User name X. Zheng
Log entry time 23:03:58 on June30,2004
Entry number 127559
keyword=Right Q2 & Q3 drifting offAround 21:49, right arm Q2 and Q3 drifted to 2.90 and 2.88 GeV/c. There is no error shown on the power supply screen.
We tried to cycle both and then typed in the set momentum, but the current refused to go to the set current. Looks like we lost lock for both.
We paged tech on call, and was told that we should ramp Q2 and Q3 to 0Amp, then reset the IOC by pressing the green button in the middle room labeled "Right spectrometer magnet control VME".
After the IOC went back, we cycled Q2 and Q3 again. But this time the power supply for the dipole did not come back to normal. On the NMR screen, it shows "MANual mode" (should be AUTO) and regulator was OFF. We couldn't set the Mode to AUTO. The tech on call said normally we should also ramp the dipole current to zero before resetting the IOC, but then it will take hours for it to come back.
After consulting the tech on call, we tried several things. We changed the set current up and down a little bit and try to find the lock, didn't succeed. Since both Q2 and Q3 had been sitting at 1400 A for a while, we typed in 2.96 in the momentum setting box. At this point the NMR came back to "AUTO" by itself and the dipole current started to ramp to the correct value.
Around 22:52 the right dipole momentum reading shows 2.96000 GeV/c. There is still something wierd: The set current is 1056 A instead of the 1061 A we had before (see plot). But since the momentum is locked to the correct value, we decided to start normal production run.
Run #2571 is with left arm only, #2572 is a normal run.
FIGURE 1
FIGURE 2
