Calibration of diamond detectors for dosimetry in beam-loss monitoring

At a Glance

Metadata	Details
Publication Date	2021-04-27
Journal	Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
Authors	G. Bassi, L. Bosisio, P. Cristaudo, M. Dorigo, A. Gabrielli
Institutions	University of Trieste, Istituto Nazionale di Fisica Nucleare, Sezione di Trieste
Citations	15
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for High-Energy Physics Dosimetry

This document analyzes the research paper “Calibration of diamond detectors for dosimetry in beam-loss monitoring” (arXiv:2102.03273v2) to highlight 6CCVD’s capabilities in supplying high-performance MPCVD diamond materials for extreme radiation environments.

Executive Summary

The research successfully validates single-crystal CVD (sCVD) diamond sensors for high-stability dosimetry and beam-loss monitoring in the SuperKEKB collider, demonstrating performance critical for high-energy physics (HEP) applications.

Application: High-radiation dosimetry and beam-loss monitoring (BLM) requiring stability up to 10 Mrad integrated dose.
Material Performance: SCD sensors achieved near-unity Charge Collection Efficiency (CCE ~100%) at an optimal bias of |V| = 100 V.
Material Quality: Transient Current Technique (TCT) confirmed high material purity, yielding an average electron-hole pair ionization energy (Eeh) of ~13 eV.
Carrier Dynamics: Measured saturation drift velocities (Vsat) were 1.3 x 10⁷ cm/s for holes and 0.9 x 10⁷ cm/s for electrons.
Calibration Accuracy: Current-to-dose-rate calibration factors (k) were determined with a low total systematic uncertainty of 8%, validated across a wide dose range using beta, X-ray, and gamma sources.
6CCVD Relevance: 6CCVD specializes in supplying the required high-purity SCD material, custom dimensions, and precise Ti/Pt/Au metalization stacks necessary to replicate and advance this detector technology.

Technical Specifications

The following hard data points were extracted from the characterization of the sCVD diamond detectors:

Parameter	Value	Unit	Context
Detector Material Type	sCVD Diamond	N/A	Single Crystal Diamond
Detector Face Dimensions	4.5 x 4.5	mm²	Sensor size
Detector Thickness	0.50	mm	SCD active layer
Electrode Area	4.0 x 4.0	mm²	Metalized contact area
Metalization Stack (Ti/Pt/Au)	100/120/250	nm	Layer thickness for non-blocking electrodes
Optimal Operating Bias	100	V	Voltage for CCE close to 100%
Maximum Dark Current (at ±500 V)	< 10	pA	Post-assembly quality control
Average Ionization Energy (Eeh)	13.1	eV	Measured via TCT (Optimized setup)
Hole Saturation Velocity (Vsat)	1.3 x 10⁷	cm/s	Charge carrier transport property
Electron Saturation Velocity (Vsat)	0.9 x 10⁷	cm/s	Charge carrier transport property
Average Calibration Factor (k)	35	(mrad/s)/nA	Dose rate per measured current
Total Systematic Uncertainty	8	%	Uncertainty on calibration factor k
Integrated Dose Requirement	> 10	Mrad	Lifetime requirement for SuperKEKB

Key Methodologies

The following ordered steps outline the critical processes used for detector assembly, characterization, and calibration:

Material Specification: High-quality sCVD diamond plates (0.50 mm thick) were sourced, featuring precise lateral and thickness tolerances (±0.2/-0 mm and ±0.05 mm, respectively).
Electrode Deposition: A specific Ti/Pt/Au metal stack (100 nm Ti, 120 nm Pt, 250 nm Au) was deposited on both faces to create 4.0 x 4.0 mm² electrodes.
Packaging: Diamond sensors were mounted on a ceramic-like Rogers printed-circuit board (PCB) using conductive glue, with electrical connections established via ball-bonded gold wires and miniature coaxial cables.
Dark Current Screening: Detectors were screened by scanning bias voltage up to ±800 V in the dark, ensuring leakage current remained below 10 pA at ±500 V.
Charge Carrier Characterization (TCT): The Transient Current Technique was employed using a collimated ²⁴¹Am alpha source (5.485 MeV) to measure drift velocity, mobility, and average ionization energy (Eeh).
I-V Stability Measurement: Current-voltage profiles were measured under steady ⁹⁰Sr beta electron irradiation to identify the optimal operating bias (|V| = 100 V) and assess current stability and transient response.
Calibration Factor Determination: The current-to-dose-rate calibration factor (k) was derived by comparing the diamond detector current to a reference silicon diode current under identical ⁹⁰Sr irradiation conditions, leveraging detailed FLUKA simulations.
High Dose Validation: Calibration factors were cross-validated using X-ray (15 keV) and ⁶⁰Co gamma ray sources to confirm linear response across the full required dose-rate range (tens of nrad/s to rad/s).

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to support the replication and advancement of this high-performance diamond dosimetry research, offering custom materials and processing capabilities that meet or exceed the specifications detailed in the paper.

Applicable Materials

The research requires high-purity, radiation-hard SCD material.

Optical Grade Single Crystal Diamond (SCD): 6CCVD supplies high-purity SCD plates, essential for achieving the near-unity Charge Collection Efficiency (CCE) and low Eeh (~13 eV) demonstrated in this study. Our SCD material ensures the long-term stability required for integrated doses exceeding 10 Mrad.
Polycrystalline Diamond (PCD) Option: For applications requiring larger area coverage or lower cost per unit area, 6CCVD offers high-quality PCD plates up to 125 mm in diameter, suitable for less stringent radiation environments or large-scale monitoring arrays.

Customization Potential

6CCVD’s in-house manufacturing capabilities directly address the specific dimensional and metalization requirements of this project.

Requirement from Paper	6CCVD Capability	Technical Advantage
Dimensions (4.5 x 4.5 mm², 0.50 mm thick)	Custom Dimensions & Thickness: Plates/wafers up to 125 mm (PCD) and SCD thicknesses from 0.1 µm to 500 µm. Substrates up to 10 mm.	Allows for scaling or miniaturization of detectors for future Belle II upgrades (e.g., 2022 silicon vertex detector).
Metalization Stack (Ti/Pt/Au: 100/120/250 nm)	Custom Metalization: In-house deposition of Au, Pt, Pd, Ti, W, Cu.	Ensures precise control over layer thickness and adhesion, critical for stable, non-blocking electrodes and minimizing hysteresis effects observed in the I-V profiles.
Surface Quality (Critical for electrode interface)	Ultra-Low Roughness Polishing: Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD).	Guarantees optimal diamond-electrode interface quality, crucial for achieving high CCE and low dark current (< 10 pA).

Engineering Support

6CCVD’s technical team provides comprehensive support for complex detector projects:

Material Optimization: Our in-house PhD team can assist researchers in selecting the optimal diamond grade (SCD vs. PCD) and processing recipe (e.g., nitrogen incorporation, doping levels) for similar High-Energy Physics (HEP) Dosimetry and Beam-Loss Monitoring applications.
Processing Consultation: We offer expert consultation on metal stack design and deposition parameters to ensure stable current-voltage characteristics and radiation hardness, directly addressing the challenges of detector uniformity and stability reported in the paper.
Global Logistics: We provide reliable global shipping (DDU default, DDP available) to ensure timely delivery of critical components to international research facilities.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

Tech Support

Original Source

DOI: https://doi.org/10.1016/j.nima.2021.165383

References

1975 - Preparation and characteristics of natural diamond nuclear radiation detectors [Crossref]
1979 - Electrical properties and performances of natural diamond nuclear radiation detectors [Crossref]
1992 - Development of diamond radiation detectors for SSC and LHC [Crossref]
1968 - Growth of diamond deed crystals by vapor deposition [Crossref]
2019 - Evolution of diamond based microdosimetry [Crossref]
2018 - Toward the use of single crystal diamond based detector for ion-beam therapy microdosimetry [Crossref]
2005 - Radiation monitoring with CVD diamonds in babar [Crossref]
2006 - A diamond-based beam condition monitor for the CDF experiment
2008 - The ATLAS beam conditions monitor [Crossref]