Scope: This policy describes requirements and authorizations necessary to initiate and perform work on radiation safety systems. It addresses mainly the administrative controls that the APS has put into place to ensure the integrity of beamline shielding. 

APS Configuration Controls are the administrative controls (i.e., the policies and procedures) that the APS has placed on beamline shielding components.

White beam is an x-ray beam whose spectral characteristics have not been modified from those produced by an insertion device or bending magnet source, except through the introduction of filters.For the purposes of this policy, the term white beam includes those x-ray beams that have been reflected from a mirror but have not passed through a monochromator.

Monochromatic beam is an x-ray beam whose spectral properties have been defined by the use of a monochromator to select an energy range (and corresponding harmonics) with a relatively narrow bandwidth, typically less than a few percent.

Under prior APS Configuration Controls, components fell into two categories: 

• Critical components: Beamline components used to stop, for shielding purposes, the white synchrotron and bremsstrahlung radiation.These include:
  • White beam stops and shutters
  • Bremsstrahlung stops and collimators
  • Masks that protect the above components
  • The APS will verify the alignment of these components, and their radiation shielding integrity will be verified by a radiation survey.
• Non-critical components: Portions of the shielding system that are not directly exposed to the white synchrotron or bremsstrahlung radiation.These include:
  • Station shielding
  • Shielded beam transport
  • Temporary local station shielding
  • The APS will verify the shielding integrity of these components with a radiation survey.

NOTE: All components are now referred to as "Radiation Shielding Systems" or components under "Configuration Control." They are no longer tagged as "critical" and "non-critical" components. This is old terminology but is, at times, still referenced. All RSS components are now tagged with a red sign reading " APS Radiation Safety - Do not remove or change this component without an approved work permit. Contact 2-0101."

Because of the higher risks associated with exposure to white synchrotron radiation, it is the APS policy that the alignment of components once deemed "critical" be verified by the APS.

Functionally, each white beam shutter and stop must stop the x-radiation as well as manage the thermal load of the white beam. Though the mechanical assemblies that perform these functions may be physically separated and may have different alignment tolerances, both parts of the assembly shall be treated as critical components.

In addition to critical components, there are many components that are exposed to the direct white synchrotron beam but whose presence and performance does not impact personnel safety. Such components include, but are not limited to, filters, white beam slits, monochromators, and mirrors. 

As part of the beamline commissioning process:

1. The CAT prepares a list of components under APS Configuration Control, which is consistent with the approved operation envelope of the beamline; the list is approved by the APS and posted in the beamline cabinet at the end of the sector.
2. Components under APS Configuration Control will be tagged by a Floor Coordinator.

Each white beam transport is to be tagged as under APS Configuration Control. For transport designs with the vacuum pipe mounted within a shielding enclosure, each removable cover shall be tagged. For transports with lead shielding as an integral part of the vacuum spool pieces, the control tags shall be installed on each section of shielded transport and on each exposed flange or flange cover.

All of the front-end components housed in the FOE will be put under APS Configuration Control and a tag placed on the support table.

Before a component under APS Configuration Control may be moved or worked on, a Configuration Control Work Permit must be completed, approved by a Floor Coordinator, and posted in the beamline cabinet. Refer to the Configuration Control Work Permit Policy and Procedure for further details.