Proton and deuteron activation measurements at the NPI and future plans in SPIRAL 2 / NFS

The protonand deuteron-induced reactions are of a great interest for the assessment of induced radioactivity of accelerator components, target and beam stoppers as well as isotope production for medicine. In the present work, the deuteron-induced reaction cross sections on zinc were investigated by stacked-foil activation technique with deuteron beam of 20 MeV energy from the cyclotron U-120M of NPI CAS Řež. Also the proton activation cross section measurement of iron is presented. The comparison of present results to data of other authors and to predictions of evaluated data libraries is discussed. The investigation shall continue for higher proton and deuteron energy interval 20–35 MeV at SPIRAL2/NFS facility using a charged particle irradiation chamber with pneumatic transport system to measure isotopes and isomers with half-lives in minutes-regions.


Introduction
The proton-and deuteron-induced activations have a great interest for the assessment of induced radioactivity in the accelerator components, targets and beam stoppers as well as isotope production for medicine.Moreover, description of deuteron-nucleus interaction represents actually an important test of the reaction mechanism models, because of the weak deuteron binding energy of 2.224 MeV [1].
We report cross section measurements of natural Zn and Fe by d and p, respectively.The radioisotopes 67,66 Ga, 61,64 Cu produced by deuteron activation of zinc isotopes are widely used in nuclear medicine.Iron belongs to main important constructing material.
The irradiation was carried out on CANAM [2] infrastructure of NPI CAS using a deuteron/proton beam of the variable-energy cyclotron U-120M operating in the negative-ion mode.

Experimental set-up
We measured the cross sections deuteron-induced reaction on natural zinc and proton induced reaction on natural iron by stacked-foil technique.High purity Zn or Fe foils interleaved with aluminium monitors were placed in a cooled reaction chamber that serves also as a Faraday cup and were impinged by collimated deuteron or proton beam.The high purity Zn, Fe (Goodfeloow product, 99.99% and 99.5% purity, 25 µm declared thickness) and Al (50 µm declared thickness) were weighed to avoid relatively large uncertainties in the foil thickness declared by producer.Duration of deuteron activation was 10.35 min with 0.328 µA mean current and duration of proton irradiation was 27 min with mean beam current 0.292 µA.
a e-mail: simeckova@ujf.cas.czAfter several minutes the activities of the irradiated foils were measured by two calibrated HPGe detectors of 50% efficiency and of FWHM 1.8 keV at 1.3 MeV.The computers registering beam current and sample activities were time synchronized.

Data analysis
The energy of reaction in subsequent foils was calculated by using SRIM 2009 [3] code taking into account the initial deuteron energy 20.0 MeV and the proton energy 20.1 MeV.
The gamma-rays from irradiated samples were measured with HPGe detectors.Activated isotopes were identified on the basis of T 1/2 , γ -ray energies and intensities [4].The measured activities were corrected for decay during and after the irradiation.
Measured errors consist of statistical error of peak determination and systematic errors of current certainty (5%), uncertainty of foil thickness (2%) and detector efficiency uncertainty (2%).The uncertainty of initial beam energy determination is 1% and beam energy spread is 1.8%.
The reaction 68 Zn(d,2n) is the main contributor to 68 Ga production in the region up to 20 MeV.Present data (Fig. 1) are in rough agreement with the data of Gilly [17] (they    measured only the (d,2n) reaction) while Nassiff [8] data are significantly lower.It is seen that while the TENDL 2014 library describes low energy part reasonably, EAF 2007 exhibits a bump, that comes from overestimation of the small contribution of the 64 Zn(d,n) reaction.
Similar case is 67 Ga production reaction (Fig. 2).Present are in agreement with previous authors except Nassiff [8].There are competitive reactions 66 Zn(d,n The main reaction producing 65 Ga is 64 Zn(d,n) in this energy region (Fig. 4).Present data are in only rough   agreement with previous measurements and also with both evaluated libraries.The picture also shows that the TENDL 2014 library describes the excitation function better than the EAF 2007 one.
At least three stable isotopes of Zn compete in 64 Cu production.The experimental data are contradictory at low energies.However the TENDL 2014 library agrees with present experimental data (Fig. 5).
Only 70 Zn(d,p) reaction produces 71m Zn isotope.Neither library agrees with experimental data, nevertheless TENDL 2014 describes the excitation function shape better (Fig. 7).The 68 Zn(d,p) is main reaction that produces 69m Zn in region up to 20 MeV.It is seen from Fig. 8. that present data are in agreement with data Khandaher [5] and Tarkanyi [6], but Nassiff [8] and Gilly [17] experimental points are too high.Neither library agrees with the experimental data as in previous case.

ND2016
The present data of 65 Zn production are in satisfactory agreement with data of previous authors (Fig. 9), except too small data by Nassiff [8].The main contributory reaction is 64 Zn(d,p) for which the evaluated libraries predictions are too low.
Only the single 64 Zn(d,t + ) generates 63 Zn isotope (Fig. 10).Present data are compatible with previous measurement of Bissem [10].The TENDL 2014 library has a worse agreement with experimental data at low energies than EAF 2007.
We observed also γ -lines from decay of 51 Cr.However the threshold of the first possible reaction 56 Fe(p,dα) is 17.74 MeV thus we ascribed the production of 51 Cr nuclei to the decay of 51 Mn generated in the reaction   54 Fe(p,α + ).The γ -lines from the 51 Mn decay are invisible for their very low intensities.For obtaining cross section of nat Fe(p,x) 51 Mn we used the Bateman's equation (1) (after and during irradiation).The resulting cross sections are shown in the Fig. 11.The data are in full agreement with Levkovskij [20] measuring the 54 Fe(p,α + ).
The data were fitted by Bateman's equation (1) (during and after irradiation) using MINUIT code to determine specific activity of mother ( 51 Mn) A 0 m and daughter ( 51 Cr) nuclei A 0 g at the end of irradiation A g is the specific activity of the sample at the cooling time t, λ g and λ m are the decay constants for daughter (grand) and mother isotope.
The similar procedure was used for determination of nat Fe(p,x) 58m Co cross sections.The data deduced for the first time are shown at Fig. 12. 58m Co fully decays to the ground state through heavily conversed (IT) 24.9 keV γ -transition.

Outlook
The data above 20 MeV and short lived isotopes are planned to be measured in the future installation at SPIRAL2/NFS, that will consist of Irradiation Chamber (IC) -it will be delivered in the frame of SPIRAL2-CZ project [21] and will be coupled to Pneumatic Transfer System (PTS) -will be delivered by KIT Karlsruhe.The system will enable a transition of the samples between atmospheric pressure and vacuum (sample insertion into the beam) and also the transfer among IC, HPGe station and storage station.Activated samples will be delivered in front of the HPGe detector in short time (currently <1 min, transfer will be yet optimized).
The experiment was conducted on CANAM infrastructure that is supported by MEYS LM2011019.Authors also acknowledge the support of the MEYS project SPIRAL2-CZ, LM 2015076.
) and 67 Zn(d,2n) in the region up to 20 MeV.The TENDL 2014 library describes experimental values while the EAF 2007 library overestimates contribution of the (d,n) reaction.Excitation function for the nat Zn(d,x) 66 Ga is shown in Fig. 3. TENDL 2014 agrees with present data.Both the evaluated libraries describe (d,2n) reaction, but EAF 2007 overestimates the small contribution of 64 Zn(d,γ ) reaction.