 1×103 to 5×103 count/s and Usupply corresponding to gain of 1×108 min0.9, max