Operation of the ion accelerators by Department 6.4

Department 6.4 operates two ion accelerators which are chiefly used to produce neutron and high-energy photon reference fields and to provide light ion beams for experiments directly, also as a micro-beam. The Van-de-Graaff linear accelerator is capable of accelerating protons, deuterons, ³He- or alpha-particles with high voltages from 0.3 MV to 3.75 MV. In the case of the compact cyclotron the ions are accelerated repeatedly to high energies in the same high-frequency electrical field whereby they pass through a magnetic field along spiral paths. High-frequency and magnetic fields can be adjusted such that ions with energies from 2 MeV to 24 MeV for protons, 3 MeV to 13 MeV for deuterons, 5 MeV to 36 MeV for ³He²⁺-ions and 6 MeV to 27 MeV for alpha particles can be extracted.

Both accelerators can provide pulsed ion beams with pulse widths of 1 ns to 2 ns and variable repetition frequencies. This mode is important for time-of-flight measurements, allowing separation of prompt photons from neutrons, which are produced simultaneously in the targets, or determination of the spectral neutron fluence with high precision.

In the period from October 1, 2005 to September 30, 2006, the two accelerators were in operation for 2750 hours in total. In order to achieve this, the accelerators had to be partially operated simultaneously in two or even three shifts around the clock. About 86% of the time in operation, i.e. 2350 hours, the beams were provided for a great variety of experiments.

In the table, the beam time is disclosed according to the applications of PTB working groups and their collaborators. It should be noted that almost the same fraction of the total beam time was used for PTB internal and external projects.

Table:	Disclosure of the beam time in the period from October 1, 2005 to September 30, 2006, according to various applications.