AUTOMATIZED DEDICATED MEASUREMENT SETUP FOR SIPM ARRAY CHARACTERIZATION - 22 FEB 2021 I ANOOP N KOUSHIK
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AUTOMATIZED DEDICATED MEASUREMENT SETUP FOR SiPM ARRAY CHARACTERIZATION
22 FEB 2021 I ANOOP N KOUSHIK
OUTLINE
I) Introduction to SiPM array
II) Motivation and objectiv
III) Irradiation experiment at JULI
IV) Instrumentation - Hardware and software development
I) Dark current characterizatio
II) Responsivity characterizatio
V) Summary and Outlook
22.02.2021 2
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INTRODUCTION TO SiPM ARRAYS
• Silicon photomultiplier (SiPM) is a solid-state photon detector with single photon counting
capability.
• Each SiPM consists thousands of Single Photon Avalanche Diode (SAPD). With SAPDs set to
Geiger mode and connected in parallel, resulting total current is proportional to the number of
the SAPDs triggered.
• SiPM array / matrix is made of 64 (8x8) SiPM.
22.02.2021 3
INTRODUCTION TO SiPM ARRAYS
• Dark current - False positive triggers of the microcell (SAPD) in absence of photon integrated
over time. Usually there are 1 to a few microcell contributing as noise.
• Photon detection efficiency (PDE) - The ratio of the number of detectable photoelectrons to the
number of photons incident on the SiPM. It is a function of the wavelength, applied overvolt
and the fill factor.
• Responsivity - Defined as the average photocurrent produced per unit optical power:
Ip
R= (measured photocurrent) / (incident optical power of wavelength)
Pop
22.02.2021 4
INTRODUCTION TO SiPM ARRAYS
• SiPMs are not very radiation hard -
- Radiation causes damage to the Si crystal structure. Damage can also be extended to the
neighbouring electronics
- These damages increases dark current (noise) from the SiPM
- Also results in lowering its photon detection efficiency
• 52 SiPMs are used in the JEDI polarimeter in COSY, along with the LYSO crystal, instead of
PMTs.
• In this thesis, all the SiPM array modules used and the results obtained are from
SensL ArrayJ 30020 8x8
22.02.2021 5
OUTLINE
I) Introduction to SiPM array
II) Motivation and objectiv
III) Irradiation experiment at JULI
IV) Instrumentation - Hardware and software development
I) Dark current characterizatio
II) Responsivity characterizatio
V) Summary and Outlook
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MOTIVATION AND OBJECTIVE
• During the beam based alignment in 2019, an accidental irradiation of these SiPMs took place.
This made characterization of the SiPMs a requisite for determining their integrity before
installation for the upcoming experiments.
• The objective of this thesis was to build a standalone characterization instrument to
characterize all the SiPM in the SiPM array without any human intervention.
• Obtaining a detailed report on the SiPMs in questions -> Helps to make the decision:
✴Using it as is.
✴Using after annealing.
✴Discarding it as damaged beyond recovery.
22.02.2021 7OUTLINE
I) Introduction to SiPM array
II) Motivation and objectiv
III) Irradiation experiment at JULI
IV) Instrumentation - Hardware and software development
I) Dark current characterizatio
II) Responsivity characterizatio
V) Summary and Outlook
22.02.2021 8
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CINVESTIGATING THE RADIATION HARDNESS OF THE
SiPM ARRAYS - EXPERIMENT
• An experiment was set up at the end of cyclotron (JULIC) for the
irradiating a healthy SiPM array.
• Housing for the SiPM array and its modules were designed and 3D
printed.
• Radiation film was placed on the SiPM array to observe the radiation
pattern and uniformity.
• Dark current was measured during irradiation and also when
radiation was switched off. Data recorded and analysed on the
Raspberry Pi.
• Live feed of the dark current was being plotted on the web interface
to observe the changes instantly.
22.02.2021 9INVESTIGATING THE RADIATION HARDNESS OF THE
SiPM ARRAYS - RESULTS
• SiPM array was irradiated up to 11 Gy in
total in steps.
• Radiation damage in the experiment was
similar to the damage caused during
beam based alignment of the SiPM
arrays in the second ring.
• Dark current of the SiPM array when the
radiation was turned off, is shown
22.02.2021 10INVESTIGATING THE RADIATION HARDNESS OF THE
SiPM ARRAYS - RESULTS
• Dark current map of the SiPM array at 26V from the
irradiation experiment is shown
• SiPM number 8 (lower right corner) was pointing down
towards the centre of the radiation beam.
• A clear pattern of the increase in the dark current is
seen where the radiating beam was incident on the
SiPM array.
1 64
8
22.02.2021 11INVESTIGATING THE RADIATION HARDNESS OF THE
SiPM ARRAYS - RESULTS
• Data of dark current which was
measured after the irradiation
Just after irradiation
experiment.
• Change in dark current over the period
of 2 months of room temperature
annealing.
2 months after irradiation
• Data was recorded every 12 hours for
different voltages for a period of 7
days.
• Reduction in dark current up to 4 times
in 2 months.
22.02.2021 12INVESTIGATING THE RADIATION HARDNESS OF THE
SiPM ARRAYS - RESULTS
• Line (black) shows average of the dark
current after the irradiation
experiment.
• Line shows average dark current
measured after 2 months.
• Few SiPMs were severely damaged.
• Few SiPMs remained healthy (due to
less incident radiation).
• Exponential dependence of dark
current on voltage can be observed.
22.02.2021 13INVESTIGATING THE RADIATION HARDNESS OF THE
SiPM ARRAYS - RESULTS Dark Current Map: Before annealing Dark Current Map: After annealing (20h) Relative Change of the Dark Current
30
Dark Current [µA]
Dark Current [µA]
3.5
Accidental damage - Annealing in oven @ 120℃
Current Reduction Factor
8 8 8
90
7 7 7
80 25 3
6 6 6
70
• Damaged SiPM array were subjected to high 5
4
60
50
5
4
20
5
4
2.5
2
temperature annealing. 3
2
40
3
2
15
3
2 1.5
30
10
• Comparison reports of SiPM which was
1 1 1
1 2 3 4 5 6 7 8
20 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
1
Dark Current Map: Before annealing Dark Current Map: After annealing (266h) Relative Change of the Dark Current
28
subjected to annealing in oven is shown on the 4
Dark Current [µA]
Dark Current [µA]
Current Reduction Factor
8 8 8
90 26
7
80
7
3.5
7
24
right. 6
5
70
6
5 3
6
5
22
20
60 18
• Change in dark current can be visualised.
4
50
4
2.5 4
16
3 3 3 14
40 2 12
2 2 2
30 10
• SiPM damaged by radiation produces much 1
1 2 3 4 5 6 7 8
20
1
1 2 3 4 5 6 7 8
1.5 1
1 2 3 4 5 6 7 8
8
Dark Current Map: After annealing (243h) Dark Current Map: After annealing (266h) Relative Change of the Dark Current
higher dark current than the rest average. Dark 4
Dark Current [µA]
Dark Current [µA]
8 8 8
Current Reduction Factor
1.15
7 4 7 7
current reduces after annealing and saturates.
3.5
6
3.5 6 6 1.1
5 5 3 5
3
• Examples: 4
2.5
4
2.5 4
1.05
3 3 3 1
➡ 0 - 20 hours annealing 2 2 2
2 2
0.95
1
1.5 1
1.5 1
➡ 0 - 266 hours annealing 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
➡ 243 - 266 hours annealing
22.02.2021 14OUTLINE
I) Introduction to SiPM array
II) Motivation and objectiv
III) Irradiation experiment at JULI
IV) Instrumentation - Hardware and software development
I) Dark current characterizatio
II) Responsivity characterizatio
V) Summary and Outlook
22.02.2021 15
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CAUTOMISED SiPM CHARACTERISATION TOOL
DARK CURRENT
• SiPM matrix has 64 SiPMs.
• 5 multiplexers (mux) used to channel each SiPM
from SensL Evaluation Board (BOB3).
• Mux channels was controlled and data recorded by
the Raspberry Pi.
22.02.2021 162 3 4 5
AUTOMISED SiPM CHARACTERISATION TOOL
DARK CURRENT
• An algorithm was devised to avoid heating issue - reads SiPM which are
always the farthest from the previous SiPM
• Simple 5 mux channeling schematics is shown below
VCC
mux channelling
A AMMETER
mux_5
mux_4
C
mux_1
FO
V DC Voltmeter A
mux_3
8x8 SiPM
array
mux_2
GND
22.02.2021 17AUTOMISED SiPM CHARACTERISATION TOOL
DARK CURRENT
• On board potentiometer in power supply circuit was
replaced by a series of resistors connected to a
multiplexer at each node.
• In simpler terms, a digital potentiometer.
• Scanning dark current through pre-determined
voltages is possible.
Multiplexer
Resistors
22.02.2021 18AUTOMISED SiPM CHARACTERISATION TOOL
DARK CURRENT - RESULTS
• This tool was used in the analysis of
the project “Investigating the radiation
hardness of the SiPM arrays”.
• Dark current for different voltages for
each SiPM in the array are recorded.
Healthy SiPM
• Data is then analysed and PDF are Vbais = 26V Vbais = 27V Vbais = 28V
generated instantly.
22.02.2021 19AUTOMISED SiPM CHARACTERISATION TOOL
DARK CURRENT
Dark Current Map of SiPM 161123-46 Dark Current Map of SiPM 161123-07
V Bias = 26V before annealing 2019.12.11 - 13:37 V Bias = 26V Annealed 266 hours 2019.10.27 - 15:20
Dark Current [µA]
Dark Current [µA]
4
8 8
REPORT 7
100
7 3.5
6 80 6
3
• Sample report of an irradiated SiPM 5
60
5
and annealed SiPM (266 hours). 4 4 2.5
40
3 3
2
• Final set-up is shown below.
2 20 2
1 1 1.5
0
1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
300
3.5
250
BOB3
3
200
µA
µA
150 2.5
100
2
50
1.5
0
0 10 20 30 40 50 60 0 10 20 30 40 50 60
Pixel number Pixel number
Total current = 3129.587 µA Total current = 150.065 µA
Average = 48.900 µA Average = 2.345 µA
RMS = 63.621 µA RMS = 0.482 µA
Maximum Current = 307.104 µA @pixel 60 Maximum Current = 3.682 µA @pixel 48
Minimum Current = -0.006 µA @pixel 7 Minimum Current = 1.434 µA @pixel 14
R-Pi V-supply
22.02.2021 20AUTOMISED SiPM CHARACTERISATION TOOL
RESPONSIVITY
• Need to illuminate each SiPM in the array with the exact same conditions.
• Instrument basic components:
➡ 2 x stepper motor with trays (1 axis of motion, each) controlled with motor driver.
➡ Illumination module with a reference SiPM inside to record the light from the LED.
➡ RedPitaya to control the motors and Arbitrary Function Generator (AFG), and record
data from oscilloscope.
• 3D design and mechanical simulation of the structure with modules in place was performed
and 3D printed
22.02.2021 21AUTOMISED SiPM CHARACTERISATION TOOL
RESPONSIVITY
Illumination Module - Key goals
• Area of illumination is as close to the area as one
SiPM in the SiPM array.
• The light from the LED is measured each time when
a SiPM is illuminated.
rSiPM
• Ability to add or remove lter for the reference SiPM
/ re ection of the beam.
• Detachable / replaceable. Instrument has 2x2cm
socket for the illumination module. LED
Image:
Top - CAD image of the illumination module.
Bottom - 3D printed with rSiPM, lters and a red LED
22.02.2021 22
fl
fi
fiOPTIMISING PARAMETERS OF THE INSTRUMENT
• Saturation of the reference SiPM
‣ Decay time of LYSO is 40 ns. So we can
operate the LED within 40 ns to stay
within the real limits.
Max voltage (mV)
‣ Saturation is not reached. More
microcells are triggered before all the
others are triggered
• Light spread of the LED
• Angular absorbance of the SiPM array
22.02.2021 23OPTIMISING PARAMETERS OF THE INSTRUMENT
Width = duration of LED on
• Saturation of the reference SiPM
• Light spread of the LED
‣ Light spread up to ±10˚ is nearly the
same regardless of the duration of
the on state or distance.
• Angular absorbance of the SiPM array
mV
22.02.2021 XOPTIMISING PARAMETERS OF THE INSTRUMENT
Width = duration of LED on
• Saturation of the reference SiPM
• Light spread of the LED
‣ Light spread up to ±10˚ is nearly the
same regardless of the duration of
the on state or distance.
• Angular absorbance of the SiPM array
mV
22.02.2021 24OPTIMISING PARAMETERS OF THE INSTRUMENT
• Saturation of the reference SiPM
• Light spread of the LED
• Angular absorbance of the SiPM array
‣ Angular absorbance for the SiPM array is
nearly the same for a wide angle.
mV
(Kink at -10˚ is due to setup anomaly)
22.02.2021 25OPTIMISING PARAMETERS OF THE INSTRUMENT
• The angle of the LED can be change by large angles to reduce the overall light intensity.
• Small change in the xy-plane or small angle in the incidence of light does not have drastic
change in the results.
• Have normal incidence of the light is ideal. In reality, there is small angle difference which
causes reflection and scattering probability illuminating other SiPM in the array.
22.02.2021 26AUTOMISED SiPM CHARACTERISATION TOOL
Relative responsivity map for SiPM 161123-24
RESPONSIVITY Bias voltage for SiPM array = 30V, 2020-12-10 17:35:00
REPORT
• Sample report of a healthy SiPM array with 2 missing SiPMs.
• SiPM 8 and 63 are missing
• The small readings are due to the reflections and scattering
and hence this is taken as the lower bound.
Highest count = 12 @ 0.92 relative charge
Average = 0.89
RMS = 0.90
Highest value = 1.02 @ SiPM [26]
Lowest value = 0.37 @ SiPM [63]
22.02.2021 29AUTOMISED SiPM CHARACTERISATION TOOL
DARK CURRENT + RESPONSIVITY
• The extent of damage to the SiPM array is now known by analysing the dark current and
relativity responsivity.
• The health status of the SiPM and its limits with a detailed printable report in PDF is obtained.
• From the report one can decide if SiPM array is healthy enough to be used in an experiment;
based on requirements.
22.02.2021 30OUTLINE
I) Introduction to SiPM array
II) Motivation and objectiv
III) Irradiation experiment at JULI
IV) Instrumentation - Hardware and software development
I) Dark current characterizatio
II) Responsivity characterizatio
V) Summary and Outlook
22.02.2021 31
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CSUMMARY AND OUTLOOK
• An experiment was conducted by irradiating a healthy SiPM array to understand the effects of
radiation of the SiPM array
• Annealing of the SiPM array at room temperate and high temperature.
• An instrument was built to measure the integrity of the SiPM array and optimised.
• Detailed report of dark current or responsivity in the form of PDF will be produced in less than
30 minutes per SiPM array.
• This instrument was built for SensL ArrayJ 30020 8x8.
• It can be easily scaled to perform characterisation of larger or smaller SiPM arrays.
Parameters in the software should be scaled appropriately.
22.02.2021 32Dark Current Map of SiPM 161123-07 Relative responsivity map for SiPM 161123-24
V Bias = 26V Annealed 266 hours 2019.10.27 - 15:20
Bias voltage for SiPM array = 30V, 2020-12-10 17:35:00
Dark Current [µA]
4
8
7 3.5
6
3
5
4 2.5
3
2
2
1 1.5
1 2 3 4 5 6 7 8
THANK YOU
3.5
3
µA
2.5
2
1.5
0 10 20 30 40 50 60
Pixel number
Total current = 150.065 µA
Average = 2.345 µA Highest count = 12 @ 0.92 relative charge
RMS = 0.482 µA Average = 0.89
RMS = 0.90
Maximum Current = 3.682 µA @pixel 48
Highest value = 1.02 @ SiPM [26]
Minimum Current = 1.434 µA @pixel 14 Lowest value = 0.37 @ SiPM [63]
22.02.2021 33BACKUP 22.02.2021 34
BACKUP
• The photon detection e ciency (PDE) is a measure of the sensitivity of an SiPM and is a
function of wavelength of the incident light, the applied over-voltage.
R⋅h⋅c
• P . D . E = e ⋅ λ ⋅ G ⋅ 100 % , where R is responsivity, G is gain and λ is wavelength, h is
planks constant and c is the speed of light
• Responsivity is de ned as the average photocurrent produced per unit optical power:-
Ip
R= = (measured photocurrent) / (incident optical power of wavelength)
Pop
22.02.2021 35
fi
ffiBACKUP
22.02.2021 36BACKUP
• The second LED re ected
the light causing this kink at
-10˚
22.02.2021 37
flBACKUP Dark Current Map of SiPM 161123-46
V Bias = 26V Annealed 0 hours 2019.12.11 - 13:37
Dark Current [µA]
8
100
7
6 80
5
60
4
40
3
2 20
1
0
1 2 3 4 5 6 7 8
300
250
200
µA
150
100
50
0
0 10 20 30 40 50 60
Pixel number
Total current = 3129.587 µA
Average = 48.900 µA
RMS = 63.621 µA
Maximum Current = 307.104 µA @pixel 60
Minimum Current = -0.006 µA @pixel 7
22.02.2021 38BACKUP - CURRENT ISSUES
• Random jumps in the current recorded
• No pattern has been found yet
✴Calibration of the setup was performed by replacing
SiPM board with 27kΩ resistor
Voltage and current were measured at all times.
Resistance of the resistor was calculated using
V
R=
I
• Measuring dark current of the whole
matrix gives comparable results but
not individual SiPM results
22.02.2021 39You can also read
