ROBOX with Multi Anode PMT’sStatus and plans

A. Mestvirishvili, I. Schmidt, S. Sen, F. OzokUniversity of Iowa

ROBOX

• ROBOX with 24 new m-anode PMT’s assembled and being tested in B904 test facility

• Box is operational, test runs were taken – SPE vs HV, LED vs HV, phase scan. Analysis is in progress

• Initially planned to be installed during January this year, just before HF leaves garage

• Postponed due to observed problem with baseboard. Particularly with the PMT socket

• New schedule for installation mid February

ROB with new adapter boards and recessed connectors

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New Base boardBaseboard with adapter board

Baseboard with PMT’s

Baseboard – view from socket side. Sockets are custom designed at FNAL

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550 V 600 V

650 V 700 V

R7600 LED vs Channels - 2012

Slide borrowed from Sercan Sen’s presentation. Full version can be found

https://indico.cern.ch/conferenceDisplay.py?confId=174973

8 channels are missing on the plot for HV=700. This is due either reconstruction program can not treat correctly saturated channels, or not proper run was used to produce this plot

LED Signal for 700 Volt

Reflections seen here appears to be feature of the test stand and QIE.

We do not have light guides and light injection path is slightly different for a test stand.

When PMT produces large signal, more 10mA QIE input circuit is not correctly impedance matched to cable and we get reflection

600Volt

750Volt

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R7600 LED vs HVs - 2012

Chan 01Chan 06Chan 13Chan 22

1. Channel      6.79401e+006. Channel      6.57143e+007. Channel      6.93455e+0012. Channel     6.48874e+0013. Channel     6.95571e+0014. Channel     6.49086e+0015. Channel     6.79958e+0016. Channel     6.82936e+0017. Channel     6.99471e+0018. Channel     6.68241e+0019. Channel     6.61797e+0020. Channel     7.16156e+0021. Channel     6.17717e+0022. Channel     6.67851e+0023. Channel     7.14078e+0024. Channel     6.47633e+00

Slide borrowed from Sercan Sen’s presentation. Full version can be found

https://indico.cern.ch/conferenceDisplay.py?confId=174973

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Last SPE Runs, Channel 13-24

https://indico.cern.ch/conferenceDisplay.py?confId=174973

Slide borrowed from Sercan Sen’s presentation. Full version can be found

Problems we hit during testingTwo from three base boards, which were shipped from FNAL in December were not working properly.

Cathode Voltage – 600V Voltagesr for last two dinodes – 95 and 47 V

Power supply was drawing too much current and tripping finally with over current protection when on a last dinodes nominal values were set. When power for last two dinodes were off, divider was setting different values for those two dinodes, then nominalMeasuring the resistances of divider chain showed that last two dinode resistor values were different than nominal.

PMT Sockets

Pics from Sergey Los

Pins are press fitted to PCB and probably this cracks the capacitors, which then alerts the resistor values in a divider chain and, as consequence changes division coefficient

Designed at FNAL

https://indico.cern.ch/conferenceDisplay.py?confId=174973

Problems we hit during testing - 2

1. New boards, which underwent more strict test were shipped from FNAL. All three boards exchanged.

2. During the test one board failed again with exactly the same signature, as previous two. •Power supply for last dinode tripped with over current protection•Operating the board without external voltages for last two dinodes resulted voltages set by divider to be 88 and 33 Volt instead of 95 and 47 for 600 Volt for cathode• Board was exchanged. ROBOX is operational now with new board installed

Two different solutions

• First press fit the pins, then solder caps

Difficulties due to space unavailability

Second solution – remove caps from socket and move them to baseboardDifficulties - (according to Sergey Los) “several extra centimeters in dinode connection which is at the edge of 1ns rise time”

Summary• After a faulty baseboards were exchanged ROBOX is operational.

Different tests were done – SPE, LED, Phase scan etc.• Analysis is in progress, but from those results which are already obtained

and provided baseboards are in normal working condition, everything looks good

• ROBOX is ready to be installed on detector. Installation postponed for four weeks, until we completely eliminate reason of failure

• Two different solutions – either first press fit the pins and then solder caps, or just move caps from socket to baseboard

• In case of baseboard last or last two dinode caps fails it can be operated without power for last two dinode, but this is not perfect solution since extra noise can be introduced due to current leakage, gain change, response linearity will be alerted.