Characterization of the transient response of diamond sensors to collimated, sub-ps, 1 GeV electron bunches
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-11-01 |
| Journal | Proceedings of 41st International Conference on High Energy physics â PoS(ICHEP2022) |
| Authors | Y. Jin, S. Bassanese, Luciano Bosisio, G. Cautero, S. Di Mitri |
| Institutions | Elettra-Sincrotrone Trieste S.C.p.A., University of Saskatchewan |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Transient Response of MPCVD Diamond Sensors
Section titled âTechnical Documentation & Analysis: Transient Response of MPCVD Diamond SensorsâExecutive Summary
Section titled âExecutive SummaryâThis research successfully characterized the transient response of high-purity Single Crystal Diamond (SCD) sensors to ultra-fast, high-energy electron bunches, a critical requirement for advanced radiation dosimetry and beam monitoring in high-luminosity colliders (e.g., SuperKEKB) and Free Electron Lasers (FERMI).
- Core Application: Diamond sensors (DS) were tested as solid-state particle detectors and dosimeters in extreme, high-radiation environments.
- Material & Dimensions: High-purity sCVD diamond (4.5 x 4.5 x 0.5 mmÂł) with custom Ti/Pt/Au metalization was utilized.
- Extreme Conditions: Testing involved sub-picosecond, 1 GeV electron bunches with a high charge density (~1017 cm-3).
- Key Finding (Non-Linearity): A salient non-linearity was observed, where the collected charge was only ~3% of the expected value, regardless of the applied bias voltage (50 V to 150 V).
- Mechanism Identified: Numerical simulation (TCAD-Sentaurus) confirmed that the non-linearity is caused by the plasma effectâthe high density of generated electron-hole pairs creates an internal electric field that screens and cancels the external bias field, delaying charge collection.
- 6CCVD Value Proposition: 6CCVD provides the high-purity SCD material and precision metalization required to replicate and advance this research, offering superior material quality and customization for next-generation high-flux detectors.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental setup and results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Material | High-purity sCVD | N/A | Single Crystal Diamond (SCD) |
| Sensor Dimensions | 4.5 x 4.5 x 0.5 | mmÂł | Crystal size |
| Electrode Area | 4.0 x 4.0 | mmÂČ | Active detection area |
| Metalization Stack | Ti/Pt/Au (100+120+250) | nm | Total thickness 470 nm |
| Electron Energy | 1 | GeV | Nominal test energy |
| Bunch Duration | Sub-picosecond | s | Ultra-fast transient pulse |
| Bunch Charge (Test) | 35 | pC | Used for non-linearity measurement |
| Transverse Beam Size | ~120 | ”m | Highly collimated beam |
| Bias Voltages (Vbias) | 50, 100, 150 | V | Applied during measurement |
| Circuit Impedance | 50 | Ω | Coaxial cable and oscilloscope matching |
| Peak Charge Carrier Density | ~1017 | cm-3 | Density causing plasma screening effect |
| Charge Collection Efficiency | ~3 | % | Observed efficiency at 150 V bias |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized a highly specialized setup combining advanced beam facilities, precision diamond fabrication, and comprehensive numerical modeling.
- Material Preparation: High-purity sCVD diamond crystals (4.5 x 4.5 x 0.5 mmÂł) were fabricated with two opposing electrodes consisting of a custom Ti/Pt/Au metalization stack (470 nm total thickness).
- Beam Source: The FERMI Free Electron Laser (FEL) facility provided highly collimated electron bunches with sub-picosecond duration, 1 GeV energy, and tunable charge (tens to hundreds of pC).
- Electrical Setup: The diamond sensor (DS) was installed in a vacuum chamber and connected via 3-meter coaxial cables to an HV power supply and a LeCroy HDO9000 oscilloscope (50 Ω impedance).
- Data Acquisition: The transient voltage response was measured under three bias conditions (50 V, 100 V, 150 V) using 35 pC electron bunches.
- Two-Step Simulation:
- TCAD-Sentaurus: Used to simulate the physical processes within the diamond bulk, including beam interaction, electron-hole pair liberation, charge carrier drift, and the evolution of the induced voltage drop, specifically modeling the high-density plasma effect.
- LTspice: Used to model the external equivalent circuit, incorporating the simulated voltage drop, resistance, capacitance, and transmission effects (reflection, attenuation) of the coaxial cables and external components.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the high-purity diamond materials and custom fabrication services necessary to replicate, optimize, and scale the detectors used in this high-energy physics research.
| Applicable Materials | 6CCVD Specification | Relevance to Research |
|---|---|---|
| Optical Grade Single Crystal Diamond (SCD) | SCD plates up to 500 ”m thick, Ra < 1 nm polishing. | Directly matches the high-purity sCVD requirement for maximum charge carrier mobility and lifetime, essential for minimizing the plasma effect and maximizing signal speed. |
| Custom Metalization Stacks | In-house deposition of Au, Pt, Pd, Ti, W, Cu. | We can precisely replicate or optimize the required Ti/Pt/Au electrode stack (100/120/250 nm) for superior adhesion and contact quality, ensuring reliable signal extraction. |
| Large-Area Polycrystalline Diamond (PCD) | PCD wafers up to 125 mm diameter, polished to Ra < 5 nm. | For scaling up beam loss monitors or dosimetry systems beyond the small 4.5 mm size, 6CCVD offers large-area PCD with excellent uniformity and surface finish. |
| Custom Dimensions & Thickness | SCD thickness control from 0.1 ”m to 500 ”m. | We provide custom laser cutting and precise thickness control, allowing researchers to test different detector geometries (e.g., thinner detectors to reduce charge density and mitigate the plasma effect). |
Customization Potential
Section titled âCustomization PotentialâThe research highlights the need for precise material and geometric control to manage high-flux effects. 6CCVD offers the following services to extend this work:
- Optimized Metalization: We provide custom electrode patterns and materials (e.g., alternative stacks for improved ohmic contact stability under high bias) tailored for high-voltage, high-frequency operation.
- Surface Engineering: Our SCD polishing capability (Ra < 1 nm) ensures minimal surface defects, which is crucial for maximizing charge collection efficiency and reducing noise in high-speed applications.
- BDD for Reference: For applications requiring stable, conductive reference layers or active components, 6CCVD supplies Boron-Doped Diamond (BDD) films.
Engineering Support
Section titled âEngineering SupportâThe observed non-linearity due to the plasma effect requires sophisticated material selection. 6CCVDâs in-house PhD team can assist with material selection for similar High-Flux Dosimetry and Beam Monitoring projects by:
- Consulting on optimal SCD growth parameters (e.g., nitrogen concentration) to tailor charge carrier lifetime and mobility.
- Providing material characterization data (e.g., defect density, resistivity) to feed into TCAD simulation models, improving the accuracy of non-linear response prediction.
- Advising on detector geometry (thickness and area) to manage the internal electric field screening effect.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. Global shipping (DDU default, DDP available) is standard for all orders.
View Original Abstract
Diamond sensors (DS) are widely used as solid-state particle detectors, beam loss monitors, and dosimeters in high-radiation environments, e.g., particle colliders. We have calibrated our DS with steady $\beta$- and X-radiation, spanning a dose rate in the range 0.1-100 mGy/s. Here, we report the first systematic characterization of transient responses of DS to collimated, sub-picosecond, 1 GeV electron bunches. These bunches, possessing a charge ranging from tens to hundreds of pC and a size from tens of microns to millimeters, are suitably provided by the FERMI electron linac in Trieste, Italy. The high density of charge carriers generated by ionization in the diamond bulk causes a transient modification of electrical properties of DS (e.g., resistance), which in turn affects the signal shape. We have modeled a two-step numerical approach, simulating the effects on the signal of both the evolution of charge carrier density in the diamond bulk and the changes in the circuit parameters. This approach interprets features observed in our experimental results to a great extent.