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U nderwater T racking S ystem

U nderwater T racking S ystem. Francesco Simeone. Goal & Outlook. Detector: The expected signal The propagation medium The signal detection The readout Physics field of applicability Reasearch plan Objectives and time schedule Experimental setup.

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U nderwater T racking S ystem

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  1. Underwater Tracking System Francesco Simeone

  2. Goal & Outlook Detector: The expected signal The propagation medium The signal detection The readout Physics field of applicability Reasearch plan Objectives and time schedule Experimental setup The aim of this work is to demonstrate the feasibility of an innovative underwater tracking system, made of planes of solar cell strips, able to detect the light induced by ionizing particles in water.

  3. Detector: the expected signal 1/3 A charged particle traversing water leaves behind it a wake of excited molecule fragments (mainly H and/or OH) that will release a fraction (≈ 1%) of the primary energy loss as optical photons H-α Minimum energy: 17.8eV Beware: it’s a discharge experiment! OH A2∑+ - X2∏ Minimum energy: 9.67eV P. Bruggeman, D. Schram, M. González, R. Rego, M. Kong, C. Leys - DOI:10.1088/0963-0252/18/2/025017

  4. Detector: the expected signal 2/3 Some process leaves the molecular fragment in an excited state Non trivial simulation are needed to evaluate the light yield Yukikazu Itikawa, Nigel Mason - DOI: 10.1063/1.1799251

  5. Detector: the expected signal 3/3 Efficiencies of energy deposition in water defined as “the value that results from the amount of energy transferred to a particular state in a gas (as the result of the complete slow-down of the primary electron and of all the generated secondaries, tertiaries, et cetera) being divided by the primary energy.” The quoted efficiency refers to the sum of all the possible emissions (Lyman and Balmer) The expected signal, evaluated from literature using optimistic assumptions, for a minimum ionizing particle (MIP) in water is ≈3 kγ/cm emitted in the OH band and ≈2 kγ/cm in the H-α lines. J.J. Olivero, R.W. Stagat, A.E.S. Green - DOI:10.1029/JA077i025p04797

  6. Detector: the propagation medium H-α OH A2∑+ - X2∏ 1m 5m Raymond C. Smith and Karen S. Baker – DOI: 10.1364/AO.20.000177 The light attenuation length in water, at those wavelengths, is ≈3m so a large surface device (≈ 1m2) can collect most of the light emitted isotropically in few meters by the muon track; the photons collected by a ≈ 1 m2 device is expected to be ≈100 kγ for a track orthogonal to the surface

  7. Detector: signal detection 1/4 298µm 0.5µm Space charge region 1µm W.J. Yang, Z.Q. Ma, X. Tang, C.B. Feng, W.G. Zhao, P.P. Shi DOI:10.1016/j.solener.2007.07.010 A solar cell is well suited to detect most of that electromagnetic radiation with high internal quantum efficiency (> 70%) in or near the visible range, 300 nm ≲ λ ≲ 900 nm. The internal quantum efficiency (IQE) is “defined as the number of minority carriers contributing to the short circuit current divided by the number of photons entering the cell” (thus without taking into account the glass and eventually the anti-reflection coatings)

  8. Detector: signal detection 2/4 Example of thin film amorphus silicon solar cell: SnO2:F p–a–SiC:H i–a–Si:H n–a–Si:H Al The silane(SiH4) concentration(SC) changes the bangap of the amorphous silicon, from about 1.6eV up to 2eV. Ni Jian et al 2011 Chinese Phys. B 20 087309 doi: 10.1088/1674-1056/20/8/087309 • The main limitations of solar cells in the UV-B range are: • window material (both SnO2 and ZnO) and its width • antirefractive coating • thickness of the p layer of the cell

  9. Detector: signal detection 3/4 J Jph JD Rs Rp U Different materials as well as production techniques change deeply the electrical characteristic of the cell as function of the irradiance Cdte/cds solar cell performance under low irradiance. 17-th EC PV solar Energy Conference

  10. Detector: signal detection 4/4 The capacitance of the solar cell is proportional to its surface and depends on the doping concentration and temperature; moreover it varies according to the illumination. Capacitance for surface unit at zero illumination of ≈10 nF/cm2 and a shunt resistance of ≈1 kΩcm2 are common values in actual solar cell production lines. R.A. Kumar, M.S. Suresh, J. Nagaraju – DOI:10.1109/TPEL.2005.869779

  11. Detector: readout 1/2 In applications where the output signal is a weak charge pulse and the detector element is itself a capacitive device, operational amplifier mode integrators using feedback capacitance are commonly used (charge amplifier). • The equivalent noise of a charge amplifier is composed of two terms: • independent of the input capacitance with 1/f2 frequency dependence • flat in frequency with amplitude proportional to the square of the input capacitance

  12. Detector: readout 2/2 Commonly charge amplifiers are designed to match input capacitance in the range 10-100 pF with an equivalent noise charge (ENC) of hundreds of e-.Special input stage composed of JFETs in parallel or a transformer can be used to match higher capacitance. ENC as a function of the shaping time for a silicon detector 2x2cm with an equivalent capacitance of 40nF. With the proper design of the input stage it is possible to obtain ENC ≈10ke- for capacitance of ≈10nF G. De Geronimo, A. Musumarra, S. Tudisco 10.1016/S0168-9002(97)01287-4

  13. Detector: conclusion • About ≈ 1% of the energy loss by particle in water goes into light • (≈5kγ/cm for a MIP) • The light produced in few meters of track could be efficiently detected • (≈100kγ for a MIP using ≈1m2 detector) • A solar cell, without polarization, could be used as light detector with high IQE • (≈70%, about 10fC, over the useful wavelengths) • A specifically designed charge amplifier could be used to acquire the signal. • (≈10ke- ENC for an input capacitance ≈40nF) • These considerations led to propose a detection device composed by a series of many small solar cells (≈1 cm2) so that the input capacitance seen by the amplifier will be the single cell capacitance, i.e. few tens of nF. In case of MIPs in water S/N greater than 4 seems feasible.

  14. Physics field of applicability As detector in water (High energy neutrinos >GeV) It appears possible to build a detector unit, able to measure the track of muons with energy in the range 1-10 GeV, made of planes of about 10x10 m2 consisting of two layers of 10 strips 10x1 m2, spaced by 4 m with an active volume of about 10 kton. This detection unit will be relatively cheap since the solar cell has a low price/surface ratio and all the relevant detector components, except the electronics, could be placed directly in water, thus reducing the cables, connectors and vessel cost. Long baseline oscillation appearance experiments: Mass hierarchy and CP phase source: accelerator neutrinos baseline ~ 1000 km or longer LBNE-LAr (USA), LBNO (EU), Hyper-K (Japan) Long baseline oscillation disappearance experiments: Mass hierarchy source: atmospheric neutrinos PINGU (South-pole), ORCA (EU)

  15. Physics field of applicability If this feasibility study will produce positive results, other experiments, based on liquid scintillator such LENA, could take benefit from the use of solar cell as light detectors; As detector in liquid scintillator(Low energy neutrinos >MeV) Short baseline appearance experiments: CP phase source: neutrinos from stopped pions baseline ~ 30 km low energies (E ~ 30 MeV) LENA, Water-Cherenkov Proton decay, Geo neutrinos, Solar neutrinos CNO (LENA) As sub-detector Moreover the same effect, measured with the same device, could be used in many sub-detectors (i.e. Cherenkov tank of the Pierre Auger Observatory; LAAHSO experiment) when a cheap muon detector or a rough calorimeter of about few tons is required.

  16. Reasearch plan: objectives Objectives and time schedule The objectives of this proposal are twofold: Objective 1: Verify that the claimed scintillation effect in water has the potential to be used (O1). Objective 2: Demonstrate that a device made of solar cells could efficiently measure this effect (O2). • First year: • Measure the claimed effect • Measure the electrical characteristics of different type of commercial solar cells • Measure the lowest detectable optical signal for a detector made of solar cells • Second year: • Develop the proper input stage for the charge amplifier • Production of prototipal solar cell with different characteristics (ARC, window material and thickness) • Measure the claimed effect with the designed electronic

  17. Reasearch plan: experimental setup 1/2 Dark box filled with water UV-B trasparent optical window (fused silica) 15cm µ Light 15cm 90 Sr, almost pure β- source 15cm Spectrometer (200-1000)nm Photomultiplier (200-800)nm Light Acquisition is triggered Used to measure the claimed effect Can integrate the signal for few tens of seconds Used to separate the cherenkov light contibution from the scintillation one

  18. Experimental setup 2/2 • Commercial solar cells of different manufacturers and materials in a dark box, used to measure the electrical characteristics in dark condition: • Capacitance • Serial and parallel resistance • Dark current • Laser source with tunable intensity working at 400nm (thust avoiding the wavelength range that needs to be optimized) • Commercial charge amplifier This information are needed to select the solar cell and to proper design the input stage of the charge amplifier. Used to measure the minimum detectable ligth signal

  19. Conclusions Scintillator effect in water Verified Not verified Full success Partial success Yes Electronic DAQ Full failure Partial failure No Full success:the detector has been produced and could be used in water as well as in other materials; A CCD camera could be used to track charged particle with high spatial resolution over small volume with a low energy threshold. Partial success: the detector has been produced but could not be used in water; it has the potential to be used with other materials (i.e. scintillators) Partial failure: the effect is confirmed but the detector itself has not the expected characteristic; investigation of different solar panel production line is needed. A CCD camera could be used to track charged particle with high spatial resolution over small volume with a low energy threshold. Full failure: the quantitative measurements of the induced emission in water due to charged particles will be useful for chemistry, biological and astronomy studies.

  20. BACKUP

  21. Reasearch plan: objectives and reasearch units The objectives of this proposal are twofold: Objective 1: Verify that the claimed scintillation effect in water has the potential to be used (O1). Objective 2: Demonstrate that a device made of solar cells could efficiently measure this effect (O2). RU1: This unit will coordinate the others RUs and will realize most of the experimental setups and will perform most of the data analysis. RU1 is composed by one member, Francesco Simeone principal investigator of this proposal. RU2: This unit will perform all the electronic development needed to fulfil this proposal. RU2 is composed by one member, Fabrizio Ameli, INFN researcher with experience in the front-end electronic design and development as well as VHDL coding on FPGA systems. RU3: This unit will contribute to the experimental setup needed to measure the electromagnetic radiation emitted due to dissociative excitation of the water molecules and will perform its simulation; RU3 is composed by one member, Paolo Postorino associate professor of the physics department at “Sapienza” university, he’s an experimental physicist expert in infrared and Raman spectroscopy.

  22. Reasearch plan: O1 Activity 1: Develop a simulation code able to evaluate the spectrum of the light induced by charged particle propagating in water. This activity is a milestone of RU3. Input from other RUs: none RUs involved: RU3 and RU1 Activity 2: Develop an experimental setup able to measure the spectrum of the light induced by charged particle propagating in water. This activity is a milestone of RU1. Input from other RUs: Calibrated PMTs RUs involved: RU1 Activity 3: Acquire the emission spectrum and validate the simulation code. Input from other RUs: The experimental setup A, the simulation code RUs involved: RU1 and RU3

  23. Reasearch plan: O2 Activity 1: Develop an experimental setup able to measure the solar cell characteristics, both electrical and optical ones, and perform the measurements. Input from other RUs: none RUs involved: RU1 and RU2 Activity 2: Development and production of the first prototype of the acquisition electronic. This activity is a milestone of RU2. Input from other RUs: Electrical characteristic of the solar cell RUs involved: RU2 Activity 3: Development and production of the second prototype of the acquisition electronic. Input from other RUs: Emission spectrum measure with the experimental setup A RUs involved: RU2 Activity 4: Measure the claimed effect using the final version of the acquisition system. This activity is a milestone of RU1, RU2 and RU3. Input from other RUs: Second version of the DAQ system, final version of the simulation code, experimental setup A. RUs involved: RU1, RU2, RU3

  24. The medium: attenuation coefficiens L R where A is the number of photons produce per unit length, R is the radius of the discus and L the track length. It is clear that the solid angle effect dominates. 109,5kγ ≈ 0.5*5kγ*(200cm+50m-206.2cm) 95,5kγ ≈ 0.5*5kγ*(100cm+50m-111,8cm)

  25. Solar cell: ARC Today multi- and monocrystaline solar cells are typically wet-chemically textured and coated with a thin layer of silicon nitride to reduce losses due to light reflection and for electrical passivation of the silicon surface. “standard” n=2 Tickness=100nm The refractive index of SiNx:H can be easily tuned from silicon rich SiNx:H films (n > 3) to nearly stoichiometric SiNx:H films by changing the gas ratio of the precursors SiH4 and NH3. Stoichiometric Si3N4 films have a refractive index of around n = 1.9. “small variation” n=1.9 Tickness=120nm M. Junghänel, M. Schädel, L. Stolze, S. Peters 10.4229/25thEUPVSEC2010-2DV.1.70

  26. Solar cell: shunt Thermal image of a linear edge shunt A shunt is a local increase in the dark forward current of a cell. This increase can be caused by material defects or it can be process induced. Material induced shunts can occur due to a high density of dislocations, voids or impurities as well as metal-decorated small angle grain boundaries, grow-in macroscopic SixNy inclusions and inversion layers crossing the wafer. Shunts can be created during processing by residues of the emitter at the cell edge, by cracks and holes, by scratches and by aluminium particles at the cell surface. S.A. Correia, J. Lossen, M. Bähr  21st European Photovoltaic Solar Energy Conference and Exhibition, 04.09.2006 - 08.09.2006, Dresden, Deutschland Thermal image of shunts at the front metallization busbar

  27. Solar cell: bandgap Pag 505-565

  28. Solar cell: bandgap

  29. Wavelength shifter Absorption cross-section 3.67x10-16 cm2 @337nm Photoluminescence quantum yield 78% Sergei A. Ponomarenko, Nikolay M. Surin et al. DOI: 10.1038/srep06549

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