Neutron Resonance Spin Echo Spectrometer Research Articles

The resolution of the MIEZE setup on the longitudinal neutron resonance spin-echo spectrometer at CMRR

A longitudinal neutron resonance spin echo (L-NRSE) spectrometer combined with a MIEZE (modulated intensity with zero effort) configuration will be constructed at the C33 beam port at China Mianyang Research Reactor (CMRR) . In the MIEZE mode, the analyzer is placed in front of the sample, and between the sample and the detector there is no other optical device. The MIEZE signal is sensitive to the neutron path length differences from the sample to the detector. In this work, we have analytically studied the effects of sample geometry, detector thickness, and experimental setup on the resolution function.

Design and performance of a superconducting neutron resonance spin flipper.

Despite the challenges, neutron resonance spin echo still holds the promise to improve upon neutron spin echo for the measurement of slow dynamics in materials. We present a bootstrap, radio frequency neutron spin flipper using high temperature superconducting technology capable of flipping neutron spin with either nonadiabatic or adiabatic modes. A frequency of 2 MHz has been achieved, which would achieve an effective field integral of 0.35 T m for a meter of separation in a neutron resonance spin echo spectrometer at the current device specifications. In bootstrap mode, the self-cancellation of Larmor phase aberrations can be achieved with the appropriate selection of the polarity of the gradient coils.

Experimental test of 3He neutron-spin filter in MIEZE spectrometer

A modulated intensity by zero effort (MIEZE) spectrometer is a type of neutron-resonance spin-echo spectrometer and can be used to analyze the slow dynamics of condensed matter by measuring the intermediate scattering function I(Q,τ). A crucial feature of a MIEZE spectrometer is it leaves completely free the space between the sample and the detector because the sample is placed after the neutron-spin analyzer. Measuring the magnetic dynamics with a conventional neutron-spin-echo spectrometer is difficult, but with a MIEZE spectrometer such a measurement may be done simply by introducing a second analyzer after the sample. Measuring the magnetic dynamics with high precision requires the background to be reduced to a minimum and is a job for which a 3He neutron-spin filter (3He-NSF) is a promising candidate as a second analyzer. However, one difficulty with this approach is the diffusion of 3He gas from the 3He-NSF, which may be measured and interpreted as dynamics. Therefore, we investigate herein whether the dynamics of gas diffusion is detected when using a 3He-NSF as second analyzer in a MIEZE spectrometer. Toward this end, we experimented with the MIEZE spectrometer installed at beamline 06 (BL06) at the Materials and Life Science Experimental Facility at Japan Proton Accelerator Research Complex (J-PARC MLF). The results confirm that the gas-diffusion dynamics of the 3He-NSF are not detected, and that the 3He-NSF, therefore, can be used as a second analyzer in this MIEZE spectrometer.

Current status of the neutron resonance spin echo spectrometer on BL06 “VIN ROSE” at MLF, J-PARC

Neutron spin echo technique is essential for high resolution inelastic and quasi-elastic neutron scattering experiments. We have developed a neutron resonance spin echo (NRSE) spectrometer at BL06 in Materials and Life Science Experimental Facility (MLF), Japan Proton Accelerator Research Complex (J-PARC), and installed a pair of 900 mm long ellipsoidal focusing m = 5 supermirrors with 2.5 m focal length. In this manuscript, we report the first result of time-of-flight neutron spin echo signals by the NRSE instrument.

Supermirror neutron guide system for neutron resonance spin echo spectrometers at a pulsed neutron source

ABSTRACTA neutron guide system for neutron resonance spin echo spectrometers has been constructed at BL06 of the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility. The spectrometers consist of two types of neutron spin echo instruments, a modulated intensity by zero effort instrument (MIEZE) and a neutron resonance spin echo instrument (NRSE), to cover a wide energy range for various sample environments. A neutron beam from the moderator is deflected by supermirror neutron guides, split, and separately guided into the MIEZE and NRSE. The characteristic wavelengths of the neutron guide tube for the MIEZE and NRSE are 2.9 and 4.9 Å, respectively. The cross sections of the exit of the MIEZE and NRSE guides are 15 mm × 50 mm and 30 mm × 50 mm, respectively. The neutronics and shielding design were optimized by using the heavy ion transport code system (PHITS), and the absolute average neutron fluxes at the exits of the MIEZE and NRSE guides are estimated to be 2.7 × 108 and 6.9 × 108 n/cm2/s/MW, respectively. The measured fluxes of the MIEZE and NRSE neutron guides are 0.56 and 0.95 times the calculated values, respectively.

Neutron spin echo spectroscopy under 17 T magnetic field at RESEDA

We report proof-of-principle measurements at the neutron resonance spin echo spectrometer RESEDA (MLZ) under large magnetic fields by means of Modulation of IntEnsity with Zero Effort (MIEZE). Our study demonstrates the feasibility of applying strong magnetic fields up to 17\,T at the sample while maintaining unchanged sub-$\mu$eV resolution. We find that the MIEZE-spin-echo resolution curve remains essentially unchanged as a function of magnetic field up to the highest fields available, promising access to high fields without need for additional fine-tuning of the instrument. This sets the stage for the experimental investigation of subtle field dependent phenomena, such as magnetic field-driven phase transitions in hard and soft condensed matter physics.

An open-source software package for data treatment in a MIEZE experiment

We present a newly-developed open-source software toolkit for handling and analysing the 4-dimensional datasets generated by modern multi-layer time-of-flight (TOF) position-sensitive detectors (PSD). Two such detectors of the type "Cascade" are in operation at the MIEZE beam line MIRA 2 and at the neutron resonance spin-echo spectrometer RESEDA at FRM II. The software consists of several modules for data analysis and instrument parameter calculations to assist the user during experiments, during simulations and in data evaluation. Specifically for the Cascade detector, it contains modules that correct phase-shifts in the MIEZE signal caused by the detector geometry and layout.

Neutron resonance spin flippers: static coils manufactured by electrical discharge machining.

Radiofrequency spin flippers (RFSF) are key elements of Neutron Resonance Spin Echo (NRSE) spectrometers, which allow performing controlled manipulations of the beam polarization. We report on the design and test of a new type of RFSF which originality lies in the new manufacturing technique for the static coil. The largely automated procedure ensures reproducible construction as well as an excellent homogeneity of the neutron magnetic resonance condition over the coil volume. Two salient features of this concept are the large neutron window and the closure of the coil by a μ-metal yoke which prevents field leakage outside of the coil volume. These properties are essential for working with large beams and enable new applications with coils tilted with respect to the beam axis such as neutron Larmor diffraction or the study of dispersive excitations by inelastic NRSE.

Concepts and Engineering Aspects of a Neutron Resonance Spin-Echo Spectrometer for the National Institute of Standards and Technology Center for Neutron Research.

Following a brief introduction, the Neutron Resonance Spin-Echo (NRSE) principle is discussed classically in Sec. 2. In Sec. 3, two idealized 4-coil NRSE spectrometers are discussed (one using single π-flipper coil units and one using paired “bootstrap” coils); some idealized (exact π-flip) expressions are given for the spin-echo signal and some theoretical limitations are discussed. A more quantum mechanical discussion of NRSE is presented in Sec. 4 and additional theory related to the spin-echo signal, including wavelength-dependence, is given is Sec. 5. Factors affecting the instrumental resolution are discussed in Sec. 6. In Sec. 7, a variety of engineering issues are assessed in the context of challenging performance goals for a NIST Center for Neutron Research (NCNR) NRSE spectrometer. In Sec. 8, some Monte Carlo simulations are presented that examine the combined influences of spectrometer imperfections on the NRSE signal. These are compared with analytical predictions developed in previous sections. In Sec. 9, possible alternatives for a NCNR NRSE spectrometer configuration are discussed together with a preliminary assessment of the spectrometer neutron guide requirements. A summary of some of the useful formulas is given in Appendix A.

Numerical simulation of BL06 neutron beamline for “VIN ROSE” at J-PARC/MLF

A new beam line for neutron resonance spin echo spectrometers is under construction at BL06 in the Materials and Life Science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). To design the radiation shielding in the setup for commissioning experiments we have performed the neutron beam transport calculation and dose evaluation via Monte Carlo method in the three-dimensional geometry. The radiation dose rates were kept below about 6 μSv/h outside of the thickness of 30 cm concrete shield surrounding the experimental area. We propose the conceptual design of radiation shielding of the beam line and simulation result playing an important role in determining engineering design and starting the construction.

Numerical Simulation of a Beam Divergence Correction for NRSE Spectrometer using Polygonal 2D-focusing Supermirrors

By inserting two-dimensional (2D) elliptical focusing mirrors between each pair of RSFs in neutron resonance spin echo spectrometer, the flight path lengths between the pair of RSFs can be made equal even for any divergent beam. We investigate numerically the feasibility of using polygonal 2D elliptical focusing mirrors as beam correction devices, and we show the relation of the energy resolution and the neutron intensity including effect of gravity.

The new polarizer devices at RESEDA

In the neutron resonance spin echo method the information about sample dynamics is encoded in the neutron beam polarization measured in the analyzer-detector unit. Thus, the method is not applicable for sample systems and environments, which depolarize the neutron beam strongly. To over come this draw back a neutron analyzer directly before the sample position may be installed to perform MIEZE-I experiments. We compared the performance of a transmission polarizer and a solid-state bender at this position for the neutron resonance spin echo spectrometer RESEDA by Monte Carlo simulations. It turned out, that the polarization as well as the intensity transmitted to the sample position is more advantageous for the transmission polarizer as for the bender. In addition, we present measurements of the polarization and intensity performance of the transmission polarizer already installed at RESEDA to polarize the neutron beam coming from the reactor FRM II. The measurements are in good agreement with Monte Carlo simulations.

High resolution NRSE spectrometer with 2D-focusing supermirrors

In the neutron resonance spin echo (NRSE) spectrometer [1] the divergent beam provides the deviation of the flight length, which makes the phase difference between neutron spin states and also decreases the contrast of the spin echo signals. The flight length can be adjusted by using parabolic focusing mirrors [11], which can be fabricated with replica technique. Correction for beam divergence effect in the NRSE spectrometer using 2D-focusing supermirrors will be discussed.

Shield evaluation of cold neutron curved guide tubes for J-PARC neutron resonance spin echo spectrometers

It is planned that three neutron resonance spin echo spectrometers will be installed in the No. 17 beam port of JSNS. In order to install these three spectrometers in one beam port, the neutron incident beam system to be installed in No. 17 port cannot only supply three polarized neutron beams to these spectrometers, but should also create very low background levels of neutron and gamma rays in the experimental area. We report based on shield evaluations how to realize the low background level by using two highly curved neutron guide tubes with high quality supermirrors.

Development of devices for beam divergence correction in the high-resolution NRSE spectrometer

Correction for beam divergence effect in the neutron resonance spin echo (NRSE) spectrometer will be discussed. The new type of devices called “coupling coils” is proposed to change the spin quantization axis for the correction. The feasibility of correction for the vertical divergence has been demonstrated by numerical calculations and Monte-Carlo simulations.

Correction for beam divergence effect in a NRSE spectrometer with high resolution

A correction for the beam divergence effect in a neutron resonance spin echo (NRSE) spectrometer will be discussed. The new type of device called ‘coupling coils’ is proposed to change the spin quantization axis for the correction. The feasibility of correction for the vertical divergence has been demonstrated by numerical calculations and Monte Carlo simulations.

RESEDA: double and multi-detector arms for neutron resonance spin echo spectrometers

RESEDA is the new cold neutron resonance spin echo (NRSE) spectrometer at the FRM II in Munich. In order to measure simultaneously at two different scattering vectors, RESEDA is equipped with two complete secondary spectrometer arms. Both the primary and the secondary spectrometer arms contain identical spin precession regions. Depending on the operation mode, they are alternatively defined by NRSE coils at both sides of 2.6 m long zero field regions or by additional NSE coils used at small spin echo times down to 1 ps. Larger spin echo times up to 10 ns are reachable by means of the bootstrap NRSE setup. Double- or multi-arm spin echo setups as built at RESEDA can only be realized with the NRSE technique, thanks to the compactness of the NRSE coils and the magnetic shielding. At RESEDA, the whole spectrometer is surrounded by double Mumetal shielding. Magnetic stray fields are suppressed very effectively and, consequently, the two secondary spectrometer arms are not interfering. We describe the design of the double-arm spectrometer RESEDA and we report on measurements using both secondary spectrometer arms. Furthermore, we present the design of a new multi-detector NRSE coil and, finally, we will give a brief outlook on the development of a multi-detector MIEZE setup planned at RESEDA.

RESEDA—The new resonance spin echo spectrometer using cold neutrons at the FRM-II

We have built a neutron resonance spin echo (NRSE) spectrometer with two secondary spectrometer arms, in order to double the solid angle of detectable neutrons. NRSE is well adapted for building up a multi-detector spectrometer, because it needs only compact magnetic coils. Compared to neutron spin echo (NSE), stray fields are much less important and can be suppressed completely by means of mumetal shielding. The second arms of the spectrometer are designed identically and allow for measuring at two different q-values simultaneously. By varying the radio frequency (RF) in the range 30–780 kHz, spin echo times up to 10 ns are achievable. Small spin echo times down to 1 ps are realized by means of additional NSE coils within the zero field regions. The instrumental resolution has been determined using a standard elastic scattering sample, and the function of the spectrometer is demonstrated by measuring diffusive dynamics in a protein solution.

Development of a resonance spin flipper for NRSE/MIEZE on a pulsed neutron beam with an oscillating frequency of 500 kHz

Currently, neutron resonance spin echo (NRSE) spectrometers are being applied to pulsed neutron sources at J-PARC. High-performance NRSE requires the development of a resonance neutron spin flipper (RSF) with high frequency. We have fabricated an RSF of pure aluminum having a frequency greater than 500 kHz and a wavelength from 0.30 to 0.75 nm.

Development of neutron resonance spin flipper for high resolution NRSE spectrometer

Neutron spin echo (NSE) is one of the techniques with the highest energy resolution for measurement of quasi-elastic scattering. In neutron resonance spin echo (NRSE), two separated neutron resonance spin flippers (RSFs) replace a homogeneous static magnetic field for spin precession in a conventional NSE. We have made a new type of RSF with pure aluminum wires in order to reduce the scattering from the surface. Test experiments have been performed at cold neutron beam line MINE1 at JRR-3M reactor in JAERI and the beam line CN3 at KUR The spin-flip probability was higher than 0.95 at a neutron wavelength of 0.81 nm and a RSF frequency of 100 kHz.