1. 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

2. 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

3. 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 25 1 - Lowering the gas pressure. Anode wire Helix cathode

4. 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

5. 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)

6. TUDelft-IRI-ST Mini TEPC(-GEM) Electric field lines From: CERN Courier Gas Electron Multiplier (GEM) 100  m 200  m 50  m

7. TUDelft-IRI-ST Gain measurements d t = 1  m 0.3 atm < p g < 0.8 atm 3.0 mm > d g > 1.0 mm d t = 1  m 0.1 atm < p g < 1.0 atm 5.0 mm > d g > 0.5 mm

8. TUDelft-IRI-ST TEPC-GEM design 76 mm  = 2 mm 9 mm

9. TUDelft-IRI-ST First calibration measurements

10. 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.