1 / 35

BNC

BNC. 18 month PNT-JRA5. Tasks. T2 Calculation and mechanical design of Fresnel coil for wide angle rectangular correction at P2-ILL

nili
Download Presentation

BNC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. BNC 18 month PNT-JRA5

  2. Tasks • T2Calculation and mechanical design of Fresnel coil for wide angle rectangular correction at P2-ILL • Preparation and test of first experimental coils at Saclay-MESS spectrometer.Calculation and design of the final Fresnel coil at P2 Detailed magnetic test of final version of Fresnel coil and neutron test at Saclay-MESS spectrometerMagnetic test at P2 of flippers Neutron Test of magnetic NSE at MESS • T4Preparation of hard magnetic foils with higher coercitive force without essential SANS contribution. Neutron test. Calculation and mechanical design of wide band polarising stack. Preparation of stacked foil set up. Neutron test.Preparation of wide band flipper • Sextupole magnet calculations for beam focussing tests in HMI/P2. Building up an experimental piece of hexapole on permanent magnets. Neutron test on NSE MESS (LLB), test of spectrometer with hexapole magnet.Neutron test of wide band polariser at ILLPreparation of new foil materials for higher magnetic field. Neutron test of new foils at HMI. Stacking of new foils and wide band polariser. Neutron test. • T5Design of upgrade of the P2 reflectometer. Design of components in cooperation with P5 and O2. Development and mechanical construction of neutron reflectometer dedicated to the off-specular scattering with 2D detector option. • Preparation for SESANS application. Reflectometer upgrade for the off- specular scattering with 2D detector. Software for data treatment and model fits in cooperation with P9. Test of magnetic shielding at P2 • .T6Development of methods of neutron magnetic spin tomography in cooperation with P1Preparation of detailed program and corrections for spin tomography Neutron test on NSE MESS (in cooperation with P9)

  3. Calculation and mechanical design of Fresnel coil for wide angle rectangular correction at P2-ILL • 1.,New type X-Y fresnel coils. The principle is: .The X and Y direction of current can be handled separately • JR2=X2+Y2 • The first part of mechanical works has been done for the IN15-ILL in BNC partner . • Spark cutting of fresnel elements (16+20 has been done) (80 mm diam) • We have some problems with high current contacts. The first experimental part was done, needs some improvement. • The quality of copper contact made by evaporation was not satisfactory. • Galvanic method commercially not available, further attempt were done, by own. • Contact paste also gives results at low current. Stability at high current under question. • Sputtering is foreseen as the best solution. Until Now were not done • First test on the IN!15 showed that the parameters are not worse than the copper fresnel till 15A . (Further better result is expected )

  4. The realisation old type flipper new flipper proptotype

  5. Test at IN15

  6. P2 Fresnel coils • Further steps • The use of cleaner Al to decrease SANS contribution at 15Å, because the non textured Al plate (probably measured at 3-4Å) is different than to use it at 15 Å • Than to use single crystal of Al (Not very expensive, available size up 15 cm of diameter should exist) is the best solution. • Contact problems for high current, stability to solve, sputtering of Cu/Au.? • Galvanic contacting to Al a possible solution.

  7. RF flipper test for  < 0.4 Å…Simulation using Vitess 2.6 package.200KHz / 40Oe no disturbance Simulation using Vitess 2.6 package.

  8. Simulation results

  9. T4 Preparation of hard magnetic foils with higher coercitive force without essential SANS contribution. Neutron test. Calculation and mechanical design of wide band polarising stack • The rolling machine for Larmor foils is on the workshop for service work.(Done) The foreseen thickness is about 10-15 micron. • Results : We have done a series of samples from clean Iron, and CuNIFe with different sample thickness from 100 micron till 25 micron. • A series of diffraction measurement were done at foils Fe, CuNiFe and the NiFe (heat treated) samples. • A magnetic measurement has been done to establish the connection of magnetic and nuclear structure (The goal is to make a less SANS or diffraction scattering at the same magnetic quality.) • Between rolling a thermal treatment is needed before for the following step of rolling. The most important is the last step to achieve the desired higher magnetic quality. • (The investigations showed that till 25 microns need not any additional thermal treatment both in Fe and CuNiFe samples) • The model calculation for foil based compensation elements for NSE are in process. (V.Lebedev)

  10. Diffraction measurements We can observe two type of foils , having high Lorentzian part and without it. The magnetic features slightly different. Both type are micro-crystalline

  11. Sample 1+2 (2x10 mircon) =2.37Å 2=71.5deg 1 ch=5.25 min Gauss width 14 ch (resolution 9ch) size/microstrain effect Peak at 50ch very broad non gaussian component Sample 3 (1x10 micron) Gauss width 14 ch (resolution 9ch) size/microstrain effect Peak at 46ch very broad non gaussian component (higher than 1+2) Sample 4 (1x10 micron) Gauss width 16 ch (resolution 9ch) higher size/ microstrain effect Peak at 45ch The peak well described with gaussian Sample 5 (1x10 micron) Gauss width 17 ch (resolution 9ch) higher size / microstrain effect Peak at 45ch The peak well described with gaussian Structural analyze of existing foils

  12. Diffraction on Fe Foils-1 The 100 micron Fe foil diffraction pattern at q perpendicular / parallelto the rolling direction. =2.37Å 2=75.5deg 1 ch=5.25 min

  13. Diffraction on Fe Foils 2=2.37Å 2=71.5deg 1 ch=5.25 min Rolled Fe samples 45, 35, 25 micron The broadening and shifting of peak (110) seen by size/strain effect The intensity of scattering much lower than in case of NiFe

  14. CuNiFemeasurement=2.37Å 2=71.5deg 1 ch=5.25 min

  15. Structural analyze • The CuNiFe patterns not show that high anisotropy as rolled Fe foils show. • The intensity is comparable with the Fe foils intensity and indicates that the material is a solid solution. • The thermal treatment will give (expected) the rectangular form of magnetisation curve. • According to the literature the magnetic saturation is: up to 1 T after proper heat treatment • In order to product a rectangular form of magnetisation curve an anisotropic structure of foil is needed , which heat treatment should be accompanied with magnetic field

  16. Magnetic measurements: Clean Iron from literature and our 40 and 25 foil measurements

  17. CuNiFe measurement foils rolled and heat treated different way. From measurement became clear that for the saturation curve needs an improvement of equipment measuring hysteresis

  18. The principle of measurement of hysteresis at high field. The instrument used in ENPI can be developed for measuring a full hysteresis. Comparing the obtained curves on the coil L we can get the magnetisaton curve.

  19. ---- The current at magnetization. ----The response function at air in coil, at diode Comparing the response we get the hysteresis of foil at the saturation limit.

  20. TASK 4 (PNT JRA5:RISSPO) Török Gy. Lebedev V.T. Development and mechanical construction of neutron reflectometer dedicated to the off-specular scattering with 2D detector option Neutron Spin-Echo on Focused and Divergent Beams • Improvements of focusing techniques (RISSPO-magnetic lenses, micro-fibres as neutron guides) serve to enhance neutrons luminosity in experiments on small samples (biology, high pressure physics etc.). • Such techniques were developed to provide applications of NSE for strongly convergent (focused) geometry. • The solution of these problems is closely related to the creating of effective wide-angle NSE (e.g. in ILL). • In a non parallel scheme of NSE we need the non-planar spin-flippers with curvature to be regulated according to beam divergence and precession field inhomogenity along neutron trajectories. • A combination of these specific features (non-parallel beam, field distribution) makes the realization of such a techniques still difficult. The first results in this way we have obtained at NSE of vertical geometry created in cooperation RISSPO-PNPI (Fig.1).

  21. Fig.1. Modified NSE-spectrometer (MNSE): 1 - reactor channel; 2 - selector (to be installed); polarizer P1 in shielding 4; 5 - flipper F1; 6,8 - /2-flippers in the 1st precession magnet 7; 9 - polarizer P2 with fl. F2 at the exit; 10 - frame; 11,12 - units for polarization vector analysis by scattering at the sample 13; 14 - movable frame; 15,16 - flipper F3 and analyzer A1; 17,18 - /2-flipper in the 2nd precession magnet 19; 20,21 - analyzer A2 and detectors in shielding 22.

  22. MNSE specifications PNPI

  23. Fig.2. Precession magnet: A). field distribution in pole plane, contours show the regions of field with inhomogeneity H/H0.02% (solid circles) and H/H0.05% (open circles); B). field vs current in magnet coils (linear dependence).

  24. Fig.3. Installation of foils /2-flippers with variation of curvature in wide angleNSE analysis of inelastic scattering : 1 - sample; 2,3 - flippers in vertical field on the plate magnet pole.

  25. Fig.4. Field distribution (1) in pole plane.

  26. We corrected the curvature using the frame with a set of screws (Fig.3). In the case of cylinders of foils (radii R1, R2) we have calculated the field integral using experimental field distribution (Fig.2) described in plane of magnet poles by (Fig.4) H(X,Y)/Ho= exp[- X2/a2 -Y2/b2]  1- X2/a2 -Y2/b2 (1) at large parameters a=7m, b=14m. In this very homogeneous field we measured weak field changes in scattered beam volume (X2/a2, Y2/b2 <<1). The field integral in cylindrical layer depends on the scattering angle IB()/IB0={(R2-R1)-(1/3)[1/a2+ +ctg()2/b2](R23-R13)sin()2}/[(R2-R1)-(1/3)(R23 -R13)b2] (2) The field integral dependence is illustrated in Fig.5 for real geometry of magnetic system: a=7m, b=14m, R1=1m, R2=1.3m (on Fig.2).

  27. Fig.5. Field integral: dependent initially on scattering angle, not dependent after correction.

  28. Then we do the curvature correction of the 1st foil to eliminate integral angular dependence. The 2nd foil curvature was not changed. To get a constant integral one has to vary the radius R1 =const  Rcor(). The magnitude and angular dependence of Rcor() was found from the equation Rcor-(1/3)[1/a2+ctg()2/b2]Rcor3 sin()2 = =R1-(1/3)[1/a2+ctg()2/b2]R23sin()2+(1/3)[R23-R13]/b. (3) In the first approximation, r/R1=(R1-Rcor)/R1<<1, we found the solution of eq.(3) r=R1-Rcor=(1/3)[R23-R13]{[1/a2+ctg()2/b2]sin()2-1/b2}/ /[1-(1/a2+ctg()2/b2)R12sin()2]. (4)

  29. Fig.6. Relative radius deviation by curvature correction vs scattering angle.

  30. We developed the method to correct the field integral changing magetic foil curvature. Changing the radius in the range r/R1 =0-0.3%, we get full compensation of field inhomogeneity in wide scattering angles interval (e.g. -/4 /4). This cannot be provided by classic coils-flippers. The flippers serve simultaneously as the devices narrowing the initial wavelength spectrum (), =/<>. The initial dispersion parameter of neutron spectrum D=[1]2()d gives the width D1/2=0.2. We have tuned the /2-flippers to m=0.65nm (at maximum). The polarization of neutrons with =m is rotated to /2. These neurons give a maximum contribution to NSE-signal, while slower or faster neutrons are focused worse. So we have the NSE-signal PNSE ~ [sin(/2m)] 2. As a result the working spectrum [sin(/2m)]2() has a smaller width Deff1/2D1/2=0.15 (Fig.7A). The NSE-signal was modeled taking into account the effective spectrum in the case of scattering function for diffusion S()~(1+2)-1. The time-dependent function shows Debye law S(t)=exp(t/) with relaxation time . At t  the calculated function deviates from the ideal one less than 3% (Fig.7B).

  31. Fig.7. Spectral effects of flippers: A). narrowing (line) of original spectrum (solid points); B). ideal scattering function S(t/) for sharp line (1) and for real spectrum (2), deviation (2) from (1) shown.

  32. deliverable: Preprint PNPI: V.T. Lebedev, Gy. Török, A.V. Lepekhin Neutron Spin-Echo on Focused and Divergent Beams PNPI report 2005 No2622 8 pages

  33. T5 Design of upgrade of the P2 reflectometer, in cooperation with P5 and O2. Development and mechanical construction of neutron reflectometer dedicated to the off-specular scattering with 2D detector option The 190*190 mm detector now is working. (Were used in the school at sextupole practice organized by BNCCETS - Training School on Neutron Scattering 2005) We have a 2D detector shielding Additional mechanics for the reflectometer is planned View of the detector

  34. The test of hexapole with new 2D detector. (Were used in the school at sextupole practice organized by BNCCETS - Training School on Neutron Scattering 2005)

  35. Fig. 1. Wavelength slice a with two lenses. Fig. 2. Wavelength slice b with two lenses. Fig. 3. Wavelength slice c with two lenses. Fig. 4. Wavelength slice d with two lenses. Fig. 5. Wavelength slice e with two lenses Fig. 6. Wavelength slices for plotted images (2 lenses)

More Related