P1-079

Do Duy KHIEM, Masaya YASHIKI, Hiroto MATSUURA, Masafumi AKIYOSHI
Graduate School of Engineering, Osaka Prefecture University
1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka 599-8531, Japan
E-mail: akiyoshi@riast.osakafu-u.ac.jp, doduy_khiem@yahoo.com

MATERIALS AND METHODSINTRODUCTIONBACKGROUNDp

The 19th International Conference on Solid State
Dosimetry (SSD19)
Hiroshima, September 15th – 20th, 2019

X-RAY SPECTROMETER In Japan, a Crookes tube, as a discharge tube, has been used in junior-highscience classes, and the primary purpose is to teach the characteristics ofelectrons and current.
 X-rays emitted by the Crookes tube might cause exposure to teachers andparticipating students.
 A radiation safety guideline has not been evaluated sufficiently yet in Japan.

CZT Detector (XR-100TCZT, Amptek Inc., USA)

Crookes tube (3C-B,Kenis Ltd., Japan)

Energy was approximately 20 keV.
Hp(10) was up to 143 mSv/h at 5 cm 1).

 On the induction coil, the desired output
voltage can be obtained by regulating:(1) The electrode distance ranges from 10 to
100 mm. Each of the distances limits a maximum
voltage to the Crookes tube.
(2) The output power controller (PW) ranges
from 0 to 20. By increasing the output power, theapplied voltage will continually increase until aspark occurs to reach the maximum voltage.
 Applied voltage is approximately 1 kV at 1 mm.

(1) Electrode distance
1mm  1kV

X-rays(2) Output powerInduction coil

SCOPES OF THE RESEARCH
 Estimating the characteristics and properties of X-rays emitted by a Crookes
tube used in educational sites.
 Investigating the relevance between electric settings and X-rays properties(energy, dose).
 Evaluating the dose distribution surrounding the Crookes tube using
Thermoluminescence (TL) dosimeters and glass badge.
 Submitting the results as the recommendation and guideline for radiation
protection at junior-high school science class.

Mechanism of a Crookes tube
1

X-rays3

2

Pocket Multichannel(MCA8000D, AmptekInc., USA)Power supply and Amplifier(PX2T, Amptek Inc., USA)

Tube vacuum:
0.005 - 0.1 PaHV1

Cations in the evacuated tube areaccelerated and impact the cathode, andknock out secondary electrons.

2

These electrons are accelerated under theapplied HV.

3Several tens of kV

DPPMCA Software(Amptek Inc., USA)TL DOSIMETER SYSTEM

Panasonic TLD Reader UD-706

Panasonic TL dosimeters,
types of UD-802PQ.

Accelerated electrons collide the glass wallto radiate bremsstrahlung X-rays.

DOSE DISTRIBUTION ASSESSMENT
CORRELATION BETWEEN APPLIED VOLTAGE AND X-RAY ENERGY

Experiment 02
CIRCLE DISTRIBUTION OF DOSE The Crookes tube emitted X-rays with soft energy of approximately 20 keV.
 The exposure and X-ray energy changed with electrical settings such as output
power, and electrode distance2,3).
81012141618202224262845

4040
X-ray Energy
Maximum Voltage
Peak Voltage

35

X-ray energy (keV)Intensity

30

45

30

25
20

Shiftedenergy

15
10
50
6810

12

1416

1820

22242628

30

Energy (keV)

30
2520

20

15

15

10

10

5

502468

10

12

14

16

18

20

1022

DOSE DISTRIBUTION ON BODY5

 Dosimeters attached on the human body shapefitting to a junior-high school student.
 A Hp(0.07) dose (mSv/h) at E1 position on dosimeter
represents a skin dose affecting to students.
 Measurement distance of 1 m, irradiation time of 1hour.
 Distribution of Hp(0.07) dose enclosing the Crookes
tube at 0.03 – 0.17 mSv/h.

34

67

8

912 131415 16
19827

7

3

64

2

10 11

8

3

1

HP(0.07) (mSv/h)
Position
Head of tube Rear of tube
1
1.52
1.82
2
1.56
1.72
3
1.51
1.38
4
1.59
0.96
52.02
0.57
6
1.91
1.03
70.81
1.46
8
1.28
1.83

12Output Power

Experiment 01

 Distance of 15 cm from the central tube todosimeters.
 Irradiation time of 30 min.

35

250

Head of tube

Rear of tube

30

PW0 (15.8 keV)
PW2 (17.0 keV)
PW4 (18.1 keV)
Gauss Fitting

35

 The tube put in the central circle.

Voltage (kV)640

 TL dosimeters attached on the circle of 31
cm in diameter.

455

6Experiment 03

17 18

 Glass badge dosimeters (FX-type,Chiyoda Technol, Japan) attachedon the X and Y axes.
 Measurement distance of 1 m,irradiation time of 30 min.
 The dose at any point on (X, Y)coordinate can be determined by
the dose distribution function.

DOSE DISTRIBUTION ON (X, Y) COORDINATE

2021 22
23 24
25 26
27 28

 The dose concentrates in the central human bodyand relatively descend to expanded area.

No.4
0

0.07

y

No.11

0.13

0.11

0.14

0.12

0.12

0.17

0.12

0.14

0.20

0.20

15cm

0.12

0.16
0.12
0.10
0.07
0.09

0.03
15cm

7.5cm

0.07

0.13

0.13

0.12
0.14

0.15
0.10
0.11
0.06
0.03

Dose equivalent (mSv)

0x

160cm

15cm

0.13

0.18

0.18

Dose equivalent (mSv)

0.05

Hp(0.07)
Hp(10)

0.16

Hp(0.07)
Hp(10)

0.14
0.12
0.10
0.08

0.16
0.14
0.12
0.10
0.08

0.06

0.06

0.04

0.04
-30-20-10

01020

X distance from the center (cm)

30-40

-20

02040

Y distance from the center (cm)

SUMMARY The Crookes tube emitted X-rays with soft energy of approximately 20 keV. The exposure and X-ray energy changed with electrical settings such as output power, and discharge distance.
 Distribution of Hp(0.07) dose on the body was 0.03 – 0.17 mSv/h at 1 m. The dose concentrates in the central human body and relatively descend to expanded area.
 The dose distributed circling the Crookes tube with higher dose at the head of the tube.
 Participants should stand at 1m from the tube during a demonstration to ensure radiation safety.
References:
1) Ohmori Giroh, X-ray exposure in the teaching of science at junior and senior high schools. NIRS-M—105, Japan, 107-112 (1995) (in Japanese).
2) M. Akiyoshi, et al., Development of evaluation techniques for low energy X-rays from a Crookes tube, Radiation chemistry, 106 (2018) 31-38 (in Japanese).
3) Do Duy KHIEM, et al., Investigation of Characteristics of Low-energy X-ray Radiated from the Crookes Tube Used in Radiological Education, Radiation Safety Management, Vol. 18, 9-15 (2019).

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