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A new Neutron Spin Echo Spectrometer on NG-A

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NSF

The University of Delaware, in collaboration with NIST, is developing a new neutron spin echo instrument at NIST.  It is funded by the Mid-scale Research Infrastructure program, one of NSF’s 10 Big Ideas.  The instrument is essentially a copy of the new J-NSE Phoenix instrument built by JCNS and located at the MLZ in Garching, Germany.

The new instrument employs optimally designed superconducting precession coils (OSCPCs), increasing the maximum Fourier time by 2.5x. It enables shorter wavelengths with significantly higher intensities and increases the data acquisition rate by roughly an order of magnitude for a given time window. Combining the new design with the increased flux provided by the future liquid deuterium cold source and several instrument elements optimized for long wavelength operation, we expect to achieve a Fourier time of 300 ns routinely, possibly reaching 700 ns for strongly scattered samples. The extended accessible time scale will expand the opportunities to study various material systems, especially in soft matter.

NG-A
Figure 1. a) The old NSE capable time and space domain is presented in orange, while the extended area shown in blue results from the upgrade project, with a possibility of reaching further to the dashed area for strongly scattered samples. b) The 2x flux gain by D2 cold source at longer wavelengths, λ > 7 Å, and the optimally designed superconducting precession coils increase the Fourier time corresponding to each routinely used wavelength.

The new main coils arrived at NIST in November of 2022 and passed inspection and site-acceptance tests. These tests aimed to ensure the superconductor coils work correctly at the below-critical temperature of ~9K for the superconducting material – NbTi. Installation of the cryo-compressors and warm zones for both OSCPCs was completed in July 2023, followed by the successful leak tests made by circulating water through the coils. The entire setup was put together at the final spot in August, and the floor was completed in December.

Primary OSCPC
Figure 2. The primary optimized superconducting precession coil (OSCPC) sitting on its stationary carriage is at the final spot. The installation of warm zones for both OSCPCs is completed. The Pythagoras coil (bottom left) is one of the correction elements of the warm zone inside the OSCPC. Each superconducting coil is cooled by two large cryocoolers (bottom middle), which are ready in place. The sample stage was installed on the epoxy, while aluminum panels were added on top of the epoxy floor for the secondary precession coil, analyzer, and detector (bottom right) to facilitate moving the coil for the scattered neutrons during operation.

Along with the main coils, several other critical components were fabricated by partner manufacturers, passed factory and site-acceptance tests, and have been delivered. These components include a neutron velocity selector (NVS) and its exchange table, a polarizer and its exchange station, an updated position-sensitive detector (PSD), warm zone components including Pythagoras coils and other correction coils mounted inside OSCPCs, new support structures, and an updated power supply system. While the new NVS and the single-V cavity polarizer are designed to work effectively with long neutron wavelengths, the old NVS, and the double-V cavity polarizer will be reused for shorter neutron wavelength applications. The new 3He PSD consists of an array of tube detectors with improved maximum count rate and sensitivity over long neutron wavelengths.

Neutron velocity selectors, control panel, correction coil, and polarizer station
Figure 3. The top left picture shows two neutron velocity selectors (NVSs) sitting on a newly fabricated exchange table, and their control panel is at the bottom left. The old NVS (smaller one) will be reused for short wavelengths, while the new NVS (bigger one) is designed for longer wavelengths. The top right picture is the state-of-the-art Pythagoras correction coil shown in Fig. 2 when mounted inside OSCPC. The bottom right is an exchangeable polarizer station, which hosts double-V (reused) and single-V cavity (new) polarizers for short and long wavelengths.

Apart from the platform for the sample area, the new NSE instrument is ready to perform hot commissioning when the shutter opens.

On September 18-21, 2023, we successfully organized the 2nd NSE workshop at the NIST Center for Neutron Research as part of our educational outreach for the NSE upgrade project. The workshop is funded by the NSF, which includes all local expenses. The Neutron Scattering Society of America (NSSA) sponsors three applicants selected by the organizers for their travel, up to $500/each. The NSF fully covers other participants. All lectures and tutorials were video-recorded and will be published on our 2023 NSE Workshop website for public access upon receiving NIST and instructors' approval.

Further information and updates on the project’s progress and the upcoming workshop can be found on the Center for Neutron Science website and social media on Twitter.

Created April 8, 2020, Updated January 26, 2024