User name Reinhold
Log entry time 11:56:21 on March18,2007
Entry number 196440
keyword=Thoughts on harp scansWe have instructions to keep sigma_y below 0.1 mm. When we took a harp scan this morning, the result was
x sig: 0.1594 +/- 0.0164
u sig: 0.1062 +/- 0.0106
v sig: 0.1214 +/- 0.0105
y sig: 0.0247 +/- 0.1263
We were concerend about the large error for y and thus about whether the result of sigma_y=0.025 is meaningful. Thus, we asked MCC to look into this. However, I'm now wondering whether just considering x, u, and v wouldn't be better. Assuming that the u and v wires are at 45 degrees and that the beam profile is elliptical, the y width has to be below 0.1 mm. Note, there is no measurement of y. It's extracted from u and v. If u and v are similar and x is larger, y should be smaller than u and v.
However, then I do not understand the second measurement by MCC that resulted in sx=0.25, su=0.12 and sv=0.99, but then only specified sy less than 0.212 (see Fig. 1 below). This seems to be an ellipses with the major axis almost aligned in x and y directions and y smaller than 0.1 mm.
After letting MCC adjust the beam, we got:
sx=0.12, su=0.16 and sv=0.07 with sy=0.13. It's not clear to me whether this is better then what we had before. It's just a rotated ellipsis now.
FIGURE 1
FIGURE 2
