23/11/2021

We would like to cycle the quadrupoles in the linac. The procedure of the cycling was provided by Cynhia (attached). 

The magnet current should be ramped from 0 to IMAX , decreased down 0 and ramped back to IMAX three more times. Measurement current will be finally reached going to nominal current ISet. (IMAX  = 12 A).  

Total cycling time is ~8 min [so ~1 min for 0 to IMAX, and the same for IMAX to 0). Waiting time at IMAX & I=0 is ~10 sec.

More probably this procedure is driven by the fact that the B(I) curves were provided for the positve values of I only I = 0..+12

As it was discussed with Cynthia: In order to set the negative current (defocusing quadrupole magnets), the  cycling procedure should be reversed. 

When the calibration curves [-12 A +12 A] will be available, the procedure has to be the following. The magnet current should be ramped from 0 to IMAX , decreased down to -IMAX and then ramped again up to IMAX. 

Measurement current will be finally reached going to nominal current ISet. (IMAX  = 12 A).  Total cycling time is ~6 min [so ~1 min for 0 to IMAX, and the same for IMAX to - IMAX). Waiting time at IMAX & I=0 is ~10 sec.

Figure attached: Quadrupole cycling layout given by Cynthia.

Figure attached: Quadrupole cycling layout in case of bipolar power supplies and corresponding calibration curves.

For the linac, to set the quadrupoles to 0, we can use the last procedure involving the + I max and -Imax (figures attached) and for later, we should discuss with Fabrice Marteau how we procceed. 

We made the cycling for the QUAD qnd still we have 5-10 G of the remaining field. To be understood....