HP 5973, Руководство по оборудованию

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7 Analyzer
Ion source
221
Filament care
Like the filaments in incandescent light bulbs, the ion source filaments will eventu-
ally burn out. Certain practices will reduce the chance of early failure:
• If you have an optional HP 59864B Gauge Controller, use it to verify that the
system has an adequate vacuum before turning on the analyzer, especially after
any maintenance has been performed.
• If you are controlling your MSD from the Edit Parameters screen, always select
MSOff before changing any of the filament parameters.
• When setting up data acquisition parameters, set the solvent delay so that the
analyzer will not turn on while the solvent peak is eluting.
• When the software prompts
Override solvent delay?
at the beginning of a run,
always select
NO
.
• Higher emission current will reduce filament life.
• Lower electron energy will reduce filament life.
Magnet
The field created by the magnet directs the electrons emitted by the filament into
and across the ionization chamber. The magnet assembly is a permanent magnet
with a charge of 350 gauss in the center of the field.
Repeller
The repeller forms one wall of the ionization chamber. A positive charge on the
repeller pushes positively-charged ions out of the source through a series of
lenses. The repeller voltage is also known as the ion energy, although the ions only
receive about 20% of the repeller energy. The repeller voltage can be varied from
0 to
+42.8 V dc. Some tune programs use a fixed repeller voltage. Others ramp the
repeller voltage to find the optimum setting.
• Setting repeller voltage too low results in poor sensitivity and poor high mass
response.
• Setting repeller voltage too high results in precursors (poor mass filtering) and
poor low mass resolution.