New cross-sections and intercomparison of proton monitor reactions on Ti, Ni and Cu
Introduction
In charged particle irradiations, both for basic research and in practical applications, the knowledge of the energy and intensity of the bombarding particles are required. Faraday cup measurements of beam current are sometimes not possible or not accurate enough. On the other hand direct energy measurement requires complicated techniques. The use of monitor reactions can be a solution. It is a simple, convenient and cheap method to determine the energy and intensity of the bombarding beam. Several reactions induced by energetic charged particles on metal targets were studied with among other aims to evaluate their potential use for monitoring the energy and intensity of charged particle beams. Monitoring of beam parameters is also essential in numerous applications, such as isotope production under optimised circumstances, charged particle activation analysis, thin layer activation, estimation of neutron yield and residual activity of accelerator components, calculation of activity for radiation safety and simulation of radiation damage etc. When using monitor reactions to characterise charged particle bombarding beams reliable and accurate cross-section data are required.
The availability of multiple induced radionuclides in the same monitor foil and the use of different metals in one experiment, leading to different reactions, will improve the internal consistency of the cross-section database.
Several authors measured cross-sections of the Ti(p,x)V, Ni(p,x)Ni, Cu(p,x)Zn, Cu(p,x)Zn and Cu(p,x)Zn processes in the past. In spite of the simple target preparation, irradiation and activation detection technique needed to assess these reactions; surprisingly large disagreements exist between the different experimental results. The excitation function reported by different authors shows unacceptable deviations both in the values of cross-sections and in the energy scales in some cases. A good summary of the available experimental data is given for the above reactions among others in the IAEA TECDOC-1211 [1].
The aim of a recent study was to investigate several frequently used proton monitor reactions and to make an inter-comparison between them to increase the reliability of the measured cross-sections and minimise the possible systematic errors in the experiments. In the present work the above five reactions were considered for a detailed study. We performed new cross-section measurements with improved experimental techniques and accuracy and we have linked the five reactions together by irradiating different types of target foils in the same stack. The acquired new experimental data were compared to the recommended data given in [1].
Section snippets
Experimental
Measurements were made using high purity Ti, Ni and Cu foils with natural isotopic composition (99.99–99.999% supplied by Goodfellow Metals, England). Two stacks were irradiated at the extracted proton beam of the CGR 560 cyclotron of the Vrije Universiteit Brussel (VUB). Stacks were placed in a Faraday type irradiation chamber equipped by long collimator and electron suppresser. Beam current was measured by a digital charge integrator, while the estimated incident beam energy was calculated
Data evaluation
The cross-section for the reaction studied was computed for each foil from the counts measured in the total energy peaks of the nuclide involved, combined with detector efficiency, nuclear data, the number of target atoms and the estimated number of bombarding particles. Possible loss of activity through recoil effects was evaluated and was always less than 1%.
Nuclear decay data used in these experiments (see Table 1) are the same as considered in determining the recommended cross-section
The process
Four reactions contribute to the formation of V by proton bombardment below 35 MeV on a natural Ti target. These are the Ti(p,γ)V, Ti(p,n)V, Ti(p,2n)V and Ti(p,3n)V reactions having Q value of +5.8, −4.8, −12.9 and −23.9 MeV, respectively. The nuclear data (half-life, gamma energy and intensity) were taken from [2] and are collected in Table 1. Foils were measured one to two days after EOB in a well-calibrated geometry of a HpGe detector. The two sets of experimental points
Conclusion
In the Co-ordinated Research Project (CRP) [1] of the International Atomic Energy Agency a detailed analysis were made on the most frequently used monitor reactions for proton beams. Among them are the Ti(p,x)V, Ni(p,x)Ni, Cu(p,x)Zn, Cu(p,x)Zn and Cu(p,x)Zn processes. The data evaluation in [1] was made independently for each of the reactions, even in those cases when the reactions take place on the same target material. Recommended cross-section values were given by
Acknowledgements
We are pleased to acknowledge the co-operation and help in performing the irradiations of the team of the VUB-CGR 560 cyclotron laboratory. This work was partly supported by the Hungarian OTKA Fund (contract no. 26556). Financial support was also received from the Fund for Scientific Research (FWO-Vlaanderen) from the Hungarian Academy of Sciences, and from OZR-VUB.
References (5)
- et al.
Determination of the external beam energy of a variable energy, multiparticle cyclotron
Applied Radiation and Isotopes
(1996) - et al.
Study of the Ni(p,x)Ni process up to 44 MeV for monitor purposes
Applied Radiation and Isotopes
(1998)
Cited by (65)
Thick target yields of proton induced reactions on natural molybdenum
2022, Applied Radiation and IsotopesExcitation functions of proton induced reactions on titanium and copper
2021, Applied Radiation and IsotopesNew cross-section data for proton-induced reactions on <sup>nat</sup>Ti and <sup>nat</sup>Cu with special regard to the beam monitoring
2020, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and AtomsCitation Excerpt :Evaluation of 65Zn activity was based on its 1115.539 keV γ-line with intensity of 50.04%. Experimental data [12,21,22,27,36,38,40,42,44–47,49–51] together with IAEA recommended cross-sections [1] and the theoretical prediction of cross-sections [7] are shown in Fig. 15. Obviously, all the data follow the same trend with a minimal scattering.
Experimental investigation and theoretical evaluation of proton induced nuclear reactions on nickel
2020, Applied Radiation and Isotopes