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TG3: Diode Read-out and signal processing C. Cattadori on behalf of the working group

TG3: Diode Read-out and signal processing C. Cattadori on behalf of the working group. Choice of FET and preamps. Strategy has been defined. For Phase I three possibilities are actually pursued: 1 cold FET and R f C f and warm hybrid preamps a la AGATA near the crystals

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TG3: Diode Read-out and signal processing C. Cattadori on behalf of the working group

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  1. TG3: Diode Read-out and signal processing C. Cattadori on behalf of the working group C.Cattadori GERDA meeting - TG3 report

  2. Choice of FET and preamps • Strategy has been defined. For Phase I three possibilities are actually pursued: • 1 cold FET and RfCfand warm hybrid preamps a la AGATA near the crystals • (inside the LN bath) • pro: ready working (from the electronic point of view) solution • cons: problems of radioactive background from the hybrid • themselves and of • the thermally insulated box needed to contain the hybrids and • keep them at proper temperature. • 2 cold FET and RfCf and warm hybrid preamps outside the LN bath. • pro: no problems with background (apart from FET etc) • cons: problems from long cables (~ 4 m) stabilization of • amplifying stage, reduced bandwith, noise increase, • noise pick up, increased possibility of cross talk between • channels, microfonic noise etc. C.Cattadori GERDA meeting - TG3 report

  3. Choise of FET and preamps • 2 possible FET • InterFET IF1331 tested in HD and MI • Philips BF862 tested in MI • 2 Hybrid preamp • EURYSIS preamp PSC823C • MARS preamp developed by INFN Milano C.Cattadori GERDA meeting - TG3 report

  4. Analog electronics • Starting point is MARS preamplifier developed by A. Pullia University and INFN Milano for AGATA. • in this month 32 of these preamps will be delivered to Cologne to be tested MARS preamps have extreme low noise figure 130 -150 e- ENC (RMS) at 20 pF input but need to be slowed down to draw 4m cable from cold FET! (ref IEEE Trans. on Nucl Sc. 49-5(2002)2436) C.Cattadori GERDA meeting - TG3 report

  5. Agata Analog electronics performances C.Cattadori GERDA meeting - TG3 report

  6. Choice of FET and preamps MARS preamps have extreme low noise characteristics 130 -150 e- ENC (RMS) at 20 pF input and very fast. Can draw 4m cable from cold FET acting on compensating capacitor in the cascode stage! For GERDA they will put a trimmer capacitor 0-3 pF. Remember: the preamps slow down! At HD they have been able to stabilize the Eurysis preamps connected to FET through a 4 m. long cable using the same technique. Needed noise measurements in this configuration. In Milano we will perform these measurements before end of february and a full report will be circulated. C.Cattadori GERDA meeting - TG3 report

  7. Analog electronics 25 mW only! C.Cattadori GERDA meeting - TG3 report

  8. Noise measurements performed in Milano 15 days ago, on hybrid ready to be delivered to Cologne C.Cattadori GERDA meeting - TG3 report

  9. C.Cattadori GERDA meeting - TG3 report

  10. Choice of FET and preamps (cont’d) 3. Use JFET based monolithic preamps mod IPA4 developped by Manfredi, Speziali, Re in a INFN-MURST project, now commercialized by InterFET co. This can be used cold! (But noise at LN never measured)  ongoing Extremely low noise obtained with buried layer technique and very high quality silicon. ref. Nucl Phys B(Proc. Suppl.) 44(1995)613-616 NIMA 380 (1996) 308-311 C.Cattadori GERDA meeting - TG3 report

  11. Room temperature noise figure of J-FET monolithic integrated preamps. C.Cattadori GERDA meeting - TG3 report

  12. C.Cattadori GERDA meeting - TG3 report

  13. Very good new: it works in LN (tested here at LNGS by myself) Noise measurements at LN ongoing here at LNGS and then we will perform a comparative study in Milano of the hybrid MARS-AGATA preamp versus the JFET monolithic. This solution will allow to have a voltage signal in the 100 mV - 5 V range flowing in the cables from the crystal to the outside of the LN2 bath! Work is going on and this solution is very promising. C.Cattadori GERDA meeting - TG3 report

  14. 4. develop an ad hoc preamps integrated on Si. We will have an integration test-run at Europractice (Belgium) within the first semester of 2005 to make the “porting” of MARS/AGATA preamp on Si. (for phase II OK, but not sure for phase I) C.Cattadori GERDA meeting - TG3 report

  15. Conclusions • Work is ongoing to look for the preamps suitable to work in our experimental conditions and a couple of solution are pursued. • Open issue: • choice of mounting, cables, gamma ray -measurements of feedback components, and of IPA4 preamplifiers in the die configuration, long term stability measurements, etc…. C.Cattadori GERDA meeting - TG3 report

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