1. 8/11/2006 FPIX TB meeting L. Perera 1 Pixel Power Supply Response Measurement Lalith Perera - Univ. of Iowa Carlos Florez, Simon Kwan, Charles Newsom, Christian Veelken Response of the CAEN power supply to transient currents Response of the power supply to remote shut down.

2. 8/11/2006 FPIX TB meeting L. Perera 2 CAEN Power supply overview SY2527 system mainframe Can install six A1676A branch control cards A1676A branch control card –Controls one E4000 crate E4000 crate –Accommodates 8 power modules CAEN E4603 power module –Each unit has two independent power units Two low voltages 2.5V, 1.75V (remotely sensed voltage control, up to 6V at the supply) Two high voltages.

3. 8/11/2006 FPIX TB meeting L. Perera 3 Objective Preliminary testing to get familiar with using the power supply with the MSC cable for the system test Make sure that power supply meet system requirements and behave well with remote sensing: –Current fluctuations changes the voltage drop across the supply cable resulting fluctuating voltage at the load. CAEN A4603 48V Pulse generator CAEN SY2527 Load Cable ~40m scope

4. 8/11/2006 FPIX TB meeting L. Perera 4 CMS pixel power cable (MSC) We used a 40m length of MSC cable Six 4mm 2 cables for LV –4 for 2.5 V –2 for 1.75 Resistance of each cable m Cables for sense wires and HV

5. 8/11/2006 FPIX TB meeting L. Perera 5 Test Setup switching transistors resistor elements Jumper switches Test Load Six resistors ~1.6 (connected through jumper switches - up to 8A current) Two 0.1 connected through switching transistors (FET) (2A pulse current)

6. 8/11/2006 FPIX TB meeting L. Perera 6 Results pulse current voltage at the load control pulse No observed oscillations Voltage drops by ~ 0.5V when load change by 2A. recovery time of the power supply –2.5V ~50  s, 1.75V 100  s There are small (50mV) spikes at ~ 80kHz likely to be coming from from switching in the power supply 2.5V1.75V

7. 8/11/2006 FPIX TB meeting L. Perera 7 response to 1s pulse after adding 13F capacitor Voltage fluctuation can be lowered by adding decoupling capacitors near the load However in the real detector load is distributed, so capacitors at each ROC should take care of the fluctuation

8. 8/11/2006 FPIX TB meeting L. Perera 8 Remote Shut Down CAEN power supply is controlled by the DCS computer so can be turned on/off through DCS. It is software controlled so would to be too slow for an emergency shut down. There are two control inputs to SY2527 to turn off all channels. KILL: input for a TTL/NIM signal “ The KILL input signal, sent through the relevant connector, allows to switch the channels off at the maximum rate available, regardless of the Ramp-Down or other parameters.” INTERLOCK: close/open circuit input “The INTERLOCK condition allows to switch off simultaneously all the channels, similar to the KILL command”

9. 8/11/2006 FPIX TB meeting L. Perera 9 Shut Down Response Time Measurement power supply Pulse generator load scope KILL power supply load scope INTERLOCK relay From PLC Test setup to measure KILL response time Test setup to measure INTERLOCK response time 5v

10. 8/11/2006 FPIX TB meeting L. Perera 10 Results: KILL KILL Power Digital Power Ana. Response time 68ms18ms 36ms 40ms96ms27ms Response time to KILL changes from few ms to ~100ms

11. 8/11/2006 FPIX TB meeting L. Perera 11 INTERLOCK Response Time 36ms 42ms68ms Measured INTERLOCK response time is tens of ms and varies It could be that both KILL and INTERLOCK is activated by software So depending on where it occurs in the control loop of the power supply it gives a different response time. This needs to be verified with CAEN. INTERLOCK Power Ana. Power Digital

12. 8/11/2006 FPIX TB meeting L. Perera 12 Conclusions Power supply behaves well to transient currents with the CMS MSC cable. No oscillations observed. Remote sensing time constant of the supply voltage is about 25  s. There are two remote hardware shut down modes (INTERLOCK, KILL) available. Both have response times in the order of tens of ms