Spikes A.Mestvirishvili, I.Schmidt University of Iowa 1

Setup 2 After blowing up two baseboards a custom divider was built. It schematically completely equivalent to baseboard. Just instead of SMD normal components are used. V set – Voltage set by PVSS V nom - Voltage set by divider chain matching the cathode voltage V cat – Cathode voltage example V cat = 600V Din. 9 V nom = 94 V Din. 10 V nom = 47 V Normal operating conditions wit all three voltages Almost all measurement were done at the dinode 10 output pin

Ramp at d10 for normal operation conditions with all three voltages 3 Ramping up all three voltages set 600 – Ramping down all three voltages set 600 –

Ramp at d10 for normal operation conditions with only cathode voltage 4 Ramping down only cathode voltages set 600 – Ramping up only cathode voltage set 600 – 0 - 0

Killer spike 5 V cat = 700V D9 V nom = 112V D10 V set = 40 V Vertical scale 50V per square Horizontal scale 2.5 sec per square V cat = 700V Din. 9 V nom = 112 V Din. 10 V nom = 56 V Normal operating conditions wit all three voltages If we set at D10 = 45 or 50 volt PSU does not trips and no spike is generated

Double ramp and Killer spike 6 V cat = 1000V D9 V nom = 160V D10 V set = 47V Vertical scale 50V per division V cat = 1000V Din. 9 V nom = 160 V Din. 10 V nom = 80 V Normal operating conditions wit all three voltages

Cathode Voltage vs D10 Voltage 7 Blue line – cathode voltage, measured with divider probe with coefficient of division - 150

Turn off spike – PSU B 8 After PSU tripped with over current protection turn OFF command was sent from PVSS display to clear alarms Voltage at last dinode = 56V

Turn off spike – PSU A 9 After PSU tripped with over current protection turn OFF command was sent from PVSS display to clear alarms Blue line – cathode voltage, measured with divider probe with coefficient of division Zoomed – vertical scale 10V/square Vertical scale 50V/square

Turn off spikes 10 1.We induced a over current trip of cathode voltage 2.Sent TOFF command – no spikes observed

Summary Study of HF PSU behavior during ramp up/down is in progress Clearly identified the conditions when the spikes occurs killing the components on a baseboard. If the voltage on either from dinode 9 or 10 is below the value main voltage divider requires – PSU trips producing the huge spikes with amplitude at the dinode 10 of 200 – 250 Volt HF PSU is able to sink some amount of current but if it exceeded then generates spikes. After this unusual spikes occurs and PSU trips another kind of spikes – so called Turn OFF spikes occurs. Operating the divider with only cathode voltage set has no abnormalities Ramping up and down is normal, without any abnormalities ROBOX can be operated with only cathode voltage at P5. Current provided by one PS module is more than enough 11