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Personnel Safety System (PSS) Introduction


  1. Description of the PSS Operation
    1. The PSS Control Panel
    2. The Door Status Control Panel and the PSS Open/Close Door Control Box
    3. Search-and-Secure Procedure
  2. Faults and Emergencies
    1. Unlikely Occurrences


The APS/XFD (XFD - Experimental Facility Division) personnel safety system (PSS) is designed to prevent radiation exposure by prohibiting personnel access to the experimental stations when permission to operate the station's beamline shutter is granted to the users. The PSS system does not protect against electrical, ozone, or oxygen-deficient hazards.

1. Description of the PSS Operation

    The PSS is a reliable and redundant safety system that utilizes two independent levels of interlock protection, chain A and chain B. The interlocks are operated by two different programmable logic controllers (PLCs) that verify the input signals to the PSS with two independent logic configurations. The PSS system requires a physical search and secure of the experimental enclosure to verify that no personnel is in the station before allowing user beamline shutter operation. A detailed description of the search-and-secure procedure is presented in the next section.

    The users have control of the experimental enclosure's x-ray beam shutters, and the pneumatic doors with magnetic locks through a PSS control panel and a door control box, respectively. A PSS door-status control panel provides door open/close information to the user.

    1.1 The PSS Control Panel

The PSS control panel (click to view the PSS Control Panels at 9-ID or 9-BM) is equipped with indicators that provide information on the status of various systems such as:

  • ACCESS CONTROL INTERLOCK SYSTEM (ACIS) - Global online permit signal, provided by the accelerator system division (ASD) operators to the experimental station. This signal is part of the ACIS interface with the PSS system and indicates no only that the x-ray beam is ready to be sent through the front end but also to the beamline experimental station.
  • STORAGE RING (SR) ACIS signal, also provided by ASD operators, is another ACIS interface with the PSS system that indicates that the accelerator system is ready for the front end shutters to be opened.
  • EQUIPMENT PROTECTION SYSTEM (EPS) permit is provided by the front-end and beamline equipment protection systems (FEEPS and BLEPS) logic, which is interfaced with the PSS system. A true EPS signal indicates that no faults exist in the vacuum, water flow, photon shutters, and front exit valve (FEV) and that they are ready for x-ray beam transport.
  • USER ENABLE signal is controlled by the user to allow or inhibit beam transmission through the experimental beamline by toggling the user-enable key lock. The key is in the user's possession.
  • APS ENABLE signal is controlled by the floor coordinator to verify the integrity of all non-PSS related systems and to allow shutter operation.
  • STATION SECURE signal is enabled after the experimental station has been properly "SEARCHED AND SECURED". The search-and-secure procedure is explained in the following subsection.

The panel also proves information on the beamline shutter status and indicates the PSS beam mode being transmitted through the experimental beamline. The possible types of beam that can be transmitted are monochromatic beam, white beam, or pink beam. For those experimental beamlines with more than one experimental enclosure, control to open the shutters at any given time is limited to one and only one station (station in which the experiment is being conducted). However, in case of an emergency, the shutters can be closed from any station associated to that particular beamline. It is worth mentioning that this is not a standard feature in all experimental beamlines and their associated enclosures at APS due to user's request. The PSS control panel also provides information on any faults in the interlock system that is discussed in the following sections.

1.2 The Door Status Control Panel and the PSS Open/Close Door Control Box

Some experimental enclosures have doors that are closed manually in addition to the pneumatic/magnetic doors; these doors are locked magnetically and through a regular floor latch. A manual door is magnetically locked/unlocked by pressing push button switches labeled lock/unlock in the door status control panel (see figure 2). To close a pneumatic/magnetic door, the user must press the green button labeled "CLOSED" in the PSS Open/Close door control box (see figure 3) and keep it pressed until the door has been completely closed. A status report of all the manual and pneumatic/magnetic doors in the experimental enclosure is provided in the door status control panel through a set of light-emitting diode (LED) indicators.

1.3 Search-and-Secure Procedure

Before beam is allowed into an experimental enclosure, a search and secure procedure must be performed by the user to ensure that no individual is in the experimental station during beam transmission through the experimental beamline. (Click to view Specific Hutch Search Procedures for 9-ID or 9-BM) One and only one PSS-trained experimenter must carry out the station's search-and-secure procedure and prevent other users from entering the station. The search procedure consists of the following steps that MUST be followed as indicated:

  • The PSS control panel contains fault indicators for major/serious and minor faults. If any of these indicators is flashing, the search procedure cannot be initiated.
  • The floor coordinator is responsible for resetting minor faults, while PSS personnel are responsible for resetting the major/serious faults. It is the user's responsibility to reset the lock labeled "USER" with a key that is in the user's possession. Reset of the lock labeled APS is the floor coordinator's responsibility. More information on the different types of faults is given in the following section.
  • Verify that all emergency stop and door-disabled buttons, located inside the experimental station, are pulled out.
  • For those experimental stations that have manual doors in addition to the pneumatic/magnetic doors, the manual doors must be closed first. The search procedure can only be started once all the manual doors are closed and locked. Some experimental enclosures may require having some of the pneumatic/magnetic doors closed before the search procedure starts.
  • At this time, a search LED indicator (amber color light) in a gray control box labeled "SEARCH BOX" inside the station should be flashing indicating that the search sequence can begin.
  • Verify that the experimental enclosure has been evacuated and that no users other than the one designated to do the search procedure have access to the station.
  • Inside the experimental station, press the button labeled "SEARCH" in a "SERACH CONTROL BOX" (gray box) to stop the flashing amber light. Depending on the size of the enclosure, some enclosures may have more than one search box. Each search box must be reset to stop the flashing amber light.
  • Then, exit the station and proceed to close the pneumatic/magnetic door, in most cases, adjacent to the search control box that has been reset. Pressing the "DOOR CLOSE" button in the PSS door control box (located outside the experimental station and adjacent to that particular door.) closes the door. The button must remain pressed until the door is completely closed. A lit green light in the door status control panel will indicate that the door is completely closed and locked. Repeat the process for station with multiple pneumatic/magnetic doors. This procedure must be completed sequentially within a programmed time limit to ensure restricted access to the station.
  • Before a station is considered secured, a 20-second audio message will be played after the last pneumatic/magnetic door has been closed. This required 20 second time period allows anyone accidentally locked inside the enclosure to react and abort the beam permit (see the following section for details.)

REMEMBER: An experimental enclosure may have more than one "SEARCH BOX" and pneumatic/magnetic door. Therefore, make sure that each search box is reset and each door closed as specified above.

Once the search procedure has been completed, the experimental station is ready for beam, and shutters can be opened provided that a floor coordinator has given an APS enable permit.

It must be emphasized that the purpose of the search procedure is to ensure that the experimental station has been completely evacuated prior to beam transmission to the station.

2. Faults and Emergencies

There are three categories of faults that can occur before of during operation. These are minor, major, and serious faults.

The floor coordinator has the responsibility to reset the system if a minor fault has occurred, while major and serious faults require PSS personnel to reset. A minor fault signal can be triggered when the pneumatic/magnetic door locks fail to close within a predetermined period of time (about 90 seconds) during a search procedure or because of alignment problems.

A major or serious fault, on the other hand occurs when:

  • Any of the emergency buttons has been pushed while beam was allowed in the experimental enclosure.
  • Any of the doors in the experimental station had been opened while beam in the station.
  • Shutters cannot be closed.

For any major or serious fault, contact a floor coordinator who will notify PSS personnel.

2.1 Unlikely Occurrences

In the unlikely case that somebody is accidentally locked inside an experimental station after a search procedure has been completed, the following steps should be followed:

  • Press the red mushroom shaped emergency stop button located in a yellow box near a magnetic door. This will close the beamline shutters and will remove the RF from the storage ring terminating the acceleration of positrons needed for production of the x-ray beam. In case the beamline shutters were still closed when the emergency button was pressed, the RF signal would not be removed from the storage ring.
  • Press the "AUTO OPEN" button in a gray emergency door control box located inside the station by the yellow box to open a magnetic door. In case of failure to open, wait about 10 seconds and the press the "MANUAL OPEN" button also in the gray control box. The disabled button will vent the compressed air and demagnetize the locks so that the pneumatic/magnetic door can be opened manually.


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