Measurement of Gamma and Neutron Dose from the Operation of the ANKA Storage Ring

ANKA is a ramped 2.5-GeV electron synchrotron light source, which can be operated at all energies from 500 MeV to 2.5 GeV. An online area monitoring network makes it possible to measure the radiation from the decaying beam at eight stations every minute. It consists of two stationary and six mobile stations with a gamma and a neutron detector, which are connected with a central computer by a bus system. Measuring devices and software were developed or customized for ANKA.

Special machine shifts were dedicated to the systematic investigation of beam lifetime and ambient equivalent dose, which depend on the beam energy, beam current, and operating conditions of the storage ring.

The highest dose rates are measured in the forward direction of insertion devices. The beam is lost at the device with the smallest aperture. Local shielding of the storage ring and operating conditions can be improved with time-resolved dose rate measurements at locations with high dose levels. Low beta optics improves the lifetime of electron beams circulating in vacuum chambers with small aperture. This helps to reduce the dose rate. Furthermore, this has the advantage of reducing the dose rate without the drawback of extra costs for additional shielding.