| 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 | University of Trieste, University of Saskatchewan |
| Citations | 1 |
| Analysis | Full AI Review Included |
- Core Achievement: First systematic characterization of the transient response of high-purity sCVD diamond sensors (DS) exposed to highly collimated, sub-picosecond (sub-ps), 1 GeV electron bunches.
- Key Finding (Non-linearity): A salient non-linearity in charge collection was observed. The sensors collected only ~3% of the theoretically expected charge (9.4 x 10-7 C expected vs. 2.4 x 10-7 C collected at 150 V bias).
- Underlying Mechanism: The non-linearity is caused by the Plasma Screening Effect. The extremely high density of generated charge carriers (~1017 cm-3) forms an internal electric field that cancels the external bias field, delaying carrier collection.
- Modeling Success: A two-step numerical simulation approach (TCAD-Sentaurus for physics, LTspice for circuit response) successfully modeled the observed signal features, including the transient voltage drop and secondary peaks.
- Circuit Effects: Secondary peaks in the signal were identified as electrical reflections caused by impedance mismatch between the diamond detector/HV power supply and the 50 Ω coaxial cables.
- Engineering Value: This data allows extrapolation of DS performance under extreme, ultra-fast radiation bursts, critical for optimizing beam loss monitoring and dosimetry in high-luminosity particle colliders.
| Parameter | Value | Unit | Context |
|---|
| Sensor Material | High-purity sCVD Diamond | N/A | Solid-state particle detector |
| Sensor Dimensions | 4.5 x 4.5 x 0.5 | mm3 | Crystal size |
| Electrode Material | Ti/Pt/Au | N/A | Layered structure (100+120+250 nm thickness) |
| Electron Bunch Energy | 1 | GeV | Nominal beam energy at FERMI linac |
| Bunch Duration | Sub-picosecond | N/A | Ultra-fast transient response test |
| Bunch Charge (Tested) | 35 | pC | Experimental test parameter |
| Transverse Beam Size (Tested) | ~120 | ”m | Collimated beam size |
| Bias Voltages (Vbias) | 50, 100, 150 | V | Experimental test range |
| Charge Carrier Density (Peak) | ~1017 | cm-3 | Density causing plasma screening effect |
| Expected Signal Charge (Theoretical) | 9.4 x 10-7 | C | Based on 5.9 x 1012 electron-hole pairs |
| Collected Charge (150 V Bias) | 2.4 x 10-7 | C | Experimental result |
| Charge Collection Efficiency | ~3 | % | Manifest non-linearity observed |
| Cable Impedance | 50 | Ω | Standard coaxial cable impedance |
- Sensor Fabrication: High-purity sCVD diamond crystals (Element Six) were metallized with 4.0 x 4.0 mm2 Ti/Pt/Au electrodes by CIVIDEC.
- Pre-Calibration: Diamond sensors were calibrated for stability and dose rate response using steady beta- and X-radiation, spanning 0.1-100 mGy/s, referencing a silicon diode.
- Beam Delivery: The FERMI electron linac provided collimated, sub-ps, 1 GeV electron bunches (35 pC charge) at a repetition rate of 10-50 Hz.
- Alignment and Positioning: A stepper motor controlled the mechanical support to perform a vertical beam scan, ensuring the beam was incident on the center of the DS. Beam parameters (position, size, charge) were monitored using a YAG screen and a beam current transformer.
- Data Acquisition: The DS electrodes were connected to an HV power supply and a LeCroy HDO9000 oscilloscope via 3-meter coaxial cables to measure the transient voltage response under 50 V, 100 V, and 150 V bias.
- Two-Step Numerical Modeling:
- Step 1 (TCAD-Sentaurus): Simulated the internal physics: beam interaction, electron-hole pair generation, charge carrier drift, and the evolution of the induced voltage drop, incorporating measured material parameters (mobility, saturation velocity).
- Step 2 (LTspice): Used the TCAD output (simulated voltage source and resistance) to model the full equivalent circuit, including the DS, coaxial cables, power supply, and oscilloscope, accounting for transmission effects and impedance mismatch.
- High-Energy Physics (HEP) Instrumentation: Essential for Beam Loss Monitors (BLMs) and radiation dosimeters in high-luminosity colliders (e.g., SuperKEKB, LHC upgrades) where extreme, transient radiation bursts must be accurately measured.
- Industrial and Medical Accelerators: Dosimetry and beam monitoring in facilities generating high-intensity, pulsed radiation fields, requiring detectors with excellent radiation hardness and fast response.
- Nuclear and Fusion Energy Research: Monitoring radiation levels and beam stability in environments characterized by high neutron and gamma fluxes, leveraging diamondâs wide bandgap and stability.
- Ultra-Fast Pulse Detection: Applications requiring the measurement of sub-nanosecond or picosecond transient electrical signals induced by particle interactions, utilizing diamondâs high charge carrier mobility.
- Radiation-Hard Electronics: Development of robust sensor systems for environments where conventional silicon-based detectors fail due to accumulated radiation damage.
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.