Trip-t testing progress report discriminator fix effects of long cables m.raymond@imperial.ac.uk - 19/12/05

linearity discontinuity linearity discontinuity removed by setting IBT to zero -> disables T-pulse circuit (advice from Paul Rubinov) m.raymond@imperial.ac.uk - 19/12/05

Trip-t schematic – front end single channel Q_IN A OUTPUT 200fF IBP 1.0 pF 3.0 pF GAIN[3] RESET Z IFF IBOPAMP GAIN[2] 160fF GAIN[1] 80fF GAIN[0] 40fF + - V_REF IFFP2 x10 IB_T IBCOMP DISCRIM_OUT V_TH PLN_CLK t OUTPUT m.raymond@imperial.ac.uk - 19/12/05

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) time offsets removed raw data 20 cm / nsec some reflection effects but not much effect on leading edge m.raymond@imperial.ac.uk - 19/12/05

Effects of long cables twisted pair (different lengths of unshielded twist-and-flat) raw data time offsets removed noticeable reflection effects on falling edge, but like coax not much on leading edge m.raymond@imperial.ac.uk - 19/12/05

Effects of long coax cables with TripT use test channel – gives access to signal just prior to pipeline (A output – see p.3) Pipe Clock coax results (with SiPM -averaged pulse shapes) lose amplitude as cable capacitance increases (Tript designed for 35 pF) non-ideal transmission line effects more obvious for longer cables note: not much reset time required PreampReset led pulse Qin ~ 1.5 pC 20 cm / nsec m.raymond@imperial.ac.uk - 19/12/05

Effects of long twisted pair cables with TripT (different lengths of twist-and-flat) instability develops for > 200 cm pedestal effects (repetitive patterns after reset removed) due to digital pickup (lack of shielding) probably OK up to ~ 100 cm PipeClock Preamp reset led pulse m.raymond@imperial.ac.uk - 19/12/05

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 m.raymond@imperial.ac.uk - 19/12/05