Neutron Optical Beam Splitter from Holographically Structured Nanoparticle-Polymer Composites

Abstract

We report a breakthrough in the search for versatile diffractive elements for cold neutrons. Nanoparticles are spatially arranged by holographical means in a photopolymer. These grating structures show remarkably efficient diffraction of cold neutrons up to about 50% for effective thicknesses of only 200 m. They open up a profound perspective for next generation neutron-optical devices with the capability to tune or modulate the neutron diffraction efficiency.

A Comprehensive Study of Photorefractive Properties in Poly(ethylene glycol) Dimethacrylate— Ionic Liquid Composites

“…We intend to use these gratings for cold and very cold neutrons [23,80,81,82], in particular looking forward to finally adapt the samples with magnetic liquids (ferro fluids) [83] that couple to the neutron spin. A further batch of IL-polymer composite gratings with a spacing of about half a micron is currently being analyzed.…”

Holographic Gratings for Slow-Neutron Optics

“…The feasibility of a beam splitter for CN has been demonstrated by such means [46,59]. The remaining limitations of neutron-optical elements based on NP-polymer composites have been the small grating diameter—decreasing the possible beam size upon tilting—and incoherent scattering/absorption of sample glass covers and the sample itself.…”

“…Such gratings were used in References [46,59,60] because they operate in the two-wave coupling regime (Bragg regime) so that no intensity is lost to unnecessary diffraction orders and—at the same time—the gratings exhibit high diffraction efficiency for relatively small grating spacing (large ${\theta }_B$), which is important for applications. The theoretical prediction given by the thick line in Figure 13 was tested in the latter two references given above, but only up to $\zeta \approx {70}^{\circ }$.…”

Effects of chain-transferring thiol functionalities on the performance of nanoparticle-polymer composite volume gratings

“…We attribute this improvement to the premature termination because of doping with thiols in free radical-mediated chain-growth polymerizations since the average polymer chain length shortens and the nonlocal photopolymer response can be reduced [19]. This result is particularly advantageous for efficient Bragg diffraction of a slow-neutron beam by an NPC volume grating, where its high spatial frequency response is required since the grating spacing enters the inverse of the KleinCook parameter quadratically [12,20,21].…”

“…In this Letter, we experimentally study the chemical modification of ZrO 2 NPC volume gratings by incorporating multifunctional thiols as CTAs to improve the spatial frequency response and mechanical/thermal stability. In particular, the former improvement is important to ensure Bragg-regime diffraction for applications in neutron optics [12]. Obtained results are compared with the case of doping with mono-thiol.…”