The Mission:

In order to produce luminosities appropriate for Run II levels, a better understanding of the Tevatron’s orbit would be required. To do that, it was necessary to create a network of survey control points and measure the positions of all components of the Tevatron. A 3D Cartesian system, with a precision of < 2.5-mm (one sigma) across the ring, was specified. With measured positions of all components in this system, a precise definition of the machine is possible. This effort is known as TeVnet.

The Mission:

In order to produce luminosities appropriate for Run II levels, a better understanding of the Tevatron’s orbit would be required. To do that, it was necessary to create a network of survey control points and measure the positions of all components of the Tevatron. A 3D Cartesian system, with a precision of < 2.5-mm (one sigma) across the ring, was specified. With measured positions of all components in this system, a precise definition of the machine is possible. This effort is known as TeVnet.

The Approach:

Using techniques similar to those used in the alignment of the Main Injector, establish a network of survey points in the tunnel and on the surface, prepare a pre-analysis of survey observations to achieve the objectives, perform the necessary measurements during the Fall shutdown, and perform a least-squares adjustment of the data.

Equipment/Task List

• Two LaserTrackers

• Seven GPS receivers

• Gyro-azimuth theodolite

• Geodimeter Autolock robotic total station

• Digital levels

• Mekometer laser EDM

• Nadir telescopes

• Create observation points in vent shafts

• Install 12 observing towers

• Install a network of 35 DRM

• Tie in principal monuments of Main Injector, P-bar, and NuMI

• Tie network to NGS-HARN

• Perform network adjustment

• Determine magnet positions

Glossary:

• DRM – Deep Rod Monument – lengths of aluminum rod, driven into the ground to refusal, approx. 10-15 meters

• NGS-HARN – National Geodetic Survey; HARN – High Accuracy Reference Network, in global coordinate reference frame

• LaserTracker – an instrument using a laser interferometer, together with horizontal and vertical angle encoders

• GPS – Global Positioning System, used in differential mode

• Murphy Line – a system of brass plugs in the tunnel, established in the early 1980s, which represent a set of tangent offset lines wrt. the quad in each cell of the Main Ring. The relationship between any two Murphy lines was only loosely known prior to the TeVnet survey.

• Sight-riser – A vertical penetration from the surface to the tunnel thereby allowing the transfer of control to the tunnel.

Network elements:

• 482 LaserTracker stations

• 69658 LaserTracker observations

• 25498 LaserTracker chords

• 612 GPS baselines

• 141 Mekometer distances

• 24 Gyro azimuths

• 82 Autolock angles

• 14 vertical drops

• 893 Tunnel elev. differences

• 86 Surface elev. difference

• 1824 network control points

• 7 months of planning

• ~200 field crew man-weeks

• 6 loaner personnel

• 3 contract personnel

• 14 staff-months of analysis

TeVnet

Surveying the Big MachineFermilab Alignment & Metrology Group

The Gazebo – the central monument for the original construction of the Main Ring

These figures represent the error ellipses (two-sigma semi-major axis) under stepwise refinement. Figure 1 depicts error ellipses equivalent to the best survey possible (using the most modern equipment available today) of the Murphy Line. Figure 2 shows the same data set as Figure 1, but constrained by 14 sight-risers of the surface network shown on the poster to the left. Figure 3 adds the LaserTracker dataset to that of Figure 2.

DRM schematic, drive rod with 60-pound rotary hammer; finished monument Gyro at workObserving tower over vent shaft

Typical distance precision (2-sigma) for various distances