Development of the Diamond based Proton Beam Monitor for COMET Experiment
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2018-01-29 |
| Journal | Proceedings of The European Physical Society Conference on High Energy Physics â PoS(EPS-HEP2017) |
| Authors | Yuki Fujii |
| Institutions | High Energy Accelerator Research Organization |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Documentation and Material Recommendation: Diamond Based Proton Beam Monitors for High Energy Physics
Section titled âTechnical Documentation and Material Recommendation: Diamond Based Proton Beam Monitors for High Energy PhysicsâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes the application of Chemical Vapor Deposited (CVD) diamond as a high-flux, fast-response proton beam monitor in the COMET experiment, aligning the findings with 6CCVDâs specialized capabilities in Single Crystal Diamond (SCD) material fabrication.
- Core Application: Development of a high-speed, radiation-tolerant proton beam monitor to measure the extinction factor (< 10-9) necessary for the COMET experimentâs search for $\mu$-e conversion physics beyond the standard model (BSM).
- Material Choice: Single Crystal CVD Diamond (SCD) was selected due to its inherent high radiation tolerance [O(1012-13) Hz flux] and exceptionally fast charge collection properties, which are unattainable with standard silicon or scintillator detectors.
- Detector Architecture: A Metal-Insulator-Metal (MIM) prototype structure was used, featuring ultra low-mass components (SCD, Aluminum, Graphite) to minimize background radiation and heating.
- Measured Performance: The detector successfully discriminated single proton signals, demonstrating an ultra-fast rise time calculated to be ~5 ns, consistent with the requirement for resolving discrete residual proton bunches.
- Radiation Validation: The prototype successfully withstood high-intensity irradiation tests up to a total dose of O(1013-14) protons/diamond area, confirming its suitability for operation within the intensive J-PARC beam-line.
- 6CCVD Value Proposition: 6CCVD provides the necessary high-purity, custom-dimension SCD wafers (4 mm x 4 mm x 0.5 mm T) and advanced metalization services required to replicate and scale this crucial detector technology.
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters summarize the key performance requirements and measured outcomes of the SCD prototype detector for the COMET extinction monitor.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Sensitivity ($\mu$-e) | < 10-16 | Branching Ratio | 10,000x improvement over current limit |
| Required Extinction Factor | < 10-9 | Ratio | Residual protons between bunches |
| Detector Material | Single Crystal CVD Diamond | N/A | Chosen for high radiation tolerance |
| Detector Thickness | 0.5 | mm | Prototype physical dimension (4 mm x 4 mm) |
| Metal Contact Structure | MIM | Type | Metal-Insulator-Metal device architecture |
| Proton Beam Operational Tolerance | O(1012-13) | Hz | Required tolerance for continuous monitoring |
| Total Irradiated Dose (Test) | O(1013-14) | protons/diamond | High Intensity Irradiation Test |
| Measured Signal Rise Time | ~5 | ns | Time resolution for single proton discrimination |
| Observed Pulse Height (Min) | A few | mV | Consistent with expected single proton signal |
| Signal Observation Window | 500-1000 | ns | After main beam bunch, utilizing $\mu$ lifetime (~800 ns) |
| Beam Energy Used (Test) | 30 | GeV | Proton beam used for high-intensity tests |
Key Methodologies
Section titled âKey MethodologiesâThe experiment focused on validating the SCD detectorâs suitability as a high-speed, radiation-hard particle monitor by testing its performance under low-intensity (single proton) and extremely high-intensity irradiation conditions.
- Detector Assembly: A prototype detector was fabricated using Single Crystal CVD Diamond (4 mm x 4 mm, 0.5 mm T) with a 2 mm rounded metal contact, mounted onto an Aluminum contact plate and a Graphite base plate (acting as ground/support).
- Installation Location: The low-mass detector system was mounted on a linear insertion system inside the âabortâ beam-line of the J-PARC Main Ring (MR).
- Off-Axis Validation: Initial measurements used secondary particles generated from beam loss, positioning the detector 120 mm from the beam axis to confirm basic functionality and observe a shorter decay time than standard plastic scintillators.
- Low Intensity Measurement: Conducted in the Slow Extraction (SX) operation mode, which distributes a small number of protons continuously over ~5 ”s. A broadband RF amplifier (G = 40dB) was used to detect the faint O(1) mV single-proton signals.
- High Intensity Irradiation Test: The detector was subjected to > 200 shots of 30 GeV proton beam, totaling an O(1013-14) protons/diamond dose, specifically to estimate performance degradation before and after the irradiation campaign.
- Performance Analysis: Discrete pulses consistent with single proton detection were observed, confirming a critical rise time of ~5 ns necessary for temporal discrimination.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the advanced diamond materials and fabrication services required to replicate, upgrade, and scale the diamond-based particle detectors described in this research.
| Requirement/Observation in Paper | 6CCVD Solution & Capability |
|---|---|
| Material Purity and Speed | High-Purity Single Crystal Diamond (SCD): We supply electronic and optical grade SCD essential for maximizing charge carrier mobility and ensuring minimal defect density. This purity guarantees the ultra-fast time response (~5 ns) and high radiation tolerance required for extinction monitors. |
| Custom Dimensions and Thickness | Precision Fabrication: The prototype utilized a 4 mm x 4 mm size and 500 ”m thickness. 6CCVD offers SCD wafers from 0.1 ”m up to 500 ”m thickness and provides custom laser cutting and dicing services to meet any specific mechanical geometry for beam-line integration. |
| Metal-Insulator-Metal (MIM) Structure | Advanced Metalization Services: The implementation of custom contacts (2 mm rounded metal contact, Aluminum/Graphite backing) is a core 6CCVD capability. We offer in-house deposition of Ti, Au, Pt, Pd, W, and Cuâcritical for creating stable Schottky or Ohmic contacts necessary for Particle Detection (PD) CVD devices. |
| Surface Finish for Reliable Contacts | Ultra-Smooth Polishing: Ensuring stable detector performance relies on pristine surface quality. Our specialized polishing achieves Ra < 1 nm for SCD, optimizing the interface required for reliable metal contacts in MIM structures. |
| Scaling and Upgrades | Large Format Capability: While this project used a small SCD prototype, 6CCVD supports scaling efforts, offering PCD wafers up to 125 mm in diameter for future, larger-area detection systems or detector arrays. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers specializes in optimizing MPCVD diamond for extreme environments, particularly High Energy Physics (HEP) and Synchrotron applications. We provide technical consultation on selecting the appropriate diamond type (SCD vs. PCD), thickness optimization for maximum charge collection, and metalization schemes tailored to specific signal readout methodologies for high-flux monitoring projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We handle global shipping (DDU default, DDP available) for seamless delivery of critical components.
View Original Abstract
The COMET experiment searches for the muon-to-electron($\mu$-$e$) conversion with a sensitivity below $10^{-16}$ which is 10,000 times better than the present upper limit. This process is strictly forbidden in the standard model because of the lepton flavor conservation law. In contrast, its branching ratio can be sizable around $10^{-15}$ in many models of physics beyond the standard model (BSM). Therefore the discovery of the $\mu$-$e$ conversion should be unambiguous evidence of BSM. Since sufficient amount of muons can be collected owing to the world most powerful pulsed proton beam at J-PARC, the background suppression is the most important to achieve the target sensitivity. In COMET, the measurement will be done between 500-1000ns after coming the beam bunch to highly suppress the beam related prompt background. Even in this case, signals can be detected because of muonâs long life time ($\tau_{\mu}\sim800$ns) in a muonic-atom in case of using aluminum. In this scheme, the âextinction factorâ, ($\equiv$(#of residual protons between two bunches)/(#of protons in a bunch)), must be less than $10^{-9}$. To ensure such an extremely low extinction factor during the data taking, an innovative diamond detector will be adopted since it has high radiation tolerance to an intensive proton beam, and a fast time response to identify a single proton after the prompt beam. Recently, a prototype detector was developed based on a single-crystal diamond with a metal-insulator-metal type structure to perform the direct proton measurement inside the abort beam-line of J-PARC main ring. The installation was completed in this Spring and the direct beam measurement was conducted with the high intensity pulsed proton beam and the low intensity continuous beam. In this paper, results of above measurements are reported together with prospects.