Log entry time 23:24:21 on October 01, 2010

Entry number 333356

Followups:

• 333888 10/07/10 16:13 M Friend Compton data from Oct 1st

I did scan the cavity by observing the counting rates versus the vertical position of the beam, using a 20uA beam current. Practically, I scanned all beam positions, from where the beam was set i.e 1.5mm, to 0.5mm., by steps of 0.1mm. I stayed a couple of minutes for each step. (Fig 1) The vertical beam position which gave the best counting rate was IPM1P02B.YPOS = 0.8mm. (Figs 1 and 2). Fig2 emphasizes that the rates are almost 20% higher at y = 0.8 that at y = 0.7 or y = 0.9.

I also estimated signal to noise ratios at different currents. The method is simple: I lock the cavity, put beam on, and estimate the rates (signal), and then I unlock the cavity and watch the counting rates (backgroung). Figs 2, 3, 4 illustrate this I did it for beam currents of 20uA, (Fig 2), 5 and 10 uA (Fig 3) and 15 uA (Fig4). Since it is not easy to see it on the figures, I did a quick recap table:

______________________________________________ Current | Signal | Background | S/B | (S-B)/B ________|________|____________|_____|_________ 5uA | 1.e4 | 5.e3 | 2 | 1 10uA | 1.3e4 | 1.3e3 | 10 | 9 15uA | 1.7e4 | 1.3e3 | 13 | 12 15uA | 2.7e4 | 2.0e3 | 14 | 13

Note that those values are rough estimations, which just give an idea opf what to expect.

Figure 1

Figure 2

Figure 3

Figure 4