Reduced ion feedback in an electron multiplier (EM) is achieved by applying a higher than normal bias voltage to the EM and degassing the EM with a relatively high concentration of self-generated particles as a result of the applied bias voltage.

Electron multipliers with reduced ion feedback

This electron multiplier uses either a single microchannel or a multiple assembly. The internal walls of the channel have the property of secondary emission and their resistivity varies by a factor of 1.5 to 10 relative to the average linear resistivity along the channel. When the value is low at the input (e) then the input field will be weaker and the parasitic electron emission will also be low giving a low signal to noise ratio. When this condition is reversed at the output (s) then a low electron dispersion is obtained.

Vincent Chalmeton

Papers

Microchannel electron multiplier - uses varying wall resistivity for low signal to noise ratio or low emission dispersion