- Email: [email protected]
D3 at the ILL: Structural studies of hydrogenous liquid and amorphous systems
Physica B: Physics of Condensed Matter xxx (2017) 1–4
Contents lists available at ScienceDirect
Physica B: Physics of Condensed Matter journal homepage: www.elsevier.com/locate/physb
D3 at the ILL: Structural studies of hydrogenous liquid and amorphous systems A. Stunault * , S. Vial, D. Jullien, G.J. Cuello Institut Laue Langevin, 71 Avenue des Martyrs, CS 20156, F-38042 Grenoble, France
A R T I C L E
I N F O
Keywords: Liquids Neutron diffraction Structure
A B S T R A C T
While neutron scattering is a powerful tool in the structural studies of liquid and amorphous systems, the method still lacks accuracy in the case of hydrogenous systems, due to the high incoherent background from 1 H. Using polarised neutrons, one can experimentally remove that background. The D3 polarised hot neutron diffractometer at ILL, has been upgraded and now offers a new setup for the studies of liquids over a wide Q-range using polarised neutrons. We detail the principle of the method and show recent results from a test experiment on lactulose.
1. Introduction The determination of the coherent structure factor of hydrogenous liquids by the usual scattering methods is very difficult: the scattering of X-rays by 1-electron hydrogen is usually too weak to be detected, while neutron scattering is largely dominated by incoherent scattering from the disordered nuclear spins: the coherent neutron scattering signal, which contains the structural information, may represent less than 5% of the measured signal, on top of a huge incoherent background, due to the large incoherent cross-section 𝜎 i = 80.27(6) barns, to compare to the coherent cross-section 𝜎 c = 1.7523(10) barns [1]. However, with polarised neutrons, one can overcome that problem: spin-incoherent scattering partially (2/3) reverses then neutron polarisation (‘spin-flip’, SF), while coherent and isotope incoherent scattering do not (‘non-spin-flip’, NSF) [2]. As a result, the coherent and incoherent intensities are linear combinations of the spin-flip and non-spin-flip measured intensities. Polarised neutrons are used routinely on long wavelength (cold neutrons) instruments such as D7 at ILL [3] or DNS at FRMII [4] to separate coherent and spin-incoherent intensities. The technique has however been little used at shorter wavelengths (hot neutrons) for technical reasons: the small scattering angles of polarising crystals at short wavelengths result in a need for huge distances, barely compatible with a wide scattering range, while polarising supermirrors may be ruled out due to the extremely small critical angles. The problem has been overcome at the D3 polarised neutron diffractometer of the ILL [5], by using a polarised 3 He spin filter for polarisation analysis [6,7]. With a wavelength of 0.5 Å, D3 can be used in structural
studies of liquid and amorphous systems, up to the high momentum transfers Q (typically 20–25 Å−1 ), needed for Fourier transforming [8]. In the first tests [5,9,10], the polarised neutrons were obtained from a Heusler Cu2 MnAl monochromator, while polarisation analysis was performed via a 3 He spin-filter. The method proved very efficient for small molecules. However, for more complex systems, it was suffering from a very poor Q-resolution from the monochromator, used in transmission and at a very small scattering angle (Bragg angle 4.3◦ at 0.5 Å). 2. Instrument The neutron beam on D3 comes from the hot source and the covered wavelength range is 0.4 Å to 0.84 Å. In the new setup (Fig. 1), the wavelength is set by a Cu(2 0 0) monochromator and the beam is polarised using a first 3 He spin-filter placed in a magnetostatic cavity (‘magic box’, [11]). The Cu monochromator reflection geometry offers a much improved Q-resolution (Fig. 2), while keeping the neutron flux at the sample unchanged, of the order of 107 neutrons/s/cm2 . To ensure the homogeneity of the magnetic field over the whole spin-filter in the presence of the neighbouring guide fields, the whole assembly, including soft iron plates at the exit of the magic box, was optimised using the RADIA software package [12] (Fig. 3). Two monitors placed respectively before and after the spin filter are used to measure its transmission T, directly related to the neutron beam polarisation before the sample, Pin :
* Corresponding author. E-mail address: [email protected] (A. Stunault).
https://doi.org/10.1016/j.physb.2017.10.130 Received 4 August 2017; Received in revised form 27 October 2017; Accepted 31 October 2017 Available online XXX 0921-4526/© 2017 Elsevier B.V. All rights reserved.
Please cite this article in press as: A. Stunault, et al., D3 at the ILL: Structural studies of hydrogenous liquid and amorphous systems, Physica B: Physics of Condensed Matter (2017), https://doi.org/10.1016/j.physb.2017.10.130
A. Stunault et al.
Physica B: Physics of Condensed Matter xxx (2017) 1–4
Fig. 1. The D3 diffractometer at ILL, modified for the study of liquids.
opacity, proportional to the 3 He pressure p, the length of the spin filter l and the wavelength 𝜆. The instrument downstream from this first spin-filter is the same as described in Ref. [5], with guide fields, an annular vanadium sample cell, a nutator to flip the polarisation, a second spin filter used for polarisation analysis, and a single 3 He detector. The detector is scanned over a total angular range of 3◦ to 120◦ , with typical data acquisition times of 1–2 min/angular step, both polarisation channels being measured at each step. Using a wavelength of 0.5 Å, the covered Q-range is 0.8–21 Å−1 . The amount of sample in the beam is about 0.9 cm3 .The analysing power of the spin-filter is monitored by measuring the polarisation of the beam scattered by a silicon crystal mounted on top of the sample cell [5]. 3. Data reduction The transmissions of the up T + and down T − neutron polarisations by a spin filter are [6]: T± =
Fig. 2. Measurement of the same nickel powder sample with the Heusler monochromator and the Cu monochromator. The same measurement on the dedicated D4 liquids diffractometer of ILL [13] is shown for comparison. The curves are offset for visibility.
√ Pin =
( 1−
T0 T
(2)
The first step of the data reduction is then the accurate determination of the efficiencies of both spin-filters, characterised by the relaxation time t1 of the 3 He polarisation, PolHe = Pol0He e−t∕t1 , where t is the time of the measurement and Pol0He is the 3 He polarisation at t = 0. Both filters have a relaxation time of the order of 80 hours. Typical fits are shown in Fig. 4.
)2 ,
1 −O(𝜆)(1∓PolHe ) , e 2
(1)
T0 = e−O(𝜆) is the unpolarised beam transmission through the fully depolarised spin filter, O(𝜆) = 7.282 × 10−2 p[bar]l[cm]𝜆[Å] at 295 K is the
Fig. 3. Magnetic field profile along the beam path, upstream from the sample. The homogeneity around the spin filter is of the order of 10−4 .
2
A. Stunault et al.
Physica B: Physics of Condensed Matter xxx (2017) 1–4
Fig. 4. Data reduction: determination of the relaxation times of the 3 He spin filters. The upstream filter (left) defines the primary beam polarisation Pin , and the downstream filter (right) gives the analysing power.
Fig. 5. Data reduction in the case of Lactulose at room temperature. Top left and right: measured and corrected intensities, respectively. Bottom left: coherent, incoherent and total signals. Note the expanded (left hand side) scale for the coherent intensities. Bottom right: comparison to a measurement of the same sample on the D7 diffractometer of the ILL. The data have not been corrected for instrument resolution, hence the different peak widths.
Fig. 5 shows the different steps of the data reduction for a lactulose (C12 H22 O11 , sugar) sample, from the top left panel (measurement) to the bottom left panel (coherent and incoherent cross sections). The first step (top right) is the correction for the decay of the spin filter analysing power. Once this critical step has been performed, one can average the corrected scans, hence improving the statistics and extract the coherent and incoherent cross sections (bottom left). In the figure, the coherent part, representative of the correlations, had to be blown up by one order of magnitude for visibility (see the different scales).
deuterated samples, and complementing with unpolarised results for more deuterated samples may be an efficient option. A new detector assembly, including a wide-angle spin filter and a multi-detector are currently studied. Acknowledgements This research was performed with the approval and support of the Institut Laue Langevin, DOI:10.5291/ILL-DATA.TEST-2708. The authors also thank F. Ngono Mebenga and A. R. Wildes from ILL for making the D7 data available for comparison.
4. Conclusion The D3 diffractometer of the ILL is now fully operational for the study of liquids using polarised neutrons. The data acquisition is currently slower than on fully dedicated instruments like D4 at ILL due to the absence of a wide-angle spin filter and a multi-detector. Typical measuring times are 1–2 days per sample, which is fortunately not forbiddingly long. Using D3 for accuracy in the case of the non-
References [1] V.F. Sears, Neutron News 3 (1992) 26. [2] R.M. Moon, T. Riste, W.C. Koehler, Phys. Rev. 181 (1969) 920. [3] J.R. Stewart, P.P. Deen, K.H. Andersen, H. Schober, J.-F. Barthlmy, J.M. Hillier, A.P. Murani, T. Hayesb, B. Lindenauc, J. Appl. Cryst. 42 (2009) 69, https://doi. org/https://doi.org/10.1107/S0021889808039162. 3
A. Stunault et al.
Physica B: Physics of Condensed Matter xxx (2017) 1–4 [10] L.A. Rodríguez Palomino, G.J. Cuello, J. Dawidowski, L. Temleitner, L. Pusztai, A. Stunault, J. Phys. Conf. Ser. 663 (2015) 012002, https://doi.org/https://doi.org/ 10.1088/1742-6596/663/1/012002. [11] A.K. Petoukhov, V. Guillard, K.H. Andersen, E. Bourgeat-Lami, R. Chung, H. Humblot, D. Jullien, E. Lelievre-Berna, T. Soldner, F. Tasset, M. Thomas, Nucl. Inst. Methods Phys. Res. A 560 (2006) (2006) 480, https://doi.org/https://doi. org/10.1016/j.nima.2005.12.247. [12] O. Chubar, P. Elleaume, J. Chavanne, J. Synchrotron Radiat. 5 (1998) (1998) 481–484. [13] H.E. Fischer, G.J. Cuello, P. Palleau, D. Feltin, A.C. Barnes, Y.S. Badyal, J.M. Simonson, Appl. Phys. A 74 (2002) S160.
[4] Heinz Maier-Leibnitz Zentrum, J. Large-Scale Res. Facil. 1 (2015) A27, https:// doi.org/https://doi.org/10.17815/jlsrf-1-33. [5] A. Stunault, S. Vial, L. Pusztai, G.J. Cuello, L. Temleitner, J. Phys. Conf. Ser. 711 (2016) 012003, https://doi.org/https://doi.org/10.1088/1742-6596/711/1/ 012003. [6] K.P. Coulter, T.E. Chupp, A.B. McDonald, C.D. Bowman, J.D. Bowman, J.J. Szymanski, V. Yuan, G.D. Cates, D.R. Benton, E.D. Earle, Nucl. Instr. Methods A 288 (1990) 463. [7] K.H. Andersen, D. Jullien, A.K. Petoukhov, P. Mouveau, F. Bordenave, F. Thomas, E. Babcock, Phys. B 404 (2009) 2652, https://doi.org/https://doi.org/10.1016/j. physb.2009.06.054. [8] see e.g. G.J. Cuello, J. Phys. Cond. Matter 20 (2008) 244109, https://doi.org/10. 1088/0953-8984/20/24/244109, or H.E. Fischer, A.C. Barnes, P.S. Salmon, Rep. Prog. Phys. 69 (2006) 233, https://doi.org/10.1088/0034-4885/69/1/R05. [9] L. Temleitner, A. Stunault, G.J. Cuello, L. Pusztai, Phys. Rev. B 92 (2015) 014201, https://doi.org/https://doi.org/10.1103/PhysRevB.92.014201.
4
Contents lists available at ScienceDirect
Physica B: Physics of Condensed Matter journal homepage: www.elsevier.com/locate/physb
D3 at the ILL: Structural studies of hydrogenous liquid and amorphous systems A. Stunault * , S. Vial, D. Jullien, G.J. Cuello Institut Laue Langevin, 71 Avenue des Martyrs, CS 20156, F-38042 Grenoble, France
A R T I C L E
I N F O
Keywords: Liquids Neutron diffraction Structure
A B S T R A C T
While neutron scattering is a powerful tool in the structural studies of liquid and amorphous systems, the method still lacks accuracy in the case of hydrogenous systems, due to the high incoherent background from 1 H. Using polarised neutrons, one can experimentally remove that background. The D3 polarised hot neutron diffractometer at ILL, has been upgraded and now offers a new setup for the studies of liquids over a wide Q-range using polarised neutrons. We detail the principle of the method and show recent results from a test experiment on lactulose.
1. Introduction The determination of the coherent structure factor of hydrogenous liquids by the usual scattering methods is very difficult: the scattering of X-rays by 1-electron hydrogen is usually too weak to be detected, while neutron scattering is largely dominated by incoherent scattering from the disordered nuclear spins: the coherent neutron scattering signal, which contains the structural information, may represent less than 5% of the measured signal, on top of a huge incoherent background, due to the large incoherent cross-section 𝜎 i = 80.27(6) barns, to compare to the coherent cross-section 𝜎 c = 1.7523(10) barns [1]. However, with polarised neutrons, one can overcome that problem: spin-incoherent scattering partially (2/3) reverses then neutron polarisation (‘spin-flip’, SF), while coherent and isotope incoherent scattering do not (‘non-spin-flip’, NSF) [2]. As a result, the coherent and incoherent intensities are linear combinations of the spin-flip and non-spin-flip measured intensities. Polarised neutrons are used routinely on long wavelength (cold neutrons) instruments such as D7 at ILL [3] or DNS at FRMII [4] to separate coherent and spin-incoherent intensities. The technique has however been little used at shorter wavelengths (hot neutrons) for technical reasons: the small scattering angles of polarising crystals at short wavelengths result in a need for huge distances, barely compatible with a wide scattering range, while polarising supermirrors may be ruled out due to the extremely small critical angles. The problem has been overcome at the D3 polarised neutron diffractometer of the ILL [5], by using a polarised 3 He spin filter for polarisation analysis [6,7]. With a wavelength of 0.5 Å, D3 can be used in structural
studies of liquid and amorphous systems, up to the high momentum transfers Q (typically 20–25 Å−1 ), needed for Fourier transforming [8]. In the first tests [5,9,10], the polarised neutrons were obtained from a Heusler Cu2 MnAl monochromator, while polarisation analysis was performed via a 3 He spin-filter. The method proved very efficient for small molecules. However, for more complex systems, it was suffering from a very poor Q-resolution from the monochromator, used in transmission and at a very small scattering angle (Bragg angle 4.3◦ at 0.5 Å). 2. Instrument The neutron beam on D3 comes from the hot source and the covered wavelength range is 0.4 Å to 0.84 Å. In the new setup (Fig. 1), the wavelength is set by a Cu(2 0 0) monochromator and the beam is polarised using a first 3 He spin-filter placed in a magnetostatic cavity (‘magic box’, [11]). The Cu monochromator reflection geometry offers a much improved Q-resolution (Fig. 2), while keeping the neutron flux at the sample unchanged, of the order of 107 neutrons/s/cm2 . To ensure the homogeneity of the magnetic field over the whole spin-filter in the presence of the neighbouring guide fields, the whole assembly, including soft iron plates at the exit of the magic box, was optimised using the RADIA software package [12] (Fig. 3). Two monitors placed respectively before and after the spin filter are used to measure its transmission T, directly related to the neutron beam polarisation before the sample, Pin :
* Corresponding author. E-mail address: [email protected] (A. Stunault).
https://doi.org/10.1016/j.physb.2017.10.130 Received 4 August 2017; Received in revised form 27 October 2017; Accepted 31 October 2017 Available online XXX 0921-4526/© 2017 Elsevier B.V. All rights reserved.
Please cite this article in press as: A. Stunault, et al., D3 at the ILL: Structural studies of hydrogenous liquid and amorphous systems, Physica B: Physics of Condensed Matter (2017), https://doi.org/10.1016/j.physb.2017.10.130
A. Stunault et al.
Physica B: Physics of Condensed Matter xxx (2017) 1–4
Fig. 1. The D3 diffractometer at ILL, modified for the study of liquids.
opacity, proportional to the 3 He pressure p, the length of the spin filter l and the wavelength 𝜆. The instrument downstream from this first spin-filter is the same as described in Ref. [5], with guide fields, an annular vanadium sample cell, a nutator to flip the polarisation, a second spin filter used for polarisation analysis, and a single 3 He detector. The detector is scanned over a total angular range of 3◦ to 120◦ , with typical data acquisition times of 1–2 min/angular step, both polarisation channels being measured at each step. Using a wavelength of 0.5 Å, the covered Q-range is 0.8–21 Å−1 . The amount of sample in the beam is about 0.9 cm3 .The analysing power of the spin-filter is monitored by measuring the polarisation of the beam scattered by a silicon crystal mounted on top of the sample cell [5]. 3. Data reduction The transmissions of the up T + and down T − neutron polarisations by a spin filter are [6]: T± =
Fig. 2. Measurement of the same nickel powder sample with the Heusler monochromator and the Cu monochromator. The same measurement on the dedicated D4 liquids diffractometer of ILL [13] is shown for comparison. The curves are offset for visibility.
√ Pin =
( 1−
T0 T
(2)
The first step of the data reduction is then the accurate determination of the efficiencies of both spin-filters, characterised by the relaxation time t1 of the 3 He polarisation, PolHe = Pol0He e−t∕t1 , where t is the time of the measurement and Pol0He is the 3 He polarisation at t = 0. Both filters have a relaxation time of the order of 80 hours. Typical fits are shown in Fig. 4.
)2 ,
1 −O(𝜆)(1∓PolHe ) , e 2
(1)
T0 = e−O(𝜆) is the unpolarised beam transmission through the fully depolarised spin filter, O(𝜆) = 7.282 × 10−2 p[bar]l[cm]𝜆[Å] at 295 K is the
Fig. 3. Magnetic field profile along the beam path, upstream from the sample. The homogeneity around the spin filter is of the order of 10−4 .
2
A. Stunault et al.
Physica B: Physics of Condensed Matter xxx (2017) 1–4
Fig. 4. Data reduction: determination of the relaxation times of the 3 He spin filters. The upstream filter (left) defines the primary beam polarisation Pin , and the downstream filter (right) gives the analysing power.
Fig. 5. Data reduction in the case of Lactulose at room temperature. Top left and right: measured and corrected intensities, respectively. Bottom left: coherent, incoherent and total signals. Note the expanded (left hand side) scale for the coherent intensities. Bottom right: comparison to a measurement of the same sample on the D7 diffractometer of the ILL. The data have not been corrected for instrument resolution, hence the different peak widths.
Fig. 5 shows the different steps of the data reduction for a lactulose (C12 H22 O11 , sugar) sample, from the top left panel (measurement) to the bottom left panel (coherent and incoherent cross sections). The first step (top right) is the correction for the decay of the spin filter analysing power. Once this critical step has been performed, one can average the corrected scans, hence improving the statistics and extract the coherent and incoherent cross sections (bottom left). In the figure, the coherent part, representative of the correlations, had to be blown up by one order of magnitude for visibility (see the different scales).
deuterated samples, and complementing with unpolarised results for more deuterated samples may be an efficient option. A new detector assembly, including a wide-angle spin filter and a multi-detector are currently studied. Acknowledgements This research was performed with the approval and support of the Institut Laue Langevin, DOI:10.5291/ILL-DATA.TEST-2708. The authors also thank F. Ngono Mebenga and A. R. Wildes from ILL for making the D7 data available for comparison.
4. Conclusion The D3 diffractometer of the ILL is now fully operational for the study of liquids using polarised neutrons. The data acquisition is currently slower than on fully dedicated instruments like D4 at ILL due to the absence of a wide-angle spin filter and a multi-detector. Typical measuring times are 1–2 days per sample, which is fortunately not forbiddingly long. Using D3 for accuracy in the case of the non-
References [1] V.F. Sears, Neutron News 3 (1992) 26. [2] R.M. Moon, T. Riste, W.C. Koehler, Phys. Rev. 181 (1969) 920. [3] J.R. Stewart, P.P. Deen, K.H. Andersen, H. Schober, J.-F. Barthlmy, J.M. Hillier, A.P. Murani, T. Hayesb, B. Lindenauc, J. Appl. Cryst. 42 (2009) 69, https://doi. org/https://doi.org/10.1107/S0021889808039162. 3
A. Stunault et al.
Physica B: Physics of Condensed Matter xxx (2017) 1–4 [10] L.A. Rodríguez Palomino, G.J. Cuello, J. Dawidowski, L. Temleitner, L. Pusztai, A. Stunault, J. Phys. Conf. Ser. 663 (2015) 012002, https://doi.org/https://doi.org/ 10.1088/1742-6596/663/1/012002. [11] A.K. Petoukhov, V. Guillard, K.H. Andersen, E. Bourgeat-Lami, R. Chung, H. Humblot, D. Jullien, E. Lelievre-Berna, T. Soldner, F. Tasset, M. Thomas, Nucl. Inst. Methods Phys. Res. A 560 (2006) (2006) 480, https://doi.org/https://doi. org/10.1016/j.nima.2005.12.247. [12] O. Chubar, P. Elleaume, J. Chavanne, J. Synchrotron Radiat. 5 (1998) (1998) 481–484. [13] H.E. Fischer, G.J. Cuello, P. Palleau, D. Feltin, A.C. Barnes, Y.S. Badyal, J.M. Simonson, Appl. Phys. A 74 (2002) S160.
[4] Heinz Maier-Leibnitz Zentrum, J. Large-Scale Res. Facil. 1 (2015) A27, https:// doi.org/https://doi.org/10.17815/jlsrf-1-33. [5] A. Stunault, S. Vial, L. Pusztai, G.J. Cuello, L. Temleitner, J. Phys. Conf. Ser. 711 (2016) 012003, https://doi.org/https://doi.org/10.1088/1742-6596/711/1/ 012003. [6] K.P. Coulter, T.E. Chupp, A.B. McDonald, C.D. Bowman, J.D. Bowman, J.J. Szymanski, V. Yuan, G.D. Cates, D.R. Benton, E.D. Earle, Nucl. Instr. Methods A 288 (1990) 463. [7] K.H. Andersen, D. Jullien, A.K. Petoukhov, P. Mouveau, F. Bordenave, F. Thomas, E. Babcock, Phys. B 404 (2009) 2652, https://doi.org/https://doi.org/10.1016/j. physb.2009.06.054. [8] see e.g. G.J. Cuello, J. Phys. Cond. Matter 20 (2008) 244109, https://doi.org/10. 1088/0953-8984/20/24/244109, or H.E. Fischer, A.C. Barnes, P.S. Salmon, Rep. Prog. Phys. 69 (2006) 233, https://doi.org/10.1088/0034-4885/69/1/R05. [9] L. Temleitner, A. Stunault, G.J. Cuello, L. Pusztai, Phys. Rev. B 92 (2015) 014201, https://doi.org/https://doi.org/10.1103/PhysRevB.92.014201.
4