These pages cover different aspects designing a VPPEM instrument
The VPPEM can be thought of as having three main subsections
with associated pumping stacks.
1. Photoelectron energy analysis and image formation,
consisting of a concentric hemispherical analyzer (CHA),
and image forming electron lenses.
2. A superconducting magnet and cooling system (cold head).
The magnet is the initial optical element in forming the
3. A sample introduction system with sample preparation
and a long throw manipulator for sample positioning.
A side elevation drawing of the main parts
of the VPPEM system is shown here.
The three core VPPEM subsections are supported on
three aluminum extrusion frames.
The support frame for the analyzer and sample
preparation subsections have levelling caster feet for
The frame is blocked and shimmed in place after
positioning with anchor bolts to the floor.
The frame for the magnet cold head (a Sumitomo
Gifford-McMahon helium refrigerator) rests on the floor
with antivibration pads.
The sample introduction and preparation subsection consists of long travel sample
manipulator with a sample mount, a side entry 6” entry port, a chamber with ports
for attachment of an ion cleaning gun, dosing, and evaporation sources.
The system is protected from over pressure from the gas supplies by a bursting
The sample introduction system pumping consists of a 300 l/s ion pump, a turbo
pump, ion gauge, vacuum safety interlocks, gate valves, and a roughing port. The
sample introduction system can be isolated from the microscope by a manually
operated gate valve.