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Layout Survey - 20100607

Distances were measured between magnets etc were measured. These were measured between centres of magnets as best as possible. Longer range measurements were also made. This only provides a rough guide as to the spacings between magnets. A better quality reference is being sought.


Figure 1: Schematic of beam line and distances.


Object Position (m) Dimension
Extraction Miles back NA
QD18X -3.79.7 0.011 Vertical
QF19X -2.342 0.009 Horizontal
QD20X 1.585 0.007 Vertical
QF21X 3.870 0.01 Horizontal
Detector 24.34 0.06 NA
Final Focus ~35m NA

Verification of $ \gamma$ path.

An attempt was made to verify the position of the detector and that there was a clear beam-line for the compton X-rays. A piece of metal was attached to a set square and placed in front of the detector so that it lined up with the beam line as shown in figure 2. Figure 3 shows a picture of piece of metal in front of the detector. From this it can be seen that the beam line and hence beam of Compton X-rays hits slightly to one side of our detector and it should be moved.


Figure 2: View of beam line with black metal strip in front of detector aligned to beam line.


Figure 3: Image of black metal strip in front of detector which is aligned to the beam line. Slightly off centre from the detector's current position.

Upon surveying the beam line, a few distinct features were recognised and were photographed. These are shown below in figures 4 and 5. Alex has said that we are not sensitive to vertical deviations as we are horizontal ones because the beam size is generally much smaller.


Figure 4: QF21X - the beam pipe here moves around vertically a lot. The BPM (copper part) through the quadrupole and hence beam pipe seems to be a bit of a downwards angle.


Figure 5: OTRs - generally set to a lower position.

An attempt was also made to see where the $ \gamma$ beam would go in relation the window from the beam line and the aperture of the magnet. Figure 6 shows a picture of a piece of string aligned to the beam line on top of the magnets. Additionally, figure 7 shows a picture of another piece of string being hung from the first one in front of the window. It would seem that the window is in a good position (not that this can be changed) and that the beam should make it through the quadrupole. However, the vacuum flanges for the bellows between the window section and the next BPM / qaudrupole interrupt the beam on the side closest to the continuing electron beam. It may be necessary to scan the beam horizontally to find the optimum transmission. Furthermore, it may be of use to scan the beam vertically to ascertain whether we are really aligned.


Figure 6: Piece of string used to indicated beam line.


Figure 7: Secondary piece of string to show beam position lower down.

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Topic revision: r3 - 07 Nov 2013 - LaurieNevay

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