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The neutron's permanent electric dipole moment dn is constrained to below 3 × 10−26e cm (90% C.L.) [1, 2], by experiments using ultracold neutrons (UCN). We plan to improve this limit by an order of magnitude or more with PanEDM, the first experiment exploiting the ILL's new UCN source SuperSUN. SuperSUN is expected to provide a high density of UCN with energies below 80 neV, implying extended statistical reach with respect to existing sources, for experiments that rely on long storage or spin-precession times. Systematic errors in PanEDM are strongly suppressed by passive magnetic shielding, with magnetic field and gradient drifts at the single fT level. A holding-field homogeneity on the order of 10−4 is achieved in low residual fields, via a high static damping factor and built-in coil system. No comagnetometer is needed for the first order-of-magnitude improvement in dn, thanks to high magnetic stability and an assortment of sensors outside the UCN storage volumes. PanEDM will be commissioned and upgraded in parallel with SuperSUN, to take full advantage of the source's output in each phase. Commissioning is ongoing in 2019, and a new limit in the mid 10−27e cm range should be possible with two full reactor cycles of data in the commissioned apparatus.

A new source of ultracold neutrons (UCNs), developed at the Institut Laue-Langevin (ILL) and named SuperSUN, is currently being commissioned. Its operational principle is the conversion of cold neutrons, delivered by ILL's existing beam H523, to UCNs in a vessel filled with superfluid helium-4, wherein the neutron's energy and momentum are transferred by inelastic scattering to phonons in the superfluid. The inverse Boltzmann-suppressed process is negligible at temperatures below 0.6 K, enabling long storage times and high in-situ UCN densities as demonstrated at the ILL for two prototype sources. These two prototypes are installed at secondary beams behind crystal monochromators, whereas a primary beam with a white cold spectrum illuminates the SuperSUN conversion volume. This provides not only higher intensity around the wavelength 0.89 nm where the dominant single-phonon process for UCN production takes place, but also a contribution to UCN production by multi-phonon processes. In the first phase of the project, material walls will trap the UCNs, while in the second phase an octupole magnet will generate a 2.1 T magnetic field at the edge of the conversion volume. For low-field-seeking UCNs, this field increases the trapping potential and reduces wall losses so that the accumulated UCNs are spin-polarized as a result. SuperSUN aims to deliver the highest possible UCN densities to external storage experiments, the first of which will be the PanEDM experiment measuring the neutron's permanent electric dipole moment. [ABSTRACT FROM AUTHOR]

We present the results of simulations to optimize a tapered neutron guide, with an initially rectangular cross-section that smoothly transitions to an irregular octagon. This guide serves as an adapter section between an existing cold-neutron guide (rectangular cross-section 120 × 60 mm2, with m = 1.2 coating), and a 3 m long circular guide (76 mm inner diameter, with m ⩾ 2.5). The circular guide is filled with superfluid 4He to convert neutrons with wavelengths around 8.9 Å into ultracold neutrons (UCN) by inelastic scattering; it serves as the centerpiece of the ILL's new UCN source SuperSUN. The octagonal guide exit provides a better match than a rectangle to the circular aperture, and the beam divergence is transformed so that a larger fraction of the 8.9 Å neutrons can be guided through the converter. The required edge-reflectivity for the circular guide is also reduced: simulations show that, with a converter coating of m = 2.5 , 85% of the 8.9 Å neutrons from the primary, rectangular beam can be made available for UCN production. Due to the aspect ratio of the initial rectangle, an irregular octagonal cross section is found to perform better than a regular one. The corresponding guide has been fabricated and delivered, with first neutron measurements expected in 2019. [ABSTRACT FROM AUTHOR]

Overview of the future guide systems at the ILL. [ABSTRACT FROM AUTHOR]

The replacement of the H16-IN5 guide has been decided in the frame of the ILL Endurance program. This guide is made of heteroclite sections and the upgrade aims at improving the performances with a modern homogeneous ballistic guide. Several constraints applied to the project: (i) the instrument will remain at the same location, (ii) considering (i), in terms of gain relative to cost, it was judged more reasonable to keep the same chopper system, (iii) many technical elements under control of the nuclear safety authorities cannot be changed within the lifetime of the project. We present the results of the McStas optimization of the replacing guide performed under these constraints. [ABSTRACT FROM AUTHOR]

Laminated metal composites (LMCs) with alternating layers of commercial pure aluminum AA1050A and aluminum alloy AA5005 were produced by accumulative roll-bonding (ARB). In order to vary the layer thickness and the number of layer interfaces, different numbers of ARB cycles (4, 8, 10, 12, 14 and 16) were performed. The microstructure and mechanical properties were characterized in detail. Up to 8 ARB cycles, the ultrafine-grained (UFG) microstructure of the layers in the LMC evolves almost equally to those in AA1050A and AA5005 mono-material sheets. However, the grain size in the composites tends to have smaller values. Nevertheless, the local mechanical properties of the individual layers in the LMCs are very similar to those of the mono-material sheets, and the macroscopic static mechanical properties of the LMCs can be calculated as the mean value of the mono-material sheets applying a linear rule of mixture. In contrast, for more than 12 ARB cycles, a homogenous microstructure was obtained where the individual layers within the composite cannot be visually separated any longer; thus, the hardness is at one constant and a high level across the whole sheet thickness. This results also in a significant higher strength in tensile testing. It was revealed that, with decreasing layer thickness, the layer interfaces become more and more dominating. [ABSTRACT FROM AUTHOR]