Calculations and measurements of the dose rate of bremsstrahlung for the three operating regimes of the Novosibirsk FEL
The powerful free electron laser of the Siberian center for photochemical research consists of an injector, an accelerator RF structure, one vertical and four horizontal paths, and dump. The 1st stage of the FEL has one vertical track, the electron energy up to 12 MeV. 2nd FEL has two horizontal tracks on the 1st track of the electron energy 10 MeV . On the 2nd track energy is equal to 20 MeV. 3rd stage FEl has four horizontal tracks, with the passage of each track energy increases by 10 MeV, on the 4th track energy is equal to 40 MeV. The electron beam current is about 10 mA. When the beam is lost on the walls of the vacuum chamber, the dose rate of bremsstrahlung reaches several kilo gray per hour. After recuperation, the beam (1.5 MeV) enters into the copper dump, the contribution to the dose rate from the dump reaches several hundred gray per hour. Levels of neutron dose rate can reach several gray per hour. The high level of radiation in the accelerator hall leads to the degradation of materials of technological structures and the activation of parts made of stainless steel and copper. The three-meter concrete walls of the acceleration hall provide reliable protection, in neighboring rooms the dose rate does not exceed the maximum permissible levels. FEL radiation monitoring system of the controls radiation in the work's rooms and in the accelerator hall. The system monitors only photon radiation. Photoneutrons are formed in the area of these energies, neutron radiation is not controlled by the system. The system does not control induced radioactivity. The paper presents calculations of the dose rate of photons and neutrons, as well as measurements of the dose near the gate of the hall accelerator, which allows to predict the radiation situation in the acceleration room.