Transcript Document
Trip-t testing progress report discriminator fix effects of long cables [email protected] - 19/12/05 1 linearity discontinuity high gain channel 3 10.5x10 ADC units IBT=80 IBT=0 10.0 9.5 low gain channel 9.0 8.5 0 2 4 6 8 10 12 14 Qin [pC] linearity discontinuity removed by setting IBT to zero -> disables T-pulse circuit (advice from Paul Rubinov) [email protected] - 19/12/05 2 Trip-t schematic – front end single channel IBOPAMP A OUTPUT IBOPAMP 200fF + - GAIN[2] 160fF GAIN[1] 80fF 80fF V_REF + Q_IN IFFP2 IBP 1.0 pF GAIN[0] 40f F IB_T t OUTPUT 3.0 pF 40fF GAIN[3] Z IBCOMP IBOPAMP V_TH IFF x10 - RESET V_REF + + PLN_CLK DISCRIM_OUT IFFP2 [email protected] - 19/12/05 3 Effects of long cables Vbias look at SiPM O/P directly on scope (Russian SiPM) 1 MW thin coax or twisted pair 100nF scope 50/100W LED SiPM coax results (average pulse shape) raw data 0 0 -1 -1 20 cm / nsec 1ns 2ns 3ns 5ns 8ns 11ns 16ns 24ns -2 Volts -2 Volts time offsets removed -3 -3 -4 -4 -5 -5 -3 -3 -6x10 -6x10 100 120 140 160 180 200 220 100 nsec. 120 140 160 180 200 220 nsec. some reflection effects but not much effect on leading edge [email protected] - 19/12/05 4 Effects of long cables twisted pair (different lengths of unshielded twist-and-flat) time offsets removed raw data 0 0 -2 -2 -4 400 cm 300 cm 200 cm 100 cm 50 cm -6 Volts Volts -4 -6 -8 -8 -10 -10 -12x10 -3 -12x10 250 300 350 400 450 nsec. 500 550 400 cm 300 cm 200 cm 100 cm 50 cm 600 -3 250 300 350 400 450 nsec. 500 600 550 noticeable reflection effects on falling edge, but like coax not much on leading edge [email protected] - 19/12/05 5 Effects of long coax cables with TripT coax results (with SiPM -averaged pulse shapes) 6 5 4 3 2 1 0 -1 -2 Pipe Clock Volts use test channel – gives access to signal just prior to pipeline (A output – see p.3) lose amplitude as cable capacitance increases (Tript designed for 35 pF) PreampReset led pulse 500 non-ideal transmission line effects more obvious for longer cables 600 700 800 900 1000 1100 nsec. 1.0 0.9 note: not much reset time required 1ns 2ns 3ns 5ns 8ns 11ns 16ns 24ns Volts 0.8 Qin ~ 0.7 1.5 pC 0.6 20 cm / nsec 0.5 500 [email protected] - 19/12/05 600 700 800 nsec. 900 1000 1100 6 Effects of long twisted pair cables with TripT 6 twisted pair (different lengths of twist-and-flat) Volts instability develops for > 200 cm PipeClock 4 2 Preamp reset 0 pedestal effects (repetitive patterns after reset removed) due to digital pickup (lack of shielding) led pulse -2 500 probably OK up to ~ 100 cm 600 700 800 1000 1100 900 1000 1100 nsec 1.1 1.0 400 cm 300 cm 200 cm 100 cm 50 cm 0.9 Volts 900 0.8 0.7 0.6 0.5 500 [email protected] - 19/12/05 600 700 800 nsec. 7 Conclusions linearity discontinuity can be eliminated if disable T-Pulse circuit – good news effects of long cables (preliminary study using TripT test channel) coax tranmission line effects (reflections) for longest lengths used loss of signal amplitude as cable capacitance increases twisted pair up to ~ 100 cm may be OK evidence of instability for > 200 cm comments miniature coax likely to be expensive – individual connectors on TFB (Trip-t Front-end Board) but unshielded twisted pair gives vulnerability to pick-up (lots of digital signals on TFB) is shielded TP an option? would be preferable even for short lengths, does it exist in suitable form? can it be connectorized at reasonable cost? any suggestions welcome effects on timing (discriminator timewalk) not yet studied (but scope pictures tend to suggest should not be a problem) personal opinion try hard to keep SiPM-Tript distances as short as possible – danger of vulnerability to problems (e.g. particularly interference with unshielded twisted pair) that may be curable in the lab, but which may re-occur in the final system and be hard and/or costly to solve [email protected] - 19/12/05 8