Development of precision elliptic neutron-focusing supermirror

Abstract

This paper details methods for the precision design and fabrication of neutron-focusing supermirrors, based on electroless nickel plating. We fabricated an elliptic mirror for neutron reflectometry, which is our second mirror improved from the first. The mirror is a 550-millimeter-long segmented mirror assembled using kinematic couplings, with each segment figured by diamond cutting, polished using colloidal silica, and supermirror coated through ion-beam sputtering. The mirror was evaluated with neutron beams, and the reflectivity was found to be 68-90% at a critical angle. The focusing width was 0.17 mm at the full width at half maximum.

A Focusing Test of a Multiple Segmented Ellipsoidal Neutron-Focusing Mirror for a Compact-Focusing SANS Instrument

“…For mirrors with supermirror coating, or for larger mirrors which exceed the stroke length of the machines used for manufacture, the figure error caused by assembly must also be taken into account. Figure alignment for such case is discussed in our recent work [13] From Fig. 8 (b), the intensity of diffusive scattering from the mirror is as small as the back ground which is as approximately several×10 -4 times smaller than the peak intensity of the focused beam.…”

Precision Mechanical Design of 900 mm Long Ellipsoidal Neutron-focusing Supermirror for VIN ROSE at J-PARC/MLF

“…The polishing ends when the surface roughness fall below 5 Å rms , which is sufficiently smooth for supermirror deposition. Details on this polishing process are given in [4,13,14]. The substrates with polished ellipsoidal surfaces are then coated with supermirrors at KURRI-IBS, whose details are found in [15].…”

“…Neutron-focusing supermirror is a class of supermirrors that is deposited on a curved surface, whose function is to converge the neutrons into a small spot on either a sample or a detector for intensification. Successful developments of such focusing supermirrors have been reported, examples of which are elliptic mirrors for one-dimensional focusing [1][2][3][4] and a series of mirrors in the Kirkpatrick-Baez configuration for two-dimensional focusing [5].…”

“…The plating is amorphous; thus, it provides surfaces with sub-nanometer roughness when polished, which is sufficiently smooth for supermirror deposition. The plating's compatibility with the supermirror coating was tested using the ion-beam sputtering facility at Kyoto University Research Reactor Institute (KURRI-IBS) [15], based on which we developed elliptic supermirrors for one-dimensional focusing [3,4].…”

Application of precise neutron focusing mirrors for neutron reflectometry: latest results and future prospects

“…On the basis of the background presented above, we have been developing focusing mirrors to enhance the neutron flux at small samples. Firstly, we attempted to realize the elliptical shape by bending a large mirror on a glass substrate Morita et al, 2016), and we manufactured a metal substrate with an elliptical shape by means of ultra-precision machining (Takeda et al, 2016;Hosobata et al, 2017Hosobata et al, , 2019. Finally, we succeeded in fabricating a sufficiently precise focusing mirror with the metal substrate to be utilized as the focusing optics for NR: the dimensions were 550 mm in length and 60 mm in width.…”