1. Multi Pixel Photon Counters (MPPC) and Scintillating Fibers (Sci-Fi)
as a trigger system for the
AMADEUS experiment
Alessandro Scordo (L.N.F.) (in behalf of AMADEUS experiment)
23° Indian-Summer School of Physics & 6° HADES Summer School 2011

2. Contents The AMADEUS experiment: a brief introduction
Trigger system requirements
MPPC working principle and status of art
10 channels prototype and MPPC characterization
Results of tests on DAFNE
New electronics and 64 channels prototype
Tests on hadronic beam
Conclusions

3. The AMADEUS experiment: a brief introduction
KLOE
- The main aim of AMADEUS is to confirm or deny the existance of Kaonic Clusters,
- EXTENDED PROGRAM: Low-energy interactions, cross sections in light nuclei, decay of resonance states and exotic channels in nuclear medium will be studied
DAΦNE

4. The AMADEUS experiment: a brief introduction
Deeply Bound Kaonic Nuclear States
First suggested by S.Wycech (1986)
Y.Akaishi and T. Yamazaki
(Phys. Rev. C65 (2002) )
“Nuclear bound states in light nuclei”
Normal Nuclear binding energy parameters:
Ebind ~ 20 MeV
G ~ MeV
DBKNS binding energy parameters:
Ebind ~ 100 MeV
G ~ 30 MeV
New kind of matter with
astrophysical implications
(Neutron stars, prof. Heuser talk)
K- + 4He reaction
(3-barionic state)

5. The AMADEUS experiment: a brief introduction

6. The AMADEUS experiment: a brief introduction
Target: A gaseous He target for
a first phase of study
First 4p fully dedicated setup!

7. The AMADEUS experiment: a brief introduction

8. Trigger system requirements
Small dimensions
Working in magnetic field
Working at room temperature
Very good time resolution (s ~ 300 ps)
High efficiency
Trigger system requirements
Multi Pixel Photon Counters (MPPC)

9. MPPC : working principle
P-N junction array working in
Geiger mode (micropixel)
Output signal is the sum of
all the micropixels
Each micropixel gives a high
gain signal (105 – 106)
indipendent of the number
of incident photons
and has a fixed amplitude
(binary mode)

10. First prototype and MPPC characterization
Is cooling
needed ?
A scintillating fiber is activated
by a beta Sr90 source
Both ends are coupled to detectors;
one is used as trigger

11. First prototype and MPPC characterization
Studying rates with and without the beta source, it turned out that starting from the 4th p.e. peak, dark count contribute is negligible
This means that non cooling is needed in this case!!!!

12. Montecarlo simulations: what are we expecting?
Momentum distribution of kaons is taken from Kloe Monte Carlo
BCF-10
1mm diameter
Kaons are expected to leave almost a factor 7 more energy than MIP electrons
GEANT3 simulation

13. Results of tests on DAФNE
22-24 January 2009

14. Results of tests on DAФNE

15. Results of tests on DAФNE
KM scintillator at 6 cm from Interaction Point
Fibers 5 cm below the lowest scintillator
RF/2 and KM coincidence as DAQ trigger
Pure KM signal also collected
MIPs coming from the I.P. are below the KM threshold

16. Results of tests on DAФNE
Kaon Monitor TDC (upper/lower coincidence)
Single peak resolution
Is ~ 100 ps
MIP/K separation ~ 1 ns K-
MIPs
MPPC tdc spectra
Single peak resolution
Is ~ 300 ps
Missing MIPs

17. New electronics and 64 channels prototype
32 Sci-Fi read at both sides
2 indipendent double layers with adjustable angle
Amplification of a factor 10
64 Constant Fraction Discr.
Logic OR of all detectors

18. Tests on hadronic beam p,m,e-,p beam (similar to DAFNE situation)
pM-1 beam at
Paul Scherrer Institute (PSI, Zurich)
Single particle conditon
(to be further checked)
Double anular setup 1 3 2 4
DAQ trigger:
Sc1&Sc2
Scintillator 1
Scintillator3&2

19. Common cuts for the whole analysis
Tests on hadronic beam
Protons
Cut fot T > 31.0 C
MIPs
Common cuts for the whole analysis

20. Tests on hadronic beam Left Right Perfect correlation and coupling
Sc1 is used as reference

21. Tests on hadronic beam: efficiency
73%
Fiber 5: eff = 99 %
92%
90%
70%
Fiber 6 : eff = 98,4 %
Double layer efficiency
Single layer efficiency

22. Tests on hadronic beam
Beam profile
Geometrical correlation

23. Tests on hadronic beam: cross talk
Fired fibers of layer 4 if fiber i of layer 4 is fired
4,6% 2%
2,4%
5,2%
6,5% 2% 1%
0,06%

24. … Conclusions… …and future plans
Small dimensions
Working in magnetic field
Working at room temperature
Very good time resolution (s ~ 300 ps)
High efficiency …
…and future plans
Temperature feedback circuit implementation
New efficiency measurements with scintillators
New tests in DAFNE
New ideas and applications for this nice setup

25. Spare slides

26. MPPC : working principle
Thermally generated electrons can activate the avalanche process in some pixel, with a high rate of Hz (dark current)
The main contribute is a peak corresponding to
1 pixel (photoeletron)‏
Luminescence of carriers can also
be absorbed by another pixel
giving a noise signal

27. First prototype and MPPC characterization
Pre-Amplifiers (X 100)‏
5 Channles HV
power supply
(stability better than
10 mV)‏
Scintillating fibers
Bicron BCF-10 (blue)‏
SiPM (HAMAMATSU U50) (400 pixels)‏
Operating voltage ~70V
Sr90 beta source (37 MBq)‏

28. First prototype and MPPC characterization
Threshold at 5 p.e.
Peak with most
counts: 5 p.e. (15%)
Black spectra are the
trigger-used MPPC
Red spectra are the
signal outputs of the
NON trigger MPPC

29. New electronics and 64 channels prototype
s ~ 80 ps
s ~ 40 ps
MPPC + Sci-Fi
Direct laser on MPPC

30. New electronics and 64 channels prototype
Fiber
Laser HV
MPPC RF
Preamp
Coincidence
TDC
RF/n
RF=90 MHz (≈ RF/4)
n ≈ 10000
s ~ 200 ps
No jitter from photon generation
(to be considered)

31. Tests on hadronic beam: “relative” efficiency
Fiber 5: eff = 27,3 %
In the case of non parallel double layers the geometrical efficiency is drastically reduced
Fiber 6: eff = 30,1 %

32. Tests on hadronic beam: “relative” efficiency
Fiber 5: eff = 27,3 %
In the case of non parallel double layers the geometrical efficiency is drastically reduced
Fiber 6: eff = 30,1 %

33. Single particle configuration !
Tests on hadronic beam: “relative” efficiency
Proton events = 6580
Proton on fibers = 1772
Nhits on fibers > 5 = 29 (1,6%)
Single particle configuration !