LAM61 Study

Phil Adamson posed the following question:

Is it possible to delay the start of the ramp for I:LAM61 from 0.38s to 0.48s or 0.53s, or would that exceed the abilities of the power supply? It looks like it's causing orbit distortions in the MI when it starts to ramp. Looking at the ramp, it looks as though it gets to flattop very early, although there's a little overshoot.

I've done a study of this with I68. The first image shows the ramp calculated with the unchanged ramp parameters (i.e. those used to calculate the ramp that was sent to the E:LAM61 ramp card).

The second image shows how the start of the ramp moves when the voltage is increased to the maximum--as specified by the "hardware" parameters for the supply.

First Image

questions/comments

Second Image

questions/comments


The 6/14 comment of Steve Hays on this subject was:

This is the correct thing to do. Also the flattop time is 0.1 sec longer than necessary (0.195 instead of 0.095). This was due to the low gain we had been running. The supply has the correct feedback gain now so we can increase the ramp voltage and change the flattop time, both things will lower the RMS current in the magnet system. This can be done while running and should have no effect but I am sure that there will be time today without beam to send the change and verify operation.