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Ion Accelerator Facility PIAF of PTB modernized


PTB’s Ion Accelerator Facility (PIAF) consists of an energy-variable CV28 isochron cyclotron and an electrostatic accelerator. It is operated by Department 6.4 “Neutron Radiation” and provides proton, deuteron and alpha particle beams with energies of up to approx. 26 MeV (depending on the particle type) which are used for the generation of neutron reference fields and for experiments with ion beams. The electrostatic accelerator which has so far been used (and which is meanwhile 40 years old) is a Van de Graaff belt generator with a maximum acceleration voltage of 3.75 MV which covers the lower ion energy range. As the original spare parts are no longer available – and due to the long useful life of the accelerator and the wear associated with it, this machine no longer reached the original specifications and could be used only to a very limited extent.

Overview of PTB’s ion accelerator facility “PIAF”. From the two accelerators, the ion beams are guided via a beam line system with several deflection magnets to different experimental areas. The two photos show the new 2 MV tandetron accelerator during the construction phase in October 2016. In the open tank, the so-called accelerator column can be seen in which the ions are accelerated by the applied high voltage.

It was, therefore, the objective of the modernization to replace the Van de Graaff accelerator with a new accelerator which is again in a position to cover the original beam parameter range and which offers, at the same time, the advantages of using modern accelerator technology. The choice fell on a tandetron accelerator of the High Voltage Engineering Europa BV company which allows proton beams and deuteron beams with a maximum energy of 4 MeV and alpha beams with a maximum energy of up to 6 MeV to be generated with improved energy sharpness and energy stability. The new accelerator will require considerably less maintenance and operating effort/costs and allows, in particular, the routine provision of alpha particle beams and of pulsed beams for the characterization of neutron energy distributions by the time-of-flight method.

In February of 2016, the old Van de Graaff accelerator was shut down and dismantled after permission had been given by the approving authority. After renovating the accelerator room, the installation of the new accelerator was started in October 2016. At the end of 2016, the new accelerator was handed over to PTB after the PTB staff had undergone intensive training provided by the operating team of the manufacturer. It is now still necessary to repair the air-conditioning systems in the accelerator area. After that, it will presumably be possible to resume regular beam operation in the summer of 2017.

With the acquisition of the new accelerator, in the future it will also be possible to completely cover the whole neutron energy range from approx. 2 keV to 20 MeV at PTB’s ion accelerator facility. The generation of mono-energetic neutrons in such a large energy range is one of PTB’s unique features. PTB has thus ensured its role as one of the leading national metrology institutes in the field of neutron metrology and will continue to be a competent partner in scientific and social questions in the field of neutron radiation.