EM-minitower experience flight hardware (SSDs, Fes, Trays, tower, TEM, PSA) ground I&T read-out tools (DAQ/online) system test tower test-plans developement and tuning (LAT-TD-00191) CR and V.D.G. 17.6MeV gamma test
Single tray test sequence towards tower testing MCM test prior to mounting onto trays: read-out redundancy - for all possible configurations: load/read back registers pulse two random channels and read them out after FE trigger request dead / noisy channels systematic search det bias isolation before micro-bonding (MCM was taped) Tray test: leakage current vs bias voltage noise trigger rate vs discriminator threshold @ 70 V and 115 V bias dead / noisy strips systematic search (@ 115 V bias voltage) noise trigger rate vs discriminators threshold (@ 115 V) with noisy strips masked full data acquisition triggering on cosmics rays or beta source
MCM test Several bad behaviours found: readout of not strobed channels and/or missing strobed channels channels masking not always working some chips do not allow the transmission of data and/or trigger (bad I/O cells) sensitivity to system CLOCK some MCMs must be read at higher than nominal 2.5V voltage (~lower clock) New V6 FE and wafer test system improved 100% yield for new chips tested up to 28MHz and down to 2.25V
Single tray test leakage current 2500 4500 TG001Down 4000 TG001Up Leakage current (na) 2000 1500 1000 Tray-lab encpsulated ladders sum ladders sum Leakage current (na) 3500 3000 2500 2000 1500 Tray-lab encpsulated ladders sum ladders sum 500 1000 Leakage current (na) 0 0 20 40 60 80 100 120 Bias Voltage (V) 12000 10000 TG002Down Tray-lab 8000 encpsulated ladders sum ladders sum Tray-lab-repaired 6000 4000 Shield bond removed as inverted traces on bias-circuit caused shorts at high voltages Leakage current (na) 500 0 2500 2000 1500 1000 0 20 40 60 80 100 120 TG002Up Tray-lab encpsulated ladders sum ladders sum Bias Voltage (V) 2000 500 0 0 20 40 60 80 100 120 0 0 20 40 60 80 100 120 2500 Bias Voltage (V) 2500 Bias Voltage (V) TS001Up TG017Down Leakage current (na) 2000 1500 1000 Tray-lab encpsulated ladders sum ladders sum Leakage current (na) 2000 1500 1000 Tray-lab encpsulated ladders sum ladders sum 500 500 0 0 20 40 60 80 100 120 Bias Voltage (V) 0 0 20 40 60 80 100 120 Bias Voltage (V)
Noise measurement grounding problem Some problems at the beginning: honeycomb basically floating, huge increase of noise when trying to ground the box containing the tray. Handles MCM ground point Good electrical contacts (handles-honeycomb and MCM ground-honeycomb) done through longer screws touching the honeycomb - all grounding problems solved. Production: honeycomb grounded via a wire welded between honeycomb and closeout
Single tray test noise trigger rate Threshold Scan @ 70 V Threshold Scan @ 115 V Counting rate of noisy strips slightly increases @ 115 V bias voltage. Threshold Scan @ 115 V with 7 noisy strips masked When noisy strips are masked the behavior of the counting rate as a function of threshold is quite uniform over the whole tray.
Threshold Scan @ 115 V with 6 noisy strips masked. Noise measurement reveals disconnected Fes (as expected) Ladder n. 4 is almost completely not connected (bad pitch adapter not) and disconnected single channels Many disconnected channels expected from pitch adapter problems (too small bonding pads, bad gluing, cracked traces) new design with: extended traces optimized layout no spheres inside glue no cover layer 25% higher bending radius PCB test board under construction to test MCM+pitch adapter with strip-like capacitance load
Single tray test noise trigger rate the working point is defined as the DAC value as to have a counting rate below a given threshold significant differences among live channels seem to suggest quite a large spread in channels amplification, even in the same chip NB: this test was performed on a reduced number of channels by masking all channels but the one under investigation and by measuring the trigger request rate to the TEM Not seen before at UCSC but seems confirmed by current measurements at SLAC FE V6 should have minimal spread
Single tray test CR hitmaps TS001FRONT TG001FRONT Y-stack TG001BACK X-stack TG002BACK TG002FRONT TG017BACK
From Online display ToT : cuts on event size giving flat distribution revealed a bug that passed stripids instead of ToT values for single-strip events cured with new TEM firmware Number of clusters Event size
Minitower test at SLAC Minitower assembled at SLAC on march 25-26 Flex cables: wrong routing (reverse orientation on TEM-side) extra length (had to be trimmed on MCM-side) weak CLOCK line, broke on all of them after cable bending repaired with extra wire MCM-side connectors fragile, subject to torque from cable, glued with fast-drying glue onto small spots new design with correct routing bending tools MUST be used for cables (only partly used for minitower); will investigate if possible to build less rigid cables new MCM-side connectors with locating pins, metal body will be glued onto cables with better epoxy, solder pins will be glued too
Minitower test at SLAC Bias detector: Had two shorts after stacking trays in the tower MCM has a diffused HV + uncovered vias which cause shorts when MCM is pressed onto the closeout at ground) one dummy MCM was changed with one that had undamaged protection on vias one plastic layer slit between MCM and closeout production: will have a thicker kapton insulating layer over the MCM backside Read-out: crazy Fes always populating the event were causing phase errors in data stream and preventing proper read-out had to mute those Fes individually will be cured with bew Fes
Conclusions ongoing work EM-Minitower is a good test bench for all system aspects: Mechanics, sensors, electronics, software, test tools and strategies weak points caused delays but were clearly identified problems involved all aspects of the system (flex cables, MCM-connectors, MCM bias lines isolation, pitch adapter, FE bad functionalities, TEM firmware) solutions required a collaboration effort starting from the tracker group and involving I&T and the electronics groups temporary solutions were provided for the minitower run more stable solutions are being tested for production A task force with people from Pisa and SLAC is currently carrying on testing (noise studies, uniformities, dead/noisy channels monitoring, alignment, hitdetection efficiencies, resolution, trigger efficiencies) The minitower will be equipped with new MCMs and flex cables, will be retested and integrated with the calorimeter (due July 03) Tower test procedures are being finalized on the minitower