A Highly Versatile X-ray and Electron Beam Diamond Dosimeter for Radiation Therapy and Protection

At a Glance

Metadata	Details
Publication Date	2023-01-14
Journal	Materials
Authors	Sara Pettinato, M. Girolami, A. Stravato, Valerio Serpente, Daniela Musio
Institutions	Azienda Ospedaliera San Giovanni Addolorata, Institute of Structure of Matter
Citations	23
Analysis	Full AI Review Included

Technical Documentation and Analysis: Versatile Diamond Dosimeter

This document analyzes the research paper “A Highly Versatile X-ray and Electron Beam Diamond Dosimeter for Radiation Therapy and Protection” and outlines how 6CCVD’s advanced MPCVD diamond materials and fabrication services can support, replicate, and extend this critical dosimetry research.

Executive Summary

Versatile Dosimetry Platform: The research successfully demonstrated a single-crystal CVD (SCD) diamond dosimeter capable of accurately measuring radiation dose and dose-rate across the full spectrum of clinical radiotherapy (RT) applications: low-energy X-rays, high-energy pulsed X-rays (EBRT), and high-energy pulsed electron beams (IORT).
Radiation Independence: The device achieved nearly identical sensitivity values for 6 MeV X-rays (0.299 ± 0.002 µC/Gy) and 6 MeV electrons (0.298 ± 0.004 µC/Gy), confirming its effectiveness as a tissue-equivalent transfer standard independent of radiation nature.
Exceptional Linearity: Excellent linearity (correlation coefficient R > 0.9999) was maintained across the entire tested dose and dose-rate range, crucial for accurate treatment planning and validation.
Ultra-Low Limit of Detection (LoD): An extremely low LoD of 23 nGy/s was achieved under low-energy X-rays, validating the device’s suitability for highly sensitive radiation protection dosimetry applications.
High-Speed Response: The dosimeter demonstrated a very fast response time (< 0.5 s rise/fall for continuous X-rays), with the intrinsic diamond response confirmed to be in the nanosecond range, ideal for tracking pulsed LINAC beams.
Material Basis: The device was fabricated using a high-quality, electronic-grade single-crystal CVD diamond sample in a Metal-Semiconductor-Metal (MSM) photoconductive configuration.

Technical Specifications

The following hard data points were extracted from the characterization results:

Parameter	Value	Unit	Context
Active Material	Electronic-Grade SCD	N/A	Single Crystal CVD Diamond
Dimensions (Active Medium)	4.5 x 4.5 x 0.5	mm³	SCD plate size
Contact Material	Ag (Silver)	N/A	300 nm thick, sputtered
Bias Voltage	10	V	Used for all characterizations
Sensitivity (6 MeV X-rays)	0.299 ± 0.002	µC/Gy	Measured in charge-mode, factoring phantom attenuation
Sensitivity (6 MeV Electrons)	0.298 ± 0.004	µC/Gy	Excellent agreement with X-ray sensitivity
Linearity Coefficient (High-E X-rays)	1.0003	∆	Near-perfect linearity (R = 0.99994)
Limit of Detection (LoD)	23	nGy/s	Low-energy X-rays, suitable for radiation protection
Sensitivity (Low-E X-rays)	1.988 ± 0.005	µC/Gy	Evaluated from linear fit (∆ = 1)
Response Time (Rise/Fall)	< 0.5	s	Measured under continuous low-energy X-rays
Active Volume	~4	mm³	Based on circular contact radius (1.6 mm)

Key Methodologies

The dosimeter fabrication and characterization relied on precise material preparation and controlled radiation sources:

Material Selection: An “electronic-grade” Single Crystal CVD (SCD) diamond sample (4.5 x 4.5 x 0.5 mm³) was chosen for its high purity and low impurity concentration (three orders of magnitude lower than natural diamond).
Surface Preparation: A rigorous cleaning procedure was implemented, including acid cleaning in a H₂SO₄:HClO₄:HNO₃ (1:1:1) mixture at boiling point, followed by an ultrasonic bath in hot acetone.
Contact Deposition: Two 300 nm thick Ag contacts were fabricated on the top and bottom surfaces via subsequent sputtering depositions, defining a Metal-Semiconductor-Metal (MSM) structure using a stainless-steel shadow mask.
Low-Energy X-ray Characterization: Continuous X-rays were generated by a Coolidge tube (Cu target) at 40 kV, with dose-rates ranging from 0.18 to 189 µGy/s. Measurements were taken using a Keithley 487 electrometer (10 V bias).
High-Energy Pulsed X-ray Characterization: Pulsed X-rays (6 MeV) were generated by a medical LINAC (Clinac iX). The dosimeter was placed at 5 cm depth in a water-equivalent Plexiglass® phantom to ensure electronic equilibrium.
High-Energy Pulsed Electron Characterization: Pulsed electron beams (6 MeV) were generated by removing the W target from the LINAC head. The dosimeter was placed at 3 cm depth in a Plexiglass® phantom.
Readout System: A dedicated front-end/readout electronics system was used for pulse-by-pulse measurement of the photocurrent signal during high-energy pulsed tests, operating in charge-mode for total dose collection.

6CCVD Solutions & Capabilities

The successful development of this highly versatile dosimeter hinges entirely on the availability of high-quality, electronic-grade SCD diamond and precise microfabrication techniques. 6CCVD is uniquely positioned to supply the necessary materials and services to replicate or advance this research for clinical and protection dosimetry.

Applicable Materials

To achieve the high sensitivity and radiation independence demonstrated in this paper, researchers require diamond with extremely low impurity concentrations.

Optical Grade Single Crystal Diamond (SCD): 6CCVD offers high-purity SCD plates that meet or exceed the “electronic-grade” requirements used in this study. Our SCD material ensures the high charge collection efficiency and minimal priming effects necessary for accurate, high-speed dosimetry.
Custom Thickness SCD: The paper utilized 500 µm thick SCD. 6CCVD provides SCD wafers ranging from 0.1 µm up to 500 µm, allowing engineers to optimize detector thickness for specific penetration depths or energy ranges (e.g., thinner detectors for enhanced spatial resolution or surface dosimetry).
Boron-Doped Diamond (BDD) for Specialized Applications: While this study focused on intrinsic SCD, 6CCVD also offers Boron-Doped Diamond (BDD) for applications requiring p-type conductivity or enhanced electrochemical stability, such as advanced water quality monitoring or specialized neutron detection.

Customization Potential

The fabrication of the MSM structure requires precise dimensioning and metal contact deposition, capabilities central to 6CCVD’s core offering.

Research Requirement	6CCVD Custom Capability	Value Proposition
Custom Dimensions	Plates/wafers up to 125 mm (PCD) and custom SCD sizes.	We can supply the exact 4.5 x 4.5 mm² plates used, or larger inch-size PCD wafers for array fabrication.
Metalization	Internal capability for Au, Pt, Pd, Ti, W, Cu deposition.	We offer custom metal stacks and geometry definition (e.g., circular pads, interdigitated electrodes) via sputtering or evaporation, ensuring optimal Schottky or ohmic contacts for MSM/MIS structures.
Surface Finish	Polishing to Ra < 1 nm (SCD) and Ra < 5 nm (PCD).	Ultra-smooth surfaces are critical for minimizing leakage current and maximizing charge collection efficiency in high-performance detectors.
Substrate Supply	SCD and PCD substrates up to 10 mm thick.	Ideal for mounting, heat sinking, or creating robust mechanical assemblies for clinical environments.

Engineering Support

6CCVD recognizes that successful implementation of diamond dosimeters requires deep material expertise.

In-House PhD Team: 6CCVD’s engineering team, composed of PhD-level material scientists, specializes in optimizing CVD diamond properties for radiation detection, high-power electronics, and quantum applications.
Application-Specific Consultation: We provide direct support for projects focused on Radiation Therapy Dosimetry and Radiation Protection, assisting researchers in selecting the optimal diamond grade, thickness, and metalization scheme to meet specific sensitivity (LoD) and linearity requirements.
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) to deliver sensitive materials directly to research facilities worldwide.

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

View Original Abstract

Radiotherapy is now recognized as a pillar in the fight against cancer. Two different types are currently used in clinical practice: (1) external beam radiotherapy, using high-energy X-rays or electron beams, both in the MeV-range, and (2) intraoperative radiotherapy, using low-energy X-rays (up to 50 keV) and MeV-range electron beams. Versatile detectors able to measure the radiation dose independently from the radiation nature and energy are therefore extremely appealing to medical physicists. In this work, a dosimeter based on a high-quality single-crystal synthetic diamond sample was designed, fabricated and characterized under low-energy X-rays, as well as under high-energy pulsed X-rays and electron beams, demonstrating excellent linearity with radiation dose and dose-rate. Detector sensitivity was measured to be 0.299 ± 0.002 µC/Gy under 6 MeV X-ray photons, and 0.298 ± 0.004 µC/Gy under 6 MeV electrons, highlighting that the response of the diamond dosimeter is independent of the radiation nature. Moreover, in the case of low-energy X-rays, an extremely low limit of detection (23 nGy/s) was evaluated, pointing out the suitability of the device to radiation protection dosimetry.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma16020824

References

2018 - Future directions of intraoperative radiation therapy: A brief review [Crossref]
2005 - Ion recombination correction for very high dose-per-pulse high-energy electron beams [Crossref]
2017 - Present state and issues in IORT physics [Crossref]
2011 - Volumetric modulated arc therapy: A review of current literature and clinical use in practice [Crossref]
2012 - Diamond detectors for UV and X-ray source imaging [Crossref]
2016 - Diamond device architectures for UV laser monitoring [Crossref]
2022 - Self-powered solar-blind ultrafast UV-C diamond detectors with asymmetric Schottky contacts [Crossref]