Targetry and nuclear data for the cyclotron productionof 55Fe via various reactions

Mahdi Sadeghi • Nahid Soheibi • Tayeb Kakavand •

Mohammad Yarmohammadi

Received: 26 September 2011 / Published online: 13 March 2012

� Akademiai Kiado, Budapest, Hungary 2012

Abstract The radionuclide iron-55 (T1/2 = 2.73 a) decays

by electron capture and consists of small percentage of

weak gamma rays. 55Fe can be employed for industrial,

medical and agriculture applications. First, calculation of

the excitation functions of iron-55 via the 55Mn(p,n)55Fe,55Mn(d,2n)55Fe and 54Fe(a,n2p)55Fe reactions were per-

formed and investigated by ALICE/ASH (hybrid model)

and EMPIRE (3.1 Rivoli) codes. Then the required thick-

ness of the target was calculated by the SRIM code;

moreover, the theoretical physical yields of 55Fe produc-

tion reactions were obtained. Consequently, the best reac-

tion, 55Mn(p,n)55Fe, was suggested to take full benefit of

the excitation function and to avoid formation of radioac-

tive and non-radioactive impurities as far as possible.

Furthermore, the optimum energy range were predicted to

be 2–18 MeV and the theoretical physical yield were

obtained to be 0.35 MBq/lA h. Lastly, manganese dioxide

(MnO2) powder was used to prepare the thick layer; it was

deposited on an elliptical copper substrate by means of

sedimentation method. Target was irradiated at 20 lA

current and 18 MeV proton beam. The radioactivity of 55Fe

was determined via X-ray detector.

Keywords Excitation function � 55Fe � Sedimentation �Physical yield

Introduction

The radionuclide 55Fe decays by electron capture and the

major radiation emitted is the Ka X-ray with energy

5.89 keV. It is commonly used as a standard source for X-ray

detectors [1]. This radionuclide can be employed for indus-

trial, medical and agriculture because of the low energy of

the radiations emitted from the electron shells. In addition,

several applications are measurements of excited and back

scattered fluorescence radiation intensity were applied for

ash content determination in coal samples [2]; moreover, it

has been used for studies on the absorption and metabolism

of iron in humans [3] and for studies of plants [4]. Natural

iron consist four isotopes: 58/57/56/54Fe. Many researchers

have experimentally worked on 55Fe radioisotope produc-

tion excitation functions measurement by different projec-

tiles induced on various targets. The 55Fe can be produced

by the following reactions: 55Mn(p,n)55Fe, 55Mn(d,2n)55Fe,56Fe(p,pn)55Fe, 56Fe(p,x)55Fe, 54Fe(a,n2p)55Fe, 59Co(p,x)55Fe, 56Co(p,2n)55Co…55Fe, 53Cr(3He,n)55Fe, 54Cr(3He,2n)55Fe and 52Cr(a,n)55Fe [1, 5–11].

Accelerator production of 55Fe is largely achieved via

nuclear reactions 55Mn(p,n)55Fe, 55Mn(d,2n)55Fe and54Fe(a,n2p)55Fe which are well suited for the low or medium

energy cyclotrons. In this paper, calculation of excitation

functions of these reactions were carried out using ALICE/

ASH (hybrid model) and EMPIRE (3.1 Rivoli) codes [12, 13].

Then the results obtained from in this study, were compared to

previous published results. Subsequently, the essential thick-

ness of targets and 55Fe theoretical physical yield were cal-

culated using the SRIM code (the stopping and range of ions in

matter) for each reaction [14]. The target was prepared by

sedimenting 55MnO2 on the copper substrate. The target was

irradiated with a high current and Production yield of Fe was

M. Sadeghi (&) � M. Yarmohammadi

Agricultural, Medical & Industrial Research School,

Nuclear Science and Technology Research Institute,

P.O. Box 31485/498, Karaj, Tehran, Iran

e-mail: msadeghi@nrcam.org

N. Soheibi � T. Kakavand

Department of Physics, Zanjan University,

P.O. Box 451-313, Zanjan, Iran

123

J Radioanal Nucl Chem (2012) 293:1–6

DOI 10.1007/s10967-012-1719-9

measured by means of X-ray spectrometry. Finally the 55Fe

separated from impurities.

Materials and methods

Nuclear model calculation

A variety of theoretical models are used for calculating

nuclear reaction cross-sections. In principle, a model gives us

complete understanding of a physical process. It allows

extrapolation and prediction of experimental data. The model

codes offer important advantages such as ensuring internal

consistency of the data by preserving the energy balance and

the coherence of the partial cross-sections with the total or the

reaction cross-sections. In addition, the model calculations

can fill gaps in the experimental results and predict data for

unstable nuclei. In this paper, theoretical calculations of cross

sections were carried out using two computer codes, namely

ALICE/ASH (hybrid model) and EMPIRE (3.1 Rivoli). The

codes are based on different nuclear models for the descrip-

tion of nuclear reactions. Some salient features of those codes

are described below and in [15].

ALICE/ASH code

The ALICE/ASH code is an advanced and modified version of

the ALICE code. ALICE/ASH code has been written to study

the interaction of intermediate energy nucleons and nuclei

with target nuclei. The code calculates energy and angular

distribution of particles emitted in nuclear reactions, residual

nuclear yields, and total non-elastic cross sections for nuclear

reactions induced by particles and nuclei with energies up to

300 MeV. The calculations are performed for nine chemical

elements produced in the nuclear reactions. Eleven isotopes

for each element are considered. The inverse reaction cross-

sections are calculated using the optical model. The Fermi gas

model with a = A/7 is used to calculate nuclear level density.

The emission of neutrons, protons, a-particles and tritons is

simulated. The GDH (geometry dependent hybrid model) is

used for pre-compound particle spectra calculation for an

initial number of excitons (n = 3). For other exciton config-

urations the hybrid model is applied. The mean free path in the

GDH model is multiplied by unity for the incident energy

62 MeV and by two for the energy 90 MeV. The pre-com-

pound a-particle emission spectrum is calculated taking into

account the multiple pre-compound emissions. The results of

calculations are written in several output files [12].

EMPIRE-3.1 code

EMPIRE is a modular system of nuclear reaction codes,

comprising various nuclear models, and designed for

calculations over a broad range of energies and incident

particles. The system can be used for theoretical investiga-

tions of nuclear reactions as well as for nuclear data evalu-

ation work. A projectile can be a photon, a nucleon, a light or

heavy ion. The energy range starts just above the resonance

region in the case of a neutron projectile, and extends up to

few 100 MeV for heavy ion induced reactions. The code

accounts for the major nuclear reaction models, such as

optical model, Coupled Channels and DWBA (ECIS06),

Coupled Channels’ Soft-Rotator (OPTMAN), Multi-step

Direct (ORION?TRISTAN), NVWY Multi-step Com-

pound, exciton model (PCROSS and DEGAS), hybrid

Monte Carlo simulation (DDHMS), and the full featured

Hauser–Feshbach model including the optical model for

fission. Heavy ion fusion cross section can be calculated

within the simplified coupled channels approach (CCFUS)

[13].

Calculation of physical yield

To predict the theoretical physical yield calculating by

means of the acquired cross section data and stopping powers

of the different projectile in the targets material, SRIM

nuclear code was employed [14]. The physical thickness of

the target layer is chosen in such a way that for a given beam/

target angle geometry (90�), the incident beam be exited of

the target layer with predicted energy range. To minimize the

thickness of the target layer, 6� geometry beam toward the

target is preferred; so required layer thickness will be less

with coefficient 0.1 [16, 17]. Therefore, physical yield was

calculated using the simulation data via Simpson numerical

integral method from Eq. 1.

Y ¼ NLH

MI 1� e�kt� � Z

E2

E1

dE

d qxð Þ

� ��1

r Eð ÞdE ð1Þ

where Y is the yield (in MBq/lA h) of the product, NL is the

avogadro number, H is the isotope abundance of the target

nuclide (%), M is the mass number of the target element (g),

r(E) is the cross section at energy E (mb), I is the projectile

current (lA), dE/d(qx) is the stopping power

(MeV mg-1 cm2), k is the decay constant of the product

(h-1), and t is the time of irradiation (h) [18]. According to

Eq. 1, enhance of the incident energy, beam current, and

using an enriched target, increases the production yield [15].

Experimental

Target preparation

High-purity of manganese-dioxide powder (Aldrich,

99.99 %) was used to prepare a MnO2 thick layer. MnO2

2 M. Sadeghi et al.

123

was deposited on the elliptical copper substrate (11.69 cm2

surface area) by means of the sedimentation method.

Therefore, the manganese-dioxide powder was mixed and

stirred with a small amount of the ethyl cellulose and

acetone. In the sedimentation method, the optimum con-

ditions of the target preparation should be obtained by

several repeated experiments.

Irradiations

The MnO2 coated layer, was irradiated by the 18 MeV

proton beams at the currents of 20 lA for 3.3 h. Addi-

tionally, the results of the thermal shock were used to

evaluate the beam current values.

Results and discussion

55Mn(p,n)55Fe reaction

To produce 55Fe with proton irradiation of manganese tar-

get, Johnson et al. [19] obtained 46 data points up to

1.499 MeV that was demonstrated the maximum cross-

section of 0.75 mb at 1.442 MeV. Albert found maximum

cross-section of 500 mb at 8.1 MeV [20]. Further, Johnson

et al. and Viyogi et al. investigated 54 data points up to

5.563 MeV and 35 data points up to 1.5631 MeV, respec-

tively [21, 22]. Later, Abyad et al. [1] reported experimental

data of this reaction between the 2.4–18.2 MeV energy

using stacked-foil technique. For nuclear data measure-

ments, MnO2 powder (mono isotopic) was used. According

to their work, the 55Mn(p,n)55Fe reaction leads to formation

of 55Fe at a threshold energy of about 2 MeV and reaches a

maximum cross-section of 588 mb at 11.4 MeV [1]. In this

work, the excitation functions of the proton-induced reac-

tion on manganese-55 were calculated by ALICE/ASH

(hybrid model) and EMPIRE (3.1 Rivoli) codes. According

to ALICE/ASH results, beneficial range of proton energy to

produce 55Fe from 55Mn target is 2 to 18 MeV with the

maximum cross-section of 713.4 mb at 10 MeV. In the

chosen energy range, 54Fe (stable) is only isotopic impurity

with a 533.2 mb cross-section at 16 MeV. Also can be seen

in Fig. 1, the 55Mn(p,n)55Fe reaction leads to formation the54Mn, 55Mn, 51Cr and 52Cr impurities. Although separation

of isotopic contaminations is not possible by chemical

methods, non-isotopic impurities can be separated in such a

way. Figure 2 illustrates the calculated cross sections were

compared with the experimental cross-sections of 55Fe

production. To produce 55Fe from manganese, the target

can be used as manganese oxide. The recommended target

thickness was calculated using the SRIM code. The physical

yield was calculated by considering cross section data and

SRIM code (Table 1).

55Mn(d,2n)55Fe reaction

The acquired data from ALICE/ASH (hybrid model) and

EMPIRE (3.1 Rivoli) codes predicted the best range of

energy for production of 55Fe to be 5–20 MeV (Fig. 3). An

optimum energy range was determined so that formation of

radionuclide impurities is avoided as far as possible, and

the excitation functions of the inactive produced impurities

would be decreased. There are 54Fe and 56Fe as an isotope

impurity in this energy range (Fig. 3). Also there are some

non-isotope impurities that can be separate with the

chemical methods. The results obtained from this study

were compared in Fig. 4. There is large disagreement of

the ALICE/ASH and EMPIRE results [23]. Moreover, the

production yield and the required target thickness were

calculated (Table 1).

Fig. 1 The excitation function of the 55Mn(p,n ? a)51Cr,55Mn(p,a)52Cr, 55Mn(p,2n)54Fe, 55Mn(p,n)55Fe, 55Mn(p,p ? n)54Mn,55Mn(p,p)55Mn reactions calculated by ALICE/ASH code (hybrid

model)

Fig. 2 The excitation function of the 55Mn(p,n)55Fe reaction calcu-

lated by ALICE/ASH (hybrid model) and EMPIRE (3.1 Rivoli) codes

and the experimental data

Targetry and nuclear data 3

123

54Fe(a,n2p)55Fe reaction

Measurements on the excitation function of 55Fe via this

reaction were done by Houck and Miller [10]. They

investigated six data points of the cross sections and found

the maximum cross-section of 681 mb at 40.8 MeV. The

calculated data by ALICE/ASH (hybrid model) and

EMPIRE (3.1 Rivoli) codes for 54Fe(a,n2p)55Fe reaction

that leads to production of 55Fe are given in Fig. 5. In fact,

the best range of energy for this reaction was obtained to be

29–50 MeV. There are some isotopic and non-isotopic

impurities in this energy range such as 52Mn, 53Mn, 54Mn,51Cr, 53Fe, 54Fe, 56Fe, 55Co and 56Co impurities. The

maximum cross sections were predicted to be 610 mb at

38 MeV and 612 mb at 45 MeV for the ALICE/ASH and

the EMPIRE-3.1 codes, respectively. The results obtained

from this study and the previous published results were

compared in Fig. 6. Also the theoretical physical yields and

the target thickness were calculated and the results were

given in Table 1.

Target preparation

Several repeated experiments obtained for finding the

optimum conditions of the target preparation. Subse-

quently, the thermal shock and the annealing were per-

formed to study the adhesion of samples of the targets. In

addition, the X-ray diffraction patterns of MnO2 were

studied by powder X-ray diffraction spectroscopy (XRD).

Moreover, homogeneity of the MnO2 layer, which may

affect the production rate of 55Fe, was determined by

standard deviation of the layer thickness measured at sev-

eral spots by a micrometer, while the morphology by a

scanning electron microscopy (SEM) technique. According

to Fig. 7 and results of Table 2, the layer was homoge-

neous and mechanically stable.

X-ray spectral analysis

Identification and assay of X-ray-emitting radio nuclides

was carried out using X-ray spectroscopy with a Si(Li)

detector. Iron-55 was mainly identified by the 5.89 keV

(16.28 %) peak. Other radio nuclides identified were

Table 1 Calculate of the

required target thickness and the

production yield

a By ALICE/ASH code (this

work)b By EMPIRE code (this work)

Reaction Beam energy

(MeV)

Thickness Calculated yield

(MBq/lA h)

References

55Mn(p,n)55Fe 15 5–20 mg cm-2 0.3 Abyad et al. [1]

18 ? 2 90 lm 0.20 This work

18 ? 2 97.3 lm 0.37a Theoretical calculation

18 ? 2 97.3 lm 0.39b Theoretical calculation55Mn(d,2n)55Fe 22 – 0.30 Dmitriev et al. [9]

24 ? 5 69.1 lm 0.66a Theoretical calculation

24 ? 5 69.1 lm 0.35b Theoretical calculation54Fe(a,n2p)55Fe 55 ? 30 27.7 lm 0.207a Theoretical calculation

55 ? 30 27.7 lm 0.207b Theoretical calculation

Fig. 3 The excitation function of the 55Mn(d,n ? a)52Cr,55Mn(d,3n)54Fe, 55Mn(d,2n)55Fe, 55Mn(d,n)56Fe, 55Mn(d,t)54Mn,55Mn(d,d)55Mn, 55Mn(d,2n ? a)51Cr reactions calculated by

ALICE/ASH code (hybrid model)

Fig. 4 The excitation function of the 55Mn(d,2n)55Fe reaction

calculated by ALICE/ASH (hybrid model) and EMPIRE (3.1 Rivoli)

codes

4 M. Sadeghi et al.

123

54Mn [T1/2:312d, 5.4 keV (14.7 %)], 51Cr [T1/2:27.7d,

4.9 keV(13.1 %)].

Conclusions

In this manuscript, the excitation function of iron-55 by the55Mn(p,n)55Fe, 55Mn(d,2n)55Fe and 54Fe(a,n2p)55Fe reac-

tions were calculated using ALICE/ASH (hybrid model)

and EMPIRE (3.1 Rivoli) codes. The 55Mn(p,n)55Fe reac-

tion was suggested as the best reaction to produce 55Fe due

to minimum impurities. 55Fe has maximum cross-section

of more than 700 mb at about 10 MeV in 55Mn(p,n)55Fe

reaction; its benefit excitation functions found between 2

and 18 MeV. The recommended target thickness and the

physical yield were found 97.3 lm and 0.35 MBq/lA h,

respectively. High-purity of manganese-dioxide powder

was employed with the aim of MnO2 thick layer deposition

on the elliptical copper substrate by means of the sedi-

mentation technique. According to the SEM scans, man-

ganese-dioxide target of high-quality morphology prepared

using sedimentation method. After irradiation of the target,

0.20 MBq/lA h of 55Fe yield was obtained. To increase

production yield, making use of a circulating flow of

chilled helium moreover the water cooling would allow

using higher beam current.

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(wt%)

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120 20 Excellent Stable Stable Unstable

150 25 Tolerable Stable Stable, brown Unstable

180 30 Tolerable Stable Stable, brown Unstable

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