To facilitate the alignment of beamline components in the Experiment Hall, a number of APS surveying network fiducials have been provided by the APS. This note provides a description of these fiducials for future reference. The fiducials include: a beam center line drawn on the floor for each bending magnet (BM) and insertion device (ID) beamline, four survey monuments per sector, and an array of reference markers along each beamline.

The beam centerline drawn on the Experiment Hall floor indicates the nominal position of the center of an undeflected BM or ID beam. This line can be used for the rough alignment of beamline components.

For higher precision, four survey monuments have been installed in the floor of each sector, two for each beamline. These monuments are located approximately 15 in. off the undeflected beam centerline toward the adjoining lower numbered sector. The monuments have been installed at the following nominal positions:

• along the BM line at 28.29 m and 52.60 m from the ratchet wall, and
• along the ID line at 27.72 m and 51.71 m from the ratchet wall.

The locations of the monuments are shown on the attached figure and in the General Library of the Design Exchange called "Beamline Survey Monuments." The monuments have been placed to within approximately 2 in. of these nominal locations, and the absolute position is measured initially to within 300 mm of the APS survey network. However, because of seasonal ground fluctuations, temperature fluctuations, and other factors that contribute to the temporal floor movement, the monuments may have an absolute position that is valid to only 2 mm within the APS survey network. The absolute position may be restored to the 300 mm value following the completion of a network quadrant survey. Similar monuments have been installed on the top of the storage ring tunnel and within the storage ring shielding tunnel.

Survey reference stickers have been placed on the Experiment Hall floor along each beamline with an approximate 5 m spacing referred to an origin at the center of the 5 m storage ring straight section for ID beamlines and referred to an origin at the center of the source of the 6 mrad bending magnet radiation. These markers are offset from the beam centerline by 380 mm in the same direction as the monuments and offset. The position of these can be determined with respect to the APS survey network to an accuracy of approximately 500 mm.

For the alignment of the beamline components, fiducials on the components can be surveyed and aligned with respect to the above survey network references. Standard components provide mounting holes for commercial tooling balls whose position can be determined with respect to the component's optics prior to installation. For installation, the tooling ball fiducials can then be aligned with respect to the APS survey network.

As the beamlines facilities continue to be constructed on the Experiment Hall floor, ready access to many of the survey monuments that have been installed within the sectors is being lost. In order to provide for the continued accurate alignment of beamline components, additional monuments are being installed in the sector-dividing aisleways. The three monuments are nominally positioned in the center of the aisleway and are separated by approximately 20 m. The first monument is located near the bend in the aisleway towards the downstream end of the sector.

The information in this Technical Update was provided by Horst Friedman of the APS Survey and Alignment Group. The services of the APS Survey and Alignment Group can be arranged through the appropriate Floor Coordinator.

For additional information contact:

Julie Cross - User Technical Interface
jox@aps.anl.gov
Telephone - 630.252.0592