Large-aperture system for high-resolution 180° electron scattering

A new system for 180° electron scattering has been put into operation at the superconducting Darmstadt linear electron accelerator S-DALINAC, using a large-aperture QCLAM spectrometer. The properties of the spectrometer allow for high-resolution 180° measurements with a larger momentum acceptance than that of any previous 180° system, together with unprecedented capabilities for solid angle definition as well as for alignment and monitoring of the system. The large angular acceptance and the precise angular definition allow the solid angle acceptance of the system to be specified by software cuts after the data have been taken, permitting the appropriate balance between maximum statistical precision and maximum longitudinal-to-transverse suppression ratio.