- Email: [email protected]
Brief review of multiple charge state ECR ion sources in Lanzhou
Nuclear Instruments and Methods in Physics Research B 235 (2005) 524–529 www.elsevier.com/locate/nimb
Brief review of multiple charge state ECR ion sources in Lanzhou L.T. Sun *, H.W. Zhao, Z.M. Zhang, B. Wei, X.Z. Zhang, X.H. Guo, X.W. Ma, Y. Cao, W. He, H.Y. Zhao Institute of Modern Physics, the Chinese Academy of Sciences, Lanzhou, 730000, People’s Republic of China Available online 29 April 2005
Abstract Electron Cyclotron Resonance (ECR) ion sources have been under development in Institute of Modern physics (IMP) for more than 25 years. With these yearsÕ study, we have done a lot in this field and developed many outstanding high performance ECR ion sources including the 10 GHz LECR1 (Lanzhou ECR ion source No.1), 14.5 GHz LECR2, the double-frequency heating ECR ion source-LECR3 and the latest being developed fully superconducting sourceSECRAL (Superconducting ECR ion source with Advanced design at Lanzhou), which is supposed to be a higher performance source with an innovative magnet design. Apart from the solenoidal coils type ECR ion sources we have also constructed some all permanent ECR ion sources, such as the LAPECR1 (Lanzhou All Permanent ECR ion source No.1) and LAPECR2. These sources mentioned above work together to deliver intense multiple charge state ion beams for HIRFL (Heavy Ion Research Facility at Lanzhou) acceleratorsÕ injection and atomic physics research. In this paper, we will have a brief review on the IMP ECR ion sources and the typical results of the gaseous element ion beams and also the metallic ion beams. The application of the ion beams on accelerators and atomic physics research will be briefly introduced. 2005 Elsevier B.V. All rights reserved. PACS: 07.77; 29.25 Keyword: Ion sources
1. Introduction
*
Corresponding author. E-mail address: [email protected] (L.T. Sun).
ECR ion sources are mainly used in cyclotrons and atomic physics research at IMP in China. The first ECR ion source (10 GHz CAPRICE
0168-583X/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.03.237
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
type) in China was introduced from Grenoble, France in 1987 [1], which was installed on an axial injection beam line of the cyclotron at IMP to provide multiple charged ion beams. After several yearsÕ optimization and modification [2] on this CAPRICE type ECR ion source, a new 10 GHz multiple charge state ECR ion source LECR1 was developed in Lanzhou [3]. With the development of nuclear experiment research in IMP, metallic ion beams and ion beams with higher energy are required. This urges the IMP ECR ion sources should be able to deliver high charge state ion beams and metallic ion beams. These requirements were well satisfied in 1997 when the first 14.5 GHz ECR ion source LECR2 was successfully constructed in Lanzhou [4]. This ion source can produce very high charge state ion beams like Ar14+, Xe28+, Ca12+ and Pb30+ for IMP cyclotrons. On the basis of LECR2, we designed and built a double-frequency heating ECR ion source LECR3 in 2001, which is mainly used to deliver high charge state ion beams for low energy atomic physics research. SECRAL source is a very high performance superconducting ECR ion source designed in Lanzhou. With the progress of this project, this source has drawn great attention from the ECR ion source community. With the setup of this ion source, the development of ECR ion source in China will advance a higher level. Atomic physics research and material research are the two major research directions in IMP. To satisfy the requirements of these research activities, some extra experiment platforms have to be built. Because of their obvious virtues like simplicity, compactness, easy operation, electricity-free, low running expense and etc, all permanent ECR ion sources are very suitable to be mounted on these platforms to provide the experiments with multiple charge state ion beams. LAPECR1 and LAPECR2 are two multiple charge state all permanent ECR ion sources designed and built in Lanzhou. They are going to provide an excellent condition for the atomic and material research activities in IMP. This article will present a brief review of the series of developed or developing ECR ion sources in Lanzhou.
525
2. Conventional ECR ion sources 2.1. 10 GHz LECR1 ion source The LECR1 ion source had been used to deliver intense medium charge state gaseous ion beams such as Ar8+, C4+, O6+, Kr17+, Xe18+ to the cyclotron at IMP for more than 5 years, and it turned out to be a reliable, good performance medium charge state ECR ion source. Because of development of ECR ion source and the reconstruction of HIRFL accelerators in IMP, this source is now not in use. 2.2. 14.5 GHz LECR2 ion source The purpose of LECR2 source is to produce intense ion beams with a sufficiently high charge state particularly for heavy elements. This 14.5 GHz ECR ion source is based on the concept of CAPRICE and GANIL ECR4 [1,5]. The schematic plot of LECR2 is shown in Fig. 1. The design of the magnetic field configuration takes into account the latest understanding that high axial and radial magnetic field, long resonance length, and reasonable magnetic field gradient are important for improving the performance of highly charged ionsÕ production. The traditional diameter and length of the plasma chamber for CAPRICE is about 65 mm and 165 mm respectively. The dimensions of the plasma chamber for LECR2 are 70 mm in diameter and 300 mm in length. The maximum axial magnetic field on the
Fig. 1. Schematic view of LECR2 source. (1) Iron yoke. (2) Coils. (3) Insulator. (4) Hexapole.
526
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
axis is as high as 1.5 T. Adopting NdFeB permanent material, the 24-segmented Halbach structure hexapole provides 1.0 T magnetic field at the inner wall of the plasma chamber. Table 1 lists the typical performance of this ion source with gas. The potential capability of this ion source should be better than the results listed in Table 1 because the total transmission efficiency of our ion source test bench was estimated about 50%. From Table 1, we can see the results of this ion source are quite good as compared with Grenoble CAPRICE-14.5 GHz and GANIL ECR4M [6,7]. It is also with this ion source the cyclotron at IMP has accelerated metallic ions for the first time. 2.3. Double-frequency heating LECR3 ion source LECR3 source is to produce high charge state ion beams for atomic physics research and also to test some new ideas and techniques. 10 GHz + 14.5 GHz or 14.5 GHz + 18 GHz microwave power can be fed to the chamber for doublefrequency operation. The schematic mechanic plot of LECR3 source is shown in Fig. 2. The magnetic field configuration of this source is mostly based on the 14.5 GHz LECR2 source, but an extra iron plug is added inside the plasma chamber at the injection side to enhance the injection magnetic field as high as 1.7 T. By adopting better NdFeB material with higher remanence and 36-segmented Halbach structure, the hexapole produces 1.0 T at the inner wall of the plasma chamber, whose inner diameter is 76 mm [8]. By the modifications mentioned above, the high-B mode and large volume effect can be tested. The typical gaseous and metallic ion beam performance of LECR3 is given in Table 2. It is obvious that the performance of LECR3 is better than LECR2Õs. When running
Fig. 2. Schematic view of IMP double-frequency heating LECR3 ion source.
with 18 GHz, 1.1 emA Ar8+ was obtained for the first time in Lanzhou. By careful tuning of the source, 500 enA Ar17+ ion beam was obtained and had been successfully used for atomic physics experiment. The high performance of LECR3 owes a lot to its adoption of many new methods and new techniques such as: higher axial magnetic field provides better plasma confinement; large plasma volume increases the high charge state ionsÕ production efficiency; rectangular waveguide off-axis rf power feeding system is more efficient and stable than the coaxial feeding system especially when feeding large rf power (e.g. more than 1000 W); the plasma chamber is made of aluminum with better cooling; an aluminum biased disk is installed inside of the plasma chamber at the injection side to produce supplementary secondary cold electrons. LECR3 was constructed in 2001 and since then, it has delivered series of different charge state ion beams of different elements for atomic and material physics research. It turns out to be a stable and reliable high charge state ECR ion source.
Table 1 Performance of 14.5 GHz LECR2 for a few typical ions Ions
O6+
O7+
Ar11+
Ar12+
Ar14+
Cl12+
Kr19+
Kr20+
Xe26+
Xe27+
Xe28+
IQ (elA)
610
140
185
105
12
20
50
25
50
25
12
Ions
Ca11+
Ca12+
Mg9+
Fe11+
Cu13+
Cu15+
Zn13+
Zn15+
Ni10+
Ni12+
Pb28+
IQ (elA)
130
70
20
45
39
30
50
30
29
15
10
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
527
Table 2 Typical performance of double-frequency heating LECR3 Ions
O6+
O7+
Ar8+
Ar11+
Ar12+
Ar14+
Xe20+
Xe23+
Xe26+
Xe27+
Xe28+
IQ (elA)
780
235
1100
240
140
30
160
130
90
56
33
Ions
Cl12+
Si7+
Si8+
Si9+
Si10+
Ni12+
Ni16+
Fe11+
Fe12+
Fe13+
Fe16+
IQ (elA)
610
140
185
105
12
74
17
210
175
141
25
3. All permanent ECR ion source 3.1. LAPECR1 LAPECR1 ion source is designed to operate at 14.5 GHz to produce intense medium charge state ion beams such as B4+, C4+, N5+, O6+, Ne8+, Ar8+, Ar9+, Xe20+. . . and low charge state ion beams such as He+, He2+, B+, C+, C2+, O+, O2+, N+, N2+, Ar+. . .. Its good compactness (outer dimension: Ø204 mm · 396 mm, weight 25 kg) and easy handling properties make it very suitable to be used on any small or removable experiment. This ion source is put on a 50 kV small platform to deliver intense multiple charge state ion beams for the successive experimental terminals. It has been successfully used for ion implantation, atomic physics, material processing and biology research. 3.2. LAPECR2 With the development of material and atomic physics research in IMP, some extra experimental platforms are needed to satisfy the requirements. A 400 kV HV (High voltage) platform is now under building in IMP. LAPECR2 (as is shown in Fig. 3) is then supposed to be built and used to deliver multiple charge state ion beams to the HV platform because of its obvious virtues such as non-electrical consumption (apart from the rf generator), little cooling water requirement and good performance etc. LAPECR2 is designed to be running at 14.5 GHz. N45M NdFeB permanent material is used to build the axial magnetic blocks, and N45M together with N42SH material compose the hexapole magnet. Magnetic field values are 1.28 T at the injection side (design value is 1.42 T and suggested value is 1.7 T by the scaling laws
Fig. 3. Sectional mechanic plot of LAPECR2 ion source.
[9]. An extra iron plug can help enhance the value to 2.2 T), 0.43 T as the minimum-B (design value is 0.43 T and 0.42 T < Bmin <0.45 T as suggested), 1.08 T at the extraction (1.12 T is the design value and 1.1 T suggested) and 1.21 T for the radial field at the plasma chamber inner wall (1.22 T is the design value and >1.1 T suggested). To allow long ion lifetime, the plasma chamber inner diameter is 67 mm, this size being comparable to that of LECR2. In addition, the double wall plasma chamber is made of aluminum to enhance the secondary electron emission which improves beam intensities. The rectangular microwave guide offaxis feeding method is also adopted to launch the rf power to the plasma. By this way the rf power coupling efficiency and stability are both greatly increased [10]. The outer dimension of the magnetic body of LAPECR2 is Ø650 mm · 560 mm. This 950 kg weight equipment is thought to be the largest of all permanent ECR ion sources in the world with the highest design performance. Because of rich store of rare earth resources in China, the building of this source is economically possible. Hundreds
528
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
of elA of Ar8+ and tens of Ar14+ are expected to be extracted from LAPECR2. This source will start its first commissioning at the end of 2004.
4. Superconducting ECR ion source-SECRAL The SECRAL source as shown in Fig. 4 is designed to produce intense high charge state ion beams for the HIRFL cyclotron which will be used as a injector to heavy ion cooling storage ring HIRFL-CSR that is under construction at Lanzhou [11]. The SECRAL source has an innovative magnet design, which realizes a minimum-B trap by means of a hexapole external to the three solenoids, i.e. contrary to what is usually done in any ECR ion source. In this way, the magnetic force
is not so high as for VENUS and GyroSERSE design [12], and a much more compact source can be built, with a plasma chamber of 126 mm inner diameter and a total length of the source of the order of 1 m only. The injection magnetic field is 4.0 T and the extraction magnetic field is 2.0 T. The maximum radial magnetic field at the plasma chamber inner wall is as high as 2 T. These magnetic parameters are well up to the requirements of running at 18–28 GHz according to the scaling laws. The magnets of SECRAL have been constructed. The solenoids have passed the first test in cryostat and the hexapole magnets are still under testing. The magnets are expected to be ready at the end of this year and the preliminary commissioning will be at the beginning of next year 2005.
Fig. 4. Mechanic plot of IMP SECRAL ion source.
Table 3 List of the typical parameters of the series of IMP ECR ion sources
LECR1 LECR2 LECR3 LAPECR1 LAPECR2 SECRAL
RF (GHz)
RF power (kW)
Mirror Field (T)
Bw (T)
Extraction HV (kV)
Chamber ID (mm)
10 14.5 10 + 14.5 14.5 14.5 18/28
2.5 2.0 2.0 0.7 2.0 4
1.1, 0.8 1.5, 1.1 1.7, 1.1 1.07a, 0.56 2.2a, 1.1 4.0, 2.0
0.7 0.9 1.0 0.75 1.2 2.0
20 25 25 30–50 30 30–40
66 70 76 40 67 125
Bw—radial magnetic field at the inner wall of the plasma chamber; ID—inner diameter. a With iron plug.
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
5. Conclusion We have achieved great success in the field of multiple charge state ion sources, especially high charge state ECR ion sources at IMP Lanzhou. The list of the typical specifications of the series of ECR ion sources is given in Table 3. Better sources and higher performances are expected in the near future.
Acknowledgement The support of the key projects of Pilot Project of the Knowledge Innovation Program launched by the Chinese Academy of Sciences through the contract of KJCX1-09 and the National Scientific Fund for Outstanding Youth through the contract of 10225523 is gratefully acknowledged.
References [1] B. Jacquot, F. Bourg, R. Geller, Nucl. Instr. and Meth. A 254 (1987) 13.
529
[2] B.W. Wei, Z.W. Liu, W. Zhang, D.Z. Wu, H.W. Zhao, P. Yuan, X.Z. Zhang, in: Proceedings of the 13th Int. Conf. on Cyclotron and Their Applications, Vancouver, Canada, 1992, World Scientific, Singapore, 1992, p. 344. [3] Z.W. Liu, W. Zhang, X. Guo, P. Yuan, X.Z. Zhang, in: Proceedings of the 12th Int. Workshop on ECRIS, Riken, Japan, 1995, p. 235. [4] H.W. Zhao, Z.W. Liu, X.Z. Zhang, X.H. Guo, J.Y. Gao, Z.M. Zhang, P. Yuan, in: Proceedings of the 15th Int. Conf. on Cyclotrons and Their Applications, Caen, France, 1998, Institute of Physics, Bristol, 1998, p. 417. [5] P. Sortais, P. Attal, M. Bish, M.P. Bourgarel, P.M. Cornen, in: Proceedings of the 10th Int. Workshop on ECRIS, Oak Ridge, ORNL, 1990, p. 35. [6] D. Hitz, F. Bourg, M. Delannay, P. Ludwig, G. Melin, M. Pontonnier, T.K. Nguyen, Rev. Sci. Instr. 67 (1996) 883. [7] R. Leroy et al. in: Proceedings of the 12th Int. Workshop on ECRIS, Riken, Japan, 1995, p. 57. [8] Z.M. Zhang, H.W. Zhao, X.Z. Zhang et al, in: Proceedings of the 15th Int. Workshop on ECRIS, Jyva¨skyla¨, Finland, 2002, p. 126. [9] D. Hitz, A. Girard, G. Melin, D. Cormier, J.M. Mathonnet, F. Lanzaque, K. Serebrenikov, L.T. Sun, Nucl. Instr. and Meth. B 205 (2003) 168. [10] L.T. Sun, H.W. Zhao, D. Hitz, Rev. Sci. Instum. 75 (5) (2004). [11] H.W. Zhao et al., Rev. Sci. Instum. 73 (2) (2002) 525. [12] S. Gammino, G. Ciavola, L. Celona, L. Ando, D. Hitz, A. Girard, G. Melin, in: Proceedings of the 2003 Particle Accelerators Conf., Oregon, USA, p. 81.
Brief review of multiple charge state ECR ion sources in Lanzhou L.T. Sun *, H.W. Zhao, Z.M. Zhang, B. Wei, X.Z. Zhang, X.H. Guo, X.W. Ma, Y. Cao, W. He, H.Y. Zhao Institute of Modern Physics, the Chinese Academy of Sciences, Lanzhou, 730000, People’s Republic of China Available online 29 April 2005
Abstract Electron Cyclotron Resonance (ECR) ion sources have been under development in Institute of Modern physics (IMP) for more than 25 years. With these yearsÕ study, we have done a lot in this field and developed many outstanding high performance ECR ion sources including the 10 GHz LECR1 (Lanzhou ECR ion source No.1), 14.5 GHz LECR2, the double-frequency heating ECR ion source-LECR3 and the latest being developed fully superconducting sourceSECRAL (Superconducting ECR ion source with Advanced design at Lanzhou), which is supposed to be a higher performance source with an innovative magnet design. Apart from the solenoidal coils type ECR ion sources we have also constructed some all permanent ECR ion sources, such as the LAPECR1 (Lanzhou All Permanent ECR ion source No.1) and LAPECR2. These sources mentioned above work together to deliver intense multiple charge state ion beams for HIRFL (Heavy Ion Research Facility at Lanzhou) acceleratorsÕ injection and atomic physics research. In this paper, we will have a brief review on the IMP ECR ion sources and the typical results of the gaseous element ion beams and also the metallic ion beams. The application of the ion beams on accelerators and atomic physics research will be briefly introduced. 2005 Elsevier B.V. All rights reserved. PACS: 07.77; 29.25 Keyword: Ion sources
1. Introduction
*
Corresponding author. E-mail address: [email protected] (L.T. Sun).
ECR ion sources are mainly used in cyclotrons and atomic physics research at IMP in China. The first ECR ion source (10 GHz CAPRICE
0168-583X/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.03.237
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
type) in China was introduced from Grenoble, France in 1987 [1], which was installed on an axial injection beam line of the cyclotron at IMP to provide multiple charged ion beams. After several yearsÕ optimization and modification [2] on this CAPRICE type ECR ion source, a new 10 GHz multiple charge state ECR ion source LECR1 was developed in Lanzhou [3]. With the development of nuclear experiment research in IMP, metallic ion beams and ion beams with higher energy are required. This urges the IMP ECR ion sources should be able to deliver high charge state ion beams and metallic ion beams. These requirements were well satisfied in 1997 when the first 14.5 GHz ECR ion source LECR2 was successfully constructed in Lanzhou [4]. This ion source can produce very high charge state ion beams like Ar14+, Xe28+, Ca12+ and Pb30+ for IMP cyclotrons. On the basis of LECR2, we designed and built a double-frequency heating ECR ion source LECR3 in 2001, which is mainly used to deliver high charge state ion beams for low energy atomic physics research. SECRAL source is a very high performance superconducting ECR ion source designed in Lanzhou. With the progress of this project, this source has drawn great attention from the ECR ion source community. With the setup of this ion source, the development of ECR ion source in China will advance a higher level. Atomic physics research and material research are the two major research directions in IMP. To satisfy the requirements of these research activities, some extra experiment platforms have to be built. Because of their obvious virtues like simplicity, compactness, easy operation, electricity-free, low running expense and etc, all permanent ECR ion sources are very suitable to be mounted on these platforms to provide the experiments with multiple charge state ion beams. LAPECR1 and LAPECR2 are two multiple charge state all permanent ECR ion sources designed and built in Lanzhou. They are going to provide an excellent condition for the atomic and material research activities in IMP. This article will present a brief review of the series of developed or developing ECR ion sources in Lanzhou.
525
2. Conventional ECR ion sources 2.1. 10 GHz LECR1 ion source The LECR1 ion source had been used to deliver intense medium charge state gaseous ion beams such as Ar8+, C4+, O6+, Kr17+, Xe18+ to the cyclotron at IMP for more than 5 years, and it turned out to be a reliable, good performance medium charge state ECR ion source. Because of development of ECR ion source and the reconstruction of HIRFL accelerators in IMP, this source is now not in use. 2.2. 14.5 GHz LECR2 ion source The purpose of LECR2 source is to produce intense ion beams with a sufficiently high charge state particularly for heavy elements. This 14.5 GHz ECR ion source is based on the concept of CAPRICE and GANIL ECR4 [1,5]. The schematic plot of LECR2 is shown in Fig. 1. The design of the magnetic field configuration takes into account the latest understanding that high axial and radial magnetic field, long resonance length, and reasonable magnetic field gradient are important for improving the performance of highly charged ionsÕ production. The traditional diameter and length of the plasma chamber for CAPRICE is about 65 mm and 165 mm respectively. The dimensions of the plasma chamber for LECR2 are 70 mm in diameter and 300 mm in length. The maximum axial magnetic field on the
Fig. 1. Schematic view of LECR2 source. (1) Iron yoke. (2) Coils. (3) Insulator. (4) Hexapole.
526
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
axis is as high as 1.5 T. Adopting NdFeB permanent material, the 24-segmented Halbach structure hexapole provides 1.0 T magnetic field at the inner wall of the plasma chamber. Table 1 lists the typical performance of this ion source with gas. The potential capability of this ion source should be better than the results listed in Table 1 because the total transmission efficiency of our ion source test bench was estimated about 50%. From Table 1, we can see the results of this ion source are quite good as compared with Grenoble CAPRICE-14.5 GHz and GANIL ECR4M [6,7]. It is also with this ion source the cyclotron at IMP has accelerated metallic ions for the first time. 2.3. Double-frequency heating LECR3 ion source LECR3 source is to produce high charge state ion beams for atomic physics research and also to test some new ideas and techniques. 10 GHz + 14.5 GHz or 14.5 GHz + 18 GHz microwave power can be fed to the chamber for doublefrequency operation. The schematic mechanic plot of LECR3 source is shown in Fig. 2. The magnetic field configuration of this source is mostly based on the 14.5 GHz LECR2 source, but an extra iron plug is added inside the plasma chamber at the injection side to enhance the injection magnetic field as high as 1.7 T. By adopting better NdFeB material with higher remanence and 36-segmented Halbach structure, the hexapole produces 1.0 T at the inner wall of the plasma chamber, whose inner diameter is 76 mm [8]. By the modifications mentioned above, the high-B mode and large volume effect can be tested. The typical gaseous and metallic ion beam performance of LECR3 is given in Table 2. It is obvious that the performance of LECR3 is better than LECR2Õs. When running
Fig. 2. Schematic view of IMP double-frequency heating LECR3 ion source.
with 18 GHz, 1.1 emA Ar8+ was obtained for the first time in Lanzhou. By careful tuning of the source, 500 enA Ar17+ ion beam was obtained and had been successfully used for atomic physics experiment. The high performance of LECR3 owes a lot to its adoption of many new methods and new techniques such as: higher axial magnetic field provides better plasma confinement; large plasma volume increases the high charge state ionsÕ production efficiency; rectangular waveguide off-axis rf power feeding system is more efficient and stable than the coaxial feeding system especially when feeding large rf power (e.g. more than 1000 W); the plasma chamber is made of aluminum with better cooling; an aluminum biased disk is installed inside of the plasma chamber at the injection side to produce supplementary secondary cold electrons. LECR3 was constructed in 2001 and since then, it has delivered series of different charge state ion beams of different elements for atomic and material physics research. It turns out to be a stable and reliable high charge state ECR ion source.
Table 1 Performance of 14.5 GHz LECR2 for a few typical ions Ions
O6+
O7+
Ar11+
Ar12+
Ar14+
Cl12+
Kr19+
Kr20+
Xe26+
Xe27+
Xe28+
IQ (elA)
610
140
185
105
12
20
50
25
50
25
12
Ions
Ca11+
Ca12+
Mg9+
Fe11+
Cu13+
Cu15+
Zn13+
Zn15+
Ni10+
Ni12+
Pb28+
IQ (elA)
130
70
20
45
39
30
50
30
29
15
10
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
527
Table 2 Typical performance of double-frequency heating LECR3 Ions
O6+
O7+
Ar8+
Ar11+
Ar12+
Ar14+
Xe20+
Xe23+
Xe26+
Xe27+
Xe28+
IQ (elA)
780
235
1100
240
140
30
160
130
90
56
33
Ions
Cl12+
Si7+
Si8+
Si9+
Si10+
Ni12+
Ni16+
Fe11+
Fe12+
Fe13+
Fe16+
IQ (elA)
610
140
185
105
12
74
17
210
175
141
25
3. All permanent ECR ion source 3.1. LAPECR1 LAPECR1 ion source is designed to operate at 14.5 GHz to produce intense medium charge state ion beams such as B4+, C4+, N5+, O6+, Ne8+, Ar8+, Ar9+, Xe20+. . . and low charge state ion beams such as He+, He2+, B+, C+, C2+, O+, O2+, N+, N2+, Ar+. . .. Its good compactness (outer dimension: Ø204 mm · 396 mm, weight 25 kg) and easy handling properties make it very suitable to be used on any small or removable experiment. This ion source is put on a 50 kV small platform to deliver intense multiple charge state ion beams for the successive experimental terminals. It has been successfully used for ion implantation, atomic physics, material processing and biology research. 3.2. LAPECR2 With the development of material and atomic physics research in IMP, some extra experimental platforms are needed to satisfy the requirements. A 400 kV HV (High voltage) platform is now under building in IMP. LAPECR2 (as is shown in Fig. 3) is then supposed to be built and used to deliver multiple charge state ion beams to the HV platform because of its obvious virtues such as non-electrical consumption (apart from the rf generator), little cooling water requirement and good performance etc. LAPECR2 is designed to be running at 14.5 GHz. N45M NdFeB permanent material is used to build the axial magnetic blocks, and N45M together with N42SH material compose the hexapole magnet. Magnetic field values are 1.28 T at the injection side (design value is 1.42 T and suggested value is 1.7 T by the scaling laws
Fig. 3. Sectional mechanic plot of LAPECR2 ion source.
[9]. An extra iron plug can help enhance the value to 2.2 T), 0.43 T as the minimum-B (design value is 0.43 T and 0.42 T < Bmin <0.45 T as suggested), 1.08 T at the extraction (1.12 T is the design value and 1.1 T suggested) and 1.21 T for the radial field at the plasma chamber inner wall (1.22 T is the design value and >1.1 T suggested). To allow long ion lifetime, the plasma chamber inner diameter is 67 mm, this size being comparable to that of LECR2. In addition, the double wall plasma chamber is made of aluminum to enhance the secondary electron emission which improves beam intensities. The rectangular microwave guide offaxis feeding method is also adopted to launch the rf power to the plasma. By this way the rf power coupling efficiency and stability are both greatly increased [10]. The outer dimension of the magnetic body of LAPECR2 is Ø650 mm · 560 mm. This 950 kg weight equipment is thought to be the largest of all permanent ECR ion sources in the world with the highest design performance. Because of rich store of rare earth resources in China, the building of this source is economically possible. Hundreds
528
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
of elA of Ar8+ and tens of Ar14+ are expected to be extracted from LAPECR2. This source will start its first commissioning at the end of 2004.
4. Superconducting ECR ion source-SECRAL The SECRAL source as shown in Fig. 4 is designed to produce intense high charge state ion beams for the HIRFL cyclotron which will be used as a injector to heavy ion cooling storage ring HIRFL-CSR that is under construction at Lanzhou [11]. The SECRAL source has an innovative magnet design, which realizes a minimum-B trap by means of a hexapole external to the three solenoids, i.e. contrary to what is usually done in any ECR ion source. In this way, the magnetic force
is not so high as for VENUS and GyroSERSE design [12], and a much more compact source can be built, with a plasma chamber of 126 mm inner diameter and a total length of the source of the order of 1 m only. The injection magnetic field is 4.0 T and the extraction magnetic field is 2.0 T. The maximum radial magnetic field at the plasma chamber inner wall is as high as 2 T. These magnetic parameters are well up to the requirements of running at 18–28 GHz according to the scaling laws. The magnets of SECRAL have been constructed. The solenoids have passed the first test in cryostat and the hexapole magnets are still under testing. The magnets are expected to be ready at the end of this year and the preliminary commissioning will be at the beginning of next year 2005.
Fig. 4. Mechanic plot of IMP SECRAL ion source.
Table 3 List of the typical parameters of the series of IMP ECR ion sources
LECR1 LECR2 LECR3 LAPECR1 LAPECR2 SECRAL
RF (GHz)
RF power (kW)
Mirror Field (T)
Bw (T)
Extraction HV (kV)
Chamber ID (mm)
10 14.5 10 + 14.5 14.5 14.5 18/28
2.5 2.0 2.0 0.7 2.0 4
1.1, 0.8 1.5, 1.1 1.7, 1.1 1.07a, 0.56 2.2a, 1.1 4.0, 2.0
0.7 0.9 1.0 0.75 1.2 2.0
20 25 25 30–50 30 30–40
66 70 76 40 67 125
Bw—radial magnetic field at the inner wall of the plasma chamber; ID—inner diameter. a With iron plug.
L.T. Sun et al. / Nucl. Instr. and Meth. in Phys. Res. B 235 (2005) 524–529
5. Conclusion We have achieved great success in the field of multiple charge state ion sources, especially high charge state ECR ion sources at IMP Lanzhou. The list of the typical specifications of the series of ECR ion sources is given in Table 3. Better sources and higher performances are expected in the near future.
Acknowledgement The support of the key projects of Pilot Project of the Knowledge Innovation Program launched by the Chinese Academy of Sciences through the contract of KJCX1-09 and the National Scientific Fund for Outstanding Youth through the contract of 10225523 is gratefully acknowledged.
References [1] B. Jacquot, F. Bourg, R. Geller, Nucl. Instr. and Meth. A 254 (1987) 13.
529
[2] B.W. Wei, Z.W. Liu, W. Zhang, D.Z. Wu, H.W. Zhao, P. Yuan, X.Z. Zhang, in: Proceedings of the 13th Int. Conf. on Cyclotron and Their Applications, Vancouver, Canada, 1992, World Scientific, Singapore, 1992, p. 344. [3] Z.W. Liu, W. Zhang, X. Guo, P. Yuan, X.Z. Zhang, in: Proceedings of the 12th Int. Workshop on ECRIS, Riken, Japan, 1995, p. 235. [4] H.W. Zhao, Z.W. Liu, X.Z. Zhang, X.H. Guo, J.Y. Gao, Z.M. Zhang, P. Yuan, in: Proceedings of the 15th Int. Conf. on Cyclotrons and Their Applications, Caen, France, 1998, Institute of Physics, Bristol, 1998, p. 417. [5] P. Sortais, P. Attal, M. Bish, M.P. Bourgarel, P.M. Cornen, in: Proceedings of the 10th Int. Workshop on ECRIS, Oak Ridge, ORNL, 1990, p. 35. [6] D. Hitz, F. Bourg, M. Delannay, P. Ludwig, G. Melin, M. Pontonnier, T.K. Nguyen, Rev. Sci. Instr. 67 (1996) 883. [7] R. Leroy et al. in: Proceedings of the 12th Int. Workshop on ECRIS, Riken, Japan, 1995, p. 57. [8] Z.M. Zhang, H.W. Zhao, X.Z. Zhang et al, in: Proceedings of the 15th Int. Workshop on ECRIS, Jyva¨skyla¨, Finland, 2002, p. 126. [9] D. Hitz, A. Girard, G. Melin, D. Cormier, J.M. Mathonnet, F. Lanzaque, K. Serebrenikov, L.T. Sun, Nucl. Instr. and Meth. B 205 (2003) 168. [10] L.T. Sun, H.W. Zhao, D. Hitz, Rev. Sci. Instum. 75 (5) (2004). [11] H.W. Zhao et al., Rev. Sci. Instum. 73 (2) (2002) 525. [12] S. Gammino, G. Ciavola, L. Celona, L. Ando, D. Hitz, A. Girard, G. Melin, in: Proceedings of the 2003 Particle Accelerators Conf., Oregon, USA, p. 81.