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MASPLAS (MAterial and fundamental Science with Positrons and LASers)  Marco G. Giammarchi - Infn Milano  Rafael Ferragut - Politecnico di Milano (e Infn)

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Presentation on theme: "MASPLAS (MAterial and fundamental Science with Positrons and LASers)  Marco G. Giammarchi - Infn Milano  Rafael Ferragut - Politecnico di Milano (e Infn)"— Presentation transcript:

1 MASPLAS (MAterial and fundamental Science with Positrons and LASers)  Marco G. Giammarchi - Infn Milano  Rafael Ferragut - Politecnico di Milano (e Infn)  Giovanni Consolati – Politecnico di Milano (e Infn)  Simone Cialdi – Università di Milano (e Infn)  Fabrizio Castelli – Università di Milano (e Infn)  Gugliemo Lanzani – Center for NanoScience of IIT  Annamaria Petrozza – Center for NanoScience of IIT  Mario Carioli – Center for NanoScience of IIT Infn CSN5 Call 2014 Participating Institutions Istituto NazionaleFisica Nucleare Politecnico di Milano (PoliMi) Istituto Italiano di Tecnologia (IIT) Bunched positron beam matched to Q-switched laser systems for: Hybrid solar cell studies, Artificial retina studies (APPLIED) Positronium Excitation, Positronium Laser Cooling (FUNDAMENTAL) Other collaborators: R. Brusa – Università di Trento (e Infn) G. Nebbia – Infn Padova D. Comparat – Universitè Paris Sud

2 MASPLAS Main Idea : matching of a pulsed positron beam to a pulsed laser system We propose to upgrade one of the two existing positron beams in Italy, the continuous positron beam at the Politecnico di Milano (at Como). 5 x 10 4 /s e+e+ …and add to it a bunching (accumulation) capability, so that the beam will have a the time structure of 0.01 – 1 sec: ≈ 0.1 s And will be naturally matched to the repetition rate of a so Q-switched laser system that we plan to add. Laser System(s)

3 Main know-how and laboratories involved in the project Slow positron beam. 1. Radioactive source; 2. Electrostatic optics; 3. Sample chamber; 4. HpGe detectors; 5. Cryostat; 6. High voltage protection cage; 7. Power suppliers; 8. Detector electronics. The positron beam is equipped with HpGe detectors for momentum distribution measurements, which can be operated in both single and coincidence mode. Samples are kept in high vacuum (~10 -9 mbar) and their temperature can be varied from 10 to 1000 K. The slow positron beam has been calibrated for positronium fraction measurements. The VPAS Laboratory at the L-Ness Politecnico di Milano at Como Center. (R. Ferragut) http://www.como.polimi.it/positron -G. Consolati et al., Mesoporous materials for antihydrogen production. Chemical Society Reviews, 48 (2013) 3821. -A. Calloni et al., Positron localization effects on the Doppler broadening of the annihilation line: Aluminum as a case study. Physical Review B, 72 (2005) 054112. -R. K. W. Marceau et al., Solute clustering in Al-Cu-Mg alloys during the early stages of elevated temperature ageing. Acta Mater 58 (2010) 4923. - A. Somoza et al., Positron Annihilation Study of the Aging Kinetics of AlCu-based Alloys. I. Al-Cu-Mg. Phys. Rev. B, 61 (2000) 14454.

4 The Laboratory of Lasers and Quantum Optics of the Dip. di Fisica dell’Università di Milano (S. Cialdi) -F. Castelli et al., Efficient Positronium laser excitation for antihydrogen production in a magnetic field. Physical Review A 78 (2008) 052512. -S. Cialdi et al., Efficient two-step Positronium laser excitation to Rydberg levels. Nuclear Instruments & Methods B, 269 (2011) 1527. - A. Smirne et al., Experimental investigation of initial system-environment correlations via trace-distance evolution. Physical Review A 84 (2011) 032112. The Positronium Laser excitation system for the Aegis experiment (at CERN), designed and built in this laboratory

5 The Center for NanoScience and Technology of the Politecnico and Istituto Italiano di Tecnologia (IIT) http://cnst.iit.it/ - D. Ghezzi et al., A hybrid bioorganic interface for neuronal photoactivation. Nature Comm. 2 (2011) 166. -D. Ghezzi et al., A polymer optoelectronic interface restores light sensitivity in blind rat retinas. Nature Photonics, 7 (2013) 400. -E. Canesi et al., Effects of selective interactions at the Interface of Polymer-Oxide Hybrid Solar Cells. Energy and Environmental Science, 5 (2012) 9068. Among the topics of common interest to the IIT and the Infn and Politecnico: - Artificial retina - Hybrid Solar Cells

6 Executive Summary ≈ 0.1 s Laser We plan to realize the following scheme of positron and laser combination: e+e+ Converter Ps=e + e - Laser e+e+ Ps=e + e - Laser e+e+ Ps=e + e - ≈ 0.1 s Converter So as to reproduce, with a repetition rate of 0.01-1 sec the following sequence of events : - e + accumulation - Positronium production - Laser excitation / Laser cooling

7 Steps of the project «Bunching» of the positron beam will be made by a two-step chamber, in analogy to what is done in the Surko traps. Surko traps accumulate typically over ~100 sec. We are instead aiming at 0.01-1 sec. A 3-stage Surko trap Our 2-stage system will feature: -A first magnetic (high vacuum) section (field of abour 150 Gauss) -A restriction -A second (higher field, ~ 1 kG) magnetic section with electrodes (Penning trap). In this section a controlled N2 flow will slow down the positrons

8 The laser systems will be made following the experimence of our Aegis experiment at CERN. We will build: 1) A Nd-Yag pumped system with non-linear crystals to excite the 2 and 3 levels, in analogy to what has been made for Aegis. This will be used to excite the Ps: Harmonic Generator 205 and 243 nm Trans sat: 10 µJ Nd:YAG 1064 nm 650 mJ Nd:YAG 1064 nm 650 mJ 4 th 2 nd 1 st OPG SUM OPA 2) A dye laser will be used to effectively couple to the 1S-2P transition of orto- Positronium. This system will be developed in collaboration with the Paris-Sud group, expert in the field. The goal of this system is to perform for the first time the process of LASER COOLING OF POSITRONIUM This system will be used to study for the first time, properties of materials with excited (n=2,3) Positronium states.

9 MASPLAS: Physics goals and applications Suitable positron converters and experimental chambers will be built by the Politecnico group, which has a long tradition in this field (and we will collaborate with our Trento colleagues as well). Here is an example of a Chamber developed for Positronium in the Aegis experiment 1)Material Science Applications We will continue the collaboration already in place with the IIT. Currently, tests with the continuous existing positron beam are made (positronium fraction and Doppler Broadening) to study the properties of the Polymer-Oxide layer interface.

10 Note: a very fruitful collaboration is already established and in place between the VPAS laboratory and the IIT on the study of Hybrid Solar Cells: Energy and Environmental Science, 5 (2012) 9068. (this is already a spin-off that involves the Infn)

11 2) Material Science Application (with the bunched beam) The bunched beam will make it possible to perform Positron Annihilation Lifetime Spectroscopy (PALS) and Time of Flight (TOF) techniques to characterize defects and interfaces in thin films. These information are of the utmost importance in porous materials such as Hybrid Solar Cells of materials used as catalysts or storage of hydrogen or contaminant gases. Artificial retina application will also profit from this analitical diagnostic technique possibility. 3) Positronium excitation for material studes The proposed laser system will excite the 2,3 levels both inside and outside porous materials. Since orto-Ps properties are very sensitive to the environment properties, detecting Zeeman and Stark shifts of the well known transition lines will be used for the first time to study the micro-environment of materials near to the surface. 4) Positronium Laser Cooling Positronium Laser Cooling will be realized for the first time. This is particularly challenging due to the short orto-Ps lifetime. Cold Positronium will open the possibility to produce a Positronium Bose-Einstein condensate (BEC). Among the possible developments the possibility of producing gamma radiation in a coherent way will be investigated (gamma-ray laser).

12 Time frame and financial plan of the project 2014: New Na-22 source for the positron VPAS system: 70 kEuro (Politecnico) Working hypotesis: co-financing between Infn, Politecnico and the IIT 2014: Bunched beam implementation: 200 kEuro (Infn) 2014: Chamber A (material science) construction: 70 kEuro (IIT) 2014: Laser system for Ps excitation: 60 kEuro (Infn) 2015: Chamber B (fundamental physics) construction: 70 kEuro (Politecnico) 2015: Laser system for Laser Cooling: 100 kEuro (Infn) Particle detectors and associated electronics: 30 kEuro (Politecnico) Total proposed sharing: 600 kEuro (Infn 360, Politecnico 170, IIT 70)


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