RPADG 400 L 4 T RBH 021 B

RPADG. 400. L 4 T. RBH. 021 B C oc las s_6 3 et han g ec efo r • Observed ~1 in every 10 pulses 3 lass_6 e to c chang fb • The voltage source gets into an oscillatory mode for about 100 ms efore Ire • Beam passes at time C Iref b A • A ramp rate change is observed between points A, B when the voltage rises to more than 400 V. • Initial diagnosis • Problem with the voltage loop of the power converter • Note that the desired Iref is still obtained (at time C) • IREF_LIM warning seen in the power converter event log (but not long enough to be easily observed, eg LASER) K. Papastergiou, O. Michels, Q. King, R. Murillo, D. Nisbet

RPADG. 400. L 4 T. RBH. 021 2: the I_loop changes the I_ref to cope with the new limit. Operation continues with an I_REF_LIM warning (active for 100 ms)… Iref, Imeas Vref Vmeas • The voltage loop of the power converter is digitally controlled by a DSP • An internal parameter is measuring an offset on the voltage and hitting a limitation • While the FGC current controller thinks the VS is more capable and asks for more. • The following action in the DSP configuration corrected the problem. # Maximum output value (0: disabled) ! S REGFGC 3. RAW. DSP_PARAM_F[25] 450 500 1: the V_loop hits an internal limit • A sync_db is performed to synchronise the database with the latest parameters. K. Papastergiou, O. Michels, Q. King, R. Murillo, D. Nisbet

RPADG. 400. L 4 T. RBH. 021 • The thresholds for the LT_MBH input to the BIS were updated to give more flexibility around the 612 A setpoint • Was: PERMIT = [603 A; 613 A] • Now: PERMIT = [605 A; 621 A] • Settings changed and validated via the BIS interface • This will allow scans to be made around the setpoint D. Nisbet, X. Munger