These shutters consist of two independently but simultaneously operated mechanical blocks. Together they absorb bremsstrahlung radiation which occurs whenever the particle beam is scattered. This scattering happens when the electron beam is injected into the Storage Ring. Now it must be noted, that the present operation methods allow for injection with shutters PS1 and PS2 open and safety shutters SS1 & SS2 open as well. This is because advanced programs for beam injection and steering have been implemented.

The safety shutter is not cooled, but does absorb all the bremsstrahlung radiation coming through the beam transport section. Because it is not cooled, it should not be exposed to the photon beam as it has no means to dissipate the heat load. Therefore, the upstream photon shutter (PS1) is interlocked and sequenced to close (down) before the safety shutter is closed (down).