- Email: [email protected]
Conversion of isotopic material from metal to compound and vice versa
ARTICLE IN PRESS
Nuclear Instruments and Methods in Physics Research A 561 (2006) 100–103 www.elsevier.com/locate/nima
Conversion of isotopic material from metal to compound and vice versa Bettina Lommel, Willi Hartmann, Birgit Kindler, Jutta Steiner Gesellschaft fu¨r Schwerionenforschung, Targetlabor, Planckstrasse 1, 64291 Darmstadt, Germany Available online 20 January 2006
Abstract Often the compound needed out of isotopically enriched material is not readily available. Frequently the isotopically enriched metals are disproportionately expensive compared to the oxide or carbonate. Physical and chemical techniques have to be applied to receive the wanted compound or metal. We describe different procedures to produce 206PbS, 207PbS and 208PbS out of enriched lead, lead nitrate and lead oxide. To obtain the fluorides of 144Sm, 142Nd, 138Ba and 82Sr, chemical techniques are introduced. 48Ca and 144Sm are needed as metal but only the oxide is affordable. The oxides are reduced in a resistively heated tantalum crucible, and the process and the efficiency are discussed. r 2006 Elsevier B.V. All rights reserved. PACS: 28.60.+s; 81.20; 52.57.Bc Keywords: Isotopic material; Compound target; Chemical synthesis
206
The most economic way is to buy isotopic material in the chemical compound required, in the wanted enrichment. However, the suitable compound is not always available or the needed compound is disproportionately expensive. Therefore we have to adapt chemical inorganic synthesis on a small scale with a high yield. In the case of the lead isotopes 206, 207 and 208 PbS was required because of its higher melting point [1]. The alkaline earth metals and the lanthanides are available as carbonate or oxide but as we need a stable compound for the thermal evaporation, the fluorides were wanted. For an experiment in the nuclear chemistry group a metallic 144Sm target was needed, while 144Sm2O3 was available. For a beam out of 48Ca, the ion sources need metallic calcium, while carbonate is readily available and much less expensive compared to the metal. The chemical synthesis is discussed. Processes for starting materials from 10 to 1000 mg are presented with yields between 93% and 99%.
For the synthesis of lead sulphide we started with the metal for 208Pb, with the oxide for 207Pb and with the nitrate for 206Pb, as these compounds were stocked in the wanted enrichment. The chemical reactions are given by
0168-9002/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2005.12.230
PbS and
208
2. Synthesis of
Corresponding author. Tel.: +49 6159 71 26 91; fax: +49 6159 71 21 66. E-mail address: [email protected] (B. Lommel).
PbS,
207
1. Introduction
PbS
Pb þ 2HNO3 ! PbðNO3 Þ2 þ H2 "; PbO þ 2HNO3 ! PbðNO3 Þ2 þ H2 O; PbðNO3 Þ2 þ 2ðNH4 Þ2 S ! PbS # þ2NH4 NO3: In case of the metal we rolled a foil down to a thickness of 20 mm to enlarge the surface. The lead or the lead oxide was mixed with nitric acid, a stoichiometric amount plus 10–20% excess. Little water was added. The lead foil or the lead oxide was dissolved completely, while the solution was stirred constantly and heated up to about 40 1C. Evaporated water had to be replaced. This took several hours and was done preferably overnight. The lightly acid solution of lead nitrate was heated nearly until boiling. Then a stoichiometric amount plus 10% excess of 5% diluted ammonium sulphide was added drop by drop into the solution. Lead sulphide precipitated in coarse grains, shiny metallic and anthracite. The precipitation was filtrated
ARTICLE IN PRESS B. Lommel et al. / Nuclear Instruments and Methods in Physics Research A 561 (2006) 100–103 Table 1 Conversion from lead to lead sulphide for Isotope
Form
206
Enrichment (%)
Pb,
207
Pb, and
101
208
PbS
Initial weight (mg)
HNO3 (65%)
(NH4)2S (20%)
Theoretical
Real
Theoretical
Real
Weight (mg)
Yield (%)
208 208 208
Metal Metal Metal
99.00 99.00 99.00
610.77 954.61 706.00 2271.38
569.66 890.36 658.48
600 930 700
998.37 1560.42 1154.04
1000 1610 1190
676.30 1082.11 801.16 2559.57
95.96 98.24 98.34 97.51
207 207
Oxide Oxide
98.90 98.90
764.09 472.09 1236.18
712.66 470.00
750 520
1248.99 775.00
1300 800
854.12 533.18 1387.30
96.87 97.88 97.38
206
Nitrate
99.46
799.30 799.30
826.02
850
572.85 572.85
99.96 99.96
completely. The lead sulphide was dried at 120–150 1C for more than 3 h. The hot precipitation ensured the coarse grains. The colloidal sulphur from the ammonium sulphide fitted through the filter. Ammonium nitrate would split into gaseous products under evaporation if there would be any leftovers. Table 1 gives an overview of the different precipitations. For the 208Pb we started with lead foils, rolled down to 20 mm, we split this into three portions with a total yield of 97.51%. For the 207Pb we applied the oxide and gained a yield of 97.38%. For the 206Pb we already started with the nitrate, so we saved one step and gained a yield of 99.96%. 3. Synthesis of
82
SrF2,
138
BaF2,
142
NdF3,
144
SmF3
Isotopically enriched alkaline earth metals can be bought as carbonates; the carbonates decompose during heating into the oxides. Isotopically enriched lanthanides can be bought as oxides. The oxides cannot be evaporated thermally because of the high melting point. For the evaporation with the electron beam gun significantly more material is needed, and the thermal stress for backing and target is much higher [2]. We started with 82SrCO3 with an enrichment of 95.8%, with 138BaCO3 with an enrichment of 95.7%, with 142Nd2O3 with an enrichment of 95.8% and with 144Sm2O3 with an enrichment of 96%. Depending on the requirements the initial weight was 10–200 mg. The carbonate or the oxide was loaded into a Teflons container and mixed with 2–3 ml of water. Then a stoichiometric amount of hydrofluoric acid was added, plus 5–10% excess. The solution was heated in a water bath of about 60–70 1C for 1 h. Water, hydrofluoric acid and carbon dioxide vaporised. A white powder was left over, which was dried at 120 1C. With this procedure a hardly soluble starting material is converted into an insoluble end product with a yield of 99%. BaCO3 and SrCO3 cannot be evaporated directly; BaF2 and SrF2 have a melting point of 1368 and 1477 1C, respectively. Sm2O3 and Nd2O3 cannot be evaporated thermally because of their high melting point of about
Fig. 1. 142NdF3 with a thickness of 200 mg/cm2 neodymium on eight banana-shaped targets.
2300 1C, the fluorides have a melting point of 1306 and 1374 1C, respectively, which is still high enough to stand an intense heavy-ion beam. The fluorides so obtained can be evaporated thermally. There is no impurity of the starting material left as it would be visible as residue in the tantalum crucible. Fig. 1 shows a wheel with eight banana targets with 142 NdF3 with a thickness of 200 mg/cm2 with respect to neodymium. 4. Reductive evaporation of
144
Sm2O3
For nuclear chemistry experiments metallic 144Sm was wanted on carbon backing, aluminium backing and titanium backing. Kobisk et al. [3] described the reduction–distillation
ARTICLE IN PRESS B. Lommel et al. / Nuclear Instruments and Methods in Physics Research A 561 (2006) 100–103
102
process for rare-earth isotope metals with lanthanum and thorium. Pengo et al. [4] discussed zirconium, hafnium, thorium and lanthanum as reducing agent for the rare-earth oxides. The corresponding vapour pressures and enthalpies are listed in detail. For the following target production a radioactive reducing agent was not feasible; this excluded thorium. Furthermore, the availability of the reducing agent as a fine powder was important for a successful reduction. A fast evaporation without any detectable impurities was wanted. So zirconium and lanthanum were applied. The chemical reactions are given by 2Sm2 O3 þ 3Zr ! 4Sm þ 3ZrO2 ; Sm2 O3 þ 2La ! 2Sm þ La2 O3 : We started with about 20 mg of Sm2O3. The reducing agent was applied with an excess of about 20%. We deposited zirconium-reduced samarium on titanium backings and carbon backings. We deposited lanthanum-reduced samarium on titanium backings and aluminium backings. Samarium oxide and the reducing agent were mixed and pressed into the tantalum crucible, which was situated in a distance of 35 mm from the turntable. We evaporated on small target frames with 9 mm aperture or banana-shaped frames 30 mm long and 10 mm wide, with a target thickness of 150–330 mg/ cm275%. The energy-dispersive X-ray analysis (EDX) did not show any impurities or any trace of the reducing agent. Zirconium-reduced samarium showed significant higher oxygen content compared to the lanthanum-reduced samarium. Lanthanum has a larger difference in enthalpy and a significant higher vapour pressure at lower process temperature compared to the zirconium. This allows a faster evaporation. Table 2 gives an overview of the production processes on titanium backings with a thickness of 2.5, 2.4 and 1.25 mg/ cm2, on carbon backings with a thickness of 41 mg/cm2 and on aluminium backings with a thickness of 1.8 mg/cm2. 5. Reduction of
48
Table 2 Reductive evaporation of samarium oxide with zirconium and lanthanum on backings out of titanium, carbon and aluminium RA
Material
1 1 1 1 1 3 1 1 1 1 1 2 1 3 1 1 2 1
Zr Zr Zr Zr Zr Zr La La La La La La La La La La La La
144 Sm target
Backing
Ti Ti Ti Ti C C Ti Ti Ti Ti Al Al Al Ti Ti Al Al Al
Thickness
Thickness (mg/cm2)
Nominal (mm)
Measured (mg/cm2)
5 5 5 5
2.5 2.5 2.5 2.5 0.041 0.041 2.4 2.4 2.4 2.4 1.8 1.8 1.8 1.25 1.25 1.77 1.77 1.77
5 5 5 5 7 7 7 3 3 7 7 7
150 170 240 330 150 160 180 205 220 250 170 200 220 250 270 220 250 270
CaCO3
The reduction of 48CaCO3 is from the application’s point of view not a target problem. Metallic 48Ca is needed for the ECR-ion sources [5] as source material. 48Ca is a popular beam out of a fairly expensive isotope. Residues from crucible and shielding as oxide or carbonate have to be recycled. Buying 48Ca as carbonate is up to 60% cheaper than the metal and instantly available. Annealing 48CaCO3 at 950 1C leads to 48CaO plus CO2m. The initial weight of CaO was about 500 mg. The chemical reaction is given by 2CaO þ Zr ! 2Ca þ ZrO2 : Zirconium was applied with an excess of about 25%. The powder were pounded and mixed in a mortar. The mixture is pressed to a pill and loaded into a tantalum crucible which is closed with a tantalum lid. The lid has an
Fig. 2. Overview of the set-up for the reduction of 48CaO with the watercooled copper plate, the tantalum crucible and the tantalum lid.
aperture of 2.5 mm; above the lid a water-cooled copper plate is situated in 1 mm distance. Fig. 2 gives an overview of the set-up. The crucible was heated cautiously to allow the outgasing. The reaction of the calcium oxide and the evaporation of the calcium happened simultaneously. The metal condensation started on the cooled copper plate; the lid was closed. In this closed system on the inner side of the lid a compact lump was deposited. Table 3 shows the different reduction processes to get a total amount of 4000 mg of metallic calcium. The starting material was
ARTICLE IN PRESS B. Lommel et al. / Nuclear Instruments and Methods in Physics Research A 561 (2006) 100–103 Table 3 Reduction of calcium oxide for Enrichment (%)
48
CaO
48
48
Ca
Ca
Zr (mg)
48
Ca (mg)
Yield (%)
512.34 503.03 504.81 506.66 500.88 503.50 501.57 501.69 538.00 779.20
388.84 418.36 399.84 336.50 412.00 408.00 393.00 393.50 397.42 631.78 4179.24 4179.24
90.71 97.78 93.24 78.36 96.29 95.10 91.97 91.93 89.96 92.15 91.76 93.29
Initial Theoretical Bought weight (mg) (mg)
82.70 82.70 82.70 82.70 82.70 82.70 82.70 82.70 89.50 84.70
571.56 570.45 571.75 572.56 570.50 572.00 569.75 570.73 589.00 914.10
428.67 427.84 428.81 429.42 427.88 429.00 427.31 428.05 441.75 685.58 4554.30 4480.00
103
tantalum crucible of the ECR source. Since this is a solid–solid reaction, which is a slow process, a close contact of the powder is required and good vacuum has to be provided. From neither EDX analysis nor from the ECR source during extraction are any impurities detectable. The fairly low consumption at the source of 0.3 mg/h for beam intensities up to 1 p mA at the experiment indicates a good quality of the converted calcium.
6. Outlook For technical and economic reasons we have to adapt chemistry on a small scale time and again. For target and beam applications synthesis is wanted for, with starting materials of 20–500 mg and yields above 90%.
References enriched above 80%. The theoretical amount of calcium calculated from the weight of the calcium oxide gives a yield of 91.8%, the amount of material originally bought gives a yield of 93.3%. Probably the annealed CaO contained still an amount of water or carbonate. A slow deposition gives a compact lump, which can be processed further into a compact cylinder to fit in the
[1] B. Kindler, et al., AIP Conf. Proc. 680 (2003) 781. [2] F. Nickel, W. Hartmann, D. Marx, Nucl. Instr. and Meth. 167 (1979) 175. [3] E.H. Kobisk, W.B. Grisham, Mater. Res. Bull. 4 (1969) 651. [4] R. Pengo, P. Favaron, G. Manente, A. Cecchi, L. Pieraccini, Nucl. Instr. and Meth. A 303 (1991) 146. [5] K. Tinschert, J. Bossler, S. Schennach, H. Schulte, Rev. Sci. Instrum. 69 (2) (1998) 709.
Nuclear Instruments and Methods in Physics Research A 561 (2006) 100–103 www.elsevier.com/locate/nima
Conversion of isotopic material from metal to compound and vice versa Bettina Lommel, Willi Hartmann, Birgit Kindler, Jutta Steiner Gesellschaft fu¨r Schwerionenforschung, Targetlabor, Planckstrasse 1, 64291 Darmstadt, Germany Available online 20 January 2006
Abstract Often the compound needed out of isotopically enriched material is not readily available. Frequently the isotopically enriched metals are disproportionately expensive compared to the oxide or carbonate. Physical and chemical techniques have to be applied to receive the wanted compound or metal. We describe different procedures to produce 206PbS, 207PbS and 208PbS out of enriched lead, lead nitrate and lead oxide. To obtain the fluorides of 144Sm, 142Nd, 138Ba and 82Sr, chemical techniques are introduced. 48Ca and 144Sm are needed as metal but only the oxide is affordable. The oxides are reduced in a resistively heated tantalum crucible, and the process and the efficiency are discussed. r 2006 Elsevier B.V. All rights reserved. PACS: 28.60.+s; 81.20; 52.57.Bc Keywords: Isotopic material; Compound target; Chemical synthesis
206
The most economic way is to buy isotopic material in the chemical compound required, in the wanted enrichment. However, the suitable compound is not always available or the needed compound is disproportionately expensive. Therefore we have to adapt chemical inorganic synthesis on a small scale with a high yield. In the case of the lead isotopes 206, 207 and 208 PbS was required because of its higher melting point [1]. The alkaline earth metals and the lanthanides are available as carbonate or oxide but as we need a stable compound for the thermal evaporation, the fluorides were wanted. For an experiment in the nuclear chemistry group a metallic 144Sm target was needed, while 144Sm2O3 was available. For a beam out of 48Ca, the ion sources need metallic calcium, while carbonate is readily available and much less expensive compared to the metal. The chemical synthesis is discussed. Processes for starting materials from 10 to 1000 mg are presented with yields between 93% and 99%.
For the synthesis of lead sulphide we started with the metal for 208Pb, with the oxide for 207Pb and with the nitrate for 206Pb, as these compounds were stocked in the wanted enrichment. The chemical reactions are given by
0168-9002/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2005.12.230
PbS and
208
2. Synthesis of
Corresponding author. Tel.: +49 6159 71 26 91; fax: +49 6159 71 21 66. E-mail address: [email protected] (B. Lommel).
PbS,
207
1. Introduction
PbS
Pb þ 2HNO3 ! PbðNO3 Þ2 þ H2 "; PbO þ 2HNO3 ! PbðNO3 Þ2 þ H2 O; PbðNO3 Þ2 þ 2ðNH4 Þ2 S ! PbS # þ2NH4 NO3: In case of the metal we rolled a foil down to a thickness of 20 mm to enlarge the surface. The lead or the lead oxide was mixed with nitric acid, a stoichiometric amount plus 10–20% excess. Little water was added. The lead foil or the lead oxide was dissolved completely, while the solution was stirred constantly and heated up to about 40 1C. Evaporated water had to be replaced. This took several hours and was done preferably overnight. The lightly acid solution of lead nitrate was heated nearly until boiling. Then a stoichiometric amount plus 10% excess of 5% diluted ammonium sulphide was added drop by drop into the solution. Lead sulphide precipitated in coarse grains, shiny metallic and anthracite. The precipitation was filtrated
ARTICLE IN PRESS B. Lommel et al. / Nuclear Instruments and Methods in Physics Research A 561 (2006) 100–103 Table 1 Conversion from lead to lead sulphide for Isotope
Form
206
Enrichment (%)
Pb,
207
Pb, and
101
208
PbS
Initial weight (mg)
HNO3 (65%)
(NH4)2S (20%)
Theoretical
Real
Theoretical
Real
Weight (mg)
Yield (%)
208 208 208
Metal Metal Metal
99.00 99.00 99.00
610.77 954.61 706.00 2271.38
569.66 890.36 658.48
600 930 700
998.37 1560.42 1154.04
1000 1610 1190
676.30 1082.11 801.16 2559.57
95.96 98.24 98.34 97.51
207 207
Oxide Oxide
98.90 98.90
764.09 472.09 1236.18
712.66 470.00
750 520
1248.99 775.00
1300 800
854.12 533.18 1387.30
96.87 97.88 97.38
206
Nitrate
99.46
799.30 799.30
826.02
850
572.85 572.85
99.96 99.96
completely. The lead sulphide was dried at 120–150 1C for more than 3 h. The hot precipitation ensured the coarse grains. The colloidal sulphur from the ammonium sulphide fitted through the filter. Ammonium nitrate would split into gaseous products under evaporation if there would be any leftovers. Table 1 gives an overview of the different precipitations. For the 208Pb we started with lead foils, rolled down to 20 mm, we split this into three portions with a total yield of 97.51%. For the 207Pb we applied the oxide and gained a yield of 97.38%. For the 206Pb we already started with the nitrate, so we saved one step and gained a yield of 99.96%. 3. Synthesis of
82
SrF2,
138
BaF2,
142
NdF3,
144
SmF3
Isotopically enriched alkaline earth metals can be bought as carbonates; the carbonates decompose during heating into the oxides. Isotopically enriched lanthanides can be bought as oxides. The oxides cannot be evaporated thermally because of the high melting point. For the evaporation with the electron beam gun significantly more material is needed, and the thermal stress for backing and target is much higher [2]. We started with 82SrCO3 with an enrichment of 95.8%, with 138BaCO3 with an enrichment of 95.7%, with 142Nd2O3 with an enrichment of 95.8% and with 144Sm2O3 with an enrichment of 96%. Depending on the requirements the initial weight was 10–200 mg. The carbonate or the oxide was loaded into a Teflons container and mixed with 2–3 ml of water. Then a stoichiometric amount of hydrofluoric acid was added, plus 5–10% excess. The solution was heated in a water bath of about 60–70 1C for 1 h. Water, hydrofluoric acid and carbon dioxide vaporised. A white powder was left over, which was dried at 120 1C. With this procedure a hardly soluble starting material is converted into an insoluble end product with a yield of 99%. BaCO3 and SrCO3 cannot be evaporated directly; BaF2 and SrF2 have a melting point of 1368 and 1477 1C, respectively. Sm2O3 and Nd2O3 cannot be evaporated thermally because of their high melting point of about
Fig. 1. 142NdF3 with a thickness of 200 mg/cm2 neodymium on eight banana-shaped targets.
2300 1C, the fluorides have a melting point of 1306 and 1374 1C, respectively, which is still high enough to stand an intense heavy-ion beam. The fluorides so obtained can be evaporated thermally. There is no impurity of the starting material left as it would be visible as residue in the tantalum crucible. Fig. 1 shows a wheel with eight banana targets with 142 NdF3 with a thickness of 200 mg/cm2 with respect to neodymium. 4. Reductive evaporation of
144
Sm2O3
For nuclear chemistry experiments metallic 144Sm was wanted on carbon backing, aluminium backing and titanium backing. Kobisk et al. [3] described the reduction–distillation
ARTICLE IN PRESS B. Lommel et al. / Nuclear Instruments and Methods in Physics Research A 561 (2006) 100–103
102
process for rare-earth isotope metals with lanthanum and thorium. Pengo et al. [4] discussed zirconium, hafnium, thorium and lanthanum as reducing agent for the rare-earth oxides. The corresponding vapour pressures and enthalpies are listed in detail. For the following target production a radioactive reducing agent was not feasible; this excluded thorium. Furthermore, the availability of the reducing agent as a fine powder was important for a successful reduction. A fast evaporation without any detectable impurities was wanted. So zirconium and lanthanum were applied. The chemical reactions are given by 2Sm2 O3 þ 3Zr ! 4Sm þ 3ZrO2 ; Sm2 O3 þ 2La ! 2Sm þ La2 O3 : We started with about 20 mg of Sm2O3. The reducing agent was applied with an excess of about 20%. We deposited zirconium-reduced samarium on titanium backings and carbon backings. We deposited lanthanum-reduced samarium on titanium backings and aluminium backings. Samarium oxide and the reducing agent were mixed and pressed into the tantalum crucible, which was situated in a distance of 35 mm from the turntable. We evaporated on small target frames with 9 mm aperture or banana-shaped frames 30 mm long and 10 mm wide, with a target thickness of 150–330 mg/ cm275%. The energy-dispersive X-ray analysis (EDX) did not show any impurities or any trace of the reducing agent. Zirconium-reduced samarium showed significant higher oxygen content compared to the lanthanum-reduced samarium. Lanthanum has a larger difference in enthalpy and a significant higher vapour pressure at lower process temperature compared to the zirconium. This allows a faster evaporation. Table 2 gives an overview of the production processes on titanium backings with a thickness of 2.5, 2.4 and 1.25 mg/ cm2, on carbon backings with a thickness of 41 mg/cm2 and on aluminium backings with a thickness of 1.8 mg/cm2. 5. Reduction of
48
Table 2 Reductive evaporation of samarium oxide with zirconium and lanthanum on backings out of titanium, carbon and aluminium RA
Material
1 1 1 1 1 3 1 1 1 1 1 2 1 3 1 1 2 1
Zr Zr Zr Zr Zr Zr La La La La La La La La La La La La
144 Sm target
Backing
Ti Ti Ti Ti C C Ti Ti Ti Ti Al Al Al Ti Ti Al Al Al
Thickness
Thickness (mg/cm2)
Nominal (mm)
Measured (mg/cm2)
5 5 5 5
2.5 2.5 2.5 2.5 0.041 0.041 2.4 2.4 2.4 2.4 1.8 1.8 1.8 1.25 1.25 1.77 1.77 1.77
5 5 5 5 7 7 7 3 3 7 7 7
150 170 240 330 150 160 180 205 220 250 170 200 220 250 270 220 250 270
CaCO3
The reduction of 48CaCO3 is from the application’s point of view not a target problem. Metallic 48Ca is needed for the ECR-ion sources [5] as source material. 48Ca is a popular beam out of a fairly expensive isotope. Residues from crucible and shielding as oxide or carbonate have to be recycled. Buying 48Ca as carbonate is up to 60% cheaper than the metal and instantly available. Annealing 48CaCO3 at 950 1C leads to 48CaO plus CO2m. The initial weight of CaO was about 500 mg. The chemical reaction is given by 2CaO þ Zr ! 2Ca þ ZrO2 : Zirconium was applied with an excess of about 25%. The powder were pounded and mixed in a mortar. The mixture is pressed to a pill and loaded into a tantalum crucible which is closed with a tantalum lid. The lid has an
Fig. 2. Overview of the set-up for the reduction of 48CaO with the watercooled copper plate, the tantalum crucible and the tantalum lid.
aperture of 2.5 mm; above the lid a water-cooled copper plate is situated in 1 mm distance. Fig. 2 gives an overview of the set-up. The crucible was heated cautiously to allow the outgasing. The reaction of the calcium oxide and the evaporation of the calcium happened simultaneously. The metal condensation started on the cooled copper plate; the lid was closed. In this closed system on the inner side of the lid a compact lump was deposited. Table 3 shows the different reduction processes to get a total amount of 4000 mg of metallic calcium. The starting material was
ARTICLE IN PRESS B. Lommel et al. / Nuclear Instruments and Methods in Physics Research A 561 (2006) 100–103 Table 3 Reduction of calcium oxide for Enrichment (%)
48
CaO
48
48
Ca
Ca
Zr (mg)
48
Ca (mg)
Yield (%)
512.34 503.03 504.81 506.66 500.88 503.50 501.57 501.69 538.00 779.20
388.84 418.36 399.84 336.50 412.00 408.00 393.00 393.50 397.42 631.78 4179.24 4179.24
90.71 97.78 93.24 78.36 96.29 95.10 91.97 91.93 89.96 92.15 91.76 93.29
Initial Theoretical Bought weight (mg) (mg)
82.70 82.70 82.70 82.70 82.70 82.70 82.70 82.70 89.50 84.70
571.56 570.45 571.75 572.56 570.50 572.00 569.75 570.73 589.00 914.10
428.67 427.84 428.81 429.42 427.88 429.00 427.31 428.05 441.75 685.58 4554.30 4480.00
103
tantalum crucible of the ECR source. Since this is a solid–solid reaction, which is a slow process, a close contact of the powder is required and good vacuum has to be provided. From neither EDX analysis nor from the ECR source during extraction are any impurities detectable. The fairly low consumption at the source of 0.3 mg/h for beam intensities up to 1 p mA at the experiment indicates a good quality of the converted calcium.
6. Outlook For technical and economic reasons we have to adapt chemistry on a small scale time and again. For target and beam applications synthesis is wanted for, with starting materials of 20–500 mg and yields above 90%.
References enriched above 80%. The theoretical amount of calcium calculated from the weight of the calcium oxide gives a yield of 91.8%, the amount of material originally bought gives a yield of 93.3%. Probably the annealed CaO contained still an amount of water or carbonate. A slow deposition gives a compact lump, which can be processed further into a compact cylinder to fit in the
[1] B. Kindler, et al., AIP Conf. Proc. 680 (2003) 781. [2] F. Nickel, W. Hartmann, D. Marx, Nucl. Instr. and Meth. 167 (1979) 175. [3] E.H. Kobisk, W.B. Grisham, Mater. Res. Bull. 4 (1969) 651. [4] R. Pengo, P. Favaron, G. Manente, A. Cecchi, L. Pieraccini, Nucl. Instr. and Meth. A 303 (1991) 146. [5] K. Tinschert, J. Bossler, S. Schennach, H. Schulte, Rev. Sci. Instrum. 69 (2) (1998) 709.