Coincidence method for the analysis of minor elements in steel by deuteron-induced prompt γ-ray spectrometry (d-PIGE)

Nuclear Instruments and Methods in Physics Research B 179 (2001) 126±132

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Coincidence method for the analysis of minor elements in steel by deuteron-induced prompt c-ray spectrometry (d-PIGE) Antoaneta Ene a b

a,*

, T. Badica b, Agata Olariu b, I.V. Popescu c, C. Besliu

d

Department of Physics, Faculty of Sciences, Dunarea de Jos University of Galatzy, Domneasca 111, 6200 Galatzy, Romania Horia Hulubei National Institute of Physics and Nuclear Engineering, 76900 Magurele, P.O. Box MG-6, Bucharest, Romania c Department of Physics, Faculty of Sciences, Valahia University of Targoviste, Targoviste, Romania d Faculty of Physics, University of Bucharest, 76900 Magurele, Bucharest, Romania Received 20 December 2000

Abstract The sensitivities of minor elements analysis in a standard steel sample irradiated with 5 MeV deuterons have been determined by the regular deuteron-induced c-ray emission (d-PIGE) method and with the selection of the (d, n) reaction channel by measuring c±n coincidences. This approach has resulted in a signi®cant improvement of the sensitivity of the analysis. A comparative study with the published results using protons as projectiles was also made. Ó 2001 Elsevier Science B.V. All rights reserved. PACS: 29.30 Keywords: Minor elements analysis; Steel target; (d, X) nuclear reactions; n±c coincidences; Deuteron-induced c-ray emission technique

1. Introduction Many elements are incorporated into steel as minor components in concentrations ranging from a few parts per million (ppm) to several percents in order to create alloys with speci®c characteristics. It is thus not surprising that the steel industry makes extensive use of multielemental analytical techniques both destructive and non-destructive. The

*

Corresponding author. Tel.: +40-36-414-871; fax: +40-36460-135. E-mail address: [email protected] (A. Ene).

attractiveness of non-destructive methods and the ability to perform simultaneous multielemental determinations has led to an extensive application of atomic and nuclear techniques based on the measurement of either delayed radiation from radioactive nuclides generated in the steel sample ± neutron activation analysis (NAA) [1±3] ± or prompt radiation generated during the bombardment, such as particle-induced X-ray emission (PIXE) [4,5] and particle-induced c-ray emission (PIGE) using protons [6±8], alpha particles [9,10], deuterons [11] and tritons [12]. Despite the high accuracy, precision and sensitivity of the three methods, they have certain limitations discussed elsewhere [13±15].

0168-583X/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 0 1 ) 0 0 4 4 1 - 4

A. Ene et al. / Nucl. Instr. and Meth. in Phys. Res. B 179 (2001) 126±132

In standard PIGE, on the one hand, the c-ray yield is dependent on the type of the incident particle, its energy and on the cross-section of the nuclear reaction and, on the other hand, the bombardment of a complex target, such as steel, with charged particles may open many reaction channels so that the spectrum becomes extremely complicated, making the identi®cation and analysis very dicult. Among the factors a€ecting the sensitivity of PIGE frequently discussed in the literature, the background in the c-ray spectrum holds a prominent place [11,16,17]. In a previous paper [14] we demonstrated the improvement of the sensitivity reducing the background by the selection only of the (p, n) reaction channel, measuring the c±n coincidences following the reactions of 5.5 MeV protons on steel. In the present work we have used deuterons as projectiles and we have selected the (d, n) reaction channel in order to improve the sensitivity of analysis. 2. Experimental The standard sample EURONORM-CRM No. 085-1 was a steel plate of 10  10 mm2 and 200 lm thick. The minor elements present in the sample and their concentrations, as speci®ed by the manufacturer, are the following: C ± 670 ppm; Si ± 80 ppm; P ± 620 ppm; S ± 3360 ppm; V ± 21 ppm; Mn ± 9770 ppm; Co ± 190 ppm; Cu ± 2910 ppm; Zn ± 25 ppm; Sb ± 73 ppm and Pb ± 10 ppm. A beam of 5 MeV deuterons has been generated with the aid of the 7 MV FN tandem accelerator of the National Institute of Physics and Nuclear Engineering (NIPNE), Bucharest. The beam current was below 10 nA. Prompt c-rays produced in the sample were measured with a GeHP detector having an active volume of about 100 cm3 and an energy resolution of 2 keV at 1.33 MeV, placed at 90° with respect to the beam. The resulted neutrons were observed by a detector with liquid scintillation (NE213, U120  100 mm3 ) placed at 0° with respect to the beam. This scintillation detector together with the pulse-shape discriminator provided the neutron±c separation [14]. The GeHP and the scintillation detectors have been coupled

127

to a coincidence scheme of the type slow±fast with a time resolution 2s ˆ 17 ns for Ec P 30 keV. Singular c and coincidence n-c…Ec ; n; Dt† spectra were measured simultaneously by means of a multiparameter analyzer system and processed o€line. We have also analyzed samples of the same type of standard by NAA at VVR-S Nuclear Reactor of NIPNE Bucharest and by PIXE using a beam of 3 MeV protons. 3. Results and discussion The prompt single c-ray and n±c coincidence spectra obtained during the bombardment of the standard steel sample with 5 MeV deuterons are given in Figs. 1±3. The interference-free c-ray lines used to identify the component elements in the steel standard, labelled in accordance with the analysts' convention [9], are given in Table 1. cenergies corresponding to the possible transitions in the nuclei of interest were extracted from the nuclear level schemes [18]. The c-rays observed in the singular spectrum shown in Figs. 1±3(a), arise in general from the reaction channels (d, p), (d, n), (d, a), (d, d0 ) and, with a smaller probability, (d, c), (d, t) and (d, 3 He). This spectrum contains some intense c lines due to the isotopes of the major element in steel ± iron ± or isotopes with a large cross-section, situated on a high background. Thus, from the singular spectrum we could establish the presence of the elements As, Pb, Sb, P, Cr, V, Ti, Cu, Fe, Ni, O, Co, Mo, Zn, Si, S, Al, Mn and C. The c±n coincidence spectrum, obtained as a result of the selection of the c transitions via the reaction channel (d, n), is substantially di€erent from the singular c-spectrum, presenting c lines of suciently high intensity to be used in the analysis, on a reduced background. The coincidence spectrum shows lines from Mo, Cr, Ni, Pb, Fe, Co, Ti, Zn, Sb, Mn, O, S, Cu, Si, V, P and Al, as apparent from Figs. 1 and 2(b). We mentioned the fact that the minor elements Ti, Mo, As, Al, Ni, O and Cr, identi®ed by us in the sample, do not appear among the elements whose concentrations have been determined by the

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Fig. 1. Prompt c-ray (a) and c±n coincidence (b) spectra from irradiation of the standard steel sample EURONORM with 5 MeV deuterons.

manufacturer. In [14] we reported the presence of Ti, Mo, Al and Cr in the same standard sample. Neutron activation and PIXE analyses of other standard-steel samples of EURONORM-CRM No. 085-1 have put in evidence W, Al, As, Cr, Na besides the certi®ed elements Mn, V, Sb, Co, Cu (NAA) and Ni, As, Mo, Rb, In, Rh besides V, Mn, Co, Cu, Pb (PIXE). Further, by taking into consideration the experimental data and the certi®ed concentrations of the elements present in the standard sample, we have determined the sensitivity both in the case of the singular c spectrum and in the case when the (d, n) reaction channel has been selected with the aid of the n±c coincidences. We de®ned the sensitivity as the lowest concentration of the element under consideration that would give a peak under which the integrated number of counts is equal to three times the square root of the background count. Our results, together with those obtained by us using 5.5 MeV protons [14], are summarized in Table 2.

While for a given energy of the protons not all the elements of interest (especially the light ones, which in¯uence the properties of steels, such as C, O, P, S, Si, etc.) lead to a (p, n) reaction, for all target nuclides the above-mentioned reactions with deuterons, including the (d, n) reactions, are either exoergic or they have a low threshold. On one hand, this is an advantage because of the possibility of analyzing a greater number of elements, a greater number of c lines being available for each element. On the other hand, the identi®cation of the elements is more dicult in the case of deuterons because of the opening of a great number of reaction channels, especially in the singular spectrum, but the nuclear interferences due to adjacent elements in the periodic table present in the steel target are eliminated in the coincidence spectrum. The sensitivities obtained for Co, Zn and Sb using deuterons are lower than in the case of protons while for Mn, Cu and Si, the protons are more ecient; for Si the sensitivities are the same in the case of common PIGE and coincidence

A. Ene et al. / Nucl. Instr. and Meth. in Phys. Res. B 179 (2001) 126±132

129

Fig. 2. Prompt c-ray (a) and c±n coincidence (b) spectra (continued from Fig. 1).

d-PIGE. For Pb, C and V the sensitivities have relative close values in both cases of irradiation. Like in proton irradiation, the sensitivities determined by the measurements with consideration of the neutron emission are improved, being lower, which demonstrates the superiority of the method of c±n coincidences. Carbon can be determined in steel from the singular spectrum from the very high yields of the 3089.4 keV (1,0), 3684.5 keV (2,0) and 3853.8 keV

Fig. 3. Prompt c-ray spectrum (continued from Fig. 2(a)).

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A. Ene et al. / Nucl. Instr. and Meth. in Phys. Res. B 179 (2001) 126±132

Table 1 Identi®cation of c-rays observed in the deuteron bombardment of the standard steel sample EURONORM Peak no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

Ec (keV)

Identity

231.3 237.4 247.0 260.4 264.6 290.4 301.0 304.9 315.0 324.5 332.5 365.6 381.4 391.3 431.2 467.3 491.0 501.9 505.3 511.0 529.7 537.1 538.5 548.0 583.5 593.5 596.0 635.8 639.7 650.5 663.2 673.4 692.7 704.9 718.7 735.0 765.7 776.2 846.8 855.5 872.1 886.0 889.2 924.4 931.3 962.0 989.0 991.6 1005.1 1011.0 1027.3

95

Mo n…12; 3† Cr n…1; 0† 61 Ni n…3; 1† 61 Ni n…6; 3† 75 As d…2; 0† ‡ p…13; 1† 94 Mo n…3; 2† 94 Mo n…7; 3† 208 Pba…2; 0† ‡ …6; 3† 207 Pb n…14; 12† 96 Mo n…3; 0† 57 Fe n…16; 9† 57 Fe n…4; 0† 123 Sb d…2; 1† 121 Sb d…12; 6† 31 P p…5; 4† 59 Co n…5; 2† 58 Ni n…1; 0† 50 Cra…16; 10† 94 Mo n…18; 7† 57 Fe n…7; 5† 95 Mo n…22; 1† 47 Ti n…10; 4† 207 Pb n…3; 1† 61 Ni n…6; 0† 208 Pb d…2; 1† 60 Ni n…7; 3† 75 As d…11; 2† 68 Zn n…13; 6† 96 Mo n…11; 2† 58 Fe n…13; 7† 57 Fe n…23; 7† 56 Fe n…6; 1† 121 Sb n…3; 1† 53 Cr n…7; 3† 53 Cr n…22; 11† 94 Mo n…40; 18† 62 Ni n…10; 3† 47 Ti n…9; 0† 55 Mn n…1; 0† 96 Mo n…11; 0† 68 Zn n…3; 0† 51 V p…13; 7† 46 Ti d…1; 0† 63 Cu d…12; 4† 56 Fe t ‡ 54 Fe p…2; 0† 63 Cu d…2; 0† 32 S n…7; 2† 63 Cu n…1; 0† 58 Ni d…2; 1† 54 Fe t…7; 32† 59 Co n…8; 2† 50

Table 1 (Continued) Peak no.

Ec (keV)

Identity

52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104

1080.5 1101.9 1117.5 1124.8 1151.9 1155.0 1162.1 1165.0 1177.3 1190.4 1195.5 1207.0 1217.0 1224.0 1229.0 1232.3 1238.3 1241.7 1246.2 1251.5 1280.0 1293.7 1303.3 1325.5 1327.0 1348.5 1377.6 1392.5 1396.2 1410.6 1419.3 1423.6 1426.5 1432.3 1441.2 1451.0 1459.6 1486.8 1490.2 1505.1 1508.3 1524.1 1548.0 1562.2 1570.9 1584.5 1592.0 1609.3 1619.0 1625.9 1660.2 1686.6 1688.6

16

Oc…3; 0† Pb n…26; 3† 52 Cr n…6; 2† 57 Fe n…13; 3† 28 Si n…4; 2† 46 Ti p…12; 2† 58 Fe p…9; 0† 59 Co n…16; 4† 58 Ni n…17; 4† 59 Co d…2; 0† 66 Zn n…9; 2† 68 Zn n…8; 1† 47 Ti n…25; 12† 56 Fe n…1; 0† 50 Cr n…19; 4† 65 Cu n…12; 2† 55 Mn n…2; 1† 52 Cr n…4; 1† 51 V n…10; 2† 52 Cr n…12; 3† 56 Fe n…23; 6† 59 Co n…5; 1† 55 Mn n…10; 2† 123 Sb n…3; 0† 63 Cu d…3; 0† 18 O n…4; 1† 56 Fe n…2; 0† 62 Ni n…8; 1† 92 Mo n…8; 1† 94 Mo n…27; 2† 59 Co n…23; 4† 48 Ti n…7; 2† 33 S n…5; 2† 98 Mo d ‡ 97 Mo p…3; 0† 52 Cr n…3; 0† 68 Zn p…14; 2† 58 Fe n…5; 0† 48 Ti n…18; 3† 48 Ti n…9; 2† 56 Fe n…26; 5† 53 Cr n…14; 0† 57 Fe n…22; 0† 31 P n…2; 1† 94 Mo n…42; 3† 48 Ti n…11; 1† 53 Cr n…3; 1† 58 Ni n…29; 5† 50 Ti n…3; 0† 51 V d…6; 2† 96 Mo d…4; 0† 60 Ni n…5; 0† 208 Pb n…6; 1† 64 Zn n…15; 2† 207

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Table 1 (Continued)

Table 1 (Continued) Peak no.

Ec (keV)

Identity

Peak no.

Ec (keV)

Identity

105 106 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159

1705.5 1714.9 1742.0 1744.5 1752.8 1757.6 1763.2 1778.9 1787.3 1799.3 1804.3 1816.8 1835.5 1853.8 1872.0 1903.4 1911.3 1919.5 1932.4 1942.8 1962.0 1966.7 1991.5 2026.9 2032.3 2036.2 2062.8 2079.1 2090.7 2110.0 2118.0 2133.1 2148.6 2155.0 2165.8 2171.0 2176.5 2184.4 2190.3 2236.8 2252.0 2259.7 2300.6 2306.7 2311.3 2329.0 2331.7 2354.2 2422.5 2479.0 2492.0 2565.8 2588.0

48

160 161 162 163 164 165 166 167 168 169 170

2598.5 2617.3 2638.6 2656.0 2665.8 2685.5 2686.0 2835.8 3089.4 3684.5 3853.8

55

Ti n…24; 4† Ni n…29; 4† 54 Cr n…20; 2† 58 Fe n…7; 0† 121 Sb n…6; 0† 56 Fe n…5; 0† 34 S n…2; 0† 27 Al n…1; 0† 60 Ni d…6; 1† 63 Cu n…2; 0† 60 Ni n…35; 4† 50 Cr n…4; 0† 47 Ti n…28; 5† 59 Co n…8; 1† 56 Fe t…29; 5† 48 Ti n…12; 1† 52 Cr n…26; 2† 56 Fe n…7; 0† 60 Ni n…8; 0† 60 Ni n…9; 0† 58 Fe p ‡ 57 Fe d…15; 0† 64 Zn n…17; 0† 47 Ti n…31; 5† 62 Ni n…23; 1† 94 Mo n…35; 0† 30 Si p…4; 1† 58 Fe n…8; 0† 53 Cr n…24; 1† 48 Ti n…14; 1† 58 Ni n…16; 2† 94 Mo n…37; 0† 56 Fe n…8; 0† 30 Si n…5; 1† 50 Ti n…9; 2† 54 Fe n…1; 0† 27 Al p…8; 1† 55 Mn p…43; 1† 16 O p…2; 1† 54 Fe3 He…3; 2† 53 Cr n…27; 1† 94 Mo n…49; 0† 47 Ti d ‡ 46 Ti p…9; 0† 53 Cr n…28; 1† 63 Cu n…4; 0† 56 Fe n…9; 0† 64 Ni n…10; 0† 92 Mo d…20; 1† 53 Cr n…28; 0† 28 Si n…3; 0† 58 Fe n…14; 0† 208 Pb n…4; 0† 54 Fe n…2; 0† 208 Pb p…10; 0† 58

Mn n…11; 1† Pb n…8; 0† 58 Ni n…20; 1† 27 Al p…13; 0† 27 Al d…7; 2† 32 S n…4; 0† 52 Cr n…11; 0† 56 Fe p…29; 0† 12 C p…1; 0† 12 C p…2; 0† 12 C p…3; 0† 208

(3,0) c-rays resulted from the reaction 12 C…d; p†13 C [19], the excellent peak to background ratio and the absence of other peaks in the 3±4 MeV energy range (Fig. 3) leading to a good sensitivity. In the coincidence spectrum the peaks observed at 2365 and 1146 keV, due to (1,0) and (2,1) c-rays resulted from the 12 C…d; n†13 N reaction, are too weak to be used for carbon analysis. Oxygen can be analyzed in steel from the yields of the 1080.5 keV 16 O c (3,0) and 2184.4 keV 16 O p…2; 1† c-rays in the singular spectrum and only from 1348.5 keV 18 O n…4; 1† in the coincidence spectrum because the most intense 495.3 keV 16 O n…1; 0† c-ray interferes with the 496.2 keV 207 Pb n…17; 11† c-ray in steels which contain lead. None of the other observed peaks in the singular and coincidence spectra can be used for oxygen analysis because of the spectral interferences, such as 2609 keV 16 O n…2; 1† and 2609.4 keV 63 Cu n…5; 0† c-rays; 1458.5 keV 18 O n…4; 0† and 1457 keV 60 Ni n…8; 1† c-rays; 870.7 keV 16 O p…1; 0† and 870.7 keV 56 Fe p ‡ 57 Fe d…5; 3† c-rays; 1020.6 keV, 1041 keV, 2053.8 keV 16 O c (6,3), (2,0), (9,3) and 1019 keV 56 Fe p (10,4), 1040 keV 57 Fe n (8,0), 2054.9 keV 56 Fe a (22,1) c-rays. Nitrogen, although existing in steels at tenths of ppm level, cannot be determined using 5 MeV deuterons either from 14 N…d; n†15 O or from 14 N…d; p†15 N reaction because the ®rst excited state of 15 O and 15 N is 5183 and 5270 keV, respectively. More than this, the observed peaks in the singular spectrum at 1146 and 2312.9 keV energy are composed ones due to both nuclear and

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Table 2 Comparison of sensitivity of common and with c±n coincidence PIGE and d-PIGE methods Element

Sensitivity (ppm) PIGE (protons) ± [14] Common

Co Mn Si Zn V Sb Cu Pb C S P

115 12

10

d-PIGE (deuterons) ± this work c±n coincidence

Common

c±n coincidence

150 18

116 870 35 10 16 30 820 8 11 890 188

65 400 15 7 10 16 630 5

20 15 60 330 7

spectral interferences, as following: 1146 keV 14 N t ‡ 12 C n…2; 1† c-ray interferes with 1145 keV 121 Sb d…8; 0† c-ray and 2312.9 keV 14 N d ‡ 12Cc…1; 0† c-ray interferes with 2311.3 keV 56 Fe n…9; 0† c-ray. Despite the good sensitivity of the coincidence method in PIGE and d-PIGE spectrometry, the limit of the method is that this type of experiment requires more complex equipment and longer irradiation times, which ®nally leads to a higher cost of the analysis. References [1] J. Hoste, F. Bouten, F. Adams, Nucleonics 19 (1961) 118. [2] I. Popescu, T. Badica, A. Olariu, C. Besliu, A. Ene, Al. Ivanescu, J. Radioanal. Nucl. Chem. Lett. 213 (1996) 369. [3] Antoaneta Ene, C. Besliu, Agata Olariu, I.V. Popescu, T. Badica, E.D. Jianu, I. Stefanescu, Al. Ivanescu, Rom. J. Phys. 44 (1±2 Suppl.) (1999) 165. [4] M. Ahlberg, Nucl. Instr. and Meth. 142 (1977) 61. [5] D.K. Wilson, J.L. Duggan, D.L. Weathers, F.D. McDaniel, S. Matteson, T. Thomson, I.L. Morgan, Nucl. Instr. and Meth. B 56±57 (1991) 690.

420 98

[6] M. Peisach, D. Gihwala, J. Radioanal. Chem. 61 (1981) 37. [7] D. Gihwala, M. Peisach, Nucl. Instr. and Meth. 193 (1982) 371. [8] D. Gihwala, M. Peisach, J. Radioanal. Chem. 70 (1982) 287. [9] D. Gihwala, I.S. Giles, M. Peisach, J. Radioanal. Chem. 47 (1978) 145. [10] D. Gihwala, I.S. Giles, C. Olivier, M. Peisach, J. Radioanal. Chem. 46 (1978) 333. [11] N.S. Chen, J.H. Fremlin, Radiochem. Radioanal. Lett. 4 (1970) 365. [12] M. Peisach, J. Radioanal. Chem. 12 (1972) 251. [13] M. Peisach, J. Radioanal. Chem. 61 (1981) 243. [14] T. Badica, C. Besliu, A. Ene, A. Olariu, I. Popescu, Nucl. Instr. and Meth. B 111 (1996) 321. [15] N. Uzunov, I. Penev, Nucl. Instr. and Meth. B 129 (1997) 137. [16] A.E. Pillay, D.K. Bewley, Int. J. Appl. Radiat. Isot. 35 (1984) 353. [17] A.F. Gubrich, Nucl. Instr. and Meth. B 129 (1997) 439. [18] R.B. Firestone, in: Table of Isotopes, eighth ed, Wiley, New York, 1996. [19] F. Papillon, P. Walter, Nucl. Instr. and Meth. B 132 (1997) 468.