Post Shift Summary

Alignment Scans

Alignment scans for software development and as a record of the alignment procedure. The wire-scanner detector is used for these alignment scans as our detector saturates long before the screen touches the beam. Firstly, a vertical manipulator scan:

Because the electron beam is much wider than in our previous location, the wings start clipping the edge of the notch and generate signal. Therefore, the vertical scan is not as sharp as it was in the previous location. It does however rise sharply at the end which is perhaps due to the relatively flat top of the notch cutting off the remainder of the beam. Secondly, a horizontal scan was conducted near the top of the notch. This shows a minimum at the centre of the notch where most of the beam is transmitted.

OTR Images

The camera was setup at the weekend and its minimum exposure is 90ms. The first image was recorded with the OTR alignment laser illuminating the screen.

• otr_screen.jpg:
  

The best OTR image obtained is shown below. Obviously there's a terrible background because the exposure was 700ms. This was chosen to ensure capture of the beam. This image was obtained with a otr lens position of 8mm.

• best.jpg:
  

The next two images are of the OTR just at the edge of the screen. Although hidden by the background, you can just see the OTR on either side of the notch. You can also see the two vertical scratches in the screen made by the laser which are near the top.

• screen_notch_horizontal.jpg:
  

• screen_notch_top.jpg:
  

No Laser-wire Signal?

From the OTR images, our alignment was pretty good horizontally and although vertical is less certain than before, we scanned over a large range with maximum 2 micron steps. When we did phase scans before the convoluted sigma was 0.6V so being within 1 sigma we should have signal - we can adjust to around ±0.1V so definitely good enough. We also checked this several times through the shift and it was pretty good.

I'm still doing the analysis on the bpm readings from our scans but I looked at the positions on the magnets before and after us and the difference was less than 100microns in each. YoungIm kindly calculated the angle in the vertical and it was 70 - 100 microradians. We shouldn't miss the detector with this. The bpms have no BBA data though but this shouldn't introduce more than ± 200 microns in each - still we shouldn't miss the detector.

The thing we found before was the position of the detector window and the detector. The detector is immediately behind the window which leaves only the window. The dipoles haven't been aligned. We'll have to wait until the weekend to have a look at its position with respect to the beam line.