Guideline
Document Number ESS-0012977
Date
Revision
Jun 25, 2014
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State Preliminary

Guideline
Document Number ESS-0012977
Date 17 Feb 2012
Most of the Survey & Alignment activities at ESS will be based on a 3D free stationing approach, using as main instrument the Laser Tracker 1 .
To align a component, the Laser Tracker will first determine its own position measuring network references which positions is already known. Then, targeting some fiducial marks attached to the component to align, the Laser Tracker will provide the deviation respect to the nominal position. The component is thus adjusted.
This guideline presents the different fiducials attached to the components to be aligned that can be used at ESS.
A fiducial is a reference which position is defined with respect to the sensitive part of the component to align (proton beam axis, neutron beam axis, mechanical center…).
As we use the laser tracker to align a component, the fiducial has to be able to receive the typical 1.5” corner cube reflector illustrated in figure 1.
Figure 1: 1,5” corner cube reflector.
To define the type of fiducial, we only focus in our case on repeatability. We do not need to place a fiducial at a high precise specific position with respect to the sensitive part, but only to have repeatability when placing the prism on the fiducial and then be able to measure its position.
3 different kinds of fiducial can be used at ESS:
 6H7 machined hole
 Cone directly machined on the component
 Threaded hole to receive M6 interface
If for any reason, a fiducial needs to be different from these 3 options, please contact the
ESS Survey Alignment and Metrology Group.
1
A Laser Tracker is a highly dynamic measuring system for three-dimensional coordinate determination using a single beam laser interferometer, precise angular encoders and a sophisticated servo-tracking system.
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Guideline
Document Number ESS-0012977
Date 17 Feb 2012
Figure 2: 6H7 Machined Hole (Drawing: ESS-0011484).
This machined hole allows to precisely place an adapter as illustrated in fig 3 to receive the prism.
Figure 3: Adapter for 1.5” Prism and 6H7 hole.
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Guideline
Document Number ESS-0012977
Date 17 Feb 2012
Figure 4: Illustration of fiducial cone machined on component- XFEL quadrupole.
This cone allows high repeatability in the positioning of the 1.5” prism. The center of the prism must be above the component surface not to obstruct line of sight as presented in figure 5.
Figure 5: Illustration of a 1.5” prism placed on machined cone.
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Guideline
Document Number ESS-0012977
Date 17 Feb 2012
The last option for fiducial is to machine a threaded hole to receive a M6 interface that needs to be screwed and then glued to be sure it remains fixed. The 1.5” prism is then place on this interface.
Figure 6: M6 Interface to be screwed and glued in a threaded hole.
Drawings of this interface can be found at:
 ESS-0010675.1.1
 ESS-0011042
 ESS-0011048
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