Electron multiplier for mass spectrometer

A secondary electron multiplier, comprising:

• a conversion dynode for emitting a secondary electron in response to an incident ion;
• a plurality of dynodes configured to have multi-stages from second to final stages for receiving the secondary electron;
• a first voltage applying device configured for applying a first negative voltage to the conversion dynode and sequentially dividing the first negative voltage to apply to each of the second-stage and subsequent dynodes, the secondary electron multiplier being configured to sequentially multiply the emitted secondary electron by the second-stage and subsequent dynodes;
• and
• a second voltage applying device separate from the first voltage applying device and configured for:
• applying a second negative voltage to independently bias a second negative voltage-applied dynode, wherein the second negative voltage-applied dynode is any of the second-stage and subsequent dynodes;
• and
• changing the second negative voltage to increase a secondary electron emission efficiency at the second negative voltage-applied dynode and a dynode subsequent thereto, and recover from a reduction of the amplification gain caused by deterioration of the electron multiplier, by increasing an absolute value of the second negative voltage.

A secondary electron multiplier, comprising:

• a conversion dynode for emitting a secondary electron in response to an incident ion;
• a plurality of dynodes configured to have multi-stages from second to final stages for receiving the secondary electron;
• a first voltage applying device configured for:
• applying a first negative voltage to the conversion dynode and sequentially dividing the first negative voltage to apply to each of the second-stage and subsequent dynodes, the secondary electron multiplier being configured to sequentially multiply the emitted secondary electron by the second-stage and subsequent dynodes;
• and
• changing the first negative voltage to increase an ion/electron conversion yield, by increasing an absolute value of the first negative voltage;
• and
• a second voltage applying device separate from the first voltage applying device and configured for:
• applying a second negative voltage to independently bias a second negative voltage-applied dynode, wherein the second negative voltage-applied dynode is any of the second-stage and subsequent dynodes;
• and
• changing the second negative voltage to increase a secondary electron emission efficiency at the second negative voltage-applied dynode and a dynode subsequent thereto, and recover from a reduction of the amplification gain caused by deterioration of the electron multiplier, by increasing an absolute value of the second negative voltage.