As one might expect, the Position Code_s must be unique for the given _DeviceType in the given Area. For instance, if there are 2 Quadrupole magnets in the Injection area beamline, they might be named QUAD : IN20 : 600 and QUAD : IN20 : 605 respectively.
The Position Code is sequential if relating to a device in a Beam Line area. Larger numbers indicate they are physically further along in the area. There are exceptions to this rule with some legacy equipment, but the rule is always followed for new equipment. Furthermore, the code must be consistent with other devices sharing that same area. For example, the Quadrupole magnets from the previous example had Position fields of 600 and 605. If there was a Toroid to be positioned between them, it would have a Position field of 601 to 604. In situations where there is too much equipment in a small area, the numbers are allowed to overlap. So, it would be acceptable if the toroid was named TORO : IN20 : 600; the Position Code is intended to give an indication of the position, not an exact location. This is not necessarily the case for devices in Surface Buildings, the Klystron Gallery, or other areas. In those cases, many devices may be colocated in adjacent rack space, with no indication of the start or end of the area.
Numbering in certain Position Codes might follow other conventions as well. For instance, a vacuum pump located on a waveguide in Sector 23 might be named VPIO : IN23LI23: W420. This indicates that it is associated with the waveguide for Klystron 4, and is located roughly 20% of the way along that waveguide, measured from the Klystron. In this example, one could find the vacuum pump upstairs near Klystron 4, in sector 23. If the name was VPIO : IN23LI23: W480, then the pump is located on the same klystron's waveguide, but at roughly 80% the distance from the klystron. Thus, the last 2 digits would indicate whether the pump is on the upstairs or downstairs runs of the waveguide.
Note that using the Klystron number in this example is reasonable, since it is numerically close to the position as a percentage of the area length. Since each Linac sector has 8 klystron, using the digit 4 to indicate Klystron 4 is easier to remember than using the digit 5 to indicate 50% of the distance, which equates to the 4th klystron.
