Transcript Experimental Results of CC2 Charge Sensitive Preamplifier

Meeting on GERDA Phase II
Front-End Electronics
R&D Status on the
Fully Integration of the
Front-End Electronics
Milano Bicocca - 16/4/2010
ASIC designed for the Gerda Experiment
- Multi Ch. Fully Integrated CMOS ASIC CSA (Heidelberg, 2007)
http://cdsweb.cern.ch/record/1034317/files/p515.pdf
- Single Ch. Fully Integrated CMOS ASIC CSA (Milano, 2007)
http://www.mpi-hd.mpg.de/gerda/public/2008/c08_IEEE_dresden_cmos_sr.pdf
- Single Ch. JFET-CMOS ASIC CSA (Milano, 2007)
http://www.mpi-hd.mpg.de/gerda/public/2008/c08_IEEE_dresden_preamp_fc.pdf
- Multi Ch. JFET-CMOS ASIC CSA (Milano, 2008)
http://ieeexplore.ieee.org/search/freesrchabstract.jsp?tp=&arnumber=5401678&queryText%3Dpullia+zocc
a%26openedRefinements%3D*%26searchField%3DSearch+All
- Multi Ch. JFET-CMOS ASIC CSA (Milano, 2009)
ASIC Development in Heidelberg
Design Features:
- 4 channels
- differential voltage output
- gain 5.8 mV/fC = 310 mV/MeV (Ge)
- dynamic range = 11 MeV (Ge)
- integrate feedback C and R
- programmable R up to 2 GΩ @LNT
- I2C interface for programming
- noise (Tsh= 10 μs, Cdet= 30 pF)
@RT: ENC ~ 220 e → 1.5 keV (Ge)
@LNT: ENC ~ 110 e (expected)
Results:
- ASIC works @LNT (77 K)
- gain 15% lower, perfect linearity
- programmable R worked !
- large noise (Tsh= 10 μs, Cdet= 30 pF)
@LNT: ENC ~ 500 e
- evidence of noise correlation
between channels
- noise (Tsh= 10 μs, Cdet= 30 pF)
calculated as (Out1 – Out2) / √2
@LNT: ENC ~ 240 e
Testboard
Kapton with ASIC
Conclusion:
- large common mode noise
- despite some effort: reason unclear
→ not usable as it is
- designer left collaboration
→ stopped ASIC development
ASIC Development in Milano
Design Features:
- 1 channel
- fully differential ASIC design
- CSA + Fully Differential Amplifier
- FDA with differential output (50 Ω)
- power supplies = ± 2.5 V
- power consumption < 50 mW
- gain 1 mV/fC = 54 mV/MeV (Ge)
- discrete C (for testing) and R
- pulsed-reset operation mode (no R)
- noise (Tsh = 50 μs, Cdet = 33 pF)
@RT: ENC ~ 200 e → 1.4 keV (Ge)
@LNT: ENC ~ 100 e (expected)
Results:
- ASIC works both at RT and LNT
- tested with C = 1 pF and R = 300 MΩ
- dynamic range > 20 MeV (Ge)
- shaping time of 50 μs is unrealistic
- large noise (Tsh = 12 μs, Cdet = 33 pF)
@LNT: ENC ~ 250 e
- energy resolution with SUB det.
(Milano 2008, Tsh = 8 μs)
@LNT: 3 kev @1.33 Mev
(60Co)
PCB with ASIC
Conclusion:
- evidence of fundamental noise only
- bad design choice of long shaping time
determined too a low input p-mos
transconductance of 2 mS
(vs better then 10 mS of BF862)
→ not usable as it is
- in order to concentrate on better CSA
→ stopped development
Set-up of the Gerda Experiment
ΔL ≈ 10 m
Electronics
CSA
(Flash ADC, …)
ΔL ≈ 10 m
Room
Temperature
Radioactivity issue:
Ge det.
∑ (Material Activity * Volume)
Δr2
CSA requirements:
Liquid
Argon
Cryogenic
Temperature
• Bandwidth ( > 10 MHz, 30 ns rise time)
• Noise (ENC < 150 e @LNT, Tsh =10 μs)
• Power consumption < 50 mW/channel
• Cross-talk between channels < 1%
Set-up of the Gerda Experiment
ΔL ≈ 10 m
Electronics
???
(Flash ADC, …)
ΔL ≈ 10 m
Room
Temperature
CSA
Radioactivity issue:
∑ (Material Activity * Volume)
Ge det.
Δr2
CSA requirements:
Liquid
Argon
Cryogenic
Temperature
• Bandwidth ( > 10 MHz, 30 ns rise time)
• Noise (ENC < 150 e @LNT, Tsh =10 μs)
• Power consumption < 50 mW/channel
• Cross-talk between channels < 1%
• Cryogenic operation
• Radioactivity issue:
(material, distance, volume)
Integration = Miniaturization
CSA far from detector means:
• increased noise
• reduced bandwidth
From the viewpoint of the
CSA design alone:
closer is better
• increased cross-talk?
100 mm
2 mm
Volume reduction ≈ 10000
Critical distance reduced by a factor of 100
Silicon Integration
easy for:
difficult for:
(Active Devices)
• CMOS
• JFET (available technology?)
• BJT (not suitable for LNT)
• Low Noise MOS (P Type)
(< 1 nV/√Hz eq. voltage noise)
(Passive Devices)
• Resistors (up to a few MOhm)
• Capacitors (up to a few pF)
(Passive Devices)
• Resistors (above 100 MOhm)
(large area or distortion with CMOS)
• Capacitors (above 100 pF)
• Inductors
(Active Devices)
also to be considered:
• Interface between ASIC and outside world
(bonding wires, glue, PCB, copper shield, connectors, pins, cables, ecc.)
Components of a CSA (on paper)
not easy to
integrate
Input
Output
Complete integration of a CSA with reasonable performances
in terms of bandwidth, noise, power consumption, etc.
is a difficult task but still possible
Components of a CSA (real world)
bonding wires
connector pins
PCB
(teflon + copper + gold)
cables (teflon + copper)
cables (teflon + copper)
Because cables have to be thin, they are far from ideal:
• High resistivity of central wire (≈ 1 Ω/m) and shield (≈ 0.2 Ω/m)
• High attenuation (10% for 10 m long cables, 50 Ω terminated)
• Electro-magnetic shielding not so effective (e.g. FM radio in Milano)
• Low voltage levels on board not perfectly the same as on the outside power supply
Components of a CSA (real world)
decoupling capacitors
• Most promising capacitors seems to be tantalum based
• Number of strictly required decoupling capacitors may change across different CSAs
• Reasonable values are n = 4 to 10; C = 10 μF; (VDC = 6 v)
• Insufficient LVPS decoupling may generate:
noise/instability in single channel CSA
noise/instability + cross-talk in multi channels CSA
Complex Optimization Problem (example)
integrate CSA
(less volume)
radioactivity
thinner cables
(less volume)
3 Ch. CSA
(less volume)
cross-talk
disturbances
noise
signal
integrity
LVPS in
parallel
50 Ω term.
receiver
more
decoupling
capacitors
radioactivity
Basic scenario to start with
ΔL1
(n)
1 wire
(n + 1 + 1)
(n + 4 + 1)
2 + 1 wires
5 + 1 wires
CSA FE
detector
noise
ΔL3
ΔL2
CSA
bandwidth, noise
10 m
(n/2n + 4 + 1)
5/6 + 1 wires
driver
not very critical
not very critical
with receiver is 50 Ω
terminated
Among open issues are:
• Single or multi channels (n) CSA
• Discrete or integrated electronics design
• For every reasonable configuration, determine radioactivity issue ( ΔL )
• Easy to deal with mechanical design
• Robustness, time, cost
receiver