Proton beam dosimetry: A comparison between the Faraday cup and an ionization chamber

Abstract

From the theoretical point of view, the Faraday cup (FC) is an absolute instrument for fluence measurements of proton beams. As the FC is easily manufactured it can be considered an 'in-house' calibration system. Moreover, at the moment no national standards for proton dosimetry are available. Up to now the experimental tests of these instruments show that much study still has to be done to better understand their use in reference dosimetry. To investigate the possibility of using an FC as a secondary standard, an FC was jointly designed by the 'TERA Collaboration' and 'Centre Antoine-Lacassagne' (Nice, France) to evaluate the main parameters of the instrument. A comparison between two FCs of different designs--the 'TERA FC' and the 'Nice FC'--and an ionization chamber (IC) used for routine proton dosimetry was carried out. Results show that the two FCs agree to within 1.5-3.6%. While the differences between FC and IC are larger--6% for the 'TERA FC' and 8.2% for the 'Nice FC', the FC giving a lower dose evaluation--they follow the same trend shown by the calorimetric measurements. The data show that once the beam characteristics are defined, the fluence measurements are reproducible and show a good accuracy.

Design and Status of the ELIMED Beam Line for Laser-Driven Ion Beams

“…As one can see, a typical flat voltage response plateau in the negative voltage range between −2400 V and −400 V can be observed; on the other hand, for positive voltages a collected charge dependence increasing with the voltage applied is evident. The charge collection response observed in the FC prototype is in agreement with the typical behavior of standard FCs used for absolute dosimetry [22,28]. The analysis of the charge measurement data using the internal beveled electrode is still on going.…”

“…In order to fulfill all the requirements new detection devices and techniques must be designed and developed. The solution proposed to perform relative and absolute dose measurements implies different alternative approaches, as for instance SEM detectors [18], CR39 solid-state track detectors [19], Gafchromic films [20], transmission ionization chamber for high intense beams [21] and Faraday Cups (FC) [22]. Figure 1 shows a schematic layout of the ELIMED beam line where the elements composing the three different sections are clearly visible in their preliminary design.…”

“…The FC technical design has been inspired to similar detectors already developed for ion-beam dosimetry [22,28], adopting innovative geometrical solutions in order to further improve the overall charge collection efficiency [29].…”

Dose-controlled irradiation of cancer cells with laser-accelerated proton pulses

“…The latter can be replaced by several reference dosimeters such as a Faraday cup (FC, design adopted from Ref. [29]), radiochromic films (RCF), or CR39 solid state nuclear track detectors to determine the applied 2D dose and spectral energy distribution in the plane of the cell monolayer. For that purpose, an absolute calibration for RCF and FC detectors was carried out before performing the irradiation experiments with laser-accelerated protons for proton energies of 5-60 MeV at the eye tumor therapy centre of the Helmholtz Zentrum Berlin (HZB), Germany [28].…”

Standard Practice for Dosimetry of Proton Beams for use in Radiation Effects Testing of Electronics

“…Useful references on Faraday cup design are given in Refs. [4][5]. The FC requires a graphite or heavier metal beam absorber that is insulated from the ground container.…”