DOI 10.1393/ncc/i2011-10781-5 Colloquia: IFAE 2010
IL NUOVO CIMENTO Vol. 33 C, N. 6 Novembre-Dicembre 2010
Silicon photomultipliers as a readout system for scintillating
calorimeters
A. Berra(∗) on behalf of the FACTOR Collaboration
Universit`a dell’Insubria and INFN, Sezione di Milano Bicocca - Milano, Italy
(ricevuto l’ 8 Ottobre 2010; pubblicato online l’8 Febbraio 2011)
Summary. — In recent years silicon photomultipliers (SiPMs) have been proposed
as a new readout system for scintillation detectors; these devices are characterized by a low bias voltage, a small dimension and the insensitivity to magnetic fields, making them a suitable alternative to the photomultiplier tubes (PMTs) in many experimental situations. The performances of FBK-irst SiPMs have been evaluated in different testbeams performed at CERN. The first setup consists of amplified SiPMs, characterized in terms of signal-to-noise ratio, efficiency and time response when connected to a tracker/calorimeter composed of plastic scintillator bars. In the second setup the performances of non-amplified SiPMs have been evaluated in terms of linearity and energy resolution when connected to two scintillator-lead shashlik calorimeters.
PACS 29.40.Mc – Scintillation detectors. PACS 29.40.Wk – Solid-state detectors. PACS 29.40.Vj – Calorimeters.
1. – The silicon photomultipliers
The Silicon PhotoMultipliers are devices composed by a matrix of pixels connected to a common output. Each pixel, which has a typical dimension of 20–100 μm, can be considered as a diode reverse biased below its breakdown voltage working in Geiger
mode [1]. The response of each pixel is digital, but the analog information can be
obtained considering the number of fired pixels (for a moderate photon flux). The main advantages of SiPMs wrt PMTs are a low bias voltage, simple readout, small dimensions, low cost and the insensitivity to magnetic fields.
(∗) E-mail: alessandro.berra@gmail.com c
240 A. BERRA on behalf of the FACTOR COLLABORATION (a) ADC 0 500 1000 1500 2000 2500 3000 3500 4000 Entries 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 S/N ratio = 18.947 FBK-IRST E5 - S/N Ratio (b) Hit Y position (cm) 2 2.5 3 3.5 4 4.5 Efficiency 0 0.2 0.4 0.6 0.8 1
SiPM Mean Efficiency = 88.63%
PMT Mean Efficiency = 88.20%
FBK-IRST E5 - Hit Position Efficiency
(c)
Fig. 1. – The EMR prototype (a); spectrum (b) and efficiency (c) obtained with a non-irradiated SiPM.
2. – Silicon photomultipliers tests
The first tests have been performed with a scintillating tracker/calorimeter, a proto-type of the Electron Muon Ranger (EMR) of the MICE experiment [2]. The protoproto-type
consists of 8 x-y planes with 10 1.5× 1.9 × 19 cm3plastic scintillator bars each; each bar
is readout by 4 0.8 mm WLS fibers, connected to a plastic mask which holds∼ 1 mm2
SiPMs. Different amplified devices has been tested before and after irradiation; for what concerns the non-irradiated and the gamma-irradiated devices, good results have been obtained in terms of signal-to-noise ratio, efficiency and linearity (see fig. 1). Worse results have been obtained with neutron-irradiated devices, which show a severe perfor-mance degradation.
The second tests have been performed using non-amplified SiPMs with a sensitive
area of∼ 1 mm2and 9 mm2connected to two scintillator-lead shashlik calorimeters; the
first one is composed by 41 tiles of plastic scintillator and 40 tiles of lead for a total of
Energy (GeV)
1 2 3 4 5
Electron Peak Position (ADC)
0 1000 2000 3000 4000 5000 6000 7000 8000 / ndf 2 χ 0.6835 / 7 p0 202.4 ± 197.6 p1 1406 ± 93.27 / ndf 2 χ 0.6835 / 7 p0 202.4 ± 197.6 p1 1406 ± 93.27 A μ Energy Response Linearity - SiPM Current 2
(a) Energy (GeV) 1 2 3 4 5 /E (%)E σ 0 5 10 15 20 25 30 / ndf 2 χ 35.82 / 7 Stochastic 14.64 ±0.2109 Constant 3.564 ±0.4115 / ndf 2 χ 35.82 / 7 Stochastic 14.64 ±0.2109 Constant 3.564 ±0.4115 A μ
Energy Resolution - SiPM Current 2
(b) Entries 3697 / ndf 2 χ 232.6 / 158 Constant 121.2 ±2.7 Mean 0.1792 ± 0.0068 Sigma 0.3958 ± 0.0056 Y Position (cm) -4 -2 0 2 4 6 Entries 0 20 40 60 80 100 120 140 Entries 3697 / ndf 2 χ 232.6 / 158 Constant 121.2 ±2.7 Mean 0.1792 ± 0.0068 Sigma 0.3958 ± 0.0056 A μ Residuals Y Direction - SiPM 1.5
(c)
Energy (GeV)
1 2 3 4 5 6 7
Electron Peak Position (ADC)
2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 22000 χ2 / ndf 0.08247 / 5 p0 95.41 ± 605.1 p1 2794 ± 179.9 / ndf 2 χ 0.08247 / 5 p0 95.41 ± 605.1 p1 2794 ± 179.9 SiPM 2
Energy Response Linearity - 9mm
(d) Energy (GeV) 1 2 3 4 5 6 7 Resolution (%) 0 5 10 15 20 25 30 / ndf 2 χ 119.4 / 5 Constant -1.388 ±0.626 Stochastic 18.02 ±0.2001 / ndf 2 χ 119.4 / 5 Constant -1.388 ±0.626 Stochastic 18.02 ±0.2001 SiPM 2 Energy Resolution - 9mm (e) Entries 7632 / ndf 2 χ 176.8 / 45 Constant 681.2 ± 10.6 Mean -0.0006177 ± 0.0050413 Sigma 0.4338 ± 0.0045 X Position (cm) -5 -4 -3 -2 -1 0 1 2 3 4 5 Entries 0 100 200 300 400 500 600 700 Entries 7632 / ndf 2 χ 176.8 / 45 Constant 681.2 ± 10.6 Mean -0.0006177 ± 0.0050413 Sigma 0.4338 ± 0.0045 Residuals X Direction (f)
Fig. 2. – Linearity (a), energy (b) and spatial resolution (c) obtained with the small shashlik calorimeter; linearity (d), energy (e) and spatial resolution (f) obtained with the large shashlik calorimeter.
SILICON PHOTOMULTIPLIERS AS A READOUT SYSTEM FOR SCINTILLATING ETC. 241
24 X0: each tile is 3.27 mm thick with an area of 8× 8 cm2. The second calorimeter
consists of 70 4 mm thick scintillator tiles and 69 1.5 mm thick lead tiles with an area of 11.5× 11.5 cm2, for a total of 19 X
0. The readout is performed using 64 0.8 mm WLS
fibers for the small device and 144 1.2 mm WLS fibers for the larger one; the fibers are then collected in bundles for a total of 16 readout channels for both the calorimeters. The performances of the devices have been evaluated in terms of linearity, energy and spatial resolution (see fig. 2), obtaining results comparable or even better to the ones obtained with the multianode PMTs.
REFERENCES
[1] Piemonte C., Nucl. Instrum. Methods Phys. Res. A, 568 (2006) 224. [2] Lietti D. et al., Nucl. Instrum. Methods Phys. Res. A, 604 (2009) 314.
