A scintillating fibre based beam profile monitor for ion therapy beams

• Applicant: Blake Dean Leverington, Ph.D.
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields ; Medical Physics, Biomedical Technology ; Measurement Systems
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 419255448

• Final Report Year: 2024

Final Report Abstract

This project developed a novel beam profile monitor based on plastic scintillating fibers, leveraging technologies from high-energy particle physics for precise beam diagnostics. The system utilizes scintillating fibers that fluoresce upon ionization, producing light signals which are converted into electrical data to reconstruct the beam’s position, shape, and intensity. Compared to traditional multi-wire proportional chambers (MWPCs), the fiber-based detector achieved faster response times, sub-millimeter precision (better than 0.2 mm for position and 0.4 mm for shape), and compatibility with a wide range of beam intensities. Key results demonstrated the successful development of lightweight, low-material fiber planes measuring 25 cm x 25 cm. These planes, designed to minimize beam disturbance, achieved a material budget of less than 0.3 mm water-equivalent thickness. The integration of mirror foils at one end of the fibers increased the optical signal by over 60%, ensuring a consistent signal-to-noise ratio across the length of the fiber. Radiation tests confirmed that green-emitting fibers maintained reliable performance for several months of operation under clinical beam intensities, requiring only routine calibration to correct for local non-uniformities. Further, the system demonstrated linear performance with beam intensity and delivered realtime beam reconstruction directly on the FPGA hardware. Simple algorithms for noise subtraction and moment calculations (mean and RMS) performed identically to offline reconstructions, meeting clinical specifications. However, FPGA limitations restricted the implementation of better performing, but more complex algorithms such as least-squares regression. The results validate fiber-based detectors as a robust and scalable solution for beam diagnostics. The system’s precision, speed, and modularity offer significant potential for applications in accelerator facilities, quality assurance procedures, and other advanced diagnostics requiring accurate beam monitoring.

Publications

• "A Scintillating Fiber-based Ion Beam Profile Monitor", HighRR Workshop: Vistas on Detector Physics 2022, Heidelberg, 12.09-14.09.2022
  Liqing Qin
  
• "The performance of scintillating fibre based beam profile monitor for ion therapy in magnetic field", DPG Spring Meeting "Heidelberg 2022", Heidelberg, 21.03- 25.03.2022
  Qian Yang, Liqing Qin & Blake Leverington
  
• "Towards Real-time Analysis for a Scintillating fiber-based Ion Beam Profile Monitor", DPG Spring Meeting "Heidelberg 2022", Heidelberg, 21.03-25.03.2022
  Liqing Qin
  
• "Towards Real-time Analysis for a Scintillating fiber-based Ion Beam Profile Monitor", HighRR Seminar, Heidelberg, 20.04.2022
  Liqing Qin
  
• “A Scintillating Fibre-based Beam Monitor for HIT – Part II”, HighRR Seminar, 4 May 2022,
  Qian Yang
  
• "Development of a Real-time Scintillating fiber-based Ion Beam Profile Monitor for HIT", DPG Spring Meeting "Dresden 2023", Dresden, 20.03-24.03.2023
  Liqing Qin
  
• "Development of a Real-time Scintillating fiber-based Ion Beam Profile Monitor for HIT", HGSFP Summer School 2023, Molveno, Italy, 11.06-17.06.2023,
  Liqing Qin
  
• "Scintillating fiber-based Ion Beam Profile Monitor for HIT",HighRR Seminar talk, Heidleberg, 20.03.2024
  Liqing Qin
  
• “The LHCb Scintillating Fibre Tracker U1 and U2 + The Ion-therapy Beam Profile Monitor”, GSI DT Detector Seminar
  Leverington, Blake D.