Post date: Jun 22, 2015 7:43:03 AM
David B and Suzie have arrived at KURRI and went to take a look at the machine room and the changes to the machine (ie. removed extra magnets and installed probes). The RF cavity (old one) has been re-installed and the water supply reconnected for the corrector. This afternoon the team have been doing powering tests on the new corrector.
We had a meeting to discuss machine status and progress. Ishi-san reported that last week the team measured the COD without the RF cavity in place, the method is as follows:
1. Reduce the coherent oscillations around the closed orbit at injection. This involved first adjusting the injection line bending magnet, and steerer before injection along with the foil position to optimise the transmission after about 20 turns. Next, they used two fluorescent screens on radial movers (one from inside & one from outside, half way round the ring) to measure the beam and to fine-tune the injection setup to reduce the coherent oscillations around the closed orbit. This they achieved to about 1cm beam size (which they believe is the intrinsic size of the beam).
2. Use the 5 installed radial probes in S1,2,3,5, and 12 to measure the COD using the qinbin method. Looking at the 20th peak height vs 0th peak height (H-) they measure the total COD amplitude to be roughly 3cm. This was surprising that such a large COD existed even without the cavity present. Ishi-san studied in simulation where the source of the COD could be, and suspects it may be from the first extraction line dipole which is both quite large and relatively close to the machine.
The first item on the list experimentally is to get circulating beam set up in the machine (obviously!) and then we will be able to move into the experimental programme looking at horizontal matching and COD as planned. There is some discussion about the horizontal orbit matching as the horizontally movable BPM may not have sufficient signal to read out the position (as the capacitance is high), Suzie will have a look at some raw data if possible to confirm this.
Next update due when we have tried circulating beam in the machine... as the corrector is new and covers more of the aperture, we expect the injection setup to be somewhat different from before.