1. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report TG3: Diode Read-out and signal processing C. Cattadori on behalf of the working group

2. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report 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 (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 R f C f 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.

3. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report 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

4. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report 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)

5. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report Agata Analog electronics performances

6. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report 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.

7. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report Analog electronics 25 mW only!

8. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report Noise measurements performed in Milano 15 days ago, on hybrid ready to be delivered to Cologne

9. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report

10. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report 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

11. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report Room temperature noise figure of J-FET monolithic integrated preamps.

12. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report

13. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report 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.

14. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report 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)

15. LNGS, 3-4 february 2005C.Cattadori GERDA meeting - TG3 report 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….