The cause was a defect motor mounting in the compressor of the cold neutron source, such that the cold source shut down and automatically shut down the reactor, too. This is protects the in-pile parts of the cold source from irreparable damage.
As the cold neutron source supplies half of the experiments at the FRM II with cold neutrons, it is important for the scientists.
The motor of the compressor is being repaired. After the reparation and the cooling of the cold source, which takes several days, the neutron source will be back in operation. The cycle will be continued, such that the foreseen beam days are at the scientists’ disposal.