Optimization of hemispherical electrostatic analyzer manufacturing with respect to resolution requirements spaceweb@oulu.fi - last update: 27 July 2001 (JV)

Electrostatic analyzers with different geometries have been used extensively in space plasma investigations. When the energy resolution requirements are such that dE/E ~ 10 % the instrument is rather simple to design and to manufacture. However, when an energy resolution of ~ 1 % is required, the manufacturing costs show a rapid increase. For analyzers with an energy resolution of ~ 10 % the calibration can also be used to correct for manufacturing errors when they appear. In this paper, it has been shown that to reach an energy resolution dE/E = (1.6 ± 0.2) % using a hemispherical electrostatic analyzer with outer and inner radii 101.25 mm and 98.75 mm respectively and plate thickness 0.4 mm, an accuracy of 25 µm of the alignment of one hemisphere with respect to the other is sufficient. It has also been shown that the effect on the energy resolution of an indentation of the surface of one of the conductors, can be neglected as long as its depth is less than ~100 µm. Larger indentations can easily be detected at the manufacturing process. For each case considered, a maximum loss of transmitted particles with respect to the transmission of an ideal instrument has been defined as 10 %. Similarly it has been specified that the deviations in the distributions of entrance angles of transmitted particles are less than 0.1 degree.