WITCH: a recoil spectrometer for β-decay

The WITCH experiment will measure the recoil energy spectrum of the daughter ions in β-decay. The main parts of the experiment are two Penning traps and a subsequent retardation spectrometer. The β-decays take place in the ion cloud in the decay trap. Since the ion cloud is in vacuum and due to the cylindrical structure of the trap, the recoiling daughter ions can leave the cloud and the trap without any significant energy loss and can be energy analyzed in the retardation spectrometer.