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Optimization of ECR singly-charged ion sources for the radioactive ion beam production
Nuclear Instruments and Methods in Physics Research B 204 (2003) 377–381 www.elsevier.com/locate/nimb
Optimization of ECR singly-charged ion sources for the radioactive ion beam production P. Jardin *, W. Farabolini, G. Gaubert, J.Y. Pacquet, T. Drobert, J. Cornell, C. Barue, C. Canet, M. Dupuis, J.-L. Flambard, N. Lecesne, P. Leherissier, F. Lemagnen, R. Leroy GANIL (Grand Acc el erateur National dÕIons Lourds), Boulevard Henri Becquerel, BP 55027, F-14076 Caen Cedex 5, France
Abstract Measurements of the transformation time of atoms into ions were carried out with two 2.45 GHz electron cyclotron resonance ion sources (ECRIS) in the case of the simple ionization of He, Ne, Ar and Kr gases. The effect of the plasma volume, of the dead volumes and of the ionization efficiency are presented. Some rules are deduced for the design of the next ECRIS dedicated to radioactive ion production with noble gases. Ó 2002 Elsevier Science B.V. All rights reserved.
1. Introduction In every case of on-line radioactive ion production, one of the main aims is to construct a production system which is more rapid than the radioactive decay, in order to preserve the maximum number of radioactive nuclei formed in the target. For a given primary beam and target, the total efficiency, i.e. the ratio of measured ion intensity over the produced nuclei depends strongly on the diffusion time of the radioactive atoms out of the target, on the effusion time in the vacuum chamber, and on the ionization time of the source. The processes of diffusion and effusion are governed by the chemistry between the atoms and the materials employed to build the target and the
*
Corresponding author. Tel.: +33-2-31454659; fax: +33-231454665. E-mail address: [email protected] (P. Jardin).
chamber, by the temperature, by the mass of the atoms and by the gas present in the chamber. These aspects explain the variety of systems [1] developed up to now, in attempting to produce a maximum of each isotopes with a minimum of losses. In the case of the production of ions of stable noble gases, the more efficient ionization sources are the electron cyclotron resonance ion sources (ECRIS), which usually allow an efficiency close to 100%. To measure the ionization efficiency, one uses the ratio between the current of ions measured at the exit from the source, and the injected gas flow. In the case of radioactive ion production, one has also to consider the time for transfer through the production system, which must be as short as possible to produce elements with short half-lives, but long enough to give the source time to ionize the atoms. Previous measurements made at GANIL with the 2.45 GHz ECRIS MONO1000 [2] showed that 50% of stable Ar atoms were
0168-583X/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(02)01980-8
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P. Jardin et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 377–381
transformed into Arþ ions in a time of the order of 0.5 s. This time was attributed to the effusion of atoms in the 2 l of dead volume of the chamber. Considering that the effusion time should be lower for a small plasma chamber (and also to reduce the cost of the operation), the small source MINIMONO [3] was designed. The magnetic principle is the same as for MONO1000 but the whole system was strongly reduced in size. For practical reasons, the time measurements presented in this paper were made with MINIMONO and with GDI5, which is similar to 4 MONO1000 and has similar features in terms of efficiency and maximum current extracted for Heþ , Neþ , Arþ and Krþ ions. 2. Measurements The measurements consisted in injecting short pulses of atoms into an ionization source. The time Tai to transform atoms into ions is measured between the time of injection of the atoms and the time of their exit in ionized form. If we assume that the duration of the pulse is negligible compared to the time Tai , the ion current gives the response of the source, i.e. the delay and the time spread. To observe the evolution of the time Tai as a function of the volume of the source chamber, we varied the volume between different measurements. 3. Description of the set up The equipment includes the ionization source, an extraction electrode, an electrostatic lens to focus the beam, a magnetic dipole to select the interesting ions and a Faraday cup. A fast valve and a calibrated leak delivering the same gas were connected to the source. The calibrated leak allowed the estimation of the ionization efficiency. The valve was fed with gas at an absolute pressure of the order of 300 mbar. The electric pulse sent to the valve trigged a scope that measured the ion current on the Faraday cup (Fig. 1). The maximum length of the pulse was 1.3 ms, much lower than the time to be measured. The height of the pulse and the quantity of atoms per pulse were adjusted to avoid noticeable perturbation of the
Fig. 1. The continuous line corresponds to a typical pulse of Arþ current observed after injecting a pulse of neutral Ar atoms into the source. The dotted line corresponds to the integral curve of the current.
plasma regime, which was controlled through the total current delivered by the source. The decrease of the current response being roughly exponential, the time between two pulses was adjusted to avoid any pile-up. During measurements, the major part of the current delivered by the source came from the ionization of the out-gassed material or from the support gas injected through a thermo-controlled valve. The voltage of the source was close to 12 kV, except in the case of Kr for which it was equal to 7 kV, owing to the low magnetic rigidity of the dipole. In this case, the transmission of the beam line was only of the order of a few percents. At 12 kV, the transmission was higher than 60%. MINIMONO and GDI5 are both 2.45 GHz ECRIS, and use similar magnetic structure. The volumes of these sources were changed by adding successive sections to the initial source chamber. In the case of GDI5, two volumes were used (the larger equivalent to three times the plasma volume), and for MINIMONO, four volumes up to fourteen times the plasma volume (see the main features of the sources Table 1). Owing to the very different plasma volumes, the RF power injected into MINIMONO was of the order of 10 W and up to 200 W into GDI5. The best efficiencies obtained with these sources are given Table 1. Owing to the several aper-
P. Jardin et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 377–381
379
Table 1 Main features of the ECRIS MINIMONO and GDI5
GDI
External volume (l)
Weight (kg)
Closed plasma volume (l)
Plasma chamber volume (l)
Volume added (l)
Plasma electrode diameter (mm)
Best efficiency obtained (%)
50
80
3
6.3
2.8
7
Heþ 38 Neþ 92 40 Arþ 93 Krþ 94 4
20
MINIMONO
0.5
2
0.03
0.117
0.063 0.153 0.304
4
Heþ 22 Neþ 95 40 Arþ 95 Krþ 95 4
20
tures used to modify the volumes and the several changes of gas, the efficiencies during the measurements presented in this paper were not optimum.
4. Results For each volume, the time Tai was measured for Heþ , Neþ , Arþ and Krþ ions. Tai was defined as the time after which a given ratio Q of all the ions induced by a pulse of atoms emerged from the source. For a given Q, the time Tai was deduced from the shape of the integrated signal obtained from the Faraday cup. For each volume and gas, Tai was extracted from the integral curve for Q equal to 10%, 50% and 90%. The influence of the signal tail on the determination of Tai gave a better precision at low Q than at high Q. That is why the scatter of the dots around the linear fit (Fig. 2) is more important for Q ¼ 90% than for Q ¼ 50% and Q ¼ 10%. The measurements show that the shorter Tai is obtained for a volume close to the plasma volume, i.e. lower than 5 ms for Q ¼ 10% and lower than 100 ms for Q ¼ 90%. Beyond 40 cm3 , it increases rapidly and linearly with the additional volume up to a volume 14 times higher than the plasma volume (30 cm3 ). In the case of GDI5 (Fig. 3), the times Tai measured were higher, from 80 ms for Heþ , Q ¼ 10% to 3.8 s for Neþ Q ¼ 90%. Except for Arþ , the graph of Tai versus the volume is almost flat for Q ¼ 10%, and increases for Q ¼ 50% and more for Q ¼ 90%.
Fig. 2. Tai in MINIMONO versus the volume of the source chamber for Q ¼ 10%, 50% and 90%.
5. Discussion In the case of MINIMONO, Tai versus the volume is linear. Moreover, for Q ¼ 10% (which
380
P. Jardin et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 377–381
Fig. 3. Tai in GDI5 versus the volume of the source chamber for Q ¼ 10%, 50% and 90%.
corresponds to the more reliable measurement of Tai ), the slopes of the linear fits depend on the square root of the mass of the gas. That corresponds to the behaviour of a gas in a volume effusing through a hole, whatever the vacuum regime, i.e. molecular or viscous. A comparison between the slopes deduced from the measurements and the slopes calculated with a simple model of atomic effusion gives the same order of magnitude. The differences can be easily explained by the uncertainty in the temperature in the vacuum chamber, and the volume used in the calculation, which did not take into account the conductances. The behaviour would be totally similar to an effusion process if the volume at Tai ¼ 0 were equal to 0, while in fact it is in the range of 40–90 cm3 . These values are close to the plasma volume (defined by the last closed equipotential surface) and to the volume of the plasma chamber of MINIMONO. These remarks suggest that the gas effuses only in the additional volume.
The plasma volume is subtracted from the whole volume as the time spent by the ions in the plasma volume was negligible compared to the effusion time. In the case of GDI5, we used only two volumes and we can not confirm the linear dependence of Tai with the volume. Nevertheless, for He, Ne and Kr the time Tai seems to increase while the volume increases. The surprising slope in the case of Arþ ions can be understood through a simple view of the dynamical behaviour of the source. Just after the injection of the pulse into the source, the chamber contains a given population of atoms. The atoms can leave the source as atoms or as ions through the electrode plasma hole. The flow of ions and atoms at the exit of the source are respectively assumed to be proportional to the population of ions and atoms contained in the source. Regarding the atom population, the plasma works as a pump, transforming them into ions. If the probability of transforming atoms into ions, (i.e. the ionization efficiency) is weak, the ionization process will slightly modify the population of atoms and the effusion speed of atoms out of the chamber. The shape of the ion current on the Faraday cup will then be governed mainly by the atomic effusion process. On the other hand, if the ionization efficiency is close to 100%, the evolution of the ion current will be governed by the effusion of the ions out of the plasma, which is necessarily faster than the atomic effusion. The response time must then decrease while the efficiency increases. In the case of MINIMONO, owing to the large volume added to the source compared with the plasma volume, the atoms had to reach the plasma volume before being ionized. The response time was thus governed by the effusion in the additional volume, regardless of the ionization efficiency in the plasma volume. In the case of GDI5, the plasma volume was important compared to the additional volume. The influence of the ionization efficiency should be then more important than with MINIMONO. During the measurements with GDI5, the ionization efficiencies were all below 25%, except for Ar. For the lower volume (i.e. 6.3 l), the ionization efficiency for Ar atoms was equal to 56% and to 71% for the volume of 9.1 l. As shown Fig. 4, the increase of the efficiency can
P. Jardin et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 377–381
Fig. 4. Tai in GDI5 versus the ionization efficiency of Ar. The main variations of the efficiency were obtained by adjusting the proportion of two support gases. For each gas mixture (symbol), the variations of Tai and of the efficiency with the RF power (indicated in watt) are shown. The line is only a guide for the eye.
381
MONO, we observed that the effect on Tai was equivalent to simply adding an additional volume with the same surface area as the SPIRAL target. Since the transformation time increases rapidly with the surface area, the production of short-lived elements with large targets will reach a maximum beyond which it will be useless to design targets for higher intensities. The reduction of the plasma volume between GDI5 and MINIMONO seems to reduce Tai . Another solution consists in limiting the plasma with a quartz tube [5]. This solution seems to lead to the same order of transformation time. The second rule is to use an efficient ionization source, not only because more atoms will be ionized but also because they will be ionized in a shorter time.
References explain the decrease of Tai versus the volume by masking the effect of the volume.
6. Conclusion Some rules to design an ECRIS dedicated to the radioactive ion beam production can be deduced from these measurements. The first rule is to reduce the volumes out of the plasma and the complex shapes as much as possible. When the target employed for SPIRAL [4] (Systeme de Production dÕIons Radioactifs Acceleres en Ligne) was inserted in a chamber attached to MINI-
[1] U. Koester, the ISOLDE Collaboration, Radiochem. Acta 89 (2001) 1. [2] P. Jardin, C. Barue, C. Canet, M. Dupuis, J.L. Flambard, G. Gaubert, N. Lecesne, P. Leherissier, F. Lemagnen, R. Leroy, J.-Y. Pacquet, F. Pellemoine, J.-P. Rataud, M.G. Saint Laurent, A.C.C. Villari, Rev. Sci. Instr. 73 (2002) 789. [3] G. Gaubert, in press. [4] A.C.C. Villari, F. Landre, C. Barue, G. Gaubert, S. Gibouin, Y. Huguet, P. Jardin, S. Kandri Rody, N. Lecesne, R. Leroy, M. Levitowicz, C. Marry, L. Maunoury, J.Y. Pacquet, J.P. Rataud, M.G. Saint Laurent, C. Stodel, O. Bageat, J.C. Angelique, N.A. Orr, in: Proceedings of the Sixteenth International Conference, 2001, p. 254. [5] K. Jayamanna, D. Yuan, M. Dombsky, P. Bricault, M. McDonald, M. Olivo, P. Schmor, G. Stanford, J. Vincent, A. Zyuzin, Rev. Sci. Instr. 73 (2002) 792.
Optimization of ECR singly-charged ion sources for the radioactive ion beam production P. Jardin *, W. Farabolini, G. Gaubert, J.Y. Pacquet, T. Drobert, J. Cornell, C. Barue, C. Canet, M. Dupuis, J.-L. Flambard, N. Lecesne, P. Leherissier, F. Lemagnen, R. Leroy GANIL (Grand Acc el erateur National dÕIons Lourds), Boulevard Henri Becquerel, BP 55027, F-14076 Caen Cedex 5, France
Abstract Measurements of the transformation time of atoms into ions were carried out with two 2.45 GHz electron cyclotron resonance ion sources (ECRIS) in the case of the simple ionization of He, Ne, Ar and Kr gases. The effect of the plasma volume, of the dead volumes and of the ionization efficiency are presented. Some rules are deduced for the design of the next ECRIS dedicated to radioactive ion production with noble gases. Ó 2002 Elsevier Science B.V. All rights reserved.
1. Introduction In every case of on-line radioactive ion production, one of the main aims is to construct a production system which is more rapid than the radioactive decay, in order to preserve the maximum number of radioactive nuclei formed in the target. For a given primary beam and target, the total efficiency, i.e. the ratio of measured ion intensity over the produced nuclei depends strongly on the diffusion time of the radioactive atoms out of the target, on the effusion time in the vacuum chamber, and on the ionization time of the source. The processes of diffusion and effusion are governed by the chemistry between the atoms and the materials employed to build the target and the
*
Corresponding author. Tel.: +33-2-31454659; fax: +33-231454665. E-mail address: [email protected] (P. Jardin).
chamber, by the temperature, by the mass of the atoms and by the gas present in the chamber. These aspects explain the variety of systems [1] developed up to now, in attempting to produce a maximum of each isotopes with a minimum of losses. In the case of the production of ions of stable noble gases, the more efficient ionization sources are the electron cyclotron resonance ion sources (ECRIS), which usually allow an efficiency close to 100%. To measure the ionization efficiency, one uses the ratio between the current of ions measured at the exit from the source, and the injected gas flow. In the case of radioactive ion production, one has also to consider the time for transfer through the production system, which must be as short as possible to produce elements with short half-lives, but long enough to give the source time to ionize the atoms. Previous measurements made at GANIL with the 2.45 GHz ECRIS MONO1000 [2] showed that 50% of stable Ar atoms were
0168-583X/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(02)01980-8
378
P. Jardin et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 377–381
transformed into Arþ ions in a time of the order of 0.5 s. This time was attributed to the effusion of atoms in the 2 l of dead volume of the chamber. Considering that the effusion time should be lower for a small plasma chamber (and also to reduce the cost of the operation), the small source MINIMONO [3] was designed. The magnetic principle is the same as for MONO1000 but the whole system was strongly reduced in size. For practical reasons, the time measurements presented in this paper were made with MINIMONO and with GDI5, which is similar to 4 MONO1000 and has similar features in terms of efficiency and maximum current extracted for Heþ , Neþ , Arþ and Krþ ions. 2. Measurements The measurements consisted in injecting short pulses of atoms into an ionization source. The time Tai to transform atoms into ions is measured between the time of injection of the atoms and the time of their exit in ionized form. If we assume that the duration of the pulse is negligible compared to the time Tai , the ion current gives the response of the source, i.e. the delay and the time spread. To observe the evolution of the time Tai as a function of the volume of the source chamber, we varied the volume between different measurements. 3. Description of the set up The equipment includes the ionization source, an extraction electrode, an electrostatic lens to focus the beam, a magnetic dipole to select the interesting ions and a Faraday cup. A fast valve and a calibrated leak delivering the same gas were connected to the source. The calibrated leak allowed the estimation of the ionization efficiency. The valve was fed with gas at an absolute pressure of the order of 300 mbar. The electric pulse sent to the valve trigged a scope that measured the ion current on the Faraday cup (Fig. 1). The maximum length of the pulse was 1.3 ms, much lower than the time to be measured. The height of the pulse and the quantity of atoms per pulse were adjusted to avoid noticeable perturbation of the
Fig. 1. The continuous line corresponds to a typical pulse of Arþ current observed after injecting a pulse of neutral Ar atoms into the source. The dotted line corresponds to the integral curve of the current.
plasma regime, which was controlled through the total current delivered by the source. The decrease of the current response being roughly exponential, the time between two pulses was adjusted to avoid any pile-up. During measurements, the major part of the current delivered by the source came from the ionization of the out-gassed material or from the support gas injected through a thermo-controlled valve. The voltage of the source was close to 12 kV, except in the case of Kr for which it was equal to 7 kV, owing to the low magnetic rigidity of the dipole. In this case, the transmission of the beam line was only of the order of a few percents. At 12 kV, the transmission was higher than 60%. MINIMONO and GDI5 are both 2.45 GHz ECRIS, and use similar magnetic structure. The volumes of these sources were changed by adding successive sections to the initial source chamber. In the case of GDI5, two volumes were used (the larger equivalent to three times the plasma volume), and for MINIMONO, four volumes up to fourteen times the plasma volume (see the main features of the sources Table 1). Owing to the very different plasma volumes, the RF power injected into MINIMONO was of the order of 10 W and up to 200 W into GDI5. The best efficiencies obtained with these sources are given Table 1. Owing to the several aper-
P. Jardin et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 377–381
379
Table 1 Main features of the ECRIS MINIMONO and GDI5
GDI
External volume (l)
Weight (kg)
Closed plasma volume (l)
Plasma chamber volume (l)
Volume added (l)
Plasma electrode diameter (mm)
Best efficiency obtained (%)
50
80
3
6.3
2.8
7
Heþ 38 Neþ 92 40 Arþ 93 Krþ 94 4
20
MINIMONO
0.5
2
0.03
0.117
0.063 0.153 0.304
4
Heþ 22 Neþ 95 40 Arþ 95 Krþ 95 4
20
tures used to modify the volumes and the several changes of gas, the efficiencies during the measurements presented in this paper were not optimum.
4. Results For each volume, the time Tai was measured for Heþ , Neþ , Arþ and Krþ ions. Tai was defined as the time after which a given ratio Q of all the ions induced by a pulse of atoms emerged from the source. For a given Q, the time Tai was deduced from the shape of the integrated signal obtained from the Faraday cup. For each volume and gas, Tai was extracted from the integral curve for Q equal to 10%, 50% and 90%. The influence of the signal tail on the determination of Tai gave a better precision at low Q than at high Q. That is why the scatter of the dots around the linear fit (Fig. 2) is more important for Q ¼ 90% than for Q ¼ 50% and Q ¼ 10%. The measurements show that the shorter Tai is obtained for a volume close to the plasma volume, i.e. lower than 5 ms for Q ¼ 10% and lower than 100 ms for Q ¼ 90%. Beyond 40 cm3 , it increases rapidly and linearly with the additional volume up to a volume 14 times higher than the plasma volume (30 cm3 ). In the case of GDI5 (Fig. 3), the times Tai measured were higher, from 80 ms for Heþ , Q ¼ 10% to 3.8 s for Neþ Q ¼ 90%. Except for Arþ , the graph of Tai versus the volume is almost flat for Q ¼ 10%, and increases for Q ¼ 50% and more for Q ¼ 90%.
Fig. 2. Tai in MINIMONO versus the volume of the source chamber for Q ¼ 10%, 50% and 90%.
5. Discussion In the case of MINIMONO, Tai versus the volume is linear. Moreover, for Q ¼ 10% (which
380
P. Jardin et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 377–381
Fig. 3. Tai in GDI5 versus the volume of the source chamber for Q ¼ 10%, 50% and 90%.
corresponds to the more reliable measurement of Tai ), the slopes of the linear fits depend on the square root of the mass of the gas. That corresponds to the behaviour of a gas in a volume effusing through a hole, whatever the vacuum regime, i.e. molecular or viscous. A comparison between the slopes deduced from the measurements and the slopes calculated with a simple model of atomic effusion gives the same order of magnitude. The differences can be easily explained by the uncertainty in the temperature in the vacuum chamber, and the volume used in the calculation, which did not take into account the conductances. The behaviour would be totally similar to an effusion process if the volume at Tai ¼ 0 were equal to 0, while in fact it is in the range of 40–90 cm3 . These values are close to the plasma volume (defined by the last closed equipotential surface) and to the volume of the plasma chamber of MINIMONO. These remarks suggest that the gas effuses only in the additional volume.
The plasma volume is subtracted from the whole volume as the time spent by the ions in the plasma volume was negligible compared to the effusion time. In the case of GDI5, we used only two volumes and we can not confirm the linear dependence of Tai with the volume. Nevertheless, for He, Ne and Kr the time Tai seems to increase while the volume increases. The surprising slope in the case of Arþ ions can be understood through a simple view of the dynamical behaviour of the source. Just after the injection of the pulse into the source, the chamber contains a given population of atoms. The atoms can leave the source as atoms or as ions through the electrode plasma hole. The flow of ions and atoms at the exit of the source are respectively assumed to be proportional to the population of ions and atoms contained in the source. Regarding the atom population, the plasma works as a pump, transforming them into ions. If the probability of transforming atoms into ions, (i.e. the ionization efficiency) is weak, the ionization process will slightly modify the population of atoms and the effusion speed of atoms out of the chamber. The shape of the ion current on the Faraday cup will then be governed mainly by the atomic effusion process. On the other hand, if the ionization efficiency is close to 100%, the evolution of the ion current will be governed by the effusion of the ions out of the plasma, which is necessarily faster than the atomic effusion. The response time must then decrease while the efficiency increases. In the case of MINIMONO, owing to the large volume added to the source compared with the plasma volume, the atoms had to reach the plasma volume before being ionized. The response time was thus governed by the effusion in the additional volume, regardless of the ionization efficiency in the plasma volume. In the case of GDI5, the plasma volume was important compared to the additional volume. The influence of the ionization efficiency should be then more important than with MINIMONO. During the measurements with GDI5, the ionization efficiencies were all below 25%, except for Ar. For the lower volume (i.e. 6.3 l), the ionization efficiency for Ar atoms was equal to 56% and to 71% for the volume of 9.1 l. As shown Fig. 4, the increase of the efficiency can
P. Jardin et al. / Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 377–381
Fig. 4. Tai in GDI5 versus the ionization efficiency of Ar. The main variations of the efficiency were obtained by adjusting the proportion of two support gases. For each gas mixture (symbol), the variations of Tai and of the efficiency with the RF power (indicated in watt) are shown. The line is only a guide for the eye.
381
MONO, we observed that the effect on Tai was equivalent to simply adding an additional volume with the same surface area as the SPIRAL target. Since the transformation time increases rapidly with the surface area, the production of short-lived elements with large targets will reach a maximum beyond which it will be useless to design targets for higher intensities. The reduction of the plasma volume between GDI5 and MINIMONO seems to reduce Tai . Another solution consists in limiting the plasma with a quartz tube [5]. This solution seems to lead to the same order of transformation time. The second rule is to use an efficient ionization source, not only because more atoms will be ionized but also because they will be ionized in a shorter time.
References explain the decrease of Tai versus the volume by masking the effect of the volume.
6. Conclusion Some rules to design an ECRIS dedicated to the radioactive ion beam production can be deduced from these measurements. The first rule is to reduce the volumes out of the plasma and the complex shapes as much as possible. When the target employed for SPIRAL [4] (Systeme de Production dÕIons Radioactifs Acceleres en Ligne) was inserted in a chamber attached to MINI-
[1] U. Koester, the ISOLDE Collaboration, Radiochem. Acta 89 (2001) 1. [2] P. Jardin, C. Barue, C. Canet, M. Dupuis, J.L. Flambard, G. Gaubert, N. Lecesne, P. Leherissier, F. Lemagnen, R. Leroy, J.-Y. Pacquet, F. Pellemoine, J.-P. Rataud, M.G. Saint Laurent, A.C.C. Villari, Rev. Sci. Instr. 73 (2002) 789. [3] G. Gaubert, in press. [4] A.C.C. Villari, F. Landre, C. Barue, G. Gaubert, S. Gibouin, Y. Huguet, P. Jardin, S. Kandri Rody, N. Lecesne, R. Leroy, M. Levitowicz, C. Marry, L. Maunoury, J.Y. Pacquet, J.P. Rataud, M.G. Saint Laurent, C. Stodel, O. Bageat, J.C. Angelique, N.A. Orr, in: Proceedings of the Sixteenth International Conference, 2001, p. 254. [5] K. Jayamanna, D. Yuan, M. Dombsky, P. Bricault, M. McDonald, M. Olivo, P. Schmor, G. Stanford, J. Vincent, A. Zyuzin, Rev. Sci. Instr. 73 (2002) 792.