MACS—a new high intensity cold neutron spectrometer at NIST

Abstract

We describe a novel cold neutron spectrometer under development at NIST optimized for wave vector resolved spectroscopy with incident energies between 2.1 meV and 20 meV and energy resolution from 0.05 meV (E i = 2.1 meV) to 3.0 meV (E i = 20 meV). By using a 1428 cm 2 double focusing PG (0 0 2) monochromator close to the National Institute of Standards and Technology (NIST) cold neutron source the instrument provides up to 5 × 10 8 neutrons cm −2 s −1 on a 8 cm 2 sample area. The measured performance is consistent with Monte Carlo simulations. The monochromating system, which includes radial collimators, three filters and a variable beam aperture, offers considerable flexibility in optimizing Q-resolution, energy resolution and intensity. The detector system will consist of an array of 20 channels which combined will subtend a solid angle of 0.2 sr. This is approximately a factor of 40 more than a conventional triple axis spectrometer. Each detector channel contains a vertically focusing double crystal analyzer system (DXAL) actuated by a single stepping motor. We find identical integrated reflectivity at approximately 10% coarser energy resolution for the 130 mosaic double bounce analyzer as compared to a conventional 25 analyzer at the same energy. The vertical focusing of the DXAL allows for smaller detectors for enhanced signal to noise with 8 • vertical acceptance. Options for post sample collimators and filters provide flexibility in the choice of scattered beam energy and wavevector resolution.

Competing spin density wave, collinear, and helical magnetism inFe1+xTe

“…An oscillating collimator is used after the detector to limit background. Further studies searching for harmonics and also establishing the magnetic wave vector were performed at the MACS (Multi Axis Crystal Spectrometer) cold triple-axis spectrometer at NIST (Gaithersburg, Maryland) [63]. The final energy was fixed at E f = 3.6 meV, and the elastic scattering plane was measured using the 20 double-bounce PG(002) analyzing crystals and detectors.…”

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and Nikitin1, Portnichenko2, Dukhnenko3 et al. 2018Phys. Rev. B123160View full textAdd to dashboardCite

“…Measurements of substituted samples were performed using the MACS spectrometer at NIST [74]. The measurement temperature was fixed just above T N for each sample.…”

CAMEA ESS – The continuous angle multi-energy analysis indirect geometry spectrometer for the European Spallation Source

“…Within ±1.4 • vertical range of CAMEA, and taking into account transmission rates, we estimate the solid angle gain of CAMEA over Flatcone to be 36 [3], or 23 over MACS at NIST [2]. Comparing CAMEA's flux gain for 2% energy resolution, and the increased solid angle coverage gives a gain factor of ∼ 900 compared to ThALES using Flatcone, provided all detected signal is of use in both cases.…”

“…Direct ToF instruments compensate a low incident neutron flux from using monochromatic pulses, by detecting the scattered neutrons of all energies over a large solid angle in position sensitive detectors. In contrast TAS focus a continuous high flux monochromatic beam of neutrons on a sample but have a low detection coverage of counting neutrons at one final neutron energy at one position, or tens of angles in the case of multiplexed TAS [1][2][3].…”