Electron Spin Resonance Sensor for Portable and Adaptable Retrospective Dosimetry

The analytical precision and molecular specificity of electron spin resonance (ESR) spectroscopy make it a highly attractive technique for sensor applications, particularly in radiation dosimetry. However, its broader deployment has been hindered by substantial practical and experimental challenges. Traditional ESR systems require bulky electromagnets to sweep magnetic fields and high-Q resonators for signal detection, which restricts portability. Additionally, conventional ESR methods often demand prolonged data acquisition and extensive signal averaging to achieve adequate sensitivity, limiting their responsiveness in field-deployable scenarios. In this work, we overcome these limitations by introducing a compact and robust ESR sensor, marking a meaningful advancement toward practical, field-ready ESR-based dosimetry with broad applicability in medical physics, radiation protection, emergency response, and environmental monitoring. This new ESR sensor incorporates a versatile sample holder and a low-power magnet component, which is made possible by a broadband nonresonant interferometric detection technique. This paper discusses the instrumentation of this sensor, including the sample holder, magnet, and detector. There is also a detailed discussion of this approach, its advantages and limitations, and its potential applications for radiation dosimetry in various settings. This demonstrates the relevance of this setup to a wide range of retrospective dosimetry applications using alanine and lithium formate, the two most studied ESR dosimeters, at doses ranging from 2 Gy to 100 kGy. Demonstration of this broadband ESR detection using the nonresonant interferometric technique crystallizes its contribution to the advancement of portable magnetic resonance sensor technology.