5
Optimizing Your Method
Modifying an Automatic Tune
Thermo Scientific
TSQ 8000 Evo User Guide
99
d.
Electron Energy
—Indicates the energy of the electrons that come off the
filament.Lowering the electron energy will extend the lifetime of your filament.
•
Default
—Select this option to use the default electron energy, which is 70 eV.
•
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.
e.
Electron Lens Positive Voltage
—Allows 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 that you
selected on 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 eV, this value also changes. 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.
f.
Electron Lens Negative Voltage
.
•
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 that you
selected on the General tab.
•
Custom
—Select this option if you do not want to use the default value for the
tune. For the electron lens negative voltage, the default is –75 V. Tune with the
same value you are planning to use for your analysis. This value affects how well
the electrons are kept from entering the ion source when they are not supposed
to. If you change your electron energy from 70 eV, this value also changes.
Ensure this voltage is at least 5 V below the voltage applied to the filament.
Note
Avoid reducing the electron energy to less than 70 eV. The calibration
compound will not be sufficiently ionized for tuning or calibrating at low
electron energies.
Note
A custom electron energy can be selected in the instrument acquisition
method even if it is not used for tuning.
Содержание TSQ 8000
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