Sweep is the state of the PSS when delivery of beam and/or RF power is not permitted and access is limited to the Jefferson Lab personnel conducting the sweep operation. The hall's entrance gates are closed from the inside to ensure that no one can enter behind the person conducting the sweep. During the sweep, an Assigned Radiation Monitor or ARM systematically searches the hall to verify the absence of people and to arm the run/safe boxes. The ARM posts a guard at the entrance to the hall as another method of ensuring that no one enters after him.
When the Assigned Radiation Monitor is ready to perform a sweep, the Machine Control Center or MCC must first place the hall in the Sweep state. The Personnel Safety System will read ``Sweep In Progress." Once the hall is placed in the sweep state, the sweep monitors enter the first gate to the hall, making sure it locks behind them. The ARM then notifies the MCC that he is ready to begin the sweep. The MCC communicates with the sweep monitors via intercom and video camera. Using the video camera, the MCC makes sure both sweep monitors are wearing the proper dosimetry. At this point the ARM also indicates that he is in possession of the key needed to arm the Run/Safe boxes placed throughout the hall. Having confirmed that the dosimetry is adequate, the MCC will unlock the second entrance gate allowing the sweep monitors to enter the hall. Once the sweep monitors pass through the second gate, they close the gate and ensure it is locked. The sweep monitors then proceed to the hall entrance where one sweep monitor is left to guard the entrance and the other begins the sweep. During the actual sweep, the ARM walks through every area and secluded workspace in the hall to ensure that no one could be left inside when the Personnel Safety System moves from the sweep state to controlled access, power permit, and finally beam permit state. Once he checks an area, he arms the run/safe box in that area. After all areas of the hall have been checked and the run/safe boxes armed, the sweep monitors will return to the entrance where the sweep began. Before arming the last run/safe box, the ARM will contact the MCC. Upon contact, the MCC will check to see if the sweep has ``dropped"; if all is well he will notify the ARM that it is okay to arm the box. Once the box is armed, the sweep monitors have 30 seconds to exit both gates or the sweep will drop, and the entire sweep process will have to be repeated. After exiting, the ARM must contact the MCC to let them know the Hall can now be moved to the controlled access state.