Electron Multipliers - Glossary

Analog modeMode of electron multiplier operation where the output is measured as a continuously variable current which is directly proportional to the input.
   
Anode Last and most positive electrode of an electron multiplier from which the signal is drawn (also called the collector).
   
Bias Current The DC current that flows through the dynode resistor chain of the multiplier. The bias current is supplied by the multiplier high voltage.
   
CDEM (or CEM, or channel multiplier) Type of electron multiplier which uses a small glass tube (or channel) to perform the multiplication process.
   
Channel Multiplier see CDEM.
   
Dark Current The signal from the output of the multiplier in the absence of any input signal.
   
Detector Alternative name for an electron multiplier.
   
Discrete-dynode Type of electron multiplier which uses a series of discrete electrodes to perform the multiplication process.
   
Dynamic Range Range of output currents over which the electron multiplier will give a linear response to an input signal.
   
Gain Ratio of the multiplier output current to the input ion current.
   
HED (High Energy Dynode) High voltage electrode used for conversion of ions to electrons. It is particularly useful for detection of high mass ions.
   
Life Time over which a multiplier can operate efficiently as an ion detector. Multiplier life depends on many factors such as usage and environmental conditions. Typical life of an ACTIVE FILM Multiplier™ in an average application is 1-2 years (but can be as long as 3-4 years).
   
Linearity Ability of the multiplier to respond to an input ion current with a current at the output which varies linearly with the input.
   
Negative Ion Mode Operating mode of the mass spectrometer (and electron multiplier) in which negatively charged ions are analysed and detected by the electron multiplier.
   
Operating Voltage The high voltage applied to the electron multiplier to obtain the required performance.
   
Positive Ion Mode Operating mode of the mass spectrometer (and electron multiplier) in which positively charged ions are analysed and detected by the electron multiplier.
   
PPINICI Pulsed Positive Ion Negative Ion Chemical Ionisation. Uses a set of re-useable conversion dynodes (originally supplied by Finnigan) for the detection of both positive ions and negative ions.
   
Pulse Counting Mode Mode of electron multiplier operation where the output is measured by counting the individual pulses present at the multiplier output. Each pulse represents one detected ion.
   
Sensitivity At a set gain, the sensitivity of an electron multiplier is the level of output for a given amount of input signal (not to be confused with gain which is the multiplier's amplification).
   
Signal-to-Noise
 The multiplier signal-to-noise is the ratio of the output signal to the background noise detected (or picked up) by the multiplier.