Axis Spectrometer Research Articles

Incident beamline design for a modern cold triple axis spectrometer at the High Flux Isotope Reactor

A modern cold triple axis spectrometer is being planned for the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. Here, we describe the design of an incident beamline that will put a flux of ∼108ncm2s on a sample with an area of 2 cm × 2 cm. It takes current physical constraints at HFIR into account and it can accommodate both single and multiplexed analyzer-detector secondary spectrometers and large superconducting magnets. The proposed incident beamline includes a multi-channel guide with horizontal focusing, a neutron velocity selector, components to facilitate an incident beam polarization option, and a double-focusing pyrolytic graphite monochromator. This work describes the process of optimizing the guide system and monochromator and summarizes the expected performance of the incident beamline for non-polarized operation.

A high resolution reaction microscope with universal two-region time-focusing method.

This paper presents a novel reaction microscope designed for ion-atom collision investigations, established at the Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China. Its time-of-flight (TOF) spectrometer employs an innovative flight-time focusing method consisting of two acceleration regions, providing optimal time focusing conditions for charged fragments with diverse initial velocities. The TOF spectrometer's axis intentionally tilts by 12° relative to the ion beam direction, preventing potential obstructions from the TOF grid electrodes. The introduced focusing method allows for a flexible time-focusing TOF spectrometer design without restricting the length ratio of the two regions. In addition, this configuration in our case significantly suppresses noise on the recoil ion detector produced by residual gas in the ion beam trajectory, which is a considerable challenge in longitudinal spectrometers. In a test experiment on the single electron capture reaction involving 62.5 keV/u He2+ ions and a helium atomic beam, the recoil longitudinal momentum resolution achieved 0.068 atomic units. This novel configuration and successful test run show excellent precision for ion-atom collision studies.

Lamellar diffraction from lipid bilayers on MIRA, a triple axis spectrometer at the MLZ

Diffraction used in conjunction with molecular deuteration provides a model independent means to examine detailed structural and compositional information of model and real biological membranes in the lamellar phase. The technique provides specific information of localization of molecules and smaller units with respect to the unit cell. Deuteration is used to provide specific labelling and to provide phasing for the crystallographic reconstruction. Typical data sets consist of a series of lamellar diffraction peaks, usually collected under conditions of 3 contrasts of the water gas phase. Accurately integrated the diffraction peaks can be used for a Fourier reconstruction of the composition of the lamellar unit cell in real space. Each diffraction peak which can be integrated for 3 contrasts contributes to an additional Fourier term in the reconstruction and optimization of the number of peaks enhances the spatial resolution of the crystallographic reconstruction. Here we report on the use of the flexibly configurable cold triple-axis spectrometer, MIRA, at the Heinz Maier-Leibnitz Zentrum (Garching, Germany) for investigations of different lamellar systems using this approach. The data sets are acquired from lamellar stacks in an sample environment with humidity and temperature control with exceptionally low background. We discuss further enhancements of the instrument and sample environment which will provide information on the composition and equilibration of the sample.

Absolute calibration of the conical crystal configuration of the zinc spectrometer (ZSPEC) at the OMEGA laser facility.

In this study, we present the absolute calibration of the conical crystal for the zinc spectrometer (ZSPEC), an x-ray spectrometer at the OMEGA laser facility at the Laboratory for Laser Energetics. The ZSPEC was originally designed to measure x-ray Thomson scattering using flat or cylindrically curved highly oriented pyrolytic graphite crystals centered around Zn He-alpha emission at 9keV. To improve the useful spectral range and collection efficiency of the ZSPEC, a conical highly annealed pyrolytic graphite crystal was fabricated for the ZSPEC. The conically bent crystal in the Hall geometry produces a line focus perpendicular to the spectrometer axis, corresponding to the detector plane of electronic detectors at large scale laser facilities such as OMEGA, extending the useful range of the spectrometer to 7-11keV. Using data collected using a microfocus Mo x-ray source, we determine important characteristics of ZSPEC such as the dispersion, spatial resolution, and absolute sensitivity of the instrument. A ray-trace model of ZSPEC provides another point of agreement in calculations of the ZSPEC dispersion and crystal response.

Current Status of the Taiwanese Cold Triple Axis Spectrometer, SIKA, at ANSTO

SIKA, a new cold neutron triple-axis spectrometer, was built on the CG4 beam port at the OPAL reactor, ANSTO. Here we report the capabilities and current status of SIKA. A versatile instrument, SIKA, provides sample environments with temperature capacities from the dilution temperature below 50 mK to the 750 K; magnetic fields of up to 12 T, the well-developed control and analysis software based on SPICE. Several scientific examples demonstrating the proficiency of SIKA are reported, such as: observation of higher harmonics in the helical magnetic phase of MnP as an example of elastic magnetic scattering; measurement of the aluminum phonon dispersion with the estimated slope of the transverse acoustic phonon at 32.4 meV; the spin-wave dispersion in MnF2 along the c axis enabled determination of exchange parameters J1 = 0.0305 meV, J2 = –0.1534 meV and D = 0.1427 meV; and observation of one of the crystal field excitations from Pr3+ in the PrFeO3 powder.

CALIBRATION OF THE EXTENDED QUADRIHEDRAL NaI(Tl) SPECTROMETER BY COSMIC MUONS

The results of cosmic muon calibration of the extended quadrihedral NaI(Tl) spectrometer are presented. The signal amplitude and energy resolution of the spectrometer in the direction transverse to the spectrometer axis have complex dependences on the photomultiplier voltage and particle entrance point to the spectrometer. At a photomultiplier divider voltage U = 1150 ± 10 V, the region of uniform signals is observed over ~90% of the spectrometer length, the relative energy resolution is δ ≈ 7%.

Kunpeng: A cold neutron triple-axis spectrometer at CMRR in China

A new cold neutron triple axis spectrometer named Kunpeng at the China Mianyang Research Reactor (CMRR), Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics has been constructed and fully tested. It can be typically used to study magnetic excitations, spin and lattice dynamics in condensed matter physics. In this contribution we present its main features and the first experimental data to demonstrate its performance.

Supermirror physics with event biasing in MCNP6

Beamlines for cold and thermal neutrons instruments use low-roughness multilayered films called supermirrors, which aim to reflect neutrons below a critical angle. Calculations related to the design of these guides are often made with optics codes like Monte Carlo Simulation of Triple Axis Spectrometers (http://www.mcstas.org/, [1]), sometimes in combination with particle transport physics codes like Monte Carlo-N Particle (MCNP, Goorley et al., 2012) or Geant4 (Agostinelli et al., 2003) [2], and more recently, supermirrors physics implemented in MCNPX (Gallmeier et al., 2009). We have ported this functionality into MCNP6, and also expanded its capabilities by implementing deterministic transport through the guides, and allowing the use of Deterministic Transports Spheres (DXTRAN) (Booth, 2008) [3]. The results have been compared to existing work with positive results.

Triple Axis Resolution Workshop at MLZ Garching

On April 3–4, 2017 the quantum phenomena group of the MLZ organized a two-day workshop on software for calculating the resolution function of a triple axis spectrometer and convoluting the data wit...

Development of Data Acquisition and Measurement Software for Neutron Triple Axis Spectrometer at BATAN-Serpong, Indonesia

The Neutron Scattering Laboratory at the National Nuclear Energy Agency of Indonesia (BATAN) possesses several neutron beam instruments for materials science research. One of the instruments is a neutron triple-axis spectrometer (TAS). Due to the malfunction of the main computer, the original main control system had to be replaced with a new one. For this reason, a new data acquisition and measurement software program based on GNU C++ programming language was developed for restoring the spectrometer's functionality. However, using the resulting control system, triple-axis mode experiments were very difficult to perform and their types that can be performed were limited. In order to conduct the experiments more effectively and efficiently, several improvements in both hardware and software have been developed. The Visual Basic programming language was used in developing the data acquisition and measurement software that makes it possible for all motors to move simultaneously, so that the time spent for the experiments is reduced significantly. Also, programmable motor controller cards were used for driving all the 23 motors of the instrument. All the 23 axes can be controlled by clicking the appropriate buttons or inputting text command in the main window of the software's user interface. The software has also been used to perform an elastic experiment, as well as an inelastic experiment for investigating the phenomenon of phonon. The software developed is more user friendly than the older ones, since the spectrometer status and the experiment results can be displayed in real time at the windows, and it also makes experiments more effective and efficient since the experiments can be automated and run without any user intervention until the experiments finish. /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0mm 5.4pt 0mm 5.4pt; mso-para-margin:0mm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:ＭＳ 明朝; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Times New Roman; mso-bidi-theme-font:minor-bidi;}

Experimental characterization of a prototype secondary spectrometer for vertically scattering multiple energy analysis at cold-neutron triple axis spectrometers

A thorough experimental characterization of a multiplexing backend with multiple energy analysis on a cold-neutron triple axis spectrometer (cTAS) is presented. The prototype employs two angular segments (2θ-segments) each containing five vertically scattering analyzers (energy channels), which simultaneously probe an energy transfer range of 2meV at the corresponding two scattering angles. The feasibility and strength of such a vertically scattering multiple energy analysis setup is clearly demonstrated. It is shown, that the energy resolution near the elastic line is comparable to the energy resolution of a standard cTAS. The dispersion relation of the antiferromagnetic excitations in MnF2 has been mapped out by performing constant energy transfer maps. These results show that the tested setup is virtually spurion free. In addition, focusing effects due to (mis)matching of the instrumental resolution ellipsoid to the excitation branch are clearly evident.

Large-scale scientific facility at China Advanced Research Reactor for neutron scattering

As a complementary role to X-rays, neutrons provide a unique, non-destructive method. Neutron scattering techniques have been widely applied to the determination of the structural details and the dynamics of atomic arrangements in materials and matters. Large-scale scientific facility of neutron scattering has played an important role in basic research and industry. This paper reviews the outstanding characteristics of neutron probe, the development status of neutron scattering facilities abroad, and especially the progress of the first phase of Neutron Scattering Project at China Advanced Research Reactor (CARR). By now, ten instruments, including a High Resolution Powder Diffractometer (HRPD), a High Intensity Powder Diffractometer (HIPD), a Residual Stress Diffractometer (RSD), a texture diffractometer (TD), a four circle diffractometer (FC), two Triple Axis Spectrometers (TAS), a reflectometer (RF), a Small Angle Neutron Scattering instrument (SANS) and a High Frame-rate Neutron Imaging Test Station (HFNIT) have been constructed in cooperation with Peking University, Institute of Chemistry of Chinese Academy of Sciences (CAS), Institute of Physics of CAS, Juelich Center in Germany and the partner from Sweden. The construction of them has been completed and they are under commissioning. CARR has run more than 200 hours for adjusting and optimizing the instruments and some promising experimental results have been attained. As one of the most powerful high-flux reactor neutron sources in the world, CARR will ensure the development and application of neutron scattering in China.

The use of selected neutron absorption resonance filters to suppress spurious events on hot neutron spectrometers

Resonant absorption can be used as a filter for high energy neutron spectroscopy. Here we report the transmission of eight thin foil filters: erbium, indium, iridium, dysprosium, hafnium, gadolinium, cadmium and samarium, measured using neutron time-of-flight techniques over a range of energies (1meV to 10eV). Measured transmission is converted into energy-dependent absorption cross-section which compares closely to tabulated values. Each resonance is characterized from 91meV (samarium) to 2815meV (gadolinium) by Lorentzian fits. Possibilities for the use of neutron filters depending on the type of spurious background are discussed and the performance is simulated for a specific example of a hot neutron triple axis spectrometer experiment.

The upgraded cold neutron triple-axis spectrometer FLEXX – enhanced capabilities by new instrumental options

The upgrade of the cold neutron triple axis spectrometer FLEXX, a work-horse instrument for inelastic neutron scattering matching the sample environment capabilities at Helmholtz-Zentrum Berlin, has been successfully accomplished. Experiments confirmed an order of magnitude gain in flux now allowing for intensity demanding options to be fully exploited at FLEXX. In this article, we describe the layout and design of two newly available FLEXX instrument options in detail. The new Heusler analyzer gives an increase of the detected polarized neutron flux due to its superior focusing properties, significantly improving the feasibility of future polarized and neutron resonance spin echo experiments. The MultiFLEXX option provides simultaneous access to large regions in wavevector and energy space for inelastic excitations thus adding mapping capabilities to the spectrometer.

Field Dependence of the Magnetic Propagation Vector of the Heavy Fermion Compound CeCu2Ge2 Studied by Neutron Diffraction

CeCu2Ge2, the counterpart of the heavy-fermion superconductor CeCu2Si2, exhibits an in-commensurate antiferromagnetically long-range ordered ground state with τ = (0.28 0.28 0.54) below TN = 4.15K. The magnetism is strongly affected by a Kondo screening of the Ce 4f-moments by conduction electrons. The similar energy scale of both, Kondo and exchange interactions, results in a complex magnetic phase diagram and gives rise to potential quantum critical phenomena at very low temperatures. We present elastic neutron diffraction data obtained on a CeCu2Ge2 single crystal employing the cold triple axis spectrometer PANDA at MLZ and the diffractometer D23 at ILL.The field dependence of the magnetic propagation vector was measured at T ≤ 400 mK in the [110]/[001] plane with vertical magnetic fields applied along [1̄10]. We observe a low-field incommensurate magnetic phase AF1, a first order phase transition around 7.8 T with the coexistence of two phases AF1 and AF2 with slightly different propagation vectors, the disappearance of AF1 at 8 T and the existence of AF2 up to 12 T with a possible modification at 10 T. At 12.6 T, yet still well below the value of 26 T of the saturation for magnetic fields in [110] direction, the AF2-type magnetic order is lost and magnetic intensities are not to be found at incommensurate positions in the [110]/[001] plane any more. These new results contradict a previously suggested scenario with a QCP located at 8 T and contribute new information to the B − T phase diagram of CeCu2Ge2 in [110] direction.

Method to compensate the dispersion of kinetic energy resolution in a velocity map imaging spectrometer

Here we present a novel method to improve the kinetic energy resolution of a velocity map imaging(VMI) spectrometer. The main modifications, compared to the original design of Eppink and Parker (1997 Rev. Sci. Instrum. 68 3477), are two additional grid electrodes. One of the electrodes is a grounded grid and the other is an arc-shaped grid with negative voltages (or positive voltages for an ions spectrometer). The arc-shaped electrode is axially symmetrical around the spectrometer axis. The field constructed by the two electrodes is to compensate the dispersion of the ‘v’-shaped energy resolution. Simulations by SIMION and reconstructions by the basis set expansion Abel transform method show that the kinetic energy resolution can be improved drastically by our new method. Furthermore, the accuracy in the determination of the kinetic energy of ion/electrons remains unchanged with respect to the original design.

Spin Waves in Ferromagnetic Phase of MnP

Inelastic neutron scattering experiments on an intermetallic compound, MnP, were performed by using a chopper spectrometer as well as triple axis spectrometers. Spin waves were observed in the ferromagnetic phase in the entire Brillouin zone along the a*- and b*-axes. The observed dispersion relations of spin waves were well described by an isotropic Heisenberg interaction adding a single ion anisotropy with two sub-lattices.

A Mirror Furnace for <i>In Situ</i> Residual Stress Measurements by Neutron Diffraction

A mirror furnace for in situ residual stress measurements by neutron diffraction is designed. Bulk and stick sample can be in situ heated up to 1000 degrees centigrade. The stability of the temperature is better than ±1 degree centigrade. This furnace is designed mainly for residual stress neutron diffraction experiments. And also it can be applied to some other neutron instruments such as neutron texture diffractometer, neutron powder diffractometer and triple axis spectrometer.

Investigation of the vibrational properties of cubic yttria-stabilized zirconia: A combined experimental and theoretical study

A combined experimental and theoretical investigation into the vibrational properties of cubic 8–9mol% yttria-stabilized zirconia (YSZ) is presented. Measurements of acoustic phonon dispersion curves have been obtained from inelastic neutron scattering investigations using a triple axis spectrometer, as well as calculations of the vibrational density-of-states (vDOS) using density-functional theory. The present measurements agree closely with, and extend, previously published results. The phonons become broader and decrease in intensity as the Brillouin zone boundary is approached, particularly in the Γ–Δ–X direction. Interestingly, there is evidence of a previously unreported low energy phonon band (8–9meV) in the Γ–Σ–X direction, which could possibly be related to the stabilization (by yttria doping) of the imaginary mode of cubic ZrO2 about the X-point. Compared to pure cubic ZrO2, the vDOS of YSZ are broader and extend to higher frequency. Furthermore, the prominent Zr-related feature in the vDOS of c-ZrO2 at ≈14meV is shifted to higher energy in the vDOS of YSZ. This behavior is consistent with the measured dispersion bands (first acoustic branch in the Γ–X direction, about the X-point) of YSZ which is higher in energy by a similar amount relative to that of c-ZrO2, thus providing support for the structural model considered.

Magnetic excitations in ferromagnetic phase of MnP

Inelastic neutron scattering experiments were performed on an intermetallic compound, MnP. We used a newly developed High Resolution Chopper Spectrometer, HRC, for energy transfers E≤75meV, besides various triple axis spectrometers; LTAS for energy transfers E≤2meV, TOPAN for E≤7.5meV and TAS-1 for E≤35meV. Spin wave excitations were observed in the ferromagnetic phase of MnP in the entire Brillouin zone along the a⁎- and b⁎-axes. The zone boundary energies of spin waves were determined to be around 60meV along the a⁎-axis and around 75meV along the b⁎-axis, and the dispersion relations showed two branches for both axes. The observed dispersion relations of spin waves were well described by an isotropic Heisenberg interaction adding a single ion anisotropy with two sub-lattices.