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Positron Production at LI 2 FE

Target. 4 mm. 70 cm. Beam spot (1 mm). 1-2-5 mm. PLASMON X. MC-INFN Since Jan 2011. Positron Production at LI 2 FE. E g = 4,10,20 MeV ;  E/E=0. E e - = 30, 150 MeV ;  E/E=0. Electrons are present too (a little bit more than positrons).

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Positron Production at LI 2 FE

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  1. Target 4 mm 70 cm Beam spot (1 mm) 1-2-5 mm PLASMON X MC-INFN Since Jan 2011 Positron Production at LI2FE Eg = 4,10,20 MeV ; E/E=0 Ee- = 30, 150 MeV ; E/E=0 Meeting LI2FE Frascati 16-mar-2011

  2. Electrons are present too (a little bit more than positrons). Protons are produced in air (g on N2), not in the target

  3. Target Material Eg = 10 MeV Target 1 mm thick Meeting LI2FE Frascati 16-mar-2011

  4. Target Length Higher production occurs at higher energy (because the cross section increases as the logarithm of the energy). The best thickness for positrons (and electrons) is 2 mm, (effect more evident for E=20 MeV). (This behaviour is probably due to a trade-off between the number of the target nuclei and the self absorption). At 4 MeV the geometry of the target seems unessential for positrons. Meeting LI2FE Frascati 16-mar-2011

  5. Eg = 10 MeV Having a primary photon flux of 109 photons/sec, about 108 forward positrons can be obtained. What about the spectrum and the angular distribution of the positrons (users want “beam”) Meeting LI2FE Frascati 16-mar-2011

  6. Photo/Electro production Meeting LI2FE Frascati 16-mar-2011

  7. Meeting LI2FE Frascati 16-mar-2011

  8. Photo/Electro production The photons available at LI2FE can be 109 per shot The primary electrons can be 1.1 nC  7x1010 “ The repetition rate can increase to 10 Hz Meeting LI2FE Frascati 16-mar-2011

  9. Different scales DE =0.5 MeV Meeting LI2FE Frascati 16-mar-2011

  10. DE =0.5 MeV Same scales The spectrum is continuous in both the situation, but photoproduction is more efficient (the energy of the maximum is relatively higher) Meeting LI2FE Frascati 16-mar-2011

  11. Positron beam will be available at LI2FE Production efficiency is about some % (considering the integral production) Efficiency for fwand monochromatic beams is about 1/104 (Dq= 5°) (25% for g=4MeV < DE/E < 3% for g=20MeV beams) The electro-production from the SPARC beam and photoproduction from PLASMON-X photons have almost the same efficiency (because of the limited charge of the electron beam, 1 nC electrons vs. 109 photons) Meeting LI2FE Frascati 16-mar-2011

  12. NeutronBeams n from g or e- beam on W are about a factor 100 less than e+ Alternative method is the photodissociation of the deuterons (g +D2O  n + …) Giving 108-109 fw neutrons F. Broggi, L. Serafini: "A Possible Neutron Source at "LIFE", EBD-09/003, 10/11/2009 Meeting LI2FE Frascati 16-mar-2011

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