Forward detectors and luminosity measurements
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-11-06 |
| Authors | G. Chiodini |
| Institutions | Istituto Nazionale di Fisica Nucleare, Sezione di Lecce |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation: CVD Diamond for HL-LHC Detectors
Section titled âTechnical Analysis and Documentation: CVD Diamond for HL-LHC DetectorsâSource Paper: Luminosity and Forward Detectors for LHC upgrades (G. Chiodini)
Executive Summary
Section titled âExecutive SummaryâThis paper outlines the critical role of CVD diamond in upgrading forward and luminosity detectors (LUCID, DBM, AFP) for the High Luminosity LHC (HL-LHC), driven by demands for extreme radiation hardness, high granularity, and unprecedented timing resolution.
- Radiation Hardness: Diamond (SCD/PCD) is the mandated replacement for conventional solid-state detectors (like Silicon) in high-rate, high-radiation zones, coping with doses up to 5x1015 p/cm2.
- Time Resolution Goal: Extensive R&D focuses on replacing Cherenkov-based timing systems (QUARTIC) with diamond detectors to achieve 10 ps time resolution for Minimum Ionizing Particles (MIPs).
- Existing Deployment: Polycrystalline CVD diamond (PCD) is currently utilized in the ATLAS Diamond Beam Monitor (DBM) due to its stability and lifetime durability in high-flux environments.
- Advanced Geometries: Achieving 10 ps requires innovative structures, including Multi-Layer-Crystal-Detectors (MLCD) using thin layers and specialized 3D diamond sensors (with graphitic electrodes) for ultra-fast charge collection.
- Engineering Challenge: Success hinges on integrating high-purity, custom-dimensioned diamond wafers with advanced, low-noise front-end electronics (CFD, HPTDC, Waveform Digitizers).
Technical Specifications
Section titled âTechnical SpecificationsâThe following table extracts key hard data points and performance requirements relevant to detector-grade CVD diamond materials.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Peak Radiation Dose (Hot Spot) | 5x1015 | p/cm2 | Required radiation tolerance for AFP forward detectors |
| Target Time Resolution (R&D) | 10 | ps | Goal for diamond timing detectors (QUARTIC replacement) |
| DBM Sensor Thickness | 500 | ”m | Polycrystalline diamond sensor thickness (18x21 mm2) |
| DBM Sensor Dimensions | 18x21 | mm2 | Active area of ATLAS Diamond Beam Monitor (PCD) |
| Corresponding Vertex Resolution | 2.1 | mm | Achieved by 10 ps time-of-flight measurement |
| MLCD Example Thickness | 250 | ”m | Layer thickness proposed for Multi-Layer-Crystal Detector |
| PMT Gain Reduction (LUCID Upgrade) | 106 â 105 | N/A | Reduction required due to aging and non-linearity in Cherenkov systems |
| Pixel Dimensions (Silicon Example) | 50x250 | ”m2 | Dimensions of 3D edge-less Silicon sensors (used for tracking) |
Key Methodologies
Section titled âKey MethodologiesâAchieving the required performance for HL-LHC operations necessitates specific material usage, processing techniques, and electronic integration recipes, particularly involving CVD diamond.
- PCD Integration for Tracking: Polycrystalline CVD diamond sensors (PCD) were fabricated at 500 ”m thickness and bump-bonded directly to custom readout chips (FEI4) to form pixel telescopes (DBM) capable of tracking in high pile-up conditions.
- Timing Measurement Chain: To achieve resolutions approaching 10 ps, detectors are integrated with specialized high-speed electronics, including:
- Low-noise RF voltage amplifiers (PreAmp).
- Custom Constant-Fraction Discriminators (CFD) for time walk correction.
- High-Precision TDCs (HPTDC) with 5 ps time dispersion per channel, or advanced 10 Gs/s Fast Waveform Digitizers (for offline correction).
- Innovative Geometries for Enhanced S/N and Speed: To improve the time resolution factor (Ît ~ trise / S/N), two primary diamond geometries are investigated:
- Multi-Layer-Crystal-Detector (MLCD): Stacking M layers of thin diamond sensors (e.g., 250 ”m thick) read out in parallel to boost the signal (S) by factor M without compromising collection time.
- 3D Diamond Sensors: Utilizing graphitic or metalized 3D electrodes to significantly reduce the charge collection path (collection time tc) while keeping the overall signal (S) proportional to the sensor thickness.
- Grazing Angle Configuration: Positioning several diamond layers parallel to the incident particle tracks to increase signal amplitude and collection efficiency.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe challenges outlined in the HL-LHC upgrade documentation directly align with 6CCVDâs expertise in high-purity, customizable CVD diamond manufacturing, positioning our products as essential for success in forward physics R&D and deployment.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate and extend the high-impact research described in this paper, 6CCVD offers two primary material solutions:
| Application / Requirement | Recommended 6CCVD Material | Key Advantage |
|---|---|---|
| Radiation Hardness & Long-Term Stability (DBM, BCM) | Detector Grade Polycrystalline Diamond (PCD) | Robust performance up to 5x1015 p/cm2 dose; cost-effective for large areas (up to 125mm). |
| Ultimate Timing Resolution (10 ps R&D, MLCD) | High Purity Single Crystal Diamond (SCD) | Highest carrier mobility, shortest signal rise time (trise), essential for achieving best S/N ratio and 10 ps goals. SCD Ra < 1 nm finish for superior surface quality. |
| Signal Boosting Geometries (3D Sensor R&D) | Custom Thickness SCD/PCD Layers | Precise thickness control from 0.1 ”m to 500 ”m, enabling the fabrication of thin layers required for MLCD stacks or optimal 3D sensor designs. |
| Graphitic Electrode Precursors | CVD Material Pre-Processing | Specialized doping or laser processing can be utilized to create precursors for the graphitic electrodes mentioned in 3D diamond sensor R&D. |
Customization Potential for HL-LHC Integration
Section titled âCustomization Potential for HL-LHC Integrationâ6CCVDâs in-house engineering and manufacturing services directly address the complex fabrication requirements of HL-LHC forward detectors:
- Custom Dimensions and Edge Finishing: The paper highlights the necessity of minimizing edge dead regions (down to 80 ”m for tracking). 6CCVD provides custom laser cutting and precise dicing services to fabricate PCD wafers (e.g., the 18x21 mm2 DBM size) with minimal edge clearance, maximizing active area acceptance.
- Multi-Layer Stack Fabrication: The MLCD concept requires multiple thin layers (e.g., 250 ”m). We guarantee tight thickness tolerance control necessary for stacking multiple SCD or PCD layers in parallel readout configurations.
- Custom Metalization Schemes: Successful operation of 3D diamond sensors and low-noise front-end electronics requires reliable contacts. 6CCVD offers internal metalization capability using materials critical for HEP applications, including: Ti/Pt/Au, W, and Cu. This is essential for robust bump bonding to specialized ASICs (like FEI4).
- Ultra-High Polishing: For detector-grade SCD utilized in high-performance timing applications, we provide polishing to an industry-leading surface roughness of Ra < 1 nm, critical for minimizing leakage current and ensuring uniform electrical contact across the detector face.
Engineering Support & Logistics
Section titled âEngineering Support & Logisticsâ6CCVDâs in-house PhD team can assist researchers and technical engineers with material selection, electrode design parameters, and optimal CVD growth specifications necessary for replicating or extending the forward detector and 4D pixel detector projects described. We ensure reliable global shipping, with DDU being the standard default, and DDP options available to simplify complex institutional deliveries worldwide.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
This paper discusses the challenge related to luminosity and forward physics measurements at ATLAS and CMS experiments after the scheduled LHC luminosity upgrades.The topics covered are not at all exhaustive of the subject but focus on activities where italian groups are involved.In addition, the author research interest in fast timing detector with tracking capability is the guiding principle of the report.Particular emphasis is given to the need of upgrading the existing detectors, in term of granularity and radiation resistance, and of pushing state-of-the-art technology to add fast timing to tracking information in the same device.Two Cherenkov based detectors for luminosity measurement (LUCID for ATLAS) and beam background monitoring (HBM for CMS) are briefly described as examples of systems placed far from the beams.Instead, near the beams, solid state devices, such as diamond detectors, are employed for luminosity measurements.In this respect, the evolution from particle counting mode to tracking mode configurations (DBM for ATLAS and PLT for CMS) is emblematic of the paradigmatic change of view needed to cope with high pile-up.The ambitious goal of forward detectors to take data in normal run condition, in order to accumulate statistics for precision EW coupling measurements and search for BSM heavy objects, is delineated.The need to develop new sensors and electronic chains to achieve very good time resolution is illustrated.The effort on diamond detectors capable to replace Cherenkov based timing detector for forward physics is clearly stated.The report concludes depicting one of the most promising new technology intended to face the challenge of a device with hundreds of micron space resolution and tens of ps time resolution: the Ultra Fast Silicon Detector (UFSD).