A little mystery of ours... The bright green line represents a radiation spike of unknown origin measured on our mercury pump (we fire a proton beam at liquid mercury). The jagged, mostly vertical pink lines are the proton beam power and typically the dose rate on the mercury pump trends with beam power. As you can see, during certain conditions when the beam is turned off, the radiation level spikes (from around 40-50 rads/hr to well over 500 rads/hr in this case) an then decays very slowly. The dark line that drops quickly with beam off is a dose rate monitor on a 6" mercury pipe that goes to the pump - it behaves like you would expect. We've seen this for years and no one has been able to explain why it happens.
