# Nuclear Analysis of High-Power LIEBE Molten Target at CERN for the Production of Radioisotopes
## 1 Introduction  
Radioactive isotopes are extensively used in medicine, industry and research. Isotope Separator Online (ISOL) facilities linked to particle accelerators are commonly used to efficiently produce radioactive isotopes in the form of Radioactive Ion Beams (RIBs). In ISOL facilities, RIBs are created by the beam interaction with a target, resulting in radioisotope production. However, increasing demand for larger amounts and more exotic radioisotopes for both research and medical applications is becoming challenging to meet for beam and target configurations of current ISOL facilities. To enhance the production of short-lived isotopes higher primary beam intensities are sought in the next generation of radioactive ion beam installations. However, current targets are unable to accommodate high-power beams. The design of high-power targets is complicated regarding the ability to maintain a uniform temperature profile in the target and a reasonable lifetime. Another challenge at high beam powers is adequate heat removal from the target [1]. The European Organization for Nuclear Research, known as CERN, operates an ISOL facility called ISOLDE (acronym for Isotope Separator Online DEvice). It directs a high-intensity proton beam from the Proton Synchrotron Booster onto specially developed thick targets. Additionally, there is a second target placed behind ISOLDEs, in CERNs MEDICIS (an acronym for Medical Isotopes Collected from ISOLDE) facility, which is focused on medical radioisotopes. Radioisotopes produced at the MEDICIS facility are extracted via mass separation, implanted in a small foil and delivered to other research facilities. In this context, a high-power target for testing in the ISOLDE facility was developed. It was proposed for short-lived isotopes by the European Isotope Separation Online (EURISOL) project. The proposed design resulted in a liquid high-power target concept instead of the currently mainly used solid targets. To operate a liquid target at high power, its conceptwas based not on the currently common static-bath design, but on a liquid metal loop. When using a liquid metal loop, beam irradiation, heat removal and isotope diffusion are functionally decoupled from each other. High heat removal rates can be achieved through the circulation of the liquid target material and the use of a heat exchanger. To validate this concept, a target prototype called LIEBE (Liquid Eutectic Lead Bismuth Loop Target for EURISOL) was designed and assembled [2]. A new target development requires several different investigations. Among them isevaluation of radiological conditions during the operation of LIEBE target. To estimate arising neutron and gamma radiation fluxes, studies of the proton beam interaction with the LIEBE target are needed. However, since LIEBE is a new target, there are only a few publications dedicated to proton beam-LIEBE interaction and the resulting radiological conditions. Design studies were published in [PERSON] Ph.D. thesis [3]. They are dedicated to the functioning of the target; for example, radioisotope yield, thermal-hydraulic parameters, LBE droplet formation, etc. There are later simulations published of proton beam-LIEBE target interaction used to evaluated energy deposition in the irradiation chamber around the proton beam path using FLUKA code [4]. However, these calculations were focused on deposited energy, since their aim was to study the thermohydraulic response of the target. Monte Carlo code calculations, including isotope generation in the LIEBE target, were performed later using ABRALA and FLUKA codes by [PERSON] et al. [1]. The production rate of tin isotopes in the vicinity of \({}^{100}\)Sn with future beam parameters of 2 GeV and 4 uA were calculated. However, these simulations were conducted for hypothetical, lanthanum-based, and not the lead-bismuth-based eutectic.