TG3: Diode Read-out
and signal processing
C. Cattadori on behalf of the working group
LNGS, 3-4 february 2005
C.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 RfCf 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 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.
LNGS, 3-4 february 2005
C.Cattadori
GERDA meeting - TG3 report
Choise of FET and preamps
• 2 possible FET
InterFET IF1331
Philips BF862
tested in HD and MI
tested in MI
• 2 Hybrid preamp
EURYSIS preamp PSC823C
MARS preamp developed by INFN Milano
LNGS, 3-4 february 2005
C.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)
LNGS, 3-4 february 2005
C.Cattadori
GERDA meeting - TG3 report
Agata Analog electronics performances
LNGS, 3-4 february 2005
C.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.
InLNGS,
Milano
we2005
will perform
these measurements
before
of
3-4 february
C.Cattadori
GERDA
meeting - end
TG3 report
february and a full report will be circulated.
Analog electronics
LNGS, 3-4 february 2005
C.Cattadori
GERDA meeting - TG3 report
Noise measurements
performed in Milano
15 days ago, on hybrid
ready to be delivered
to Cologne
LNGS, 3-4 february 2005
C.Cattadori
GERDA meeting - TG3 report
LNGS, 3-4 february 2005
C.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
LNGS, 3-4 february 2005
C.Cattadori
GERDA meeting - TG3 report
Room temperature noise
figure of J-FET monolithic
integrated preamps.
LNGS, 3-4 february 2005
C.Cattadori
GERDA meeting - TG3 report
LNGS, 3-4 february 2005
C.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.
LNGS, 3-4 february 2005
C.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)
LNGS, 3-4 february 2005
C.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….
LNGS, 3-4 february 2005
C.Cattadori
GERDA meeting - TG3 report