Log entry time 23:10:53 on December 13, 2011

Entry number 359839

Here's a first pass at B vs I curve for the septa, based on the field measurements Jack and I took yesterday. The probes were located roughly at the center of each bore, about 2 inches from the floor. (We were only looking at reproducibility so did not make careful measurement of the positions). The currents were ramped up to 850 Amps and back down three times. The first ramp was in 100A steps, and the remaining two were in 200A steps. The field is fairly reproducible (about 7-8 gauss) from the attached fits. This represents a worst case scenario, since the fit includes all three ramps, and I'm only including a small fraction of all the measured data.

Min and Jixie estimated that the field corresponding to 1.7 GeV at the rough position of the probes is 8077 gauss, which implies we need about 697 A on the left and 701 A on the right power supply. These currents seem high, so I suspect I'm misjudging the offset from center of bore, or just that the off-axis field components can't be neglected as I've done. From rough scaling of the expected max momentum and current, I'd expect something more like 520 A for 1.7 GeV. Anyway, this gives us a rough setting to start with until we can do a more careful field measurement or check with elastic.

Figure 1

Figure 2