ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Прямое наблюдение эффекта Бормана при дифракции нейтронов по Лауэ в кристаллах кремния Е.О.Вежлев 1,2, В.В. Воронин. - презентация

1 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Прямое наблюдение эффекта Бормана при дифракции нейтронов по Лауэ в кристаллах кремния Е.О.Вежлев 1,2, В.В. Воронин 1,2, И.А. Кузнецов 1, С.Ю. Семенихин 1, В.В. Федоров 1,2 1 Петербургский институт ядерной физики 2 Санкт-Петербургский государственный политехнический университет

2 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Outline Motivation Kato theory of diffraction for deformed (bent) crystal Influence of external force on diffracting neutrons Two-crystal scheme introduction Borrmann effect Experimental observation of theory effectiveness for proposed scheme m i / m G experiment with neutron Summary

3 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Motivation For Laue diffraction with Bragg angles close to the right one there is a significant diffraction enhancment factor of an external affect on the neutron*: This factor can be used for observation of small external forces affecting the diffracting neutrons But, we must be sure that all of the dynamical diffraction predictions work well in thin (up to the 220 mm) crystals *V.V. Fedorov et.al. JETP Lett. 85, 82 (2007)

4 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Laue neutron diffraction in weakly deformed crystal Neutron difraction in weakly deformed crystal can be described by imposing Kato forces*: (hkl) k kgkgkgkg g y z B (1) (2) *N.Kato, J. Phys. Soc. Japan (1963) 19, 971 Deviation from exact Bragg condition Kato trajectories are determined by the equation: 2F g V/d (1) or (2)

5 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Influence of an external force Parameter of deviation from exact Bragg condition: Deformation changes the reciprocal lattice vector External force changes the incident neutron wave vector In fact, F ext ||g is equivalent to the gradient of interplanar distances with the value F ext /2E n The Kato force for the neutron in this case:

6 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Influence of an external force k kgkgkgkg g y z B F n ||Z Force affecting the neutron Neutron trajectory equation (Laue diffraction case): Equation for freely flighting neutron: We obtain a gain factor for the diffracting neutron For silicon (220) planes

7 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Two-crystal scheme of the experiment External force shifts the spot of the neutron beam at the exit surface: Due to well known Borrman effect* amplitudes will be different for two Bloch waves ψ(1) and ψ(2). In fact, we got different values of absorption for this two types of waves: *H. Rauch, D. Petrachek, in Neutron Diffraction (Springer, Berlin, 1978) Where Zero-harmonic of absroption g-harmonic of absorption

8 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Two-crystal scheme of the experiment In case of strong Borrmann effect (strong absorbing crystal): The resolution for this setup is: For (220) plane of Silicon: So, only one Bloch wave comes to the exit surface of the crystal.

9 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Experimental observation of Laue diffraction in the large silicon crystal (L=220 mm) 220 silicon plane intensity reflex One-crystal scheme Two-crystal scheme Theoretical prediction wtihout taking Borrmann effect into account Effective crystal length can reach few meters for 220 mm silicon crystal

10 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Experimental observation of Laue diffraction in the large silicon crystal (L=220 mm) The intensities ratio for one- and two-crystal schemes of the setup Ratio depends on two-crystal scheme setup geometry Experimental results coincide with the theory Ratio varies from 3/2 to 1/2

11 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Possible applications. m i /m G experiment with neutron (I) FrFrFrFr FGFGFGFG Sun Earth neutron F G = F r F G = F r for the Earth F G F r F G F r for the neutron Possible arrearence of the non zero force:

12 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Possible applications. m i /m G experiment with neutron (II) FrFrFrFr FGFGFGFG F m g c gcgc gcgc 0:00 12:00 F m changes its sign in the laboratory coordinate system Daily oscillations of the F m value The possible sensitivity of the setup: *Present accuracy (Schmiedmayer, 1989)

13 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Possible applications. m i /m G experiment with neutron (III) Layout of the experimental setup (Already mounted on the beamline of WWR-M) Large silicon crystal (220 mm)

14 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) WWR-M reactor (PNPI, Gatchina) Silicon (220)

15 ИТЭФ, 11/22/2011Вежлев Егор (ПИЯФ) Summary Two-crystal scheme of the Laue diffraction with bragg angles close to the right one is a very sensitive experimental instrument (resolution to the external force reaches eV/cm) The uncertaintity of measuring inertial to gravitational mass ratio for the neutron (in fact, direct test of PoE) can reach magnitude ~10 -5 Its possible the new instrument for measuring e n