Hardware manual

Maintenance 4
Agilent 7500 Series ICP-MS Hardware Manual 4-129
Maintaining the Electron Multiplier
The detector used in the Agilent 7500 is an Electron Multiplier (EM).
The EM converts incident ions into an electric current and amplifies the
current so the ion signal can be measured. As the voltage applied to the EM
increases, the amplification factor (gain) of the current also increases. The EM
outputs electric currents in pulses corresponding to each of the incident ions.
Replacing the EM
There are two EM voltage parameters, Analog HV and Pulse HV.
The EM will need replacing when the Analog HV reaches about 3300 V or the
Pulse HV reaches about 1800 V after adjusting the EM voltage.
To replace the EM, complete the following steps:
1 Set both Analog HV and Pulse HV to 0 V
Select Instrument>>Tuning from the Top menu to display the tuning
window.
Set 0 V into both Analog HV and Pulse HV in the tuning parameters.
2 Shut down the Agilent 7500.
See Chapter 3, “Startup, Shutdown and Status” in this manual.
CAUTION
The EM is designed to be used under high vacuum and rapidly deteriorates if it is
contaminated with organic substances or left in an environment with high humidity.
Always
wear clean gloves when handling the EM, complete the necessary work in the
open as quickly as possible and place it under a vacuum as soon as possible. If the EM
is to be stored for a long time in the open, place it in a desiccator.
NOTE
To adjust the EM voltage, refer to the ‘Tuning’ chapter in the Agilent 7500 Series ICP-MS
Tuning and Application Handbook.
WARNING
The Agilent 7500 has many interlocks to protect the system and the operator, we
suggest you switch off the power before working on the system.