The Karlsruhe Fast Neutron Time-of-Flight Facility

Abstract

Although the area of resonance neutron spectroscopy is presently dominated by pulsed neutron sources based on electron linacs, the highest instantaneous neutron intensities are provided by acceleration of positive charged particles to high energies. While advanced types of circular and linear accelerators hold great promise for the future, this concept has not in general been realized because of technological problems such as heat transfer, etc. Certain existing machines do, however, permit us to partially realize this concept already at present. A high energy proton linear accelerator to be used as a high intensity neutron source will be described by Dr. Moore in an other invited talk of this conference. Of the circular accelerators the sector-focussed cyclotron is currently best able to take advantage of this capability. This machine combines both, high beam intensity and narrow pulse width of a few nanoseconds. For proper use of this machine additional equipment is necessary because sector-focussed cyclotrons run continuously with a microstructure pulse recurrence frequency of 10–30 MHz which is far too high in view of frame overlap problems. It is obvious that for long flight paths the time interval of 30–100 nsec between two subsequent pulses is so short that slow neutrons from a preceeding pulse can be overtaken by fast neutrons from the following pulse. A reduction of the recurrence frequency by suppression of most of the microstructure pulses would entail a tremendous sacrifice in intensity.