Posted in | Particle Detectors

Detection of Positive and Negative Ions with Capability of Measuring Large Proteins – Electron Multiplier R6985-80

When positive ions strike the conversion dynode it emits electrons in proportion to the quantity of input ions. The resulting electrons are then directed into the electron multiplier for secondary multiplication.

When negative ions strike the conversion dynode it emits positive ions in accordance with the amount of input ions. The resulting positive ions are then guided into the electron multiplier, where they receive energy from the variation in potential between the electron multiplier and conversion dynode and strike the electron multiplier’s first dynode, releasing electrons in proportion to the quantify of input positive ions. The emitted electrons are then directed to the second and successive dynodes for secondary multiplication.

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Parameter Description / Value Unit
Input Aperture Diameter F11 mm
Dynode Structure Conversion + box and linear focused
Number of Dynode Stages 19
First Dynode Material Al2O3
Total Built-in Resistance 17.15 MO
Operating Ambient Temperature -30 to +50 °C
Storage Temperature -80 to +50 °C
Polarity of Detected Ions Positive / Negative


Maximum Ratings

Parameter Value Unit
Anode to First Dynode Voltage -3000 V
Anode to Last Dynode Voltage 350 V
Conversion Supply Voltage ±10 kV
Operating Vacuum Level 1 x 10-2 Pa
Bake-Out Temperature (at 5 x 10-3 Pa) No baking
Average Anode Current* 10 µA
Operating Gain 1 x 108



Parameter Value Unit
Recommened Supply Voltage -1900 V
Gain (Typ.) 1 x 106
DC Linearity (Typ.) 5 µA
Dark Current (Max.) 1 PA
Rise Time (Typ.) 4.5 ns
Anode to All Other Electrode Capacitance 1.8 pF

NOTE: * Averaged over any interval of 30 seconds maximum. Figure 2: Dimensional Outline (Unit: mm)

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