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TC detector

TC detector. Flavio Gatti - Univ. and INFN of Genoa on behalf of the TC Group PSI- Review Meeting, 17 Feb. 2010. Status in RUN 2009. Longitudinal detector (Bars+PMTs): it has operated as in RUN 2008 without HW changes.

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TC detector

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  1. TC detector Flavio Gatti - Univ. and INFN of Genoa on behalf of the TC Group PSI- Review Meeting, 17 Feb. 2010

  2. Status in RUN 2009 • Longitudinal detector (Bars+PMTs): it has operated as in RUN 2008 without HW changes. • Transversal detector (Fiber+APD): the readout electronics has been modified for achieving faster output pulses. Total output 80 ns ~20 ns risetime Diff. out (-) Diff. out (+)

  3. Longitudinal Detector Performance • Small worsening of timing resolution (see next talk by Cecilia) • Check under way: • Baseline noise/EMI at the Disc input worse than in 2008 • Optical coupling (silicone grease, air gap, absorption) • PMT Gain: Re-measure PMT gain of 4 selected bars (8-PMT) 2008 2009 Intrinsic resolution (jitter of e+ time of flight not included)

  4. Most probable origin: higher baseline noise @ discriminators (DTD) input • Baseline oscillates (50Hz) with amplitude of 15 mV • While a moderate threshold decrease improves timing res., a further decrease gives worse results (10mV). • But 10 mV threshold was the value used in the beam test! • High level of signal cleanliness is needed for best performances. Some further improvement must be achieved, taking care (monitoring) the baseline noise Baseline @ Disc input Baseline sampled at high freq.

  5. New APD FE electronics • New electronics based on voltage amplification of APD current signal on noise matched resistor R3 • The boost capacitor reduce the quenching effect of HV line resistors enhancing signal in proximity of breakdown point • RMS noise value of 25mV in the 20MHz BW achieved at the output of the 8 summing channels Amplitude [V] Time [A.U.]

  6. New APD FE electronics • Improved PCB layout (better separation of Analogic and Digital grounding, lower coupling even if higher bandwidth- about 20 MHz) • New components instead of ones that have shown failures. • Control bus (I2C) improved Old FE Board New FE Board

  7. Electronics production and commissioning actual schedule • Design of the new electronics in Dec.09 • Prototype and test: Mar.09 • Component procurement and PCB production: Apr. 09 • Delay in delivery and bad production. First 32 channels at the end of July and second 32 channels in a second production at end of august. • Mounting and commissioning: • TC US 1st week of August, • TC DS 1st week of September. • Positive stand-alone tests before entering in COBRA. • Due to the tight mounting schedule and the priortary DAQ tuning before starting stable data taking, we were forced to skip the full integration test with DCH inside COBRA. Test were made only accessing the electronics outside COBRA.

  8. APD ON APD ON APD OFF DAQ Problem APD DS OFF APD US OFF ? Katia F. First TC Full operating test with DCH: found a not strict correlation with DCH noise from APDs US/DS • From Run 50225-50358 APD ON, • From Run 50359 APD off for DAQ problem • From Run 50506 APD ON • From Run 50590-50659 APD ON -> DS OFF-non effect -> US off noise disappear

  9. APD OFF APD ON Comparison with Run2008 • Effect of APD on the DCH in run 2009 of old electronics • From run 38104 al run 39349 gli APD OFF, in the remaining runs APD ON. • Negligible effect on DCH Katia F.

  10. APD ON Katia Negative results acting outside COBRA • A full survey of all possible sources of noise/EMI outside COBRA results with no improvement: conditions of stable performance were not achieved • Need of working directly on the TC on-Board electronics → wait for the shut-down APD OFF

  11. Work under way in Jan.-Mar. • Level of EMI/noise signal at the input: • 20-50 uV if not coherent, • 3-6 uV if coherent. • Due to high amplification: • 0.1-1 V signal on output cable--> possible irradiation to DCH • Positive feedback if input couple with outputs • Work planned with the US and DS TC:1- test an EM shielding on the preamplifier input2- test the effect of pick-up on HV and LV cable3–reduce the cable emission inside COBRA 4- eliminate any cause of coupling of the output to the input5- change the not working boards and  a few resistors on I2C bus receiver • Test the effect of these changes with the TC inside the COBRA. • Two phase work:1-the first just after the Xtmas holidays (jan 11 to 29) in order to find the causes of the excess noise and study/test the solutions2-the second period after a while in order to have enough time to build the shielding tool in our workshop (2nd half of February)

  12. 1St Phase done • Balanced the I2C bus from Pacth Panel to F.E. boards (change of pull-up resistors) → now bus signal in the specifics in any conditions and stable when idle • Inserted a shield on to APD-Preamplifier input → decoupled input from EMI and HV or output (digital or analogic cables) • Reduced the analogic output band from 150 Mhz to approx 50 MHz with further feedback capacitor → reduced the capability to emits high frequency signals • Decoupled differential amplifier output from twisted pairs cable with small resistor (60ohm/polarity) → reduced back action from electronics rack • Reduced HV- output coupling by choosing different cable paths and proper shielding → output signal decoupled from FE input through HV cables • Burst signals generated by HV where filtered ( do be done properly later) • Improved Power supply of F.E boards by changing cables from Patch Panel → decoupling of different F.E. Board respect supplied by the same Patch Panel

  13. Few snapshot of the work under way Decoupling HV-input-output Shield of APD-Preamplifier input Test of improved supply sables Insert 2 capacitors, change 1 resistor Insert 2 output matched resistors

  14. Before/After (few examples) Typical EMI from HV HV filtered Out Out HV-500MHz BW HV-20MHz BW Clean I2C transmission Pattern and stable after transmission I2C with high freq oscillation after the transmission

  15. Example of self-sustained and/or picked-up oscillations • 100MHz, 20 MHz, 8.3 MHz oscillations were observed but not found a clear origin • Most probable conclusion: mix of picked-up signal that were amplified and sustained by electronics through output-input coupling inside COBRA. 8 MHz 100 MHz

  16. Effect on the DCH noise: at the beginning of the 1st phase test } Various Grounding and filtering configuration In on In off In off Out off

  17. Effect on the DCH noise: at the end of the 1st phase test In On partial init. In On full not init In On full init In On partial Out off In off

  18. Presently achieved an average noise RMS of 25 mV as in the APD test with standalone electronics at Genoa and PSI (outside COBRA), Aug 09.

  19. Conclusions • The goal of the 1st Phase beam-off has bee achieve successfully. • After working on shielding, filtering and signal matching, we are now at the target performance of APDs in operating conditions inside COBRA. • Negligible effects on DCH noise. • We need to perform these modifications for all channels and both TC in the next month • Most of February needed for preparing these modification (shields, cables, filters on HV,…) • Completion of work: end of March 2010

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