Cross-section and beam energy measurements

Cross-section measurements are mandatory in the field of theranostics, where the suitable quantity and quality of the produced radionuclides is of the utmost importance.

A novel method has been developed at the Bern cyclotron, to improve nuclear data of production cross sections up to the maximum proton beam energy of 18 MeV. This procedure is based on the irradiation by an online-monitored flat beam and on the measurement of the current on target.

Specific target “coins” were conceived to contain foils or powder material compressed in pellets. The addition of passive absorbers allows for variation of the energy. A specific target station is used to perform the experiment using the Beam Transfer Line (BTL).

For cross-section measurements and for an optimised radioisotope production, the accurate knowledge of the beam energy is mandatory. Our group is developing several methods to assess this quantity, based on magnetic deflection and passive absorption of the beam. We studied the variation of the beam energy as a function of the main operational parameters of the cyclotron for the first time. 

Working principle of the cross-section measurement setup. The beam is flattened by means of the quadrupoles of the BTL, collimated and attenuated before hitting the target material contained in the coin. The flatness of the beam is monitored on-line by means of the UniBEaM detector. Hitting the entire mass of the target material is here essential to correctly measure the cross section, as the uniformity of the powder material cannot be assumed.

 

Cross section measurement of Scandium-43

The cross section of several nuclear reactions has been measured at the Bern cyclotron, improving nuclear data. In particular, we measured the production cross section of Sc-43 and Sc-44, challenging but promising radioisotopes for theranostics. 

Cross-section of Scandium-43 as a function of the proton energy. The Bern measurements are represented in red, while the other curves refer to other measurements (Levkovskij_91, DeWaal_71) or theoretical prediction (TENDL-2015).

 

Beam energy measurements

We have performed a detailed study of the beam energy in the BTL as a function of the main operational parameters of the cyclotron. In particular, we have found a dependence as a function of the position of the stripper foil. Studies are ongoing to assess the beam energy on the exit port where the Solid Target Station is installed. 

Measured beam energy as a function of the angle of the extraction carousel for both foils.

 

Selected publications

G. Dellepiane, C. Belver Aguilar, T. S. Carzaniga, P. Casolaro, P. D. Häffner, P. Scampoli, M. Schmid, S. Braccini, Research on theranostic radioisotope production at the Bern medical Cyclotron, Il Nuovo Cimento, 2021; DOI: 10.1393/ncc/i2021-21130-6

T. S. Carzaniga, M. Auger, S. Braccini, M. Bunk, A. Ereditato, K. Pawel Nesteruk, P. Scampoli, A.Türler, N. van der Meulen, Measurement of Sc-43 and Sc-44 production cross-section with an 18 MeV medical PET Cyclotron, App. Radiat Isot. 2017 Nov. 129:96-102; https://doi.org/10.1016/j.apradiso.2017.08.013

P. Häffner, C. Belver-Aguilar, S. Braccini, P. Scampoli, P. A. Thonet, Study of the Extracted Beam Energy as a Function of Operational Parameters of a Medical Cyclotron, Instruments 2019, 3(4), 63; https://doi.org/10.3390/instruments3040063