Infrared emission in Xenon gas/liquid

1. Infrared emission in Xenon gas/liquid Kirill Pushkin Department of Physics and Astronomy, University of Alabama, Tuscaloosa Workshop on Xenon-Based detectors Lawrence Berkley National Laboratory November 16-18, 2009

2. IR emission was first was observed: • S. Arai and R.F. Firestone, J. Chem. Phys., 50, (1969), 4575-4589. • G.L. Braglia, G.M. de’Munariet al., NuovoCimento 43B, (1966), 130. • Yu.A. Butikov, B.A. Dolgoshein, V.N. Lebedenko et al., Soviet physics JETP, 30, (1970), 24-28. • G.M. de’Munari, G. Mambriani et al., Lettere Al NuovoCimento, 2, (1971), 68-72. • Y. Saamero, A. Birot, H. Brunet, et al., J. Phys. B., 21, (1988), 2015-2025. • Extensive research was carried out both in liquid and gaseous noble gases (Xe, Ar) from 1998-2000, see references.

3. IR scintillation shows really interesting features • It is possible to have a good reflector contrary to what happens with VUV/UV photons. • It is not perturbed by impurities present in the gas itself. • The diffusive scattering is much less compared to the VUV/UV light, see reference [1]. • At the preliminary estimation amount of IR light, 0.7-1.6 um, seems to be comparable with VUV light. • For the record, both Ar and Xe turn out to be good IR emitters. Problems • Detection devices

4. IR emission occurs both at electric fields and without electric fields and increases with an increase of the electric field (see ref.[2]). As reminder VUV light is emitted due to excitation and recombination processes: Xe*+2Xe→Xe2*(1Σu+, 3Σu+)+Xe, Xe2*→2Xe+hν – excitation (5-6 ns and 100-110 ns, respectively) 2) Xe+2Xe→Xe2++Xe Xe2++e-→Xe**+Xe Xe**+Xe+Xe→Xe2**+Xe → → Xe*+Xe+Xe→ Xe2*→2Xe+hν – Recombination (long process, ~100 us). IR light increases linearly with the increase of the electric field Source: 3.5 MeV proton beam from the Legnaro Van derGraaf accelerator Current and IR light signals (arbitrary units) versus voltage applied to ionization chamber (the figure is reproduced from [2].

5. Dependence of the light emission and ionization signal versus voltage applied to the wire of the ionization chamber. (reproduced from [1]) A lower limit of IR light has been set using InGaAs photodiodes: Y ≥ N/QEεE ≥ (2.1 ± 0.3)×104 (IR photons/MeV), where N – the number of photoelectrons, QE – the InGaAs quantum efficiency, E – the energy released by the alpha particles and ε – the light collection efficiency of the ionization chamber (see ref [1]).

6. Michelson spectrometer spectrum of IR scintillation in gaseous Xe at room temperature and pressure of 3.5 bar (reproduced from [3]). Comparison between IR spectra in gaseous and liquid Xe obtained by means of optical IR filters (reproduced from [3]). Source: 80 keV electron beam The signal produced in gas was two orders of magnitude higher than the signal in liquid!!!

7. Multiphoton excitation See ref. [7]

8. 3P2 + 2S10 → (3Σ+u )ν ~ 1st continuum → 1S0 →(3Σ+u )0 ~ 2nd continuum • 3P1 + 2S10 → (1Σ+u )ν ~ 1st continuum → 1S0 →(1Σ+u )0 ~ 2nd continuum • Some energy levels of xenon gas: 3P2 – 8.31 eV, 3P1 – 8.43 eV, 3P0 – 9.44 eV, 1P1 – 9.57 eV Other paper: 1s-2p transitions, lifetime of 2p states ~10-7-10-6 s [see ref. 8], 1053 nm – Infrared light yield, (200-1500 torr).

9. Detection devices The authors [1] used InGaAs photodiodes with an active area of ~5 mm. InGaAs sensitivity - 0.7-1.6 um. Quantum efficiency ~ 78% from 0.95 to 1.55 um. Should be cooled down continuously. Expensive: • InGaAs, 5 mm active area - $1400 – recent quote from Hamamatsu • Photodiode cooler - $1400 – recent quote from Hamamatsu • HgCdTe devices – expensive as well

10. The responsivity of a black-silicon detector for Silicon, Black silicon and InGaAs photodiodes • Recently developed Black silicon photodiodes seem to be promising • Cheap • Effective • Shifting VUV (175 nm) light will enable high light yield detection using waveshifting materials. 380 nm 1300 nm reproduced from [ref. 4]

11. Waveshifters • P-terphenyl (C14H18) has two emission peaks at 350 and 450 nm (does not contaminate XenonGAS) – Emission Tomography of PET and SPECT, A. Bolozdynya. A. Bolozdynya and D. Akimov, private communication. • Buthyl – PBD – emission peak at 370 nm • Tetraphenyl butadiene (TPB) – emission peak at 440 nm • Diphenylstilbene – emission peak at 409 nm

12. Measurements of Ws • Ws value ~ 59.4 ± 2.4 eV [see ref. 5]. • Using (5) at [5] the amount of detected scintillation light was on average ~(7.1±0.3)×104 phat 1 atm and ~(6.2±0.3)×104 ph at 2 atm. Taking into account the deposition energy the scintillation light works out to be ~18000 ph/MeVBUT it looks like that that is only due to excitation processes. Thus, since the authors [1] set a rough limit on IR light, ≥ (2.1 ± 0.3)×104 (IR photons/MeV), then the amount of IR light yield may be comparable with the amount of VUV light but it is not clear yet. Another measurements of IR light are required.

13. See ref. 6

14. Oscillograms of scintillation pulses in gaseous xenon (1) PMT, (2) blue, (3) green Neither UV nor IR were observed in Liquid Xenon!!!

15. Summary • IR light is emitted in the region of 0.7-1.6 um having a maximum of IR emission at ~1.27 um. • Limit for IR photons, ≥ (2.1 ± 0.3)×104 (IR photons/MeV), has been set making use of InGaAs photodiodes. • IR emission is likely to occur due to excitation processes although there are not clear results enough to fully claim it. It is the fact though that the IR light increases linearly with the increase of the electric field which may result in production both primary and secondary scintillation. • IR scintillation light in GAS phase was found two orders of magnitude higher than in liquid phase. • Detection devices, InGaAs ($2800 per PD+cooler). It is suggested that IR scintillation light can be detected by recently developed black photodiodes which seems to be very effective having a high light sensitivity from ~380 nm to ~1750 nm and considerably cheap compared with the modern IR detection devices. • It is also suggested that following the above technique one could detect both VUV and IR light in Gaseous Xenon by shifting the VUV light making use of waveshifters, which in turn seem not to contaminate xenon, and therefore substantially increase light collection and boost energy resolution of the detectors.

16. References • [1] S. Belogurov, G. Bressi, G. Carugno et al., Nuclear Instruments and Methodsin Physics Research A 452, (2000), 167-169. • [2] G. Carugno, Nuclear Instruments and Methodsin Physics Research A 419, (1998), 617-620. • [3] G. Bressi, G. Carugno, E. Conti et al., Nuclear Instruments and Methodsin Physics Research A 461, (2001), 378-380. • [4] J. Carey and J. Sickler, “Black silicon sees further into IR”, Laser Focus World. • [5] M. Saito, T. Nishikava, M. Miyajima, Nuclear Instruments and Methodsin Physics Research A 593, (2008), 407-413. • [6] D. Akimov, A. Akindinov, A. Burenkov et al., Instruments and Experimental Techniques, 52, (2009), 345-351. • [7] Y. Salamero, A. Birot, H. Brunet et al., J. Phys. B, At. Mol. Opt. Phys., 21, (1988), 2015-2025. • [8] S. Arai and R.F. Firestone, J. Chem. Phys., 50, (1969), 4575-4589.

17. THANK YOU VERY MUCH FOR YOUR ATTENTION!

18. Photon detection efficiency as a function of wavelength for multipixel Geiger photodiodes Blue Green