GALAXI: Gallium anode low-angle x-ray instrument

The high brilliance laboratory small angle X-ray scattering instrument GALAXI, which is operated by JCNS, Forschungszentrum Jülich, permits the investigation of chemical correlations in bulk materials or of structures deposited on a surface at nanometre and mesoscopic length scales. The instrument is capable to perform GISAXS experiments in reflection at grazing incidence as well as SAXS experiments in transmission geometry. The X-ray flux on sample is comparable or higher than the one obtained at a comparable beamline at a second generation synchrotron radiation source.

Structural and magnetic properties of [\lbrackErTb]\rbrackmultilayers

Abstract.: We have investigated the structural and magnetic properties of $\lbrack$ Er|Tb $\rbrack$ multilayers by different scattering methods. Diffuse X-ray scattering under grazing incidence reveals the interface structure in $\lbrack$ Er|Tb $\rbrack$ bilayers and trilayers, indicating vertically correlated roughness between the Er and Tb interfaces. The magnetic properties of $\lbrack$ ErnEr|TbnTb $\rbrack$ superlattices have been studied as a function of the superlattice composition (indices denote the number of atomic layers). Coupled ferromagnetic structures exist in all investigated samples. The phase transition temperature varies with the Tb layer thickness. Modulated magnetic order is short range for all samples beside the $\lbrack$ Er20|Tb5 $\rbrack$ superlattice, the sample with the smallest Tb layer thickness. We observe dipolar antiferromagnetic coupling between single ferromagnetic Tb layers in all samples, with the onset of this ordering depending on the Tb layer thickness. Due to competing interactions, exchange coupling is limited to the interface near region. Therefore long range modulated magnetic order is observed in the $\lbrack$ Er20|Tb5 $\rbrack$ superlattice only, where the interface regions overlap. The distinct differences to the magnetic structure of an Er0.8Tb0.2 alloy film are explained by a highly anisotropic arrangement of neighbouring atoms due to the correlated roughnes

PENGARUH PENAMBAHAN POTONGAN KARUNG PLASTIK SEBAGAI BAHAN CAMPURAN UNTUK MEMPERKUAT TIMBUNAN TANAH LEMPUNG

Terbatasnya lahan untuk pembangunan yang diperlukan mengakibatkan tidak dapat dihindarinya pembangunan di atas tanah lempung seperti tanah yang ada di Indonesia. Oleh karena itu, sangat penting untuk mencampurkan bahan tambahan sebagai campuran ke dalam tanah lempung tersebut untuk meningkatkan kualitas daya dukung tanah pada tanah lempung. Karena banyaknya permintaan karung plastik, limbah karung plastik menjadi semakin banyak, maka peneliti mencoba untuk memanfaatkan serat karung plastik tersebut sebagai bahan campuran pada tanah lempung benda uji. Dengan mencampurkan potongan serat karung plastik ke dalam tanah lempung, diharapkan tanah lempung campuran serat karung plastik tersebut dapat meningkatkan kepadatan tanah dan dapat memperkuat kuat geser tanah. Studi ini meliputi, studi literatur dan penelitian di Laboratorium Mekanika Tanah ITN Malang pada tanggal 7 April – 19 Juli 2019. Tanah benda uji dalam penelitian ini berasal dari Ds. Argotirto, Kec. Sumbermanjing Wetan, Kab. Malang dan bahan campuran potongan serat karung plastik sepanjang ≥ 1cm - ≤ 3cm dengan variasi kadar campuran; 1%, 1,5%, 2%, 2,5%, 3% dari berat total tanah saat kadar air optimum. Penelitian ini meliputi pengujian sifat fisik dan sifat teknis. Pengujian sifat fisik meliputi; Kadar Air Tanah Asli (w), Berat Jenis (Gs), Analisa Saringan, Analisa Hidrometer, Uji Plastisitas (LL, PL, SL), Tingkat Pengembangan, dan Tingkat Keaktifan (Activity). Pengujian sifat teknis meliputi; Compaction Standard dan Modified, Triaxial UU, dan Unconfined Compression, masing-masing pengujian terdiri dari 3 sampel. Dengan dibantu uji hipotesis data untuk mengetahui adanya pengaruh atau tidak adanya pengaruh dalam pengujian tanah lempung campuran serat karung plastik tersebut. Berdasarkan hasil pengujian, tanah benda uji penelitian tersebut termasuk dalam tanah MH (Lanau anorganik atau pasir halus diatomac, atau lanau diatomac, lanau yang elastis). Nilai hasil pengujian campuran serat karung plastik cenderung meningkat dibandingkan tanah tanpa campuran. Nilai tertinggi untuk bahan timbunan mendapatkan prosentase kadar campuran serat karung plastik sebanyak 3% pada pengujian Modified Compaction sebesar; 1,528g/cm3, dengan nilai kadar air (w) sebesar; 26,89%. Pada pengujian Triaxial UU, mendapatkan nilai Kohesi (c) sebesar; 0,350kg/cm², dengan nilai Sudut Geser (φ) sebesar; 6,277 pada kadar campuran 3%. Dan pada pengujian Unconfined Compression, mendapatkan nilai Tegangan Normal (qu) sebesar; 0,681kgf/cm2 pada kadar campuran 1%

The Complexity of Flat Freeze LTL

We consider the model-checking problem for freeze LTL on one-counter automata (OCAs). Freeze LTL extends LTL with the freeze quantifier, which allows one to store different counter values of a run in registers so that they can be compared with one another. As the model-checking problem is undecidable in general, we focus on the flat fragment of freeze LTL, in which the usage of the freeze quantifier is restricted. Recently, Lechner et al. showed that model checking for flat freeze LTL on OCAs with binary encoding of counter updates is decidable and in 2NEXPTIME. In this paper, we prove that the problem is, in fact, NEXPTIME-complete no matter whether counter updates are encoded in unary or binary. Like Lechner et al., we rely on a reduction to the reachability problem in OCAs with parameterized tests (OCAPs). The new aspect is that we simulate OCAPs by alternating two-way automata over words. This implies an exponential upper bound on the parameter values that we exploit towards an NP algorithm for reachability in OCAPs with unary updates. We obtain our main result as a corollary

Feasibility of study magnetic proximity effects in bilayer "superconductor/ferromagnet" using waveguide-enhanced Polarized Neutron Reflectometry

A resonant enhancement of the neutron standing waves is proposed to use in order to increase the magnetic neutron scattering from a "superconductor/ferromagnet"(S/F) bilayer. The model calculations show that usage of this effect allows to increase the magnetic scattering intensity by factor of hundreds. Aspects related to the growth procedure (order of deposition, roughness of the layers etc) as well as experimental conditions (resolution, polarization of the neutron beam, background etc) are also discussed. Collected experimental data for the S/F heterostructure Cu(32nm)/V(40nm)/Fe(1nm)/MgO confirmed the presence of a resonant 60-fold amplification of the magnetic scattering.Comment: The manuscript of the article submitted to Crysstalography Reports. 23 pages, 5 figure

Diffuse scattering

Diffuse neutron scattering covers a wide range of phenomena related to short range nuclear and magnetic orderings. Although it is “a priori” simple to measure, the underlying physics is often quite complex. Extracting useful and reliable information requires careful corrections and calibrations, and appropriate models of analysis, specifics for each physical case. This paper yields a partial and subjective glance on this specific subject, showing studies about chemical orderings in binary alloys and magnetic correlations in frustrated “spin ices” as examples