Neutrons colliding with atomic nuclei can transfer all of its energy, or parts of it. Neutrons that are scattered multiple times could induce signals in multiple places in a detector array, and this is exploited in TOFOR.

In TOFOR the neutrons enter through a small scintillation detector at the bottom. There they can be scattered on a proton, and the recoil gives a signal in the detector. The neutron itself can travel on to the upper detector array, resembling an umbrella.

The detector electronics selects the coincidences between an event in the bottom detector and a signal from one of the upper scintillators. The time between the first and the second pulse gives a measure of the neutron energy. The principle is time of flight spectrometry.

TOFOR has excellent time resolution, and also high efficiency since many of the neutrons entering the instrument give signals that can be used in analysis. TOFOR is used to study fast ions and how they interact with instabilities in the plasma.

Selected publications

M. Gatu Johnson et al.
The 2.5-MeV neutron time-of-flight spectrometer TOFOR for experiments at JET
Volume 591, Issue 2, 21 June 2008, Pages 417–430
doi: 10.1016/j.nima.2008.03.010