Application of a precise fiber-optical dee position measurement system in the cyclotron RF system design

A new fiber-optical dee position measurement system is developed for the VINCY cyclotron. The system includes a sensor head, a coherent optical fiber bundle and a light detector with control electronics. The sensor head is placed in the dee, all the electronic components are placed out of the vacuum chamber of the machine, while the position information is carried by the optical fiber bundle. Two sensor heads on the dee enable the measurement of the position of the dee tip in all three dimensions, as well as the “twist” of the dee, with a resolution better than 50 μm. The precise dee position measurement can be useful for beam optimization, study of sparking phenomena, and study of phenomena causing errors in RF cavity geometry (vacuum, heating, etc.) These points tend to be even more important in future high current machines.