Technical data

Overview 1
Front-end ion optics
Agilent 6200 Series TOF and 6500 Series Q-TOF LC/MS System Concepts Guide 41
which helps in creating a much denser and thinner ion beam
that passes through a narrower slit leading into the slicer and
pulser region.
In the TOF, ions enter a second octopole ion guide of similar
design to the first octopole but with a lower direct current
potential. This second octopole ion guide accelerates the ions
and prepares them for beam shaping. For TOF, the fourth
vacuum stage contains Octopole 2 and the beginning of the
slicer assembly.
To facilitate beam shaping, lenses focus the ions so that as they
pass through the 4th vacuum stage they will enter the
time-of-flight analyzer as a parallel beam. The more parallel the
ion beam, the higher the resolution in the resulting mass
spectrum. After the ions have been shaped into a parallel beam,
they pass through a slit opening into the fifth and last vacuum
stage where the time-of-flight analysis takes place.
Flight tube/Mass Analyzer (Vacuum stage 4 for 6224/6230 TOF)
(Vacuum stage 5 for 6220 TOF and 6500 Series Q-TOF)
Ion pulser The nearly parallel beam of ions passes into the time-of-flight
ion pulser. The ion pulser is a stack of plates, each one (except
the back plate) with a center hole. The ions pass into this stack
from the side just between the back plate and the first plate
with its center hole. To start the flight of the ions to the
detector, a high voltage (HV) pulse is applied to the back plate.
The applied pulse accelerates the ions through the stack of
pulser plates, acting as a rapid-fire ion gun.
Flight tube The ions leave the ion pulser and travel through the flight tube,
which is about one meter in length (see Figure 8). At the
opposite end of the flight tube is an ion “mirror”, which reflects
the ions that arrive near the end of the flight tube towards the
ion pulser. Because the ions entered the ion pulser with a
certain amount of forward momentum orthogonal to the flight
direction in the flight tube, they never return to the ion pulser,
but move to where the ion detector is mounted.
The ion mirror increases the resolving power of the instrument
by effectively doubling the flight distance (from one meter to
two meters) in the same space, and by performing a refocusing