Wide-angle diamond cell for neutron scattering
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-10-02 |
| Journal | High Pressure Research |
| Authors | Bianca Haberl, Sachith Dissanayake, Feng Ye, Luke L. Daemen, Yongqiang Cheng |
| Institutions | Carnegie Institution for Science, Geophysical Laboratory |
| Citations | 22 |
| Analysis | Full AI Review Included |
Wide-Angle High-Pressure Neutron Diamond Cell: 6CCVD Technical Analysis and Material Solutions
Section titled âWide-Angle High-Pressure Neutron Diamond Cell: 6CCVD Technical Analysis and Material SolutionsâExecutive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates a versatile, wide-aperture Diamond Anvil Cell (DAC) optimized for low-temperature, high-pressure neutron scattering experiments at major facilities (SNS, HFIR). 6CCVD analyzes the findings and offers high-purity CVD diamond solutions to eliminate current material limitations and significantly expand the pressure regime.
- High-Aperture Design: A novel DAC featuring steep conical angles achieved a large aperture (±60°), critical for maximizing scattered neutron capture.
- Pressure and Temperature: The system achieved pressures near 10 GPa (up to 9.6 GPa measured) and operated reliably down to cryogenic temperatures (5 K).
- Material Validation: SiC-sintered Polycrystalline Diamond (PCD, VersimaxÂź) anvils were validated for neutron transparency, achieving results comparable to Single Crystal Diamond (SCD) below 10 meV.
- Current Limitation Identified: The 20% SiC binder in the PCD anvils introduces parasitic scatter peaks (3C SiC peak at ~2.5 Ă ), limiting the useful d-spacing range for certain applications.
- Path to 20+ GPa: Researchers project a routine pressure regime up to 20 GPa with optimized culet scaling (2.5 mm culets) and explicitly note that future use of large CVD Single Crystal Diamond (SCD) anvils is the necessary step to expand the pressure range significantly beyond 20 GPa while eliminating binder background.
- 6CCVD Value Proposition: 6CCVD is positioned to supply the necessary large, high-purity MPCVD SCD anvils and custom-machined components to meet the stringent requirements for next-generation neutron scattering experiments.
Technical Specifications
Section titled âTechnical SpecificationsâThe table below summarizes the critical hard data extracted from the experimental results and design parameters of the neutron diamond cell.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Max Pressure Achieved (Measured) | 9.6 | GPa | 8 metric tons load (3 mm culets, NaCl standard) |
| Max Pressure Achieved (Extrapolated) | 20 | GPa | Projected capability with 2.5 mm culets |
| Minimum Temperature | 5 | K | Achieved using Closed Cycle Refrigerator (CCR) |
| Anvil Material Used | VersimaxÂź PCD | N/A | SiC-sintered PCD (80% Diamond, 20% SiC) |
| Anvil Dimensions (D x H) | 10 x 10 | mm | Custom size for large forces and aperture |
| Anvil Cone Angle (Included) | 60 | ° | Provides ±60° wide aperture |
| Clamping Mechanism Max Load | 10+ | Metric Tons | Elastic limit of custom simple disc spring |
| Gasket Material | 15-5 PH | N/A | Heat treated stainless steel, non-Co-sintered |
| Gasket Dimensions (Hole x Height) | 1.5 x 0.5 | mm | Used for initial pressure calibration |
| Minimum Sample Volume Required | 1.0 - 1.5 | mmÂł | Suitable volume for VISION INS detection |
| SiC Parasitic Peak Location | ~2.5 | Ă | (111) 3C SiC peak, limiting d-range |
| Relevant Neutron Energy (VISION) | 3.5 | meV | Energy range where PCD transmission matches SCD |
Key Methodologies
Section titled âKey MethodologiesâThe following ordered list outlines the critical steps and material specifications required to replicate or extend the development of the wide-angle neutron DAC.
- DAC Body Fabrication: The steel cylinder body was fabricated from Maraging Steel (C300) using conventional milling or wire-EDM to produce large, simple cut-outs for maximum aperture.
- Anvil Preparation: Polycrystalline diamond (PCD) anvils (10 mm diameter, 10 mm height, 60° included cone angle) were precision machined using simple EDM (possible due to the materialâs similar conductivity to Co-sintered PCD).
- Spring/Clamping Mechanism: Simple disc springs (30 mm diameter, 5 mm thickness) were employed to reliably clamp forces exceeding 10 metric tons in the fully elastic regime, ensuring pressure retention during offline pressurization.
- Gasket Machining: Gaskets were precision machined from 15-5 PH heat treated stainless steel to provide adequate material strength, minimize neutron absorption (avoiding TiZr or Co-containing alloys), and ensure accurate anvil alignment.
- Offline Pressurization: Pressure was applied in a hydraulic press via a pin pushing the top piston, and clamped by tightening the end cap; this method was necessary due to beamline space constraints precluding online membrane pressure control.
- Pressure Calibration: The pressure-load curve was established using NaCl as a pressure calibrant on the SNAP beamline by measuring the shift of the (200) NaCl peak.
- Data Collection and Background Reduction: Measurements were conducted in a âthrough-gasketâ geometry at low temperatures (5 K). Background noise was mitigated by masking the cell and anvils with Cadmium (Cd) and subtracting empty-cell measurements.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research validates the critical need for robust, high-purity diamond material to push neutron scattering beyond the 10 GPa regime while accommodating large-aperture geometries. 6CCVD, as an expert in MPCVD diamond, is uniquely positioned to supply the materials required for future high-pressure neutron experiments, specifically addressing the limitations found in SiC-sintered PCD.
Applicable Materials for Next-Generation DACs
Section titled âApplicable Materials for Next-Generation DACsâTo eliminate the parasitic scatter caused by the SiC binder and achieve the predicted >20 GPa range, researchers require large, high-quality Single Crystal Diamond.
| Material Requirement | 6CCVD Solution | Technical Advantage |
|---|---|---|
| High-Pressure Anvils | Optical Grade SCD | Eliminates 3C SiC parasitic peaks (d-range > ~2.0 Ă ). Superior compressive strength enables pressures significantly >20 GPa. |
| Anvil Substrates | SCD Substrates (up to 10 mm thick) | Provides the required 10 mm height and robust base necessary for high-load applications (10+ metric tons). |
| Large Aperture/Volume | Polycrystalline Diamond (PCD) | For applications where scatter is non-critical, 6CCVD can supply large wafers (up to 125 mm) for cost-effective PCD anvil manufacturing. |
| Pressure Transmitting Media Support | Boron-Doped Diamond (BDD) | Future designs requiring thermal/electrical management can utilize custom BDD materials. |
Customization Potential
Section titled âCustomization PotentialâThe success of the wide-angle cell relies heavily on the precise geometry and machining of the diamond components. 6CCVD offers in-house engineering and fabrication services that directly match the needs outlined in the paper:
- Precision Geometry: 6CCVD provides custom MPCVD growth and machining of SCD anvils (10 mm diameter, 10 mm height) with specified steep conical angles (60° included angle) and extreme geometric precision necessary to replicate or improve upon anvil alignment (a critical factor noted in initial SCD failures).
- Advanced Polishing: We guarantee SCD polishing with surface roughness Ra < 1 nm. Achieving this ultra-low roughness is crucial for high-load DACs to reduce stress concentrations and prevent premature failure referenced in the paperâs initial SCD trials.
- Custom Culet Machining: We can laser-cut or machine complex culet geometries, including dimples or recessions (e.g., the 1.5 mm diameter, 0.25 mm depth used here), to maximize sample volume while maintaining high pressure capability.
- Metalization Services: Although not primary to the anvils in this study, 6CCVD provides in-house metalization (Au, Pt, Ti, W, etc.) for integrated sensors, heaters, or contacts for future experiments requiring electrical leads on the diamond surface.
Engineering Support & Logistics
Section titled âEngineering Support & Logisticsâ6CCVDâs in-house PhD team can assist with material selection for similar high-pressure neutron scattering projects, ensuring optimal diamond purity, crystal orientation, and thickness for minimized background absorption and maximal mechanical stability. We support researchers globally with flexible shipping options (DDU default, DDP available) to facilitate seamless delivery to international neutron and synchrotron facilities (e.g., ORNL, J-Parc, ESS).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Here, a new diamond cell with extreme apertures is described. It is tailored for a large variety of neutron scattering techniques such as inelastic neutron scattering and single-crystal diffraction both at the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor at the Oak Ridge National Laboratory. Simple springs enable forces of over 10 metric tons to be clamped in for low-temperature measurements. At present, low-cost polycrystalline diamond (Versimax<sup>Âź</sup>) pressure anvils are used. We predict a routine pressure regime up to 20 GPa with sample volumes of ~0.5 mm3. Future use of large CVD single-crystal diamond anvils will significantly expand this pressure range. We show examples for measurements at the SNAP, VISION and CORELLI beamlines of the SNS.