1. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 1 Development of Liquid Nitrogen Time Projection Chambers A. Ereditato, M. Hess, S. Janoŝ, I. Kreslo, S. Lehmann, M. Messina, U. Moser, B. Rossi, H.-U. Schütz, M. Zeller Presented by Igor E. Kreslo, Ph.D. LHEP, University of Bern

2. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 2 Multi-energy X-ray cargo radiography – can still something be hidden? Sensitive to: Metal objects High density objects Characteristic shapes Not very sensitive to: Specific chemical composition 2D shaped objects (sheet explosives)

3. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 3 Gamma Nuclear Resonant Absorption method of Nitrogen detection (Soreq NRC, 1985) 14 N 9.17 MeV γ 13 C p ~1.5 MeV

4. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 4 Gamma Nuclear Resonant Absorption method of Nitrogen detection (Proposed by Soreq NRC* to US FAA in 1985) 14 N Resonant γ Detector 14 N 13 C p e-e- e-e- e-e- Intensity N content e-e- e-e- e-e- Non-Resonant γ e-e- * Sorec National Research Center, Yavne, 81800, Israel

5. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 5 Detector for GRNA radiography High spatial resolution (order of 1 mm or better) Large active volume High density High Nitrogen content TPC on liquid Noble gases (LAr, LXe) LNitrogen ?

6. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 6 Plans and Perspectives Ionisation signals in Liquid Argon - Nitrogen

7. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 7 Charge transport in Liquid Argon - Nitrogen

8. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 8 Detector scheme Electron mobility in Liquid Argon - Nitrogen

9. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 9 LAR TPC prototype Mixture LAr-LN is prepared directly in the cryostat. The content of Nitrogen is monitored by density sensor. ρ LAr = 1.4 g/cm 3 ρ LN = 0.8 g/cm 3 Density sensor: Floater C = f( ρ )

10. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 10 LAR TPC prototype 8mm 100 x 100 mm Wire pitch 2 mm To preamp HV power supply 0-30kV

11. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 11 LAr TPC prototype Argon used: Carbagas 1, Commercial grade “48” ( < 2*10 -7 impurities concentration) Nitrogen used: Carbagas, Commercial grade “50” ( < 10 -7 impurities concentration) No additional purification is done for the first tests. 1 Carbagas, Hofgut, 3073 Gumligen, Switzerland

12. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 12 LAR TPC prototype and performance Detector readout, amplifier, DAQ CAEN V1724 VME 8xADC Shaping Q-integrating preamplifier, ~ 25 mV/fC Wire chamber

13. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 13 LAR TPC prototype and performance Muon 0-30 kV

14. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 14 LAR TPC prototype and performance Cosmic Muon Tracks recorded ~ 5 mm drift

15. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 15 I-I- LAr TPC prototype and performance TPC response to a primary ionization Particle Ar + e - E Recombination losses q 0 =A*Q 0 Primary ionisation Q 0 e-e- Attachment losses q=q 0 e -(D/ λ ) collection wires D, drift distance I-I- I-I-

16. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 16 LAR TPC prototype and performance TPC response to a Compton electrons - simulation Losses during the charge drift affect the shape of the spectrum, but not the end point ! End point can be used to measure recombination.

17. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 17 LAR TPC prototype and performance TPC response to Compton electrons from 60 Co (1.17 and 1.33 MeV gammas) (measured data)

18. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 18 LAR TPC prototype and performance 60 Co (1.17 and 1.33 MeV gammas) “Box model” :

19. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 19 LAR+N TPC prototype and performance A=1 Recombination vs Nitrogen content (vol. %) 60 Co (1.17 and 1.33 MeV gammas)

20. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 20 LAR+N TPC prototype and performance A=1 A~0.5 Recombination vs Nitrogen content, (vol. %)

21. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 21 LAR+N TPC prototype and performance A=1 A~0.5 Recombination vs Nitrogen content, (vol. %) Similar effect was observed by D.W. Swan in 1963, with about 0.6 vol. % of LN ( for reference see slide 7) but not explained !

22. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 22 LAR+N TPC prototype and performance Box model parameters evolution with LN content (vol. %) Betha A

23. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 23 LAR+N TPC first test conclusions 1.First prototype TPC with Liquid Argon-Nitrogen mixture operates well in Bern. 2.Collected charge at 8 mm drift and 6 vol. % of Nitrogen is sufficient to see MIPs and 1 MeV electrons (signal / noise >10). 3.At 6% of Nitrogen such TPC is already more efficient for GRNA, than liquid scintillator detectors. 4.Further study on recombination mechanisms in LAr-N is needed. 5.The technology is very promising for security applications !

24. I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 11-12 June 2008. 24 LAR+N TPC Plans and Perspectives 1.More detailed study on recombination vs Nitrogen content with non-resonant gammas. 2.Study of charge attachment cross-section vs Nitrogen content. 3. Proton - electron separation study (simulation) 4. Tests with resonant gammas on a proton accelerator. 5. Optimization of the detector geometry for GRNA scenario. 6. Contacts with industry - building a cargo screener prototype