1

DEVELOPMENT OF MOBILE RADIATION MONITORING SYSTEM UTILIZING SMARTPHONE AND ITS FIELD TEST IN FUKUSHIMASpeaker: Li-Wei Wu

Advisor: Dr. Kai-Wei Ke

2013/10/14

2

OUTLINE IntroductionWhat is RadiationHardware designSoftware designField testingConclusion Reference

3

INTRODUCTION 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.

4

INTRODUCTION 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.

5

WHAT IS RADIATION?

• 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 )

6

HARDWARE DESIGN充氣式偵檢器 閃爍偵檢器 半導體偵檢器

7

HARDWARE DESIGN – TYPE 1 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.

8

HARDWARE DESIGN – TYPE 1 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.

9

HARDWARE DESIGN – TYPE 1

n = αr

α : conversion factor

r : dose rate [μSv/h]

n : count rate [cpm]

α

10

HARDWARE DESIGN – TYPE 1

11

HARDWARE DESIGN – TYPE 2 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.

12

HARDWARE DESIGN – TYPE 2

脈動直流

整流

濾波

13

HARDWARE DESIGN – TYPE 2

14

HARDWARE DESIGN – TYPE 3 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

15

HARDWARE DESIGN – TYPE 3

16

HARDWARE DESIGN – TYPE 3

17

HARDWARE DESIGN – TYPE 4 The Type 4 device was developed to reduce measurement time.

The Type 4 device uses a large-area X 100-7 PIN photodiode.

18

HARDWARE DESIGN – TYPE 5 It was designed for remote sensing using embedded microcontrollers.

19

SOFTWARE DESIGN The software is designed to visualize radiation measurements.

20

SOFTWARE DESIGN

21

FIELD TESTING

22

FIELD TESTING

23

CONCLUSIONThere 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.

24

REFERENCE• 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/