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What is next after SPIRAL at GANIL?
Nuclear Physics A 701 (2002) 343c–347c www.elsevier.com/locate/npe
What is next after SPIRAL at GANIL? Danas Ridikas a,∗ , Wolfgang Mittig b , Antonio C.C. Villari b a CEA Saclay, F-91191 Gif-sur-Yvette, France b GANIL, BP 5027, F-14076 Caen, France
Abstract The aim of the considerations below is to estimate the orders of magnitude for the production of RNBs at GANIL with possible evolutions of the present accelerator complex. This study was requested by the “Conseil Scientifique du GANIL”. We present and compare methods to produce ISOL beams by fission and/or low-energy spallation. Such reactions would complement the present SPIRAL beams which are limited to light elements if high intensities are required. 2002 Elsevier Science B.V. All rights reserved. Keywords: Neutron sources; Fission yields; Radioactive beams
1. Introduction For the RNB facilities based on the charged particle induced reactions, a major limitation is defined by the maximum allowable heat deposition, say ∼ 20 kW, in the RNB production target. An alternative way of producing the RNBs in the mass region of 75 < A < 160 can be achieved utilizing a target–converter (neutron source) [1]. The emitted neutrons then interact with a fissionable target. Contrary to the charged particles, the neutrons will heat the target indirectly and mainly by the “useful” fission reactions. In this context we will discuss mainly two possibilities: (a) the neutron induced fission, where the neutrons are produced in a converter from a primary proton or deuteron beam; (b) the charged particle induced fission/spallation, where the primary beam directly hits a heavy target. The major goal is to reach 1014 fissions/s in order to be compatible with reactor-driven RNB facilities. We employ a coupled LAHET + MCNP + CINDER code system [2] for all numerical calculations presented in this work. * Corresponding author.
E-mail address: [email protected] (D. Ridikas). 0375-9474/02/$ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 5 - 9 4 7 4 ( 0 1 ) 0 1 6 0 8 - 6
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D. Ridikas et al. / Nuclear Physics A 701 (2002) 343c–347c
Under proton or deuteron bombardment, light-element targets (Li or Be) yield high neutron intensities [3]. For very intense primary beams (∼ 1 MW), cooling requirements indicate the use of a liquid target, i.e. Li (melting point 181◦ ) rather than Be (melting point 1287◦) [4]. Therefore, we will limit our discussion to the d + Li and p + Li reactions. High beam currents (> 10 mA) suggest the use of a linac, i.e., comparing protons and deuterons of equal energy. Fig. 1 presents the ratio of neutron yield from the d + Li reaction over p + Li. For a given energy the neutron yields, both angle-integrated and at forward direction, are higher for d-induced reaction. This difference increases with incident energy. The same holds for the average neutron energies: more energetic neutrons are produced by deuterons [3]. Similarly, the neutron angular distribution from the (d, xn) reaction is strongly forward peaked compared with the angular distribution from (p, xn) [3]. We have chosen 1 MW as the maximum deuteron beam power we feel can be reached and deposited in the target–converter [4]. For details on the flowing jet of liquid Li target we refer to Refs. [4,5]. Table 1 lists the major Li target parameters. Fig. 2 illustrates the principle of the setup. The expected neutron flux is of the order of 3 × 1014n/(s cm2 ) at the back side of the target–converter. Similar neutron fluxes are available only in the high flux nuclear reactors. We assume that the main goal for the future RNB factory is to reach fission rates ∼ 1014 fissions/s. Tables 2 and 3 summarize the main beam and target characteristics within this constraint for both converter (C) and direct (D) methods. The in-target fission yields are presented in Table 4 for some isotopes.
Fig. 1. Ratio of neutron yields from the d + Li reaction over the p + Li reaction as a function of the incident energy. The yields are extrapolated from [3].
Table 1 Target–converter parameters Beam power (energy) Beam dimension Lithium flow rate Lithium entrance (exit) temperature
1 MW (35 MeV) 3.82 cm diameter 5.14 l/s ∼ 200 ◦ C (∼ 300 ◦ C)
D. Ridikas et al. / Nuclear Physics A 701 (2002) 343c–347c
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Fig. 2. Schematic of a two-step, neutron-generator-type, high-power target–source for the production of the fission fragments. Design: Y. Huguet. A deuteron beam on a lithium target produces secondary neutrons. The secondary uranium carbide target is heated to 2000 ◦ C by a combination of the fission power and additional electrical power. The ion source represented is the ECRIS MONO1000 [6].
Table 2 Projectile/target combinations to produce high fission yields defined by ∼ 1014 fissions/s in the RNB production target. Also see Table 3 Scenario S1 S2 S3 S4 S5
Particle type
Energy (MeV)
d p d d p
35 35 35 200 200
Min. primary beam power (current) 196 kW (5.6 mA) 525 kW (15 mA) 560 kW (16 mA) 13.8 kW (69 µA) 13 kW (65 µA)
In-target power (kW) 3.2 3.2 3.2 17.0 16.2
Target type (material) C1 (liquid 238 U) C1 (liquid 238 U) C2 (solid UCx ) D1 (liquid 238 U) D2 (liquid 238 U)
Table 3 Target parameters for the production of fission yields by the fission/spallation reactions. See Table 2 for details. Note: Ci—converter, Di—direct Target type C1 C2 D1 D2
U density (g/cm3 )
Volume (cm3 )
238 U mass
18 1.5 18 18
169 2055 21 35
3055 3055 382 636
Geometry specification
(g) cylinder: r = 3 cm, l = 6 cm cone: 1r = 3 cm, 2r = 10.5 cm, l = 13 cm cylinder: r = 1.5 cm, l = 3 cm cylinder: r = 1.5 cm, l = 5 cm
Here we have considered the possibility of having solid UCx and liquid U targets with the assumption that the diffusion of liquid and porous solid targets have similar behaviour. If all the suggested cases are technologically feasible, there is another question which runs
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D. Ridikas et al. / Nuclear Physics A 701 (2002) 343c–347c
Table 4 Estimate of projected in-target fission yields, normalized to a primary beam intensity resulting in 1014 fissions/s in the RNB production target. Also see Table 2 Beam 91 Kr 36 94 Kr 36 97 Rb 37 119 Ag 47 132 Sn 50 142 Xe 54 144 Xe 54 144 Cs 55
T1/2 (s)
Liquid U (S1) (at./s 6 mA p)
UCx (S3) (at./s 18 mA p)
Liquid U (S4) (at./s 70 µA p)
8.57
3.2 × 1012
2.2 × 1012
1.1 × 1012
0.21
6.0 × 1011
4.5 × 1011
2.4 × 1011
0.17
2.2 × 1011
3.4 × 1011
1.1 × 1011
2.1
5.2 × 1011
3.2 × 1011
8.8 × 1011
40.0
1.6 × 1012
1.2 × 1012
3.2 × 1011
1.22
1.3 × 1012
1.0 × 1012
2.9 × 1011
1.10
9.6 × 1010
7.4 × 1010
2.0 × 1010
1.02
1.6 × 1012
1.3 × 1012
3.6 × 1011
out of the present study. We have not reached yet the final agreement on the projected overall efficiency (i.e. release * delay * ion-source efficiency). Therefore, the numbers in Table 4 have to be corrected accordingly for the expected final RNB intensities. Due to ∼ 1014 fissions/s the total activity of ∼ 14 kCi of the source is predicted after 90 days of irradiation. High radioactivity due to the noble gases and halogens will require a special treatment. We estimate that the source will still be highly radioactive (∼ 0.2 kCi) even after 3 months of cooling. Similar activities are reported for PIAFE project [7] where ∼ 1014 fissions/s were expected. The results we present show that very high fission yields may be obtained. For massive targets (∼ 3 kg) the neutron induced fission from a converter can provide 1014 fissions/s with a primary beam intensity of 196 kW and 525 kW for deuterons and protons of 35 MeV, respectively. The total power dissipated in the target is ∼ 3 kW. For less massive targets (∼ 0.5 kg), a direct p or d beam is preferred. 1014 fissions/s are reached with a deuteron beam of 14 kW at 200 MeV. The total power dissipated in the target is ∼ 17 kW. However, the C-method may reach the highest final intensities: 7.5 × 1014 fissions/s can be obtained employing the d beam of 1.6 MW (35 MeV) which results in 24 kW fission power (perhaps being the limit). The D-method provides similar yields but with smaller targets, and ∼ 1014 fissions/s being very close to the allowable heat deposition due to the primary beam and fissions all together (∼ 17 kW). On the other hand, in this case other targets than U could be used (e.g., Nb, La, Ta, Th). So this method provides a higher versatility than the C-method. In addition, the direct bombardment of these targets by α-particles would lead to the production of proton-rich nuclei. A promising technical aspect in the case of liquid targets could be the use of beams incident vertically on the target. This would avoid to the hostile conditions of a high intensity beam on a window separating the vacuum and a high-temperature liquid. A vertical beam could create a very high temperature inside the liquid, with moderate temperatures of the container walls. This together with convection currents should favour fast and efficient effusion. But the space around the target must be confined so as to guide the fission products towards the ion source and also because of the extreme chemical
D. Ridikas et al. / Nuclear Physics A 701 (2002) 343c–347c
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aggressiveness of molten uranium, so that there will always be some material between the incident beam and the surface of the liquid target. More detailed calculations and some exploratory experiments are necessary in this domain. Finally we add that the radioactivity problems will be crucial in the construction of such a RNB facility.
References [1] J.A. Nolen, in: D.J. Morrissey (Ed.), Proc. of the 3rd Int. Conference on RNB, Gif-sur-Yvette, France, 24–27 May, 1993, Éditions Frontières, 1993, p. 111. [2] D. Ridikas, PhD thesis, report GANIL-T 99 04, October, 1999, and references therein. [3] M.A. Lone, A.J. Ferguson, B.C. Robertson, Nucl. Instrum. Methods 189 (1981) 515; M.A. Lone et al., Nucl. Instrum. Methods 143 (1977) 331. [4] P. Grand, S.N. Goland, Nucl. Instrum. Methods 145 (1977) 49; C.M. Logan, R. Booth, R.A. Nickerson, Nucl. Instrum. Methods 145 (1977) 77. [5] A. Hassanein, J. Nucl. Materials 233–237 (1996) 1547. [6] R. Leroy et al., Ion source developments for stable and radioactive ion beams at GANIL, in: Proc. of the 14th Int. Workshop on ECR Sources, CERN, Geneva, Switzerland, 3–6 May, 1999. [7] PIAFE Collaboration, Technical report of the project covering the period 1993–1996, Report ISN 97-52, July, 1997.
What is next after SPIRAL at GANIL? Danas Ridikas a,∗ , Wolfgang Mittig b , Antonio C.C. Villari b a CEA Saclay, F-91191 Gif-sur-Yvette, France b GANIL, BP 5027, F-14076 Caen, France
Abstract The aim of the considerations below is to estimate the orders of magnitude for the production of RNBs at GANIL with possible evolutions of the present accelerator complex. This study was requested by the “Conseil Scientifique du GANIL”. We present and compare methods to produce ISOL beams by fission and/or low-energy spallation. Such reactions would complement the present SPIRAL beams which are limited to light elements if high intensities are required. 2002 Elsevier Science B.V. All rights reserved. Keywords: Neutron sources; Fission yields; Radioactive beams
1. Introduction For the RNB facilities based on the charged particle induced reactions, a major limitation is defined by the maximum allowable heat deposition, say ∼ 20 kW, in the RNB production target. An alternative way of producing the RNBs in the mass region of 75 < A < 160 can be achieved utilizing a target–converter (neutron source) [1]. The emitted neutrons then interact with a fissionable target. Contrary to the charged particles, the neutrons will heat the target indirectly and mainly by the “useful” fission reactions. In this context we will discuss mainly two possibilities: (a) the neutron induced fission, where the neutrons are produced in a converter from a primary proton or deuteron beam; (b) the charged particle induced fission/spallation, where the primary beam directly hits a heavy target. The major goal is to reach 1014 fissions/s in order to be compatible with reactor-driven RNB facilities. We employ a coupled LAHET + MCNP + CINDER code system [2] for all numerical calculations presented in this work. * Corresponding author.
E-mail address: [email protected] (D. Ridikas). 0375-9474/02/$ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 5 - 9 4 7 4 ( 0 1 ) 0 1 6 0 8 - 6
344c
D. Ridikas et al. / Nuclear Physics A 701 (2002) 343c–347c
Under proton or deuteron bombardment, light-element targets (Li or Be) yield high neutron intensities [3]. For very intense primary beams (∼ 1 MW), cooling requirements indicate the use of a liquid target, i.e. Li (melting point 181◦ ) rather than Be (melting point 1287◦) [4]. Therefore, we will limit our discussion to the d + Li and p + Li reactions. High beam currents (> 10 mA) suggest the use of a linac, i.e., comparing protons and deuterons of equal energy. Fig. 1 presents the ratio of neutron yield from the d + Li reaction over p + Li. For a given energy the neutron yields, both angle-integrated and at forward direction, are higher for d-induced reaction. This difference increases with incident energy. The same holds for the average neutron energies: more energetic neutrons are produced by deuterons [3]. Similarly, the neutron angular distribution from the (d, xn) reaction is strongly forward peaked compared with the angular distribution from (p, xn) [3]. We have chosen 1 MW as the maximum deuteron beam power we feel can be reached and deposited in the target–converter [4]. For details on the flowing jet of liquid Li target we refer to Refs. [4,5]. Table 1 lists the major Li target parameters. Fig. 2 illustrates the principle of the setup. The expected neutron flux is of the order of 3 × 1014n/(s cm2 ) at the back side of the target–converter. Similar neutron fluxes are available only in the high flux nuclear reactors. We assume that the main goal for the future RNB factory is to reach fission rates ∼ 1014 fissions/s. Tables 2 and 3 summarize the main beam and target characteristics within this constraint for both converter (C) and direct (D) methods. The in-target fission yields are presented in Table 4 for some isotopes.
Fig. 1. Ratio of neutron yields from the d + Li reaction over the p + Li reaction as a function of the incident energy. The yields are extrapolated from [3].
Table 1 Target–converter parameters Beam power (energy) Beam dimension Lithium flow rate Lithium entrance (exit) temperature
1 MW (35 MeV) 3.82 cm diameter 5.14 l/s ∼ 200 ◦ C (∼ 300 ◦ C)
D. Ridikas et al. / Nuclear Physics A 701 (2002) 343c–347c
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Fig. 2. Schematic of a two-step, neutron-generator-type, high-power target–source for the production of the fission fragments. Design: Y. Huguet. A deuteron beam on a lithium target produces secondary neutrons. The secondary uranium carbide target is heated to 2000 ◦ C by a combination of the fission power and additional electrical power. The ion source represented is the ECRIS MONO1000 [6].
Table 2 Projectile/target combinations to produce high fission yields defined by ∼ 1014 fissions/s in the RNB production target. Also see Table 3 Scenario S1 S2 S3 S4 S5
Particle type
Energy (MeV)
d p d d p
35 35 35 200 200
Min. primary beam power (current) 196 kW (5.6 mA) 525 kW (15 mA) 560 kW (16 mA) 13.8 kW (69 µA) 13 kW (65 µA)
In-target power (kW) 3.2 3.2 3.2 17.0 16.2
Target type (material) C1 (liquid 238 U) C1 (liquid 238 U) C2 (solid UCx ) D1 (liquid 238 U) D2 (liquid 238 U)
Table 3 Target parameters for the production of fission yields by the fission/spallation reactions. See Table 2 for details. Note: Ci—converter, Di—direct Target type C1 C2 D1 D2
U density (g/cm3 )
Volume (cm3 )
238 U mass
18 1.5 18 18
169 2055 21 35
3055 3055 382 636
Geometry specification
(g) cylinder: r = 3 cm, l = 6 cm cone: 1r = 3 cm, 2r = 10.5 cm, l = 13 cm cylinder: r = 1.5 cm, l = 3 cm cylinder: r = 1.5 cm, l = 5 cm
Here we have considered the possibility of having solid UCx and liquid U targets with the assumption that the diffusion of liquid and porous solid targets have similar behaviour. If all the suggested cases are technologically feasible, there is another question which runs
346c
D. Ridikas et al. / Nuclear Physics A 701 (2002) 343c–347c
Table 4 Estimate of projected in-target fission yields, normalized to a primary beam intensity resulting in 1014 fissions/s in the RNB production target. Also see Table 2 Beam 91 Kr 36 94 Kr 36 97 Rb 37 119 Ag 47 132 Sn 50 142 Xe 54 144 Xe 54 144 Cs 55
T1/2 (s)
Liquid U (S1) (at./s 6 mA p)
UCx (S3) (at./s 18 mA p)
Liquid U (S4) (at./s 70 µA p)
8.57
3.2 × 1012
2.2 × 1012
1.1 × 1012
0.21
6.0 × 1011
4.5 × 1011
2.4 × 1011
0.17
2.2 × 1011
3.4 × 1011
1.1 × 1011
2.1
5.2 × 1011
3.2 × 1011
8.8 × 1011
40.0
1.6 × 1012
1.2 × 1012
3.2 × 1011
1.22
1.3 × 1012
1.0 × 1012
2.9 × 1011
1.10
9.6 × 1010
7.4 × 1010
2.0 × 1010
1.02
1.6 × 1012
1.3 × 1012
3.6 × 1011
out of the present study. We have not reached yet the final agreement on the projected overall efficiency (i.e. release * delay * ion-source efficiency). Therefore, the numbers in Table 4 have to be corrected accordingly for the expected final RNB intensities. Due to ∼ 1014 fissions/s the total activity of ∼ 14 kCi of the source is predicted after 90 days of irradiation. High radioactivity due to the noble gases and halogens will require a special treatment. We estimate that the source will still be highly radioactive (∼ 0.2 kCi) even after 3 months of cooling. Similar activities are reported for PIAFE project [7] where ∼ 1014 fissions/s were expected. The results we present show that very high fission yields may be obtained. For massive targets (∼ 3 kg) the neutron induced fission from a converter can provide 1014 fissions/s with a primary beam intensity of 196 kW and 525 kW for deuterons and protons of 35 MeV, respectively. The total power dissipated in the target is ∼ 3 kW. For less massive targets (∼ 0.5 kg), a direct p or d beam is preferred. 1014 fissions/s are reached with a deuteron beam of 14 kW at 200 MeV. The total power dissipated in the target is ∼ 17 kW. However, the C-method may reach the highest final intensities: 7.5 × 1014 fissions/s can be obtained employing the d beam of 1.6 MW (35 MeV) which results in 24 kW fission power (perhaps being the limit). The D-method provides similar yields but with smaller targets, and ∼ 1014 fissions/s being very close to the allowable heat deposition due to the primary beam and fissions all together (∼ 17 kW). On the other hand, in this case other targets than U could be used (e.g., Nb, La, Ta, Th). So this method provides a higher versatility than the C-method. In addition, the direct bombardment of these targets by α-particles would lead to the production of proton-rich nuclei. A promising technical aspect in the case of liquid targets could be the use of beams incident vertically on the target. This would avoid to the hostile conditions of a high intensity beam on a window separating the vacuum and a high-temperature liquid. A vertical beam could create a very high temperature inside the liquid, with moderate temperatures of the container walls. This together with convection currents should favour fast and efficient effusion. But the space around the target must be confined so as to guide the fission products towards the ion source and also because of the extreme chemical
D. Ridikas et al. / Nuclear Physics A 701 (2002) 343c–347c
347c
aggressiveness of molten uranium, so that there will always be some material between the incident beam and the surface of the liquid target. More detailed calculations and some exploratory experiments are necessary in this domain. Finally we add that the radioactivity problems will be crucial in the construction of such a RNB facility.
References [1] J.A. Nolen, in: D.J. Morrissey (Ed.), Proc. of the 3rd Int. Conference on RNB, Gif-sur-Yvette, France, 24–27 May, 1993, Éditions Frontières, 1993, p. 111. [2] D. Ridikas, PhD thesis, report GANIL-T 99 04, October, 1999, and references therein. [3] M.A. Lone, A.J. Ferguson, B.C. Robertson, Nucl. Instrum. Methods 189 (1981) 515; M.A. Lone et al., Nucl. Instrum. Methods 143 (1977) 331. [4] P. Grand, S.N. Goland, Nucl. Instrum. Methods 145 (1977) 49; C.M. Logan, R. Booth, R.A. Nickerson, Nucl. Instrum. Methods 145 (1977) 77. [5] A. Hassanein, J. Nucl. Materials 233–237 (1996) 1547. [6] R. Leroy et al., Ion source developments for stable and radioactive ion beams at GANIL, in: Proc. of the 14th Int. Workshop on ECR Sources, CERN, Geneva, Switzerland, 3–6 May, 1999. [7] PIAFE Collaboration, Technical report of the project covering the period 1993–1996, Report ISN 97-52, July, 1997.