Hardware manual

Technical Information 6
Agilent 7500 Series ICP-MS Hardware Manual 6-15
Einzel Lens
The purpose of this lens assembly is to focus the ions that are accelerated by
the extraction lenses.
The Einzel lens consists of three lens plates. The same voltage is applied to the
first and the third lens plates (E1 and E3) to get the same potential at the
entrance and exit of the lens, - 100V, it should not normally be adjusted during
tuning. Changing the voltage of the middle lens, the Einzel 2 lens, affects the
focal point of the ions.
Omega Lens
This lens block consists of 5 lenses; Omega bias, Omega (+), Omega (- ), QP
focus and Plate bias. The purpose of this lens assembly is to separate photons
and ions and to steer the ions onto the Q- pole.
The Omega (+) and (- ) lenses are placed between two Omega bias lens plates.
The same voltage is given to the Omega bias lenses. In general, the Omega bias
must be used at voltages more positive than - 40V, e.g. - 20 V. The more negative
the voltage, the higher the sensitivity that can be obtained, but the background
signal might also be increased.
The Omega (+) and (- ) lenses consist of two pairs of crescent- shaped lenses;
the Omega (+) Front and the Omega (+) Back which are alternately placed and
driven at the same voltage, and the Omega (- ) Front and Omega (- ) Back
which are placed alternately and driven at the same voltage. The ions are bent
by the Omega (+) Front and the Omega (- ) Front toward the Omega (- ) Front
direction, then the ions are bent again by the Omega (- ) Back and the Omega
(+) Back toward the Omega (- ) direction. While the ions are bent, photons
remain unaffected and hit the Omega bias back plate (Figure 132). This is
sometimes called the off- axis ion lens system. The Omega lens bends the
focused ions and steers them into the Q- pole, so the loss of ions is minimized.