Thermo Scientific ISQ, Руководство пользователя

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7
Optimizing Your Method
Modifying an Automatic Tune
92 ISQ User Guide Thermo Scientific
– Custom —Select this option if you want to use a value other than 50 μA when
increasing or decreasing the sensitivity of the instrument. For the emission
current, the default is 50 μA. You should tune with the same value you are
planning to use for your analysis. The use of emission currents above 100 μA
may lead to the generation of too many ions in the source, lower filament
lifetime, and cause unnecessary source degradation.
• Electron Energy —Use this field to indicate the energy of the electrons that come off
the filament and to extend the lifetime of your filament.
– Default —Select this option to use the default electron energy, which is 70 V.
– Tune File —Select this option to use the value in the tune file you selected in the
General tab.
– Custom —Select this option to set the energy of the electrons emitted by the
filament. For example, you could change the voltage if you wanted to change the
ionization efficiency and fragmentation of the sample. This is typically set to
70 V because the standard EI libraries are based on 70 eV electron beams.
• Electron Lens Positive Voltage —Use this field to allow the electrons to enter the ion
volume.
– Default —Select this option to use the default electron lens positive voltage,
which is 15 V.
– Tune File —Select this option to use the value used in the tune file you selected
in the General tab.
– Custom —Select this option if you do not want to use the default value for the
tune. For the electron lens positive voltage, the default is 15 V. You should tune
with the same value you are planning to use for your analysis. This value affects
the focusing of the electron beam into the source. If you change your electron
energy from 70 V, this value will also change. This voltage must always be at least
45 V above the voltage applied to the filament. The voltage applied to the
filament is the same number, but the opposite sign, of the electron energy.
• Electron Lens Negative Voltage . This field is used to allow the electrons to enter the
ion volume.
– Default —Select this option to use the default electron lens negative voltage,
which is -75 V.
– Tune File —Select this option to use the value used in the tune file you selected
in the General tab.
Note Reducing the electron energy to less than 70 eV is not recommended. The
calibration compound will not be sufficiently ionized for tuning or calibrating at low
electron energies.