Ce- and B-Doped Silica Fibers for Monitoring Low-Energy Proton Beams on a Medical Cyclotron

Abstract

<jats:p>Many medical isotopes can be produced on a small cyclotron. The alignment and profiles of low-energy proton beams from cyclotrons used for medical radioisotope production, such as the TR13 cyclotron at TRIUMF, Canada, cannot be directly quantified during dose delivery with simultaneous constant feedback and sharp spatial resolutions. Doped silica fibers are a potential solution that has been tested at TRIUMF. To measure the effects of irradiation inside an isotope production target, we attached fibers to the outside of an 18O gas target and measured the light output during irradiation. Different dopants, fiber diameters, and target materials were investigated. It was found that 200 µm diameter Ce- and B-doped fibers produce signals linearly proportional to the beam current. This only deviated when the target was moved such that the beam was steered into the target wall, increasing the production of prompt radiation and causing the beam current to decrease but the fiber signal to increase. With the technique described here, the beam can be monitored on the target, including its steering and its overall alignment with the target.</jats:p>

Optical fibre array detector to monitor irradiations for medical radioisotope production

“…at 200 s),, albeit not as strongly as in the top-bottom direction. This is most likely because the extraction at 13 MeV is at the lower energy limit and the proton beam is already curved in this direction when entering the target [5]. We suspect the beam is curved to the right so an increase in the right collimator current decreases target pressure more than any other direction.…”

“…The ideal monitor would be able to measure the beam shape, alignment and current during the irradiation in more than one position along the beam axis without disrupting the production. In a previous study, we demonstrated that one fibre placed on the outside of the target body can measure the beam current in a linear relationship as well as indications about the beam alignment, via the beam induced ionization and excitation of secondary radiation (mainly photons and neutrons) and subsequent photon formation [5]. Here, we present a prototype of our Target Fibre Monitor (TFM) with four fibres mounted on the outside of a gas target for the production of 18 F along the beam axis.…”

Radiochromic Films for the Two-Dimensional Dose Distribution Assessment

“…RCF radiation type and energy dependence has been deeply investigated over the last few years mainly for the RCF types used in medical dosimetry, such as Gafchromic™ EBT series and XRQA-2. The dose response of EBT-3 Gafchromic™ films is very weakly (less than 1%) dependent on photon and electron energies of clinical interest (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16), as well as on 60 Co gamma rays, while, at very low x-ray energies (50 keV), the energy dependence is observed [9,103,104]. EBT-3 films show an under response at energies less than 100 keV and this under response increases as the energy decreases [105,106].…”

“…Ionization chambers and Faraday Cups are usually installed in beam lines to measure the beam current. Beam profiles are measured by means of beam viewers, plastic scintillators, optical fiber-based detectors, scintillation screens, and secondary electron emission detectors [1][2][3][4][5][6][7].…”

Effect of gamma radiation on optical properties of PVA/PEG/EY blend, and radiochromism.

“…Many types of equipment's are used to detect radiation, as well as to determine the doses delivered from radiation sources. Geiger-Muller counters, Ionization chambers, scintillation detectors, and others are usually used for such duties [6][7][8][9][10][11][12]. Radiation doses are also detected and measured by scintillation screens, thermoluminesce dosemeters, TLD, optical ber-based detectors, plastic scintillators, and secondary electron emission detectors.…”