Pion Production in Proton Induced Spallation Reactions in the Energy Range of Few Gev Order

Abstract

Our understanding of physical phenomena is expressed as modelling. At present, the broadest platform for such modelling is quantum mechanics approach. Unfortunately, many -body systems are usually an extreme challenge for existing methods of quantum mechanics. One has to rely on rather simple, much more straight formed concepts. In this Chapter, such general basic concepts will be shown as ingredients of typical models of nuclear reaction.Several microscopic models have been constructed in order to describe the first stage of proton -nucleus reaction. All of them have the same basis, they describe the reaction as a cascade of nucleon -nucleon collisions, but employing different assumptions. The main difference concerns implemented potential of nucleon -nucleus interaction. One can distinguish the simplest models, which neglect features of the mean field dynamics and employ constant static potential, like a class of Intra -Nuclear Cascade (INC) models. Other, more sophisticated approaches comprise dynamically changing field and minimal fluctuations obtained due to use of test particle method, i.e. models based on Boltzmann -Uehling -Uhlenbeck (BUU) transport equation. There are also models, which include real fluctuations and particles correlations, employing two-and three-body potentials, e.g. Quantum Molecular Dynamics models. The main ideas of the different types of nuclear reaction approaches are described below.In this Chapter, devoted for model-like approach of investigation of nucleon -nucleus reactions, also so-called percolation model is presented. This rather basic model describes fragment mass distributions very well (Section 2.3). 9

Centrality dependence of particle production inp−Pbcollisions atsNN=5.02TeV

“…The relative fraction of black and gray neutrons is evaluated by assuming that 90% of the emitted neutrons are black, as measured in proton-induced spallation reactions in the energy range between 0.1 and 10 GeV [49]. The number of nucleons emitted from 208 82 Pb is finally calculated event by event as a function of N coll , assuming binomial distributions with probabilities p = N slow p /82 for protons and p = N slow n /126 for neutrons.…”

“…III A, is fit to the experimental distribution of the ZDC energy in calculated for centrality classes defined by dividing the energy spectrum in percentiles of the hadronic cross section. The systematic uncertainty on the N coll values reported in Table III, has been evaluated by varying the model parameters within reasonable ranges: (i) using for the relative fraction of black over gray protons N black p = 0.43 N gray p from spallation reaction results [49], (ii) including a saturation effect for black protons, (iii) decreasing the ratio of black over gray neutrons to 0.5 as obtained from DPMJET [52], (iv) neglecting the linear term in Eq. (5) and assuming complete saturation for the neutrons, (v) varying γ by ±10%, and (vi) assuming different parametrization for the fluctuations in the number of slow nucleons for a fixed N coll value.…”

Estimation of Induced Activity in an ADSS Facility

“…At the highest energy 1.2 GeV of the entire energy range considered 3 H still have maximum activity of 2.3x10 12 Bq while 45 Ca has a slightly lower activity of 6.3x10 11 Bq than that at 800 MeV. This observation is explained from the fact that as we go to higher energies, production of high energy neutrons and projectile-like fragments increase [14,15], competition between a larger number of evaporation channels also come into play [5]. It has been observed from figure 1 that for the nuclide species and the energy range considered, saturation activity is not reached for any of the products for 30 days of irradiation.…”

“…In Table 4 we have given these calculated activities of several radionuclides for proton energies of 600 MeV and 1.0 GeV. From the table we see that for both the projectile energies considered maximum activities of the order of 6.0x10 14 Bq and 1.0x10 15 Bq, respectively are obtained for 201 Tl while minimum activity is produced for 205 Pb. This minimum activity is of the order of 3.6x10 6 Bq and 7.7x10 6 Bq respectively.…”

“…Since the codes do not distinguish between formation in the ground or metastable state, in the case of such radionuclides, we have considered the half-life of the ground state unless the metastable state is much longer lived than the ground state. Figure 1 shows the activity build-up of 3 H, 14 C, 22, 24 Na, 45 Ca and 60 Co. 3 H, 45 Ca and 60 Co are nuclides of concern for radiotoxicity of the environment while 14 C and 22 Na are biologically important. It has been observed that for 400 MeV incident proton energy the activity build-up for 30 days of irradiation is in the range of 10 10 to 2x10 11 Bq for all the species except for 14 C. Maximum activity of the order of 2.3x10 11 Bq is produced for 45 Ca.…”