Modern Physics Letters A

The LNS Superconducting Cyclotron, named “Ciclotrone Superconduttore” (CS), has been in operation for more than 20 years. A wide range of ion species from hydrogen to lead, with energy in the range 10 to 80 AMeV, have been delivered to users. The maximum beam power is limited to 100 W due to the beam dissipation on the electrostatic deflectors. To fulfil the demand of users aiming at studying rare processes in nuclear physics, an upgrade of the cyclotron is necessarily intended to increase the intensity of ion beams with mass lower than 40 a.m.u. up to a power 10 kW. This will be achieved by means of extraction by stripping. This solution needs to replace the cryostat including the superconducting coils. The present capability of the cyclotron will be maintained, i.e. all the ion species allowed by the operating diagram will be available, being extracted by electrostatic extraction. In addition to the high power beams for nuclear physics, it will be possible to produce medical radioisotopes like ${}^{211}\mathrm{\text{At}}$ using an internal target.

In 2016, Laboratori Nazionali di Legnaro (Italy) started the commissioning of a new accelerator facility based on a high-power cyclotron able to deliver proton beams up to 70 MeV of energy and 700 $\mu$A current. Such a machine is the core of the Selective Production of Exotic Species (SPES) project whose main goal is to provide exotics beam for nuclear and astrophysics research and to deliver high-intensity proton beams for medical applications and neutrons generator.

The most important radioisotope for nuclear medicine is ${}^{99m}$Tc. After the supply crisis of ${}^{99}$Mo starting in 2008, the availability of ${}^{99m}$Tc became a worldwide concern. Alternative methods for producing the medical imaging isotope ${}^{99m}$Tc are actively being developed around the world. The reaction ${}^{100}$Mo(p, 2n)${}^{99m}$Tc provides a direct route that can be incorporated into routine production in nuclear medicine centers that possess medical cyclotrons for production of other isotopes, such as those used for Positron Emission Tomography. This paper describes a new approach for manufacturing targets for the (p, 2n) nuclear reaction on ${}^{100}$Mo and the foundation for the subsequent commercial separation and purification of the ${}^{99m}$Tc produced. Two designs of targets are presented.

The targets used to produce ${}^{99m}$Tc are subject to a number of operational constraints.They must withstand the temperatures generated by the irradiation, accommodate temperature gradients from cooling system of the target, must be resilient and must be easily post-processed to separate the ${}^{99m}$Tc. After irradiation, the separation of Tc from Mo was carried out using an innovative two-step approach.

The process described in this paper can be automated with modules that easily fit in standard production hot cells found in nuclear medicine facilities.

The ${}^{99\mathrm{\text{m}}}$Tc isomer was produced using the $(p,2n)$ reaction on highly enriched ${}^{100}$Mo samples. The Thick Target Yields were determined in the energy range from 16 MeV to 26 MeV and compared with the values calculated using the most recent cross-section recommendations from the literature. The generated impurities were also determined. It was shown that for 99.815 ± 0.010% enriched samples, only reactions induced on ${}^{100}$Mo are of importance. The ratio of the number of atoms of ${}^{99\mathrm{\text{m}}}$Tc to all produced Tc nuclei was studied as a function of irradiation time and bombarding energy.

This work describes the production of two clinically relevant metal radioisotopes ${}^{64}\mathrm{\text{Cu}}$ and ${}^{68}\mathrm{\text{Ga}}$ with a medical cyclotron by the irradiation of liquid targets. New results are presented for the implementation of this methodology in a fully automated system, using commercially available equipment. Liquid target solutions containing enriched ${}^{64}\mathrm{\text{Ni}}$ and ${}^{68}\mathrm{\text{Zn}}$ were loaded, bombarded and transferred to synthesis modules where a purified solution containing the desired radiometal is obtained and can then be used to further radiolabeling within only one hour after End-Of-Bombardment (EOB). Typical production runs using enriched material lead to the production of 5 GBq and 6 GBq (0.14 MBq/($\mu$Ah ⋅ mg) and 1.5 MBq/($\mu$Ah ⋅ mg)) of ${}^{64}\mathrm{\text{Cu}}$ and ${}^{68}\mathrm{\text{Ga}}$; although the technique can be used to obtain up to 25 GBq and 40 GBq, respectively, by simply scaling up the amount of the enriched material. Purified solutions containing ${}^{64}\mathrm{\text{Cu}}$ and ${}^{68}\mathrm{\text{Ga}}$ were obtained within 30 min after EOB and used to produce ${}^{64}\mathrm{\text{Cu}}$-ATSM and ${}^{68}\mathrm{\text{Ga}}$–DOTA–NOC, respectively, with quality parameters suitable for human use.

In the production of Positron Emission Tomography (PET) nuclides at a medical cyclotron facility ${}^{41}$Ar (T${}_{1/2}$ = 109.34 m) is produced by the activation of air due to the neutron flux, according to the ${}^{40}$Ar(n, $\gamma$)${}^{41}$Ar reaction. In this work, we describe a relatively inexpensive and readily reproducible methodology of air sampling that can be used for quantification of ${}^{41}$Ar during the routine production of PET nuclides. We report the results of an extensive measurement campaign in the cyclotron bunker and in the ducts of the ventilation system, before and after final filtering of the extracted air. Air Samples were analyzed using a gamma-ray spectrometry system equipped with HPGe detector, with proper correction of the efficiency calibration to account for the samples density. The results of measurement were then used to evaluate the Total Effective Dose (TED) to the population living in the surrounding areas, due to routine emissions in the operation of the cyclotron. The average ${}^{41}$Ar saturation yield per one liter of air emitted in the environment resulted to be (0.044 ± 0.007) Bq/($\mu$A ⋅ dm³). The maximum value of TED for the critical group of the population, even considering an overestimated workload, was less than 0.19 $\mu$Sv/year, well below the level of radiological relevance.

The general principles for the safe management of a medical cyclotron dedicated to $\beta +$ emitter isotope production, energy range 10–18 MeV for proton beams, are presented.

The goal of this work is to increase the beam transmission from the cyclotron to the patient location of ocular tumor treatment facility Optis 2 at the Paul Scherrer Institute and thus to reduce the patient treatment times. The examined options for such transmission increase were the installation of local degraders in the patient treatment room and modification of the energy selection collimator settings. The experiments have shown that an improvement of the beam transmission is possible to achieve, however on a cost of an increase in lateral or distal penumbra of the beam. The benefits and drawbacks of the examined options are discussed.