Analyzer Simulations

A high resolution electron detector on the main payload will look along the field line.

Design Goals:

Tight energy resolution
High deltaV to energy factor to allow fast sweep to 2KV with low sweep voltage
G0 larger than HEEPS-E (1.4e-4) to allow short accumulation times
Angular acceptance at 6 to 8 deg off axis to allow for payload misalignment
Focus onto 25-mm MCP

The toroidal shape gives a very high G0 and tight energy resolution but it also has narrow angular acceptance.

Increasing the toroid large radius opens up the angular acceptance in one dimension (YZ plane). The limit is a cylindrical analyzer which can have a wide acceptance in one dimension. For a large radius, only a segment of the toroid fits in the payload but a segment can still have a large G0 compared to HEEPS.

Entrance Deflector

An input deflector can be used to expand the angular acceptance in the XY plane. A positive voltage on deflector plates (green) at the entrance slit will cause off-angle paths entering near the edge to be deflected into the analyzer.

Parallel paths near the edge will be deflected out of the analyzer so the response to a parallel beam is decreased.

Simulation Runs

These plots show particle trace simulation results for a few different analyzer geometries and deflection voltages. The first panel shows the energy acceptance summed over all angles. The second panel shows the summed angular acceptance in the XY and YZ planes. The skew is the mean acceptance angle in the XY plane. The third panel shows the relative sensitivity vs. both input angles. A reference circle shown is at 6 degrees.