Posted in | Particle Detectors

Compact Electron Multiplier for Positive Ion Detection - R8811

The problem of limited installation space for quadrupole mass spectrometers has been addressed by downsizing them. This downsizing trend is expected to increase even more in the coming years. To achieve this, reducing the size of quadrupole electrodes and ion sources is just not enough. It is also essential to have small ion detectors.

For this purpose, a compact ion detector has been developed by Hamamatsu. The novel ion detector overcomes the performance barriers on traditional electron multipliers and will provide the most suitable results to meet users’ requirements.

Structure

Electron Multiplier R8811 features an off-axis structure and a Faraday cup, required for ion detection in Quadrupole mass spectrometers that can make accurate measurements over a broad dynamic range with a superior signal-to-noise ratio. The structure also consists of a voltage divider that is a crucial component for discrete type electron multipliers. The simple wiring of the high voltage, the Faraday cup, and the signal helps achieve reliable operation without the need for the addition of other components.

The multiplication of the ions released by the Quadrupole takes place when they are being focused and deflected by the electron lens formed by the combination of the electron multiplier electrodes, the ion deflection electrodes, and the Faraday cup. Special 3D simulation of electron and ion trajectories is used to design the layout of the electron multiplier electrodes, the ion deflection electrodes, and the Faraday cup. This layout enables highly efficient detection of the input ions.

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Specifications

General

Parameter Description / Value Unit
Input Aperture Diameter F3 mm
Dynode Structure Circular cage
Number of Dynode Stages 13
First Dynode Material AI2O3
Total Built-in Resistance 13 MO
Operating Ambient Temperature -30 to +50 °C
Storage Temperature -80 to +50 °C
Polarity of Detected Ions Positive

Maximum Ratings

Parameter Value Unit
Anode to First Dynode Voltage -2000 V
Anode to Last Dynode Voltage 200 V
Faraday Cup Voltage 200 V
Operating Vacuum Level 1 x 10-2 Pa
Bake-Out Temperature (at 5 x 10-3 Pa) 350 °C
Average Anode Current* 10 µ A
Operating Gain 1 x 107

Characteristics

Parameter Value Unit
Recommened Supply Voltage -1500 V
Gain (Typ.) 1 x 105
DC Linearity (Typ.) 5 µA
Dark Current (Max.) 1 pA
Rise Time (Typ.) 1.6 ns
Anode to All Other Electrode Capacitance 0.75 pF

NOTE: * Averaged over any interval of 30 seconds maximum.

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