TUDelft-IRI-ST

A new Tissue-Equivalent

Proportional Counter design

M. Farahmand, A.J.J. Bos, J. Huizenga

and

C.W.E. van Eijk

Radiation Technology Group, IRI

Delft University of Technology

TUDelft-IRI-ST

Experimental microdosimetry

gamma radiation alpha particles

Study of the effects of ionising radiation on biological targets by investigating the statistical distribution of energy deposition at micrometer level.

From: Broerse et al.

d = 14 m

d = 1 m

TUDelft-IRI-ST

• Tissue-Equivalent Proportional Counter (TEPC)

- Wall and gas are tissue-equivalent.

- Determine energy deposition in the wall

by measuring in gas.

- Single-event measurements.

TEPC

dcavity = 2 cm

Pgas[mbar] dtissue[m]

1000 40

25 1

- Lowering the gas pressure.

Anodewire

Helixcathode

TUDelft-IRI-ST

Applications

• Radiobiology - link between experimental microdosimetry & radiobiology based on site measurements

• Radiotherapy

- FNT, BNCT, Proton Therapy, Heavy ions Therapy

• Radiation protection

- estimating dose equivalent (H)

- unknown radiation

• Air and Space

- aircraft crews and manned missions

TUDelft-IRI-ST

Small counter cavity

• High flux radiation sources in radiotherapy facilities

- Pile-up effect (Mini TEPC)

• Measuring low dose rate for radiation protection purposes

- Increasing sensitivity of the counter (Mini multi-element TEPC)

• Main target size of few tens of nm (chromatin fibre)

- Limitation of decreasing gas pressure (Mini TEPC)

TUDelft-IRI-ST

Mini TEPC(-GEM)

Electric field lines

From: CERN Courier

Gas Electron Multiplier (GEM)

100 m

200 m

50 m

TUDelft-IRI-ST

Gain measurements

dt = 1 m

0.3 atm < pg < 0.8 atm

3.0 mm > dg > 1.0 mm

dt = 1 m

0.1 atm < pg < 1.0 atm

5.0 mm > dg > 0.5 mm

400 440 480 520 560 600 640 680100

1000

10000

propane-based

0.1atm

0.2atm

0.3atm 0.4atm

0.6atm

0.8atm 1atm

GE

M g

ain

GEM voltage [V]

360 400 440 480 520 560 600 640 680 720100

200

300

400

500

600700800900

1000

2000

0.2atm

0.3atm

0.4atm

0.5atm 0.6atm

0.7atm0.8atm

1atm

methane-based

GE

M g

ain

GEM voltage [V]

TUDelft-IRI-ST

TEPC-GEM design

76 mm

= 2 mm 9 mm

TUDelft-IRI-ST

First calibration measurements

0 50 100 150 200 250 3000

200

400

600

800

1000

1200

TE-C3H

8

P = 1 atm

Yie

ld [

a.u

.]

channel number0 50 100 150 200 250

0

500

1000

1500

2000

2500

3000

TE-CH4

P = 1 atm

Yie

ld [

a.u

.]

channel number

TUDelft-IRI-ST

Conclusion & Future development

• Calibration of TEPC-GEM works properly.

• Comparing microdosimetric measurements of TEPC-GEM

with traditional TEPC.

• Employing in high flux radiation sources (Therapy facilities).

• Employing in low radiation field intensity (Aircraft).

• Investigating the minimum possible site simulation size

and cavity size.