A new Tissue-Equivalent

1
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
2
Experimental microdosimetry
Study of the effects of ionising radiation on
biological targets by investigating the
statistical distribution of energy deposition at
micrometer level.
d 14 ?m
d 1 ?m
gamma radiation alpha particles
From Broerse et al.
3
TEPC

• Tissue-Equivalent Proportional Counter (TEPC)
• - Wall and gas are tissue-equivalent.
• - Determine energy deposition in the wall
• by measuring in gas.
• - Single-event measurements.

Anode wire
Helix cathode
- Lowering the gas pressure.
25 1
4
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

5
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)

6
Mini TEPC(-GEM)
Electric field lines
200 ?m
100 ?m
50 ?m
Gas Electron Multiplier (GEM)
From CERN Courier
7
Gain measurements
dt 1 ?m 0.1 atm lt pg lt 1.0 atm 5.0 mm gt dg gt
0.5 mm
dt 1 ?m 0.3 atm lt pg lt 0.8 atm 3.0 mm gt dg gt
1.0 mm
8
TEPC-GEM design
? 2 mm
9 mm
76 mm
9
First calibration measurements
10
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.