Development of a timing detector for the TOTEM experiment at the LHC
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-02-06 |
| Journal | Proceedings of 38th International Conference on High Energy Physics â PoS(ICHEP2016) |
| Authors | N. Minafra |
| Institutions | University of Kansas |
| Citations | 2 |
| Analysis | Full AI Review Included |
6CCVD Technical Analysis & Product Solution Brief:
Section titled â6CCVD Technical Analysis & Product Solution Brief:âHigh-Precision Single Crystal CVD Diamond Timing Detectors for High Energy Physics
Executive Summary
Section titled âExecutive SummaryâThis research details the successful development and implementation of high-precision timing detectors utilizing Single Crystal Diamond (SCD) grown via Chemical Vapor Deposition (CVD) for the TOTEM experiment upgrade at the Large Hadron Collider (LHC).
- Core Application: Reconstruction of longitudinal vertex position and suppression of event pile-up during high $\beta$* dedicated runs within the LHC/TOTEM experiment.
- Material Selection: Sensors rely exclusively on high-purity Single Crystal CVD (SCD) diamond due to its high carrier mobility and excellent radiation hardness required for high-rate timing applications.
- Key Performance Metrics: Individual prototype detectors achieved a time precision below 100 ps and a detection efficiency exceeding 99% for Minimum Ionizing Particles (MIPs).
- System Goal: The final system, utilizing four aligned detectors in the Roman Pots, is designed to reach a vertex precision below 50 ps.
- Custom Geometry: Each detector incorporates four 4.5 x 4.5 mm2 SCD crystals, highly segmented into 4-pixel, 2-pixel, and single-electrode configurations to optimize capacitance and time resolution.
- Readout Optimization: Achieved a critical Signal-to-Noise Ratio (SNR) greater than 20 by integrating low-noise front-end electronics and utilizing the SAMPIC chip (10 GSa/s sampling capability).
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters define the performance and design requirements of the TOTEM timing detectors:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target System Time Precision | Below 50 | ps | Achieved using 4 aligned SCD detectors |
| Individual Detector Time Precision | Below 100 | ps | Measured prototype performance |
| Detector Efficiency (MIPs) | Above 99 | % | Required efficiency for operational conditions |
| Single Crystal Size | 4.5 x 4.5 | mm2 | Dimensions of individual diamond crystals |
| Number of Crystals per Detector | 4 | N/A | Total crystals installed on one detector board |
| Signal-to-Noise Ratio (SNR) | > 20 | N/A | Required minimum ratio for MIP detection |
| Number of Channels | < 10 | N/A | Optimized maximum channel count per detector |
| SAMPIC Sampling Rate | 10 | GSa/s | Readout electronics capability (fast sampler) |
| Sensor Capacitance | Critical | N/A | Optimized by close placement of single transistor amplifier |
| Installation Distance (LHC) | ~ ±220 | m | Approximate distance from the interaction point |
Key Methodologies
Section titled âKey MethodologiesâThe development of the TOTEM timing detector focused on optimizing material selection, sensor geometry, and minimizing system capacitance to achieve picosecond resolution.
- Material Selection & Characterization: Conducted extensive beam tests on commercially available Single Crystal Diamond (SCD) to understand material performance limits and validate suitability for ultra-fast timing requirements.
- Geometry Optimization: Designed the detector shape (four 4.5 x 4.5 mm2 crystals) to guarantee uniform occupancy and align with the expected proton hit distribution in the Roman Pots.
- Custom Segmentation: Segmented the SCD crystals (4-pixel, 2-pixel, and single electrode configurations) to ensure that the region closest to the beam (highest hit rate) is covered by the smallest pads (lowest capacitance).
- Capacitance Management: Implemented a stringent low-capacitance design strategy, including placing a single transistor amplifier immediately adjacent to the active diamond area, minimizing contributions from bonding wires and PCB lines.
- Front-End Integration: Developed proprietary fast low-noise electronics specifically optimized for SCD sensor characteristics to achieve the required SNR of > 20.
- High-Speed Readout: Utilized the SAMPIC ASIC, a dedicated picosecond time sampler with high rate capabilities (up to 10 GSa/s acquisition rate), for fast digitization and analysis of the output signal.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the detector-grade materials and custom engineering services required to replicate, scale, or advance the work demonstrated by the TOTEM Collaboration. The precision and complexity of this application are perfectly matched to our core MPCVD diamond manufacturing and processing capabilities.
Applicable Materials
Section titled âApplicable MaterialsâTo meet the high timing resolution (sub-100 ps) and extreme operational demands of high-energy physics detectors, Optical/Detector Grade Single Crystal Diamond (SCD) is required.
| 6CCVD Material Solution | Specifications | Relevance to Application |
|---|---|---|
| Optical/Detector Grade SCD | High Purity (< 5 ppb N), Ultra-low defect density. | Essential for maximum charge collection efficiency and achieving fast signal rise times (critical for SNR and timing resolution $\sigma \approx \tau / SNR$). |
| SCD Thickness | Custom tailored from 0.1 ”m to 500 ”m. | Allows precise tuning of charge collection distance based on required bias voltage and noise constraints. |
| High-Purity PCD | Available up to 125 mm diameter wafers. | While SCD was used here, PCD is available for future large-area, cost-sensitive radiation monitoring or beam diagnostics applications requiring fast timing. |
Customization Potential
Section titled âCustomization PotentialâThe TOTEM detector relies heavily on custom dimensions, precise segmentation, and optimized electrical contactsâall of which are standard 6CCVD services.
- Precision Cutting & Sizing: 6CCVD provides custom laser cutting services to achieve the exact 4.5 x 4.5 mm2 dimensions used in the research, ensuring minimal chipping and clean edge definition required for reliable bonding. We can supply SCD wafers up to 10mm thick for substrate requirements.
- Pixel Segmentation & Geometry: We offer advanced laser etching and lithography services necessary to create the required 4-pixel and 2-pixel segmented electrodes and isolation trenches, guaranteeing optimal geometry control.
- Ultra-Low Roughness Polishing: Our internal polishing capability achieves surface roughness Ra < 1 nm on SCD. This ultra-flat surface is crucial for subsequent reliable metalization and bonding, minimizing parasitic capacitance contributions.
- Custom Metalization Stacks: The functionality of the electrodes is dependent on highly reliable, low-resistance ohmic contacts. We provide comprehensive in-house metalization services, including common stacks like Ti/Pt/Au or W/Au, deposited with high precision to customer specifications.
Engineering Support & Logistics
Section titled âEngineering Support & Logisticsâ6CCVDâs in-house PhD team can assist researchers and technical engineers with material selection, geometry optimization, and metalization design specifically for Minimum Ionizing Particle (MIP) timing, high-rate spectrometry, and radiation monitoring projects. Our global logistics network ensures prompt and reliable delivery (DDU default, DDP available) worldwide, supporting time-sensitive scientific schedules like those at CERN and other international accelerator facilities.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The upgrade program of the TOTEM experiment foresees the installation of timing detectors in- side vertical Roman Pots to allow the reconstruction of the longitudinal vertex position in presence of event pile-up in high ÎČ â dedicated runs. The small available space inside the Roman Pot and the required time precision led to the study of a solution using single crystal CVD diamonds. The sensors are read-out using fast low-noise front-end electronics developed by the TOTEM Col- laboration, achieving a signal-to-noise ratio larger than 20 for MIPs. A prototype was designed, manufactured and tested during a test beam campaign, proving a time precision below 100 ps and an efficiency above 99%. The geometry of the detector has been designed to guarantee a uniform occupancy in the expected run conditions keeping, at the same time, the number of channels be- low ten. In fact, each detector uses four diamond crystals of 4 . 5 Ă 4 . 5mm 2 : one is segmented in four pixels, another in two, while the remaining pair is metallized with a single electrode. The de- tectors are read-out using the SAMPIC chip, a fast sampler designed specifically for picosecond timing measurements with high rate capabilities. Four aligned detectors will be installed in each Roman Pot to achieve a final precision below 50 ps. The first set of prototypes was successfully installed and tested in the LHC in November 2015.