Transcript Temperature Compensated Power Supply For Silicon Photo

A Temperature Compensated Power
Supply for Silicon-Photomultiplier
PANKAJ RAKSHE
WAPP – 2014
20th December 2014
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Acknowledgment
 Prof. S. R. Dugad (TIFR)
 Prof. P. D. Khandekar (VIIT)
 Mr. Sergey Los (FNAL)
 Prof. C. S. Garde (VIIT)
 Mr. Raghunandan Shukla (TIFR)
 Prof. S. K. Gupta (TIFR)
 Ms. Sarrah Lokhandwala (TIFR)
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Introduction
 Sensitive Photo-detectors like PMT’s are of great interest to scientific
community due to their use for examining processes that emit very low photon
signal.
 For example, In GRAPES-3 experiment PMT’s are used to detect scintillation
light from wavelength shifting fibres.
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Photo-Multiplier Tube (PMT)
 Gain ~ 106
 Response time ~ 2 ns
 Size : Dia 2”, Length 6”
 Operating Voltage ~ 2000 V
 Quantum Efficiency < 20 %
 Affected by Magnetic fields
 Expensive !
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Silicon Photo-Multiplier (SiPM)
 Compact Device
1-3 mm
 Operating voltage (30-120V)
 Resolution - Single photon detection
 Response time – ~100 ps
1-3 mm
 High gain - 106
 High Quantum Efficiency – 90%
 High Photon Detection Efficiency –
60%
 Immunity to Magnetic Field
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SiPM
 SiPM is a 2-D array of Avalanche Photo
Diode’s (APD’s) , all resistively coupled
together.
 SiPM is generally biased above its
breakdown voltage , called as Geiger mode.
 Each pixel (APD) acts as a binary device,
indicating presence or absence of photon.
Device as whole gives analog signal
indicating number of pixels fired.
 Typical size of each APD (pixel) is 50 µm ×
50 µm and a typical gain of ~ 106
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Limitations of SiPM
 Dark Counts
 Thermally Generated Carriers will give signal that appears as genuine photon signal
 After Pulsing
 Carrier Trapping and Delayed Release
 Cross-Talk
 Pixel Firing Due to Photon Detection in Adjacent Pixel
 Temperature Dependence of Breakdown Voltage
 SiPM Gain is Affected by Changes in Applied Over-Voltage
(Applied Voltage – Breakdown Voltage)
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SiPM Temperature
Dependence
 Geiger mode: above breakdown
 VS = VBR + Over-Voltage
 Gain dependant on amount of Over-voltage
applied
 But, Breakdown Voltage is dependent on
temperature
* Bajarang Sutar
 Effectively, gain changes by 3-5%/˚C
 Over-Voltage should be constant for constant
gain
 𝑽𝑺 𝑻 = 𝑽𝑩𝑹 𝑻 + 𝑶𝒗𝒆𝒓 𝑽𝒐𝒍𝒕𝒂𝒈𝒆
* S. R. Dugad and K. C. Ravindran
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Solutions to Temperature Dependency
Constant Temperature
 Indoor Applications - applicable
 Temperature control of detectors in
outdoor environment is not possible
e.g. GRAPES-3 experiment containing
400 detectors in large area outdoor
field of about 25000 m2 with
temperature variations 5 - 30 ˚C
Temperature Dependant Biasing
Conditions
 The Bias Voltage of SiPM can be
controlled for changing the operating
point
 Temperature dependent Power
Supply that will keep over-voltage
constant (i.e. Gain constant)
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Approaches To Temperature Compensation
Method
Used
Dark
Current
Control
Author
Miyomoto
et al.
Li et al.
Year
Remarks
2009 Dark Current and Temperature relation approximated to
exponential function and use of Thermistor (similar relation) for
compensation
2012 Dark current and Bias Voltage relation used for designing the
voltage controlled current sink that changes bias condition
Bencardino 2009 Use of Temp. to voltage converter and a Op-amp based circuit for
et al.
changing the bias return potential w.r.t. temperature variations
Bias
Voltage
Control
Licciulli et
al.
2013 Blind SiPM used as a temperature sensor and amplitude of Dark
pulses of Blind SiPM is maintained constant using Op-amp based
feedback circuit for constant gain of other SiPM in parallel
Gil et al.
2011 External Input of the power supply is controlled by a microcontroller based system to change the output voltage w.r.t. temp.
Dorosz et
al.
2013 LabVIEW based feedback system for controlling the power supply
output
Limitations
1. Uses Expensive
Commercial
Power Supply
2. Limited to
one/two
channels
3. External control
required for
temperature
compensation
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Specifications
Sr.
No.
Parameter
Value
1.
Output Voltage
0 to 100V
2.
Temperature Reading Resolution
3.
Temperature Compensation Factor
4.
Number of Channels
5.
Output Voltage Resolution
10 mV
6.
Maximum Current Limit per Channel
100 µA
7.
Full Scale Leakage Current per Channel
40 µA
0.1 ˚C
10 to 100 mV/˚C
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Block Diagram
High Voltage
Generation
(Voltage
Multiplier Chain)
PC
USB
Temperature
Sensors
Control Unit
(Microcontroller)
Current Sense
DAC
Voltage
Regulation
Scheme
SiPM
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Prototype Power Supply (SiPM-PPS-v1)
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Features of SiPM Power Supply
 Programmable Output Voltage (0 - 100 V) with resolution of ~12 mV
 Programmable Temperature Compensation Factor (~12 – 100 mV/˚C)
 In-built Data Acquisition System for recording Temperature and Leakage
Current via USB
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0.04113% for 10% change in line voltage
0.03% for 20% change in line voltage
Ripple = 5 mVP-P
No load to Full load (100uA) regulation
0.6025%
Stable within 10 mV for 0 – 100 V
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Compensation Algorithm Verification
Comp. factor = 240 mV/˚C
Comp. Factor = (0.029x2-1.4x) /˚C
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SiPM Experimental Setup
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SiPM Test: Without Compensation
Gain Variation of about 4 %/˚C
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SiPM Test: With Compensation
Gain Variation of 0.8 %
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In Conclusion
 Without compensation gain variation
nearly 4 %/˚C
 With compensation gain variation
0.08 %/˚C
 Output Ripple of 5 mV with the
Resolution of 12.5 mV in 100 V with
temperature correction at each 0.2 ˚C
change
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Compared to Keithley 6487 Unit
 Voltage Source and Pico-ammeter
SiPM Programmable Power Supply
 Temperature Compensation Feature
 Small Size and Light Weight (portable)
 Multi-channel (8/16 channels)
 Cost – Inexpensive !!!
(₹ 750/channel) which is 400 times less
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SiPM-PPS-v2
• Number of channels = 16
• Better output resolution = 6.25 mV
• DAC resolution = 14 bits
• Better current sensing resol. = 1 nA
• ADC resolution = 16 bits
• Provision for expandability
• I2C for multiple boards
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Specifications Comparison
Sr.
No.
Parameter
Required Value
Prototype Board
SiPM_PPS v2
0 to 100V
0 to 100 V
0 to 100 V
8
8
16
1.
Output Voltage
2.
Number of Channels
3.
Output Voltage Resolution
10 mV
12.5 mV
6.25 mV
4.
Maximum Current Limit per Channel
100 µA
100 µA
100 µA
5.
Full Scale Leakage Current per Channel
40 µA
40 µA
35 µA
6.
Temperature Reading Resolution
0.1 ˚C
0.1 ˚C
0.1 ˚C
7.
Temperature Compensation Factor
12.5 to 100 mV/˚C
12.5 to 100 mV/˚C
6.25 to 100 mV/˚C
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Summary
 SiPM has some outstanding features that in some respect could replace PMT in
near future.
 Newer versions of SiPM are being developed to overcome its limitations.
 The temperature dependence is one of the major limitation preventing the use
of SiPM in outdoor applications. The programmable temperature compensated
power supply is useful for operating the SiPM in different environmental
conditions.
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