Forward angle electron spectroscopy at the ESR

In fast heavy ion-atom collisions electron emission from the projectile permits high resolution studies of ionization and transfer. For corresponding experiments an electron spectrometer has been built at the jet target zone of the ESR. Located 90 cm downstream from the Gas target, it is built to detect electrons emitted during ion-atom collisions, having a velocity comparable to the ion beam velocity ve ≈ vi (i.e. cusp electrons). Electrons within a forward angle of up to 3.6◦ horizontally and 1.6◦ vertically with respect to the ion beam axis are collected, which gives a solid angle of ∆Ω ≈ 4 · 10−4. The spectrometer has already shown successful operation in a pioneering coincidence measurement of electrons and photons originating from the high energy end of electron-nucleus bremsstrahlung [1]. The electrons which are to be detected, are bent by a 60◦ magnet away from the ion beam, focused by a magnetic quadrupole lens, bent again by a 60◦ magnet, after which they pass momentum defining slits and hit a position sensitive MCP delay line detector. The electron optics (Figure 1) have been calculated using the GSI beam simulation softwareMIRKO [2].