Transcript Development of Mobile Radiation Monitoring System Utilizing

Speaker: Li-Wei Wu
Advisor: Dr. Kai-Wei Ke
2013/10/14
1
 Introduction
 What is Radiation
 Hardware design
 Software design
 Field testing
 Conclusion
 Reference
2
 The Daiichi Nuclear Power Plant accidents in Fukushima have
stimulated desire of ordinary people to own radiation sensors.
 March 16, 2011, the SAFECAST team started data collection of air
dose-rates using mobile sensors.
 Conventional radiation sensing instruments are too expensive for
members of the general public , as well as being difficult to obtain
and use.
3
 Radiation-watch.org This is an open-source and non-profit project
involving a number of volunteer engineers and scientists. we initially
released a unique radiation detector named Pocket Geiger(POKEGA)
in August 2011, designed to be connected to a smartphone.
 In order to reduce costs while maintaining accuracy and flexibility,
they used a combination of a PIN photodiode detector and a
smartphone connected via a microphone cable.
4
• 輻射是一種具有能量的波
或粒子。
• 無線電波、微波、可見光、
X射線、ϒ射線等、超音波，
以及從放射性物質發射出
來的微小粒子(如α粒子、
β粒子、中子等)
5
 充氣式偵檢器
 閃爍偵檢器
 半導體偵檢器
6
 The first model of the POKEGA series, was marketed in an unfinished,
easy-to-assemble kit-style package in order to facilitate rapid
development and cost reductions.
 The output pulse from a photodiode is quite low and narrow, while
the input gain and sampling rate of a smartphone are extremely low
and slow.
 Charge amplifier optimized the narrow radiation pulses, so it can be
detected using the low sampling rate of the smartphone audio circuit.
7
 The input gain and frequency characteristics of the analog-to-digital
(A/D) circuits vary somewhat depending on the model or generation
of the smartphone.
 Application software discriminates radiation pulses from background
noise by means of thresholds.
8
n = αr
α
α : conversion factor
r : dose rate [μSv/h]
n : count rate [cpm]
9
10
 The Type 2 model was designed to power from the smartphone.
 They have implemented an internal voltage-generation circuit that
uses an earphone stereo tone generated by the application software.
 In order to prevent hearing damage in situations where users
accidentally connect headphones to the smartphone while the
POKEGA application is running, the signal frequency was set at 20
kHz, which is just above audio frequency for human.
11
整
流
濾
波
脈動直流
12
13
 The Type 3 device has a comparator circuit and digital output for
radiation pulses along with a pull-up resistor that allows it to be
connected to various smartphones.
 Type 3 device equipped with a noise-detection circuit because, PIN
diodes are susceptible to noise vibrations. There are two thresholds
in the circuit; one is used to detect radiation pulses, while the other is
used to detect the noise vibrations
14
15
16
 The Type 4 device was developed to reduce measurement time.
 The Type 4 device uses a large-area X 100-7 PIN photodiode.
17
 It was designed for remote sensing using embedded
microcontrollers.
18
 The software is designed to visualize radiation measurements.
19
20
21
22
There are now approximately 12,000 POKEGA users
and more than 1 million data have been collected from them.
Currently, about 1,800 people have subscribed to the
Facebook group, where they have posted thousands of
comments. That group was primarily created to support
users, the majority of the topics relate to sharing dose rate
reports in various areas, as well as followups by nearby
inhabitants or radiation specialists. Such interactions have
contributed to improving radiation literacy of the general
public and POKEGA’s hardware and software.
23
• Yang Ishigaki, Yoshinori Matsumoto, Ryo Ichimiya, and
Kenji Tanaka, “Development of Mobile Radiation
Monitoring System Utilizing Smartphone and Its Field
Tests in Fukushima” Sensors Journal, Oct. 2013 IEEE
• http://www.radiation-watch.org/
24