Pyroelectric crystal based neutron source and neutron detector

Transcription

1 Dipartimento di fisica G. Occhialini Università Degli Studi di Milano-Bicocca Seminar for summer school on Neutron Detectors and Related Applications-NDRA 2016 June 29th July 2nd, 2016, Riva del Garda, Trento, Italy Pyroelectric crystal based neutron source and neutron detector Song FENG (XXXI cycle Ph.D Student) October 14 th, 2016 Tutor: Dr. Marco Tardocchi Cotutor: Prof. Giuseppe Gorini

2 2 Seminar for summer school on Neutron Detectors and Related Applications-NDRA 2016 June 29th July 2nd, 2016, Riva del Garda, Trento, Italy What s the summer school about? Topics: Neutron interaction with materials Physics of neutron detectors Material for neutron detection Monte Carlo simulation My Topic But based on pyroelectricity Gas detectors for neutrons Neutron sources Application of neutron detectors

3 3 Outline Introduction Method Neutron source Neutron detector

4 Introduction Nature, 434: , 2005 Nature, 434: , /31

5 Introduction Physical Review Letters, 96: , 2006 Thermally stimulated field emission from pyroelectric LiNbO 3 Applied Physics Letters, 25(1): 17-19, 1974 Pyroelectric X-ray generator Nature 358: , 1992 What is the pyroelectric crystal? How can it be used to produce neutrons? How high neutron intensity can it produce? Setup for paired-crystal neutron generation experiments 5/31

6 6/31 Outline Introduction Method Neutron source Neutron detector

7 2. Method_I. Pyroelectricity It is a Greek word derived, means electricity generated by heat. 7/31

8 2. Method_I. Pyroelectricity +Z -Z LiTaO 3 Shinobu Aoyagi, et al. Jpn. J. Appl. Phys NB03, 2015 Polarizing of a pyroelectric crystal Left: random orientation of a polar domains prior to polarization; Right: polarization after temperature changed. S.B. Lang., Physics Today 58 (8) (2005) Attention: Curie temperature LiTaO 3: ~620 o C LiNbO 3 : ~1200 o C 8/31

9 2. Method_I. Pyroelectricity Schematic diagram of the response to temperature changes of a pyroelectric crystal in a dilute gas environment. James D. Brownridge, et al. Journal of Electrostatics, 63(3-4): , 2005 A. Peláiz-Barranco, et al. Advances in Ferroelectrics. chapter5: Relaxor Behaviour in Ferroelectric Ceramics, P E hysteresis loops of the pyroelectric crystal A virgin crystal begins at the origin, with no polarization. a-b: As temperature is increasing, electric field increases and the polarization increases along a curve to point b. b-c: Once all of the dipoles in the crystal are aligned, the polarization saturates, at point c. c-d: As the external field is removed, the polarization doesn t return to zero. Instead, it is reduced only slightly from the saturation polarization, to the remnant polarization (d). 9/31

10 2. Method_II. X ray generator e - e - Fig. Schematic representation of the arrangement James D. Brownridge, et al. J. Appl. Phys., 86(1): , (A) Peltier effect cooler; (B) Crystal and heater support; (C) Heater resistor of 62 V; (D) Pyroelectric crystal (E) Temperature probe (F) Small contact connected to electrometer (G) Photomultiplier (H) Target(either metallic or nonmetallic) (I) X-ray detector with thin Be window (J) Vacuum pump outlet (K) Thin mylar absorber to prevent electrons from striking the Be window. During temperature increasing: electrons are accelerated to the -z base of the pyroelectric crystal and are repelled from the +z base of the crystal. During temperature decreasing: electrons are repelled from the -z base and accelerated to the +z base. The electrons striking the crystal may have sufficient energy to excite x-ray absorption edges of the elements in the crystal and the electrons repelled to a target may have sufficient energy to excite the elements in the target. 10/31

11 2. Method_II. X ray generator Lifetime: 1000 hours for intermittently use (about 1-3 h/day). 200 hours for continuous use. Controller System 9 V AC adapter and a 9 V battery; automatically change the heating and cooling phases. Radiation Precautions (distance: 10cm) Maximum radiation: 5 msv/hr (500 mr/hr); Peak counting rate ~ counts/cm 2 /s. (~75% < 10 kev). 11/31

12 2. Method_II. X ray generator The radiographic image was produced over 3 cycles at 10 cm Used to analyze a material with an X-ray detector Jun Kawai, et al. X-Ray Spectrom. 2012, 41, /31

13 2. Method_II. Neutron generator Schematic of a typical pyrofusion system V. Tang, et al. LLNL-PROC , /31

14 2. Method_II. Neutron generator Pyroelectric neutron generator. Lines of constant electric field are shown. Nature, 434: , 2005 B. Naranjo et al. Nuclear Instruments and Methods in Physics Research A 632 (2011) /31

15 15/31 Outline Introduction Method Neutron source Neutron detector

16 3. Neutron source Motivation for Pyroelectric Fusion Create a new source of high-energy neutrons for use in applications where portability was very important Comparison with other fusion sources Radioisotope Sources Reactors and Linear Accelerators Portable Neutron Generators Pyroelectric Size weight Can be very small large ~100cm in length; ~15kg in weight ~30cm in length; 3 kg in weight Price/$ Not expensive Expensive ~100, Yield/ns -1 Decided by mass Powerful Remarks 1. can t be closed 2. disposal problem Can t be moved Requires high voltage power supplies Enough for luggage scanning Jeffrey A. Geuther. Radiation Generation with Pyroelectric Crystals. PhD thesis of RPI, US, /31

17 3. Neutron source Experimental setup 1 Effect of target thickness on acceleration potential Choice of fill gas Gas Ionization Target Preparation deuterated polyethylene ~45μm layer Schematic of a generator with closeup views of the modular crystal assembly V. Tang, et al. Rev. Sci. Instrum. 78, (2007). 17/31

18 3. Neutron source Experimental setup 2 Results Schematic of the two crystal system inside the vacuum chamber D. Gillich et al. Nuclear Instruments and Methods in Physics Research A 602 (2009) /31

19 3. Neutron source Influence of the tip W. Tornow, et al. J. Appl. Phys. 104, /31

20 3. Neutron source Influence of the tip Photograph of the actual experimental setup showing the chamber containing the double-crystal arrangement, the two large neutron detectors (surrounded by cylinders made of lead) and the HPGe X-ray detector (with a lead attenuator placed in front of the detector) positioned in the horizontal plane and the two small neutron detectors (placed in cups made of lead) and the end-window Geiger counter on top of the chamber. W. Tornow, et al. Nuclear Instruments and Methods in Physics Research A 624 (2010) /31

21 3. Neutron source Influence of the tip Don Gillich, et al. Tip Length Optimization for a Pyroelectric Crystal Neutron Source. Influence of crystal dimension A. M. Kovanen, et al. D-D Nuclear Fusion Using Different Size Pyroelectric Crystals, /31

22 3. Neutron source Improve the intensity Donald J. Gillich, et al. Nano Today (2009) 4, /31

23 3. Neutron source Comparison of deuterated target Surface crack W deposition The best target material available for pyroelectric crystal fusion experiments in terms of the theoretical neutron yield is CD 2. Further experimental investigations using different metal targets are necessary to compare differences between plastic and metal targets in pyroelectric crystal fusion experiments. Donald J. Gillich, et al. Journal of Nuclear Materials 405 (2010) /31

24 3. Neutron source Virtual experiment of pyroelectric fusion The arrangement of virtual experiment for pyroelectric X-ray generator Schematic view of the virtual experiment for pyroelectric fusion Mohammad Mehdi Nasseri. Nuclear Instruments and Methods in Physics Research B 358 (2015) Mohammad Mehdi Nasseri. Nuclear Instruments and Methods in Physics Research B 362 (2015) /31

25 3. Neutron source Applications Calibration (for neutrino and dark matter detectors) Luggage scanning or examination Education The pyroelectric neutron source can be installed stationary into a neutrino or dark matter detector. Advantages and Disadvantages A S Chepurnov1, et al. Journal of Physics: Conference Series 675 (2016) Portability Low power supply Cheap Pulse generator with long pulse width Low neutron yield 25/31

26 26/31 Outline Introduction Method Neutron source Neutron detector

27 4. Neutron detector Pyroelectric neutron generator Pyroelectric neutron detector Supply heat Neutron irradiation Change polarization Change temperature/polarization Cause a strong electric field Cause a potential difference Ionization and neutron production Amplify electric signal 27/31

28 4. Neutron detector The physical effects, which result in flow of electric charges in pyroelectric detector circuit under irradiation, have been used to detect: X-ray, gamma ray, ion and atom beams Klaus H. Berkner, et al. Review of Scientific Instruments 39, 1204 (1968) V. A. BORISDIOK, et al. IEEE 7 th International Symposium on Applications of Ferroelectrics: , C. Cote, A. W. DeSilva. Review of Scientific Instruments 67, 4146 (1996). V. A. Borissenok, et al. Instruments and Experimental Techniques, 2009, Vol. 52, No. 4, pp and neutron Converter: high enriched 235 U or 10 B Can monitor thermal neutron flux >10 3 n/cm s. Advantages: -simple construction and low costs; -possibility of operating as a portable device; -does not require external bias field; -stable output signal (long term operation); -low sensitivity to gamma radiation; -responds linearly to 10 B enrichment. S.B. Crestana, et al. Nuclear Instruments and Methods in Physics Research A311 (1992) E.A. de Souzaa, et al. Nuclear Instruments and Methods in Physics Research A 365 (1995) /31

29 4. Neutron detector Containing either in a molecular form or in a nano-particulate form, 6 Li or 10 B or both; Detect the presence of neutrons. Does not required the photomultiplier tubes; Can sense with high gain individual neutron events; Not sensitive to other types of radiation. Ivan M. Lorkovic, et al. United State Patent. (No. US 8,354,641 B2), /31

30 4. Neutron detector Application of LiTaO 3 pyroelectric crystal for pulsed neutron detection Does not need any additional neutron converter. The slight temperature increase caused by neutron pulse will lead to the release of bound charges and giving rise to a pyroelectric signal. The feasibility of LiTaO 3 pyroelectric crystal for pulsed neutron detection was confirmed. W.F.Liang et al. Nuclear Instruments and Methods in Physics Research A 827 (2016) /31

31 Seminar for summer school on Neutron Detectors and Related Applications-NDRA 2016 June 29th July 2nd, 2016, Riva del Garda, Trento, Italy Thank you for your attention! Song FENG Pyroelectric crystal based neutron source and neutron detector October 14th, /31