Demonstration of simultaneous experiments using thin crystal multiplexing at the Linac Coherent Light Source
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2015-04-09 |
| Journal | Journal of Synchrotron Radiation |
| Authors | Y. Feng, Roberto Alonso‐Mori, T.R.M. Barends, В. Д. Бланк, Sabine Botha |
| Institutions | Technological Institute for Superhard and Novel Carbon Materials, Max Planck Society |
| Citations | 21 |
| Analysis | Full AI Review Included |
6CCVD Technical Analysis & X-ray Optics Solutions
Section titled “6CCVD Technical Analysis & X-ray Optics Solutions”Diamond Thin-Crystal Multiplexing at LCLS
Section titled “Diamond Thin-Crystal Multiplexing at LCLS”This documentation analyzes the application of thin diamond single-crystals (SCD) as spectral beam splitters for high-brilliance hard X-ray Free-Electron Lasers (FELs), demonstrating superior performance for simultaneous scientific experiments under high thermal load.
Executive Summary
Section titled “Executive Summary”The research validates thin diamond single-crystals (SCD) as the material of choice for spectral division beam multiplexing in hard X-ray FELs (e.g., LCLS), offering significant improvements over traditional silicon optics in high-power applications.
- Core Achievement: Successful demonstration of simultaneous experiments (Serial Femtosecond Crystallography (SFX) and femtosecond time-resolved XANES) using a single FEL beam split by a thin SCD crystal (105 µm thickness).
- Material Superiority: Diamond (Type IIa) eliminated FEL-pulse-induced vibrations (thermal-acoustic shock waves) observed in thin Si membranes, owing to its high stiffness, high thermal conductivity, and low thermal expansion coefficient.
- Dimensional Requirement: The beam splitter utilized a near-perfect single-crystal diamond with a thickness of 105 µm, optimized for achieving high transmission (>50%) at 8 keV while maintaining sufficient diffraction quality.
- Performance Metrics: The resulting transmitted and reflected beams maintained high wavefront and coherence properties, with measured transmittance and reflectivity within 10% of theoretical calculated values, confirming excellent crystalline quality.
- Validation: Data quality for both simultaneous experiments (protein structure determination and spin dynamics measurement) was comparable to that obtained using dedicated, non-multiplexed beamlines.
Technical Specifications
Section titled “Technical Specifications”The following critical parameters highlight the operational requirements and material performance validated in the multiplexing setup:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Beam Splitter Material | Type IIa C* (111) SCD | N/A | High-purity single crystal diamond |
| Splitting Crystal Thickness | 105 (± 5% uniformity) | µm | Bragg geometry first crystal |
| Redirecting Crystal Thickness | 300 | µm | Second diamond crystal in DCM |
| Minimum Si Thickness for >50% T | 12 | µm | Required for Si at 8 keV, highly susceptible to vibration |
| Required Diamond Thickness for >50% T | 170 | µm | Maximum thickness for diamond at 8 keV |
| Operating X-ray Energy | 7.125 | keV | Fe K-edge (Hard X-ray) |
| Repetition Rate | 120 | Hz | Maximum operational frequency |
| Peak Incident Photon Flux | 1 x 1012 | per pulse | Estimated flux onto the splitting crystal |
| Observed Temperature Rise | 2 | K | Maximum steady-state rise on the 105 µm crystal |
| Static Strain Reduction (Diamond vs. Si) | >4 | Orders of magnitude | Due to stiffness/thickness |
| SFX Resolution Achieved | 2.3 | Å | Limited by 7.125 keV photon energy |
| XANES Spin Transition Time (τ) | 139 ± 6 | fs | Measured exponential rise time |
Key Methodologies
Section titled “Key Methodologies”The core of the successful multiplexing demonstration relies on stringent material specifications and precise mechanical mounting of the Single-Crystal Diamond (SCD) optics.
- Material Selection & Preparation:
- Material: High-quality Type IIa single-crystal diamond, orientation (111), grown via the temperature-gradient method (HPHT).
- Miscut: Crystal surfaces were intentionally miscut by 2° to facilitate high-precision polishing.
- Dimensional Control: Custom thicknesses of 105 µm (splitter) and 300 µm (redirector) were utilized, both polished to high uniformity.
- Mounting and Strain Mitigation:
- Crystals were mounted onto custom CVD diamond miniature frames.
- Held by CVD diamond fingers (clips) under optimal tension to minimize mechanical lattice strain and prevent “walking” of the reflections.
- Optical Configuration (Spectral Division):
- The 105 µm diamond functioned in the Bragg geometry as the first crystal in a large-offset Double-Crystal Monochromator (DCM).
- The reflected beam, which was monochromatic (narrow bandwidth, few spectral spikes), was used for time-resolved XANES (XPP instrument).
- The transmitted beam, which retained the broadband SASE spectrum but with a notch created by the Bragg reflection, was sent 200 m downstream for SFX (CXI instrument).
- Operational Performance Verification:
- Wavefront and coherence properties of both beams were measured to ensure preservation.
- Thermal stability was verified by IR camera, observing a small 2 K rise at maximum power (120 Hz repetition rate).
6CCVD Solutions & Capabilities: Enabling High-Brilliance X-ray Optics
Section titled “6CCVD Solutions & Capabilities: Enabling High-Brilliance X-ray Optics”This research confirms the essential role of highly controlled, thin, high-purity single-crystal diamond (SCD) for next-generation hard X-ray FEL beam delivery systems, where stability under extreme thermal load is paramount. 6CCVD is uniquely positioned to supply the diamond materials and fabrication expertise required to replicate, extend, or improve this spectral multiplexing technology.
Applicable Materials
Section titled “Applicable Materials”To meet the demanding specifications for LCLS/FEL optics, 6CCVD recommends:
- Optical Grade Single Crystal Diamond (SCD): Required for achieving the necessary “near-perfect” crystalline quality, Type IIa purity, and extremely low internal strain critical for diffraction efficiency.
- Custom Thickness SCD Wafers: The paper utilized 105 µm and 300 µm thicknesses. 6CCVD routinely supplies SCD material ranging from 0.1 µm up to 500 µm thickness, allowing researchers to tune the crystal thickness precisely for required transmission efficiency and energy range.
Precision Fabrication & Customization Potential
Section titled “Precision Fabrication & Customization Potential”The success of the experiment hinged on precise dimensions and extremely low strain mounting. 6CCVD addresses these needs directly:
| Requirement (Paper) | 6CCVD Capability | Value Proposition |
|---|---|---|
| Custom Dimensions | Plates/wafers up to 125 mm (PCD) and custom SCD sizes (e.g., 5 mm x 5 mm square pieces). | We provide the exact lateral dimensions needed for specialized holders and miniature frames (e.g., CVD diamond frames). |
| Thickness Control | SCD and PCD thickness control from 0.1 µm to 500 µm. | Critical for tuning transmission/reflectivity and optimizing crystal stiffness to avoid thermal-acoustic vibrations. |
| Surface Finish & Miscut | SCD polishing to Ra < 1 nm. Ability to control crystal orientation and polishing miscut. | Essential for minimizing wavefront distortion and achieving the required high diffraction quality and Bragg reflection performance. We can provide crystals with custom miscuts (e.g., the 2° miscut used here). |
| Metalization/Framing Interface | Metalization capability (Au, Pt, Pd, Ti, W, Cu). | While the paper used custom CVD frames, 6CCVD can assist in preparing the diamond surface (e.g., application of Ti/Pt layers) to improve adhesion or thermal contact required for subsequent mounting processes. |
| Substrate Options | Substrates up to 10 mm thick. | Ideal for use as high-stability, high-thermal-conductivity mounts or heat spreaders for related X-ray optics components. |
Engineering Support & Logistics
Section titled “Engineering Support & Logistics”6CCVD’s in-house PhD engineering team is available to assist research groups in material selection and optimization for similar complex X-ray optics projects:
- Thermal Management Analysis: Consultation on selecting the optimum diamond thickness and purity grade (e.g., Type IIa, high thermal conductivity) necessary for mitigating dynamic thermal effects in high-repetition rate FEL environments.
- High-Resolution Optics: Support in defining SCD specifications for applications requiring ultra-high coherence, extreme surface flatness, or low-strain single-crystal performance (as needed for crystallography and XPCS experiments).
- Global Project Fulfillment: We ensure reliable, secure global shipping (DDU default, DDP available) of sensitive, high-value diamond optics to major research facilities worldwide (e.g., LCLS, SACLA, European XFEL).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Multiplexing of the Linac Coherent Light Source beam was demonstrated for hard X-rays by spectral division using a near-perfect diamond thin-crystal monochromator operating in the Bragg geometry. The wavefront and coherence properties of both the reflected and transmitted beams were well preserved, thus allowing simultaneous measurements at two separate instruments. In this report, the structure determination of a prototypical protein was performed using serial femtosecond crystallography simultaneously with a femtosecond time-resolved XANES studies of photoexcited spin transition dynamics in an iron spin-crossover system. The results of both experiments using the multiplexed beams are similar to those obtained separately, using a dedicated beam, with no significant differences in quality.