User`s guide

Voyager-DE™ (Delayed Extraction™) Technology
Voyager
™
Biospectrometry
™
Workstation User’s Guide 1-15
1
Velocity focusing Delayed Extraction technology facilitates tuning modes, when
the time-of-flight of an ion is independent of the initial velocity.
After ions are released from the sample surface, their position
in the ion source is correlated with their initial velocity.
When the extraction voltage pulse is applied, initially slower
ions acquire slightly higher energy from the accelerating field
than initially faster ions. By careful tuning of variable-voltage
grid in the source and the delay time applied to
acceleration, slow and fast ions of the same mass reach the
detector plane at the same time. This is referred to as “velocity
focusing”.
Linear mode Figure 1-9 and Figure 1-10 illustrate velocity focusing in linear
mode. Ions are focused at the detector.
Figure 1-9 Velocity Focusing of Ions in Linear Mode—
Field Free Expansion and Extraction
Detector
Broad velocity distribution
of laser desorbed ions
v
0
slow
fast
Number
of ions
+
+
Voltage (
U
)
Ion source Flight tube
Field-free expansion - no extraction
Ions generated by the laser pulse drift
into a field free region of the ion source
and separate based on their initial
velocity gained from the plume expansion.
Detector
U
slow
> U
fast
Voltage (
U
)
+
+
Extraction
After a well-defined delay time an
extraction pulse is applied in the
ion source so the initially slower
ions will be accelerated to slightly
higher energy than the initially
faster ones.
PB100791