Hi Mike, Tom,

 

My engineers Douglas Bruce and Julius Fazekas have prepared the following information for you with regards to constructing a global survey network. It is listed below. I might also add that I have also discussed the PPPL project with my management.  They/we are pleased to provide your organization with as much assistance as we can without infringing upon our commitments to the Spallation Neutron Source.  

 

The two attachments above are the exact same document in different format.  Additionally, I will be sending a dxf drawing file depicting our monument layout plan. It should be coming momentarily.  If you have any questions please give me a call. 

 

Regards

 

Joe

 

 

Joe,

 

Here are some points regarding the tentative network design for PPPL.

 

1. Monuments.  The initial network is composed of 40 floor monuments, and 60 wall monuments.  The floor monuments are sited in a grid pattern on the floor, placed over structural supports below.  The wall monuments are placed on the shielding block around the perimeter, in groups of three (above each other) at heights of 0.5 m, 2.15 m, and 3.5 m above the floor.  A fourth set of 20 wall monuments, at 5.15 m above the floor, will be incorporated into the network in a separate campaign later.  It is not worth the additional time and effort of including them in the first network, because the expected deformation will likely render them inaccurate before they would ever be used for aligning the experiment.

 

2. Measuring Equipment.  The network observations are to be performed with two instruments: the LTD500 laser tracker and the NA3003 digital level.  The network is small enough that total station observations are not required.

 

3. Manpower.  This initial network can be observed in three days by four S & A personnel.  This includes a full calibration of the laser tracker on the first day of observations.

 

4. Checking and outlier detection.  The network has been designed with sufficient redundancy that outlier detection and removal can be reliably performed after return to SNS, without requiring a return trip to the site.

 

5. Network precision (horizontal).  Horizontal network precision is commonly quoted by computing the relative error ellipses between pairs of network monuments (all combinations, exhaustively), and scaling them to the 95% confidence level, and then examining the lengths of all the semimajor axes.  The maximum value found provides a worst-case precision for the x- and y-coordinate differences between any pair of monuments in the network.  With the present network design, preanalysis (variance-covariance propagation) shows that the average 2-sigma semimajor axis length is 47 microns, and the maximum at 2-sigma is 82 microns. My understanding is that the overall alignment error budget is going to be dominated by deformation of the components themselves, therefore requiring a negligible error budget contribution from the network.

 

6. Network precision (vertical).  Similarly, the average 2-sigma precision for elevation difference between pairs of points is predicted to be 69 microns, and the maximum elevation difference uncertainty at 2-sigma is 188 microns.  The vertical precision among the floor monuments, taken as a group, is much better (25 microns).  This provides an excellent baseline for very precise vertical deformation monitoring of the floor.

 

7. Network useability.  When using the finished network to align components, the density of the monument pattern guarantees that a tracker could be positioned anywhere in the room and have 7-10 monuments within 5 meters of the instrument.  Lines of sight will be lost as components are installed due to obstructions, but this density of monuments should still allow any future laser tracker setup to be transformed into the network coordinate system with a likely positional precision of 20-40 microns, for the purpose of component installation.  Naturally this figure depends on the exact geometric relationship between the tracker and available monuments, and also upon the amount of accumulated network deformation.

 

8. Re-observation and deformation monitoring.  This network should be expected to degrade in accuracy as installation proceeds, due to the weight of the experiment applied to non-ground-level floor.  It is likely that the floor will sag unevenly as the load is applied, and the shielding walls may lean in response to the floor motion.  Therefore we make two recommendations: (1) that the network be re-observed and readjusted after the majority of the experiment is installed (but before the platform is installed), and (2) that a new set of 20 wall monuments be placed at a height of 5.15 meters above the floor and incorporated into the network during (or after) this re-observation campaign.  The exact locations of these last 20 monuments, and the design of the network to incorporate them, will be finalized after we see the available lines of sight available at that point.

 

 

A. Trip #1: Layout of monuments

 

SNS S&A will supply:

1. Total station and data collector/battery cable.
2. Batteries, chargers
3. Ranger data collector and charger.
4. Monument layout file for Ranger.
5. Two swoxed ball reflectors.
6. Layout puck.
7. Several sharpie markers.
8. 10-m measuring tape (to speed layout).
9. Two 30-m tape (to check building structural dimensions and maybe for actual layout).
10. Epoxy and 6 glue-on monuments (to establish rough network in case we need another setup).
11. Paper coordinate list, drawings.
12. Laptop (for unanticipated computations during layout).
13. Floor monuments (40)
14. Wall monuments (60)
15. Flashlights.
16. Kneepads.

 

 

PPPL will supply:

1. Climate-controlled and obstruction-free work area.
2. One industrial stand with adaptor to 5/8-11 thread.
3. Core drill (they will drill the floor mons).
4. Epoxy and screws (they must BOTH drill and screw the wall mons).
5. 10-ft stepladder.

 

Schedule:

Day 1: Travel.

Day 2: Pre-job safety meeting; verify location of floor supports; lay out monuments; perform asbuilt/check on monument locations.

Day 3: Travel.

 

 

B. Trip #2: Measurement campaign

 

SNS S&A will supply:

1. Two 1.5” tracker reflectors (checked before leaving).
2. Two 5/8-11 nests for 1.5” reflectors (for birdbath check).
3. Duct tape (for cleaning iron filings out of mons and birdbath).
4. Two 10-m measuring tapes (for marking ball bar calibration positions).
5. Several sharpie markers (for marking ball bar calibration positions).
6. Monument layout file for Ranger.
7. Laptop (for unanticipated calcs and preliminary adjustment for blunder detection).
8. Two 2-meter bar code level rods.
9. Two 1.5” ceramic spheres.
10. NA3003 digital level.
11. Data collector cable.
12. Level batteries and chargers.
13. Ranger data collector and charger.
14. Fiber optic illuminator and spare bulb.
15. Zip disks and thumb drives (for bringing tracker data home).
16. Tracker and NA3003 manuals (for unanticipated problems).
17. Allen wrenches for opening floor mons.
18. Rags for cleaning floor mons.
19. Epoxy and 6 extra glue-on monuments (just in case).

 

PPPL will supply:

1. Climate-controlled and obstruction-free work area, at intended operating temperature.
2. Laser tracker (acclimated in the room for at least 24 hrs prior to our arrival).
3. Ball bar calibration equipment (with new battery).
4. Three industrial stands with adaptors to 5/8-11 thread.
5. 10-ft stepladder.
6. Standard 120-v electrical outlets and two extension cords capable of reaching throughout room.

 

Schedule:

Day 1: Travel

Day 2: Pre-job safety meeting; tracker calibration; begin leveling.

Day 3: Perform laser tracker network observations; finish leveling. (Outlier detection check at night.)

Day 4: Finish observations, and repeat any outlier observations, if necessary.

Day 5: Travel.

 

 

C. Trip #3: Re-observation campaign

 

SNS S&A will supply: (same as trip #2)

 

PPPL will supply: (same as trip #2)

 

Schedule: (same as trip #2)

 

 

D. Trip #4: Densify network high on shielding walls (possibly combined with #3)

 

SNS S&A will supply: (same as trip #2)

 

PPPL will supply: Same as trip #2, but also

1. Prior to our arrival, PPPL will install an additional 20 monuments (screw+epoxy) on the shielding walls, at a height of about 5.15 meters above the floor.  Exact locations tbd.

 

Schedule: Four days (two for travel, and two for measurement).  However, if done in conjunction with trip #3, simply add two days of measurement to the trip #2 schedule.

 

 

 

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Doug Bruce

Survey and Alignment Group

Spallation Neutron Source

Oak Ridge National Laboratory

Mail Stop 6462

Building 8600, Room C-284

Oak Ridge, TN 37831

865.748.2713 (cell)

865.576.9209 (fax)