In between a velocity selector (3) is placed. The dimensions of the velocity selector are identical to those of the selector developed by Trujillo et al..
The theory (Hostettler and Bernstein) for this type of selector can easily be extended to beams with an angular spread due to the finite width of the collimating slits (see also Dash and Sommers).
This leads to a value of the velocity spread
in which v0,vmax and vmin are respectively the nominal, maximal and minimal velocity, selected at a certain angular velocity.
The selector was carefully aligned by a cathetometer and this alignment was checked by measuring the velocity distribution of a potassium beam produced by a thermal oven, the temperature of which was measured by platinum resistors.
The accuracy of the nominal energy is determined by the
alignment and calibration of the velocity selector. This is
estimated to be 1%, much less than the energy spread.
See the resulting error