1. SIDDHARTA: the future of exotic atoms research at DAFNE
Silicon Drift Detector for Hadronic Atom Research by Timing Applications
DAFNE-2004: Physics at meson factories
Mihai Iliescu
INFN-LNF

2. The goal of KH and KD measurements
a few eV determination of both shift and width of the 1s
level induced by the strong interaction in the Kp and KD
atomic systems
The main feature to deal with, in order to obtain the
desired accuracy, is the S/B ratio.
This requires to pass from 1:70 (KH today)
to at least 1:1 (KH) and 1:5 (KD-first time)

3. Experimental requirements for the measurements
a triggerable, large area, high resolution, high efficiency
in the energy region of interest (1-20 KeV)
X-ray detector

4. Triggerable SDDs
A large area Silicon Drift Detector (SDD), equipped with
trigger electronics, presently under development
(SIDDHARTA project), satisfies the experimental
requirements

5. Working principles of the SDD

6. The classical PIN (Positive-Intrinsic-Negative) diode detector
Entrance window n + p - V c
ANODE
The anode capacitance is proportional to the detector active area

7. The Semiconductor Drift Detector
The electrons are collected by the small anode,
characterised by a low output capacitance.
Anode
Advantages: very high energy resolution at fast shaping times, due to the small anode capacitance, independent of the active area of the detector

8. The Silicon Drift Detector with on-chip JFET
JFET integrated on the detector
capacitive ‘matching’: Cgate = Cdetector
minimization of the parasitic capacitances
reduction of the microphonic noise
simple solution for the connection detector-electronics in monolithic arrays
of several units

9. The integrated JFET
Detector produced at Max-Planck-Institute for Extraterrestrial Physics, Garching, Germany

10. Performances of the SDDs

11. Silicon Drift Detector QE and resolution
Quantum efficiency of a 300 mm thick SDD
55Fe spectrum measured with a SDD
(5 mm2) at –10°C with 0.5 ms shaping time

12. Spectroscopic resolution: detector comparison - 1
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9 1
100
200
300
400
500
600
700
800
A (cm-2)
FWHM (eV)
SDD PIN Si(Li) K keV line
PIN Tsh=20us
Si(Li) Tsh=20us
SDD Tsh=1us

13. Spectroscopic resolution: detector comparison - 2
FWHMmeas of monoenergetic emission line 5.9 keV
1cm2 detector at 150 K
SDD FWHM=140eV tshap =1ms
Si(Li) FWHM=180eV tshap =15ms
PIN diode FWHM=750eV tshap =20ms
CCD FWHM=140eV tframe= ~ s

14. Timing resolution with SDD
A=0.1cm2  Tdrift = 70ns
A=0.5cm2  Tdrift =350ns
A= 1cm2  Tdrift =700ns
With:
r = 2kW/cm
H = 450mm

15. Timing with the anode signalhn IK IA hn t IA
tdr max

16. Triggered acquisition
Kaon trigger
Concidence windows
Detected pulses
Considered pulses
X-ray pulse
Background pulse
Tdr max

17. Background reduction with triggered acquisition
Machine Background
NK = number of detected kaons per detected Ka X-ray = 103 Br = background rate = 103 events/s over 200 cm2, full spectrum (1-20 KeV) -->50 Hz/1KeV
Tw = gate window
Tw = NK x Tdrift max = 103 x 1 ms = 1ms
B = Br x Tw = 50 s-1 x 10-3 s = 5 x 10-2
S/B=20/1 negligible
Hadronic background (Kp-pS interaction, synchronous)
preliminary simulation (typical SDD thickness 300 mm)
S/B = 5/1 (KH), 1/4 (KD)

18. SDD test setup electronics layout
P.S.
Temp.
control
SDD canister
7 Shapers, peak stretchers
& discriminators HV
control
Amplified
SDD
output
signal
Stretcher
reset
DAQ
Analog output
Shapers control
motherboard
Discrim. output
Trigger
(NIM
logic)
NIM 2
TTL
Trigger signal
Scintillators

19. Detector biasing parameters
Test of the 30 mm2 SDD
Detector biasing parameters
Current
Voltage
electrode
400mA
+12 V
Drain -
gnd
IS,OS
20.9mA
- 178 V
R#N
<0.1mA
- 91 V
Back
0.5mA
- 18 V
IGR
20.8mA
- 10 V
R#1

20. T = - 40°C,
tsh=0.75ms

21. SIDDHARTA setup version 1
beam pipe
and kaon trigger
vacuum chamber
feed-throughs for
SDD electronics
port for
SDD cooling
target
cooling line
SDD pre-amplifier
electronics
SDD detector
chip
target cell
lead table

22. SIDDHARTA setup version 2
SDDs array
Beam pipe e- e+
Kaon trigger
Cryogenic target cell

23. Kaons stopped inside target
Kaon stopping distribution inside hydrogen target
for a toroidal setup
Signal: ~ 30 times more than in DEAR
Kaons stopped inside target
~ 30% (all generated)
MonteCarlo simulation

24. integrated luminosity
SIDDHARTA Kaonic hydrogen simulated spectrum
MonteCarlo simulation
Precision on shift ~1 eV
integrated luminosity
60 pb-1
S/B = 5/1

25. Precision on shift < 10 eV integrated luminosity
SIDDHARTA Kaonic deuterium simulated spectrum
Precision on shift < 10 eV
S/B = 1/4
MonteCarlo simulation
integrated luminosity
100 pb-1

26. SIDDHARTA collaboration
LNF, Frascati (Italy)
MPE, Garching (Germany)
PNSensor, Munich (Germany)
Politecnico, Milan (Italy)
IMEP, Vienna (Austria)
IFIN-HH, Bucharest (Romania)

27. Assembly on DAFNE and data taking
Conclusions
Results obtained with DEAR and evaluations done for SIDDHARTA show that DAFNE represents an ideal machine for hadronic atoms research
Continuing tests on detectors to obtain best performance prototype, compatible with a large area setup.
Finalizing the design of the new experimental setup:
front-end electronics, mechanics, cryogenics, vacuum
2006
Assembly on DAFNE and data taking