Real-time electron spectrometer utilizing a permanent magnet and diode detector array.

Area of Science:

• Medical Physics
• Radiation Oncology
• Accelerator Engineering

Background:

• Existing magnetic spectrometers for therapeutic electron beams are often large, heavy, and lack real-time capabilities, limiting their clinical use.
• A need exists for a compact, lightweight, and cost-effective electron energy spectrometer with real-time readout for practical clinical application.

Purpose of the Study:

• To develop a practical, real-time electron energy spectrometer for therapeutic electron beams by integrating a commercial diode detector array with a permanent dipole magnet.

Main Methods:

• A 4 kg, 0.55 T permanent dipole magnet was coupled with a Sun Nuclear SRS MapCHECK diode array.
• The device was integrated into an Elekta electron applicator, using a 0.6 cm aperture to select the electron beam.
• The Lorentz force dispersed electrons onto diode arrays for measurement, with corrections for background dose, diode sensitivity, and array separation.
• Energy calibration was performed by correlating spectral peak positions with central-axis dose-depth data, and Monte Carlo simulations were used to extract energy spectra.

Main Results:

• The developed spectrometer is compact (4 kg) and capable of real-time measurements (≥1 Hz) with identical energy spectra obtained from 1-second and 15-second intervals.
• Background dose to electronics and detectors was minimal, allowing for extended operational use.
• Measurements from six accelerators revealed distinct spectral differences, highlighting the spectrometer's utility for beam tuning and quality assurance.

Conclusions:

• The integrated diode array and permanent magnet system successfully creates a compact, lightweight, and practical real-time electron energy spectrometer.
• This device offers accelerator engineers a valuable tool for improving electron beam tuning efficiency and effectiveness.
• It provides medical physicists with an efficient method for machine quality assurance in radiation oncology.