Since we use the middle window as a reference for the laser pulse timing, the fact that the window is 2.25 m behind the target has to be taken into account. From here the ions have 10 ns less time of flight to the middle of the electron cooler than they need for half a revolution. The signals were still symmetrically aligned around the reference bunch as it was done yesterday. Therefore, the delay of the laser pulse was reduced by 10-ns on the oscilloscope, which led both photodiode histograms move 3 bins further to the right (towards larger times till common stop, since the pulse arrives earlier).
Since the RF frequency is turned down from ~ 1 MHz to ~ 400 kHz during injection/preparation, the laser does not fire reliably and the beam stabilization does not work very well during this period. This was solved by increasing the window in which the Q-Switch signal is accepted from 2 microseconds to 5 microsececonds. The laser is now firing regularly and with high power also during the preparation time and the beam position stabilization works very well. |