Single and multiple electron--impact ionization of Kr as a function of momentum transfer

Measurements of electron--impact ionization cross sections of Kr are being performed for an incident electron beam with energies between 100 eV and 500 eV, colliding with a Kr gas jet target. Scattered electrons are detected by means of a channeltron detector which can be positioned at angles ranging from 0\r{ } up to 60\r{ } with respect to the beam direction. An electrostatic spectrometer is used to determine the energy loss of the projectile. Ionized Kr is detected by a second channeltron detector. Signals coming from both detectors are measured in coincidence by means of a TDC. Producing time of flight spectra in which Kr$^{1+, 2+, 3+}$ can be distinguished. A pulsed extraction field for detecting the Kr ions has been used in order to reduce the background. Ionization yields as a function of momentum transfer will be presented.