(x4-x2) - (y4-y2) ≈ (x1-x3) - (y1-y3)
There are offsets for each CCD in each DCOPS. The difference between these is of interest here. Let the offsets for X be offsetX_1, etc and those for Y be offsetY_1 etc.
Δ1 = offsetX_1 - offsetY_1
If the apertures are the same then you'd expect ((x4-x2) - (y4-y2)) - ((x1-x3) - (y1-y3)) to be pretty much the same no matter which pair you use: but the reference DCOPS have a different aperture from the rest in an SLM.
In the above expression the offsets drop out. It can be used for the same DCOPS with different lasers. Bob did some work with this quantity. Unfortunately Bob found that the number of DCOPS with all 4 CCDs having good profiles in both laser directions was rather small. Looking just at ME+2/ME+3, I find 3 such DCOPS out of 60, only two of which are in the same SLM (and for them the quantity differs by about .5mm).
If I only look at the tilt differences for each pair of sides I get points that usually cluster fairly well:
These are the difference between the tilt between opposite pairs found using one laser and tilt using the other laser. It only requires pairs (4 good values instead of 8). Notice that several of the distributions are tight.
Note that if the laser crosshair is not 90 degrees, the U/D and L/R measuments should be clustered in different places. There is no information about L/R for ME+2/SLM1, only one point each for L/R in ME+2/SLM2 so I can't tell if there is any clustering at all, and ME+2/SLM3 L/R is not clustered. The ME+3/SLM3 do seem do cluster at the same place for U/D and L/R.
| Line | Tilt Diff |
| ME+2/SLM1 | .47 ± .09 |
| ME+2/SLM2 | .53 ± .34 |
| ME+2/SLM3 | .05 ± .47 |
| ME+3/SLM1 | -1.30 ± .04 |
| ME+3/SLM2 | .47 ± .05 |
| ME+3/SLM3 | .08 ± .18 |
I fit all the transfer lines again, with the pictures in pictures and the fit log file in grunge.log, and grunge.fit.
I reviewed the profiles and created a list of means in grunge.list.reviewed
Modified 27-January-2011 at 10:58
http://hep.physics.wisc.edu/~jnb/cms/27Jan2011
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