Full characterization of an old HPGe detector GEROS

Full characterization of an old HPGe detector (GEROS) V. Angelopoulou E. Kouvaris V. Lagaki T. J. Mertzimekis P. Papagiannis 1

2 Outline: v Story of GEROS v Motivation v Characterization Techniques v Simulations v Conclusion

3 What is GEROS ü GEROS stands for Germanium for Environmental Radi. Oactivity Studies ü An old, p-type, 20% HPGe detector, coaxial crystal geometry ü Has already been used for some environmental γ-ray spectroscopy

4 Why ? üOnly information available: üA full characterization was needed before putting it back to operation 53. 4 mm 53. 6 mm 14 mm 48. 6 mm

At 15 cm : Sources 60 Co 137 Cs 152 Eu 226 Ra 5

Linearity: Fit with 2 nd order polynomial E = A+B(chn)+C(chn)2 152 Eu, 15 cm Parameters Curve fit A 9. 2 B 0. 6435 C 9. 2∙ 10 -8 Resolution (FWHM): 6

7

Weight (g) 3. 245 2. 956 19. 781 32. 736 92. 48 Element 137 Cs 40Κ 137 Cs 40Κ Energy (ke. V) 661. 75 1460. 97 ε (%) δε (%) 2. 78 2. 03 0. 04 661. 38 1461. 29 1. 96 1. 43 0. 04 661. 68 1460. 84 1. 427 0. 361 0. 012 0. 007 661. 7 1460. 83 1. 192 0. 228 0. 009 0. 004 661. 71 1460. 97 1. 155 0. 125 0. 011 0. 004 IAEA Ref. 154, C. Potiriadis 8

9 Liquid N 2 Dewar container X-Y motion platform The experimental setup Pb collimator 134 Cs source Alignment laser ü Shield consists of four 5 -cm thick Pb bricks: ü 2 used for vertical dimension and 2 for parallel ü 3 x 3 mm 2 collimation hole

10 The 134 Cs spectrum (t 1/2 = 2. 0652 y) Δt = 10 min The energy spectrum of 134 Cs, from GEROS, taken at (x, y)=(0, 0) position More than 700 spectra were collected analyzed Spectr. W, C. Kalfas

11 Results of gamma ray tomography ü Diagrams of counts in a vertical scanning, for fixed x position x = -9 mm x = -3 mm x = 0 mm x = 3 mm x = 6 mm x = 9 mm ü Diagrams of counts in a horizontal scanning, for fixed y position y = -12 mm y = -6 mm y = -3 mm y = 0 mm y = 3 mm y = 9 mm

12 Reconstructed 3 D model

13 Study of the results ü Estimation of the center of the crystal : (0, -2)

14 ü The crystal appears to be tilted 25 mm 18 mm 21 mm 19 mm

15 ü Estimation of the crystal’s diameter Int. Diam. : 8 ± 1. 5 mm Ext. Diam. : 46 ± 1. 5 mm Int. Diam. : 12 ± 3 mm Ext. Diam. : 48 ± 3 mm

16 Can we confirm this? GEROS was CT scanned (X-ray Computed Tomography) Side view Full view Front view

17 MCNP simulation Eu-152 964 ke. V

18 Conclusions ü An old HPGe detector was put back to operation and fully characterized ü From γ-ray and CT tomographies the exact geometry was deduced and fully reconstructed in 3 D ü The detector has suffered some loss of efficiency due to prolonged inactivity (dead layer built up) ü MCNP simulations have been performed and found to agree well with the experimental data ü Efficiencies for several bulk sample geometries were estimated by means of an IAEA reference material ü Overall the detector can be used for γ-ray spectroscopy and educational activities at Uo. A

19 Thanks to v. The TANDEM accelerator staff, and especially Dr. M. Axiotis v. The Lefkos Stavros hospital and staff v. Dr. C. Potiriadis for the IAEA reference material v. Dr. C. Kalfas for Spectr. W licences

20 Thank you for your attention!

21 Additional slide The inside-out of the detector