Development of the LHCb VELO Detector Modules into a Standalone, Non-Invasive Online Beam Monitor for Medical Accelerators

Roland Schnuerer,Carsten Welsch,Olivier Girard,Tomasz Szumlak,Guido Haefeli,Hao Zhang,Tomasz Cybulski,Jacinta Yap,Tony Smith

doi:10.3390/instruments3010001

Abstract

Knowledge of the beam properties in proton therapy through beam monitoring is essential, ensuring an effective dose delivery to the patient. In clinical practice, currently used interceptive ionisation chambers require daily calibration and suffer from a slow response time. A new non-invasive method for dose online monitoring is under development based on the silicon multi-strip sensor LHCb VELO (VErtex LOcator), originally used for the LHCb experiment at CERN. The proposed method relies on proton beam halo measurements. Several changes in the system setup were necessary to operate the VELO module as a standalone system outside of the LHC environment and are described in this paper. A new cooling, venting and positioning system was designed. Several hardware and software changes realised a synchronised readout with a locally constructed Faraday Cup and the RF frequency of a medical cyclotron with quasi-online monitoring. The adapted VELO module will be integrated at the 60 MeV proton therapy beamline at the Clatterbridge Cancer Centre (CCC), UK and the capability as a beam monitor will be assessed by measuring the beam current and by monitoring the beam profile along the beamline in spring 2019.

Highlights

Cancer therapy, involving medical accelerators, has the potential to enhance healthcare benefits for patients
In contrast to the experiments in the LHC, in a clinical environment, the Vertex Locator (VELO) modules will be operated in air and the liquid CO2 cooling had to be replaced
Heat transfer simulations are performed in [16], leading to the selection of the high cooling capacity K3 chiller, Applied Thermal Control Ltd., Whitwick, UK, of 3200 W, which operates with low viscosity HYCOOL cooling liquid to achieve the required temperature

Summary

Introduction

Cancer therapy, involving medical accelerators, has the potential to enhance healthcare benefits for patients. Proton therapy shows significant advantages in the dose distribution profile, described by the Bragg peak, in comparison to radiotherapy with photons or electrons. Online beam monitoring is essential to ensure patient safety as well as a high quality and efficacious treatment. The energy, energy spread, current, position and lateral profile of the beam must be precisely determined and recorded. Ionisation chambers are the current practice in particle therapy to monitor the beam [1]. While such detectors are robust and easy to operate, they require daily calibration and their response time is slow, despite efforts to optimise material and readout time [2]. Developments are ongoing and, in [3], Instruments 2019, 3, 1; doi:10.3390/instruments3010001 www.mdpi.com/journal/instruments

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Conclusion