The design is based on criteria that allow operation at very high beam intensities : an open structure of four large and powerful RF-cavities providing a high acceleration voltage, and a flat-top cavity operating at the third harmonic of the accelerating RF-voltage.
12.
Where ? is the deflection angle, k is a deflection constant, V p is the wire voltage ( + V p on one wire set and-V p on the other ), and V 0 is the ion acceleration voltage in eV . The deflection constant k can be calculated by
13.
The terms \ Delta I _ \ text { obj } / I _ \ text { obj } and \ Delta V _ \ text { acc } / V _ \ text { acc } represent instabilities in of the total current in the magnetic lenses and the acceleration voltage . \ Delta E / V _ \ text { acc } is the energy spread of electrons emitted by the source.
14.
The above effects can be approximated by a simple two-gaussian model where a perfect point-like electron beam is broadened to a superposition of a Gaussian with a width \ alpha of a few nanometers to order tens of nanometers, depending on the acceleration voltage, due to forward scattering and a Gaussian with a width \ beta of the order of a few micrometers to order tens due to backscattering, again depending on the acceleration voltage but also on the materials involved:
15.
The above effects can be approximated by a simple two-gaussian model where a perfect point-like electron beam is broadened to a superposition of a Gaussian with a width \ alpha of a few nanometers to order tens of nanometers, depending on the acceleration voltage, due to forward scattering and a Gaussian with a width \ beta of the order of a few micrometers to order tens due to backscattering, again depending on the acceleration voltage but also on the materials involved:
