Спектральные и амплитудно-временные характеристики излучения Черенкова при возбуждении прозрачных материалов пучком электронов
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | Оптика и спектроскопия |
| Authors | В. Ф. Тарасенко, Е. Х. Бакшт, М. В. Ерофеев, А. Г. Бураченко |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: MPCVD Diamond for Cherenkov Detectors
Section titled “Technical Documentation & Analysis: MPCVD Diamond for Cherenkov Detectors”Reference: Spectral and amplitude-time characteristics of Cherenkov radiation when exciting transparent materials with an electron beam. (Optics and Spectroscopy, 2021, Vol. 129, Issue 5)
Executive Summary
Section titled “Executive Summary”This research confirms the critical role of high-purity synthetic diamond as the optimal radiator material for Vavilov-Cherenkov Radiation (CR) detectors, particularly those designed to monitor high-energy Runaway Electrons (REs) in extreme environments like TOKAMAK reactors.
- Material Superiority: Single Crystal Diamond (SCD) is validated due to its low Cherenkov threshold energy (Eth = 50 keV), high refractive index (n = 2.42), and exceptional radiation hardness.
- CR Signal Confirmation: CR was successfully registered in high-purity synthetic CVD diamond (C5, C6) in the critical Ultraviolet (UV) range (250-400 nm), where CR intensity is maximized.
- Time Resolution Requirement: The primary technical challenge is isolating the fast CR signal (sub-nanosecond) from competing, slower background signals like Cathodoluminescence (CL) and Exciton Luminescence (decay time ~10 ns).
- Purity is Paramount: Maximizing the CR signal relative to background noise requires diamond materials with extremely low intrinsic defect concentrations (e.g., Type IIa equivalent) to minimize CL in the visible/UV spectrum.
- 6CCVD Value Proposition: 6CCVD specializes in delivering custom, high-purity MPCVD SCD and PCD wafers with superior surface quality (Ra < 1nm) and precise dimensions, meeting the stringent requirements for advanced, time-resolved CR detection systems.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the research, highlighting the material requirements for effective Cherenkov radiation detection:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Cherenkov Threshold Energy (Eth) | 50 | keV | Required minimum energy for CR in Diamond (n=2.42) |
| Refractive Index (nD) | 2.42 | - | Diamond (High index favors low Eth and high CR angle) |
| CR Wavelength Range (Diamond) | 250 - 400 | nm | Region where CR intensity is maximized (UV/Blue) |
| Exciton Luminescence Peak | 235 | nm | Competing signal in diamond (requires filtering/fast timing) |
| Exciton Luminescence Decay Time | ~10 | ns | Slower background signal in diamond |
| CR Time Resolution Potential | 10-12 - 10-11 | s | Theoretical limit of the Cherenkov effect (ultra-fast response) |
| Electron Beam Energy Range | 40 - 6 | keV - MeV | Range tested across various accelerators |
| Electron Beam Pulse Duration (T0.5) | 0.1 - 12 | ns | Sub-nanosecond pulses used for time-resolved CR measurements |
| Quartz Glass (KU-1) Eth | 190 | keV | Significantly higher threshold than diamond (n=1.46) |
Key Methodologies
Section titled “Key Methodologies”The experimental approach focused on generating high-flux, short-pulse electron beams and measuring the resulting light emission (CR and CL) with high spectral and temporal resolution.
- Electron Beam Generation: Utilized a suite of sub-nanosecond and nanosecond pulsed accelerators (e.g., GIN-55-01, SLEP-150M, GIN-600, RADAN-220) to excite samples with electron energies ranging from tens to hundreds of keV (up to 420 keV) and up to 6 MeV (Microtron).
- Sample Geometry and Excitation: Samples (plates/wafers) were positioned perpendicular or at specific angles (e.g., 4 = 70° for quartz) relative to the electron beam path to optimize the extraction of the directional Cherenkov cone into the detector.
- Spectral Analysis: Light emission spectra (dE/dλ) were measured using fiber-optic spectrometers (HR2000+ ES, AvaSpec-3648) covering the 190-1100 nm range, allowing for the differentiation of broadband CR from narrow-band CL peaks.
- Time-Resolved Analysis: Ultra-fast photodetectors (Photek PD025, rise time ~80 ps) coupled with high-bandwidth oscilloscopes (Agilent DSO-X6004A, 6 GHz) were used to measure the amplitude-time characteristics, confirming the sub-nanosecond nature of the CR signal.
- Background Suppression: Optical filters (UFS-1) were employed to selectively transmit the UV CR signal (240-400 nm) while suppressing the slower, longer-wavelength CL and exciton luminescence background.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The research highlights that the success of Cherenkov detectors hinges on the quality, purity, and geometry of the diamond radiator. 6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials required to replicate and extend this critical research.
Applicable Materials
Section titled “Applicable Materials”To achieve the low CL background and high UV transparency necessary for effective CR detection, the following 6CCVD materials are recommended:
- Optical Grade Single Crystal Diamond (SCD): Required to replicate the high-purity synthetic diamond (C5, C6) used in the study. Our SCD is grown with extremely low nitrogen incorporation, ensuring minimal CL defects (like the 3H or N3V centers mentioned) and maximum transparency down to the 225 nm band edge.
- High-Purity Polycrystalline Diamond (PCD): For applications requiring larger radiator areas (e.g., inch-size wafers for large-area beam diagnostics), our high-purity PCD offers excellent UV transparency and radiation hardness, providing a cost-effective alternative to SCD for certain detector geometries.
Customization Potential
Section titled “Customization Potential”The study emphasizes the need for specific sample geometries and the potential use of metalization for contacts or reflective coatings. 6CCVD offers comprehensive customization capabilities:
| Research Requirement | 6CCVD Capability | Technical Advantage |
|---|---|---|
| Custom Dimensions | Plates/wafers available up to 125mm (PCD) and large-area SCD. | Supports large-area beam diagnostics (e.g., TOKAMAK RE monitoring). |
| Thickness Control | SCD and PCD thickness controlled from 0.1µm to 500µm. | Allows precise tuning of electron stopping power and CR generation volume. |
| Surface Quality | Polishing to Ra < 1nm (SCD) and Ra < 5nm (PCD). | Essential for maximizing directional CR light extraction and minimizing scattering losses. |
| Electrode Integration | Internal capability for custom Metalization (Au, Pt, Pd, Ti, W, Cu). | Enables integration of electrodes for bias voltage or specialized optical coatings for enhanced UV reflection/filtering. |
| Substrate Options | Custom diamond substrates up to 10mm thick. | Provides robust mechanical support for high-energy beam experiments (e.g., 6 MeV Microtron tests). |
Engineering Support
Section titled “Engineering Support”The successful separation of CR from CL/Exciton signals relies heavily on precise material selection and understanding defect physics.
- Defect Engineering: 6CCVD’s in-house PhD team can assist researchers in selecting materials with specific defect profiles (e.g., minimizing N3V centers) to ensure the lowest possible Cathodoluminescence background in the 350-650 nm range, crucial for maximizing the signal-to-noise ratio in Cherenkov Detector projects.
- Time-Resolved Optimization: We provide consultation on material properties relevant to ultra-fast response times, ensuring the SCD/PCD radiator is optimized for sub-nanosecond pulse detection, matching the requirements demonstrated in the paper (e.g., using PD025 detectors).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Interest in the study of the characteristics of the Vavilov-Cherenkov (VCR) radiation has increased in connection with the work on the creation of runaway electron (RE) detectors for TOKAMAK-type installations. This review presents the results of studies of the spectral, amplitude-temporal, and spatial characteristics of VCR, obtained mainly in recent years when transparent substances are excited by an electron flux with energies of tens to hundreds of keV. The VCR spectra in diamond (natural and synthetic), quartz glass, sapphire, leucosapphire are given, and the VCR registration in MgF2, Ga2O3 and other transparent samples is reported. A comparison of the spectra and amplitude-time characteristics of the VCR and pulsed cathodoluminescence (PCL) at various electron energies is carried out. For a number of samples, the VCR spectra were calculated taking into account the dispersion of the refractive index, as well as the energy distribution of the beam electrons and the decrease in the electron energy during their deceleration in the sample material. The emission spectrum of polymethyl methacrylate (PMMA), which is used as a material for radiators in Cherenkov detectors and optical fibers transmitting radiation in scintillation dosimeters, as well as a plastic base in organic scintillators, has been investigated.