Development of FPGA-based readout electronics for cosmic rays detector and
environmental radiation real-time monitoring system
Vo Hong Hai1,2, Nguyen Quoc Hung1, Tran Kim Tuyet2 Masaharu Nomachi3
1
Faculty of Physics - Physics Engineering, VNU-Ho Chi Minh University of Science, 227 Nguyen
Van Cu, District 5, HCM City, Vietnam;
2
Nuclear Technique Lab., VNU-Ho Chi Minh University of Science, 227 Nguyen Van Cu, District 5,
HCM City, Vietnam;
3
RCNP, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
Abstract
Field-programmable gate array (FPGA) technology has been widely used in setting up triggering
systems and DAQ systems for radiation detectors, because it has the advantages such as fast digital
processing, compact, programmable and high stability. Since 2010, with the scientific collaboration
with Professor Masaharu Nomachi group, Osaka University of Japan, Department of Nuclear Physics,
University of Science-VNUHCM has been developed FPGA-based trigger systems and FPGA-based
DAQ systems used for radiation detectors. Namely, we developed triggering systems for cosmic ray
measurements, readout electronic for an environmental radiation real-time monitoring system in air;
we also developed nuclear electronic equipment such as spectrum analyzer MCA (Flash-ADC/FPGA
based), the pulse generator, counters, etc. Furthermore we cooperated with KEK, Japan in the
development of readout electronic for multiple radiation sensors. In this work, we would like to
present our results achieved, namely, the detection response of comic-rays in the high-pure
Germanium (HPGe) gamma-spectrometers in the energy region from 0.2 MeV to 50 MeV; and the
environmental radiation real-time monitoring system in air.
Keywords
Cosmic ray, background radiation, HPGe, and FPGA.
1. General details
Natural background radiation always exists in
any places on the surface of the earth. It comes
from the cosmic rays, terrestrial radiation and
internal bodies. For cosmic-rays component,
the outer space sends a constant stream of very
high-energy primary cosmic rays to the earth.
With atmospheric conditions, at the surface of
the earth, there is the finite amount of
secondary cosmic rays. For terrestrial radiation
component, the earth itself is the main source,
including uranium, thorium and radium
existing in the soil and rock. All people have
internal radiation, mainly from radioactive K40 and C-14 inside the body.
In the field of radioactive isotope analysis for
environmental and food samples, the HPGe
gamma-spectrometer is used commonly due
to high efficiency. For the spectrometer,
ambient radiation and cosmic rays may exist in
the gamma spectrum as a background. In this
work, we study the cosmic-rays component
from the total background in the HPGe
gamma-spectrometer by experiment and
Geant4 Monte-Carlo simulation. Also in this
work, we study the environmental radiation in
the air. We develop the system for monitoring
the environmental radiation in real time. The
readout electronic is developed from
embedded FPGA technology.
Embedded FPGA technology has been
increasingly used in the development of trigger
systems, DAQ signal processing systems for
nuclear radiation detectors. Embedded FPGA
technology has advantages such as fast
processing speed, programmable, low power
consumption, compactness and high stability.
Since 2010, in collaboration with Professor
Masaharu Nomachi, Osaka University, Japan,
we has been developing trigger systems, DAQ
uses embedded FPGA technology for nuclear
radiation detectors [1], [2], [3].
2. Detail set up and analysis
2.1. Cosmic ray studies in the HPGe gammaspectrometer
Cosmic-rays
muon
Lead chamber
(a)
Fig.2b shows the detection response of each
component of cosmic rays. We study for
muon, neutron, photon, election, positron and
proton. The result shows that comic muon (red
curve) is the main contribution in the total with
86% of events. Neutron count contributes of
8.6% in the total, mostly in the very low
energy region of several ten keV. Because
neutrons are able to penetrate deep inside lead
shield happen nuclear reaction with materials
of the spectrometer, and generate secondary
gamma and charged particle. Components of
electron, positron and proton do not contribute
much to total background spectrum.
Count rate
[cpd/0.0012Me
V]
Ge
(b)
Nitrogen liquid
(c)
Count rate [cpd/0.023MeV]
(a)
Energy [MeV]
 Experiment of background radiation
 Cosmic-ray component by Geant4 Simulation
Energy [MeV]
Fig.1. Experiment and Geant4 Monte-Carlo
simulation to study detection response of
cosmic-rays for the HPGe gamma-spectrometer.
a. Schematic view of the HPGe gammaspectrometer.
b. Geant4 Monte-Carlo simulation of the HPGe
gamma-spectrometer.
c. Photo of HPGe gamma-spectrometer.
For cosmic ray studies in the HPGe gammaspectrometer, we carried out the experiment
and Geant4 Monte-Carlo simulation. Fig.1a
shows the scheme of HPGe gamma
spectrometer. HPGe detector is installed in the
lead chamber which is purposed to reduce
ambient radiation. Fig.1b is the detection
construction model in the Geant4 toolkit.
Fig.2a shows experimental data of radiation
background spectrum (green curve) which is
carried out in the energy region up to 50 MeV.
With Geant4 simulation, black curve in Fig.2a
is cosmic rays component in the total radiation
background.
Count rate [Counts/23keV/day]
Nitrogen
liquid
511keV
HPGe
 Total
 muons
 neutron
 photon
 electron
 positron
 proton
(b)
Energy [MeV]
Fig.2. Detection response of cosmic rays in
the HPGe gamma spectrometer
a. Experiment and Geant4 Monte-Carlo
simulation. Black curve is background
radiation measured by HPGe detector.
Green curve is the cosmic-ray component
simulated by Geant4 tool kit.
b. Geant4 simulation of components of
cosmic rays including muon, neutron,
photon, electron, position and proton.
2.2. Monitoring the environmental radiation in
real time
Geiger–Müller
FPGA-based
Detector
Readout Electronic
(a)
LabVIEW-based
Computer interface
(b)
Control
Wi-Fi
Signal
input
Trigger
Digitizer
Memory
CPS, CPM
(c)
radiation, such as cosmic ray and dose rate
studies. Readout electronic system is
developed from embedded FPGA technology.
For cosmic ray study, we investigate cosmic
ray component in the total background
spectrum of the gamma HPGe spectrometer in
the energy region up to 50 MeV. Along with
Geant4 Monte-Carlo simulation, we evaluate
each cosmic ray components in the total
cosmic rays. For environmental radiation
study, we develop the system which can be
used to monitor dose rate in the real time scale.
References
Fig.3 Development of environmental radiation
real-time monitoring system
a. Schematic view of the system
b. Readout electronic using FPGA technology.
c. LabVIEW-based computer interface.
Count rate (CPM)
CPM
Time (minute)
Fig. 4. Environmental radiation monitor in a
room air with one day measurement. Left and
right horizontal scale show count rate (count per
minute) and dose rate (µSv/h), respectively.
For environmental radiation real-time monitor,
as shown in Fig.3a, we developed FPGAbased readout electronic (Fig.3b) to read the
radiation sensor and data (CPM) will then
transfer to computer via Wi-Fi connection with
LabVIEW-based computer interface (Fig.3c).
Fig.4 is the measurement of environmental
radiation in a room air. Data is up-to-date via
real-time.
3. Conclusions
We
develop
radiation detectors for
investigating
environmental
background
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detectors and Flash-ADC/FPGA-based
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[2] Nguyen Quoc Hung, Vo Hong Hai,
Masaharu Nomachi, Nguyen Trong Tin.
(2015). Discrimination of cosmic-ray in
scintillation region and light-guide for
plastic scintillation detectors using 5GSPS
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gamma spectroscopy employing NaI(Tl)
detector 3inch x 3inch and readout
electronic of flash-ADC/FPGA based
technology. Independent Journal for
Nuclear Engineering Kerntechnik, Vol.80,
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