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

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

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

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

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

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

9. LAR TPC prototype ρLAr = 1.4 g/cm3 ρLN = 0.8 g/cm3
Mixture LAr-LN is prepared directly in cryostat. The content of Nitrogen is monitored by density sensor.
ρLAr = 1.4 g/cm3
ρLN = 0.8 g/cm3
Density sensor:
Floater
C = f(ρ)
I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, June 2008.

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

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

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

15. LAR TPC prototype and performance
TPC response to a primary ionisation
Primary
ionisation Q0
Recombination
losses q0=A*Q0
Attachment
losses q=q0e -(D/λ)
Particle E
collection wires I-
Ar+ e- I- I-
Ar e- e-
D, drift distance
I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, 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.
I.Kreslo CHIPP workshop on Detector R&D, University of Geneva, June 2008.

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

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

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

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

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

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

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

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