Progress of superconducting electron cyclotron resonance ion sources at Institute of Modern Physics (IMP)a) L. Sun, W. Lu, Y. C. Feng, W. H. Zhang, X. Z. Zhang, Y. Cao, Y. Y. Zhao, W. Wu, T. J. Yang, B. Zhao, H. W. Zhao, L. Z. Ma, J. W. Xia, and D. Xie Citation: Review of Scientific Instruments 85, 02A942 (2014); doi: 10.1063/1.4825164 View online: http://dx.doi.org/10.1063/1.4825164 View Table of Contents: http://scitation.aip.org/content/aip/journal/rsi/85/2?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Studies on a Q/A selector for the SECRAL electron cyclotron resonance ion source Rev. Sci. Instrum. 85, 083301 (2014); 10.1063/1.4891418 Study of ion beam transport from the SECRAL electron cyclotron resonance ion source at the Institute of Modern Physicsa) Rev. Sci. Instrum. 83, 02B726 (2012); 10.1063/1.3680545 Studies of emittance of multiply charged ions extracted from high temperature superconducting electron cyclotron resonance ion source, PKDELISa) Rev. Sci. Instrum. 81, 02B713 (2010); 10.1063/1.3298846 Results with the electron cyclotron resonance charge breeder for the C 252 f fission source project (Californium Rare Ion Breeder Upgrade) at Argonne Tandem Linac Accelerator Systema) Rev. Sci. Instrum. 81, 02A907 (2010); 10.1063/1.3272803 Effect of electron cyclotron resonance ion source frequency tuning on ion beam intensity and quality at Department of Physics, University of Jyväskyläa) Rev. Sci. Instrum. 81, 02A319 (2010); 10.1063/1.3267287
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REVIEW OF SCIENTIFIC INSTRUMENTS 85, 02A942 (2014)
Progress of superconducting electron cyclotron resonance ion sources at Institute of Modern Physics (IMP)a) L. Sun,1,b) W. Lu,1,2 Y. C. Feng,1 W. H. Zhang,1 X. Z. Zhang,1 Y. Cao,1 Y. Y. Zhao,2 W. Wu,1 T. J. Yang,1 B. Zhao,1 H. W. Zhao,1 L. Z. Ma,1 J. W. Xia,1 and D. Xie3 1
Institute of Modern Physics, CAS, Lanzhou 730000, China University of Chinese Academy of Sciences, Beijing 100049, China 3 Nuclear Science Division, LBNL, Berkeley, California 94720, USA 2
(Presented 11 September 2013; received 5 September 2013; accepted 24 September 2013; published online 20 December 2013) Superconducting ECR ion sources can produce intense highly charged ion beams for the application in heavy ion accelerators. Superconducting Electron Resonance ion source with Advanced Design (SECRAL) is one of the few fully superconducting ECR ion sources that has been successfully built and put into routine operation for years. With enormous efforts and R&D work, promising results have been achieved with the ion source. Heated by the microwave power from a 7 kW/24 GHz gyrotron microwave generator, very intense highly charged gaseous ion beams have been produced, such as 455 eμA Xe27+ , 236 eμA Xe30+ , and 64 eμA Xe35+ . Since heavy metallic ion beams are being more and more attractive and important for many accelerator projects globally, intensive studies have been made to produce highly charged heavy metal ion beams, such as those from bismuth and uranium. Recently, 420 eμA Bi30+ and 202 eμA U33+ have been produced with SECRAL source. This paper will present the latest results with SECRAL, and the operation status will be discussed as well. An introduction of recently started SECRAL II project will also be given in the presentation. © 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4825164] I. INTRODUCTION
SECRAL was available at IMP in 2005. This is a 3rd generation ECRIS designed to be operated at the frequency 18–28 GHz. The maximum mirror field at source injection is 3.7 T and the field at source extraction is 2.2 T. A 2.0 T radial field is measured at the Ø126 mm ID plasma chamber inner wall surface. The effective plasma chamber volume of SECRAL is 5.2 l. With a maximum of 3.0 kW 18 GHz microwave injection, ∼0.6 kW/l power density could be achieved. The preliminary test results obtained in 2006 with these source conditions mentioned above, set many recorded beam intensities at 18 GHz, some even comparable to those obtained with VENUS at 28 GHz.1 The source was removed and connected to the Heavy Ion Research Facility in Lanzhou (HIRFL) injection line in 2006 and the first beam was delivered for accelerator operation in 2007. Since then, SECRAL has become the main working horse to provide intense highly charged ion beams for the accelerators. In 2009, a GyCOM 24 GHz/7 kW gyrotron microwave generator was delivered to IMP and connected to the source instantly. The successive commissioning with the maximum microwave power of 4 kW validated the frequency scaling laws also works well with SECRAL source, for instance, Xe30+ 101 eμA/18 GHz increased to 236 eμA/24 GHz (a factor of 2.3), Xe35+ 16 eμA/18 GHz increased to 64 eμA/24 GHz (a factor of 4), which indicates that the higher the charge states, the higher the gain by frequency scaling. a) Contributed paper, published as part of the Proceedings of the 15th
International Conference on Ion Sources, Chiba, Japan, September 2013. b) Author to whom correspondence should be addressed. Electronic mail:
[email protected]. 0034-6748/2014/85(2)/02A942/3/$30.00
The HIRFL facility is now mainly composed of two cyclotrons, i.e., the K69 SFC and the K450 SSC, two radioactive beam lines RIBLL1 and RIBLL2, and two cascade storage rings, i.e., CSRm and CSRe. CSRm is the main acceleration and accumulation synchrotron ring for stable nuclei ion beams with a maximum beam intensity of 1 × 109 ppp.2 CSR cannot achieve its full performance with the present operation scheme, i.e., ECR + SFC + CSRm or ECR + SFC + SSC + CSRm, mainly because the injection beam intensity (from cyclotron) to CSRm is too weak, especially for heavier ion beams (heavier than Kr). Therefore, an upgrade project of design and fabrication of a dedicated Linac injector to CSRm is proposed at IMP. A high performance ECR ion source SECRAL II is thus funded and expected to be delivered by 2015. II. METALLIC ION BEAM PRODUCTION
Production of gaseous ion beams with ECR ion source is quite straightforward, which needs no special technical support. While for the case of solid material or metallic ion beam production, special instrument is needed to produce sufficient vapor of incident material that could be delivered and ionized by the hot ECR plasma. At IMP, sputtering, micro-oven, and MIVOC methods had been used for metallic beam production. In the case of highly charged ion beam production with SECRAL, only micro-oven and sputtering methods are used. A. Micro-oven method
Three types of micro-ovens have been designed and tested at IMP, i.e., resistor oven with the highest operating temperature of 1600 ◦ C but moderate material loading
85, 02A942-1
© 2013 AIP Publishing LLC
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02A942-2
Sun et al.
Rev. Sci. Instrum. 85, 02A942 (2014)
routine operation, an average of 40 eμA Ni19+ could be delivered from SECRAL, while more intense beam needs a higher temperature oven. A high temperature resistor oven similar to the LBNL 2000 ◦ C oven design3 is now under development at IMP. Different from the LBNL one, no cooling water is needed in the design, and therefore to lower the needed heating currents. Off-line test with the oven current around 200 A, it can provide a temperature up to 2000 ◦ C. When installed to SECRAL operating at an 18 GHz field, the oven failed to work at the current of 140 A which corresponds to a temperature of 1600 ◦ C. Later inspection of the oven found obvious damages caused by localized over-heating on the oven and strong twisting force stemmed from Lawrence force. Some R&D is now still going on to modify the structure to make the oven durable at high temperature. FIG. 1. Spectrum of intense bismuth ion beam production.
B. Sputtering method
capacity, low temperature oven with the highest operating temperature of 800 ◦ C and much larger material loading capacity, and high temperature oven that could reach the temperature of 2000 ◦ C mainly designed for refractory material ion beam production. The low temperature oven is a design incorporated with a commercial 100 W Watt-Flex Cartridge Heater and a large capacity crucible for long term uninterrupted routine operation of intense low melting point metallic ion beams, such as bismuth beams, lead beams, etc. This design works fine at IMP, especially in terms of very intense metallic ion beam production. With a maximum load of 2 g bismuth material, this oven can be used for a long term intense beam production test. The high yield production test was done with 24 GHz microwave heating. At 3.5 kW 24 GHz microwave power, a maximum beam current of 422 eμA Bi30+ was obtained. When optimized for Bi31+ , 396 eμA beam current was measured at the faraday cup (Fig. 1). A 3 h stability test with a Bi31+ beam intensity of 330 eμA showed very small variation. The average material consumption rate was estimated to be around 8.7 mg/h with an ionization efficiency of 5.2% (not counting in the transmission efficiency). During the test, the beam intensity of Bi30+ and Bi31+ did not show any tendency of saturation. Present beam intensity record was limited by the highest temperature of 800 ◦ C that could be provided by the oven. At higher oven temperature and thereby more bismuth vapor, more intense highly charged bismuth beam is possible. Intense highly charged tin ion beams were produced with resistor oven on SECRAL. At about 950 ◦ C, obvious tin ion beam peaks could be observed in the spectrum. With better source conditioning, highly charged Sn ion beams were obtained at the main yield temperature of 1100 ◦ C. Since 112 Sn isotope is an expensive material, the oven was not further pushed for more intense beam test. But 50 eμA 112 Sn27+ was easily achieved at 18 GHz with 1.2 kW rf power feeding. During the 61 days straight routine operation, 50 eμA 112 Sn26+ beams were delivered to the cyclotrons. The average material consumption rate was estimated to be 1.4 mg/h. Resistor oven has also been used to produce nickel ion beams, which needs to push the oven to work at its temperature limit 1600 ◦ C. For
For very refractory materials, such as uranium, tantalum, and so on, sputtering method is very easy and feasible method to produce highly charge ion beams with an ECR ion source. At 24 GHz, SECRAL has produced 202 eμA 238 U33+ with 18 O2 as the support gas, while 238 U33+ beam intensity saturates at 160 eμA with 16 O2 as the support gas. This indicates a significant mass effect of 18 O over 16 O. At IMP, the uranium sample was on-axis positioned which resulted in very high load current to the sputtering sample. During the test at 24 GHz, more than 10 emA drain current from the sample and 15 emA of drain current from the source were detected, which could be problematic for intense beam operation in term of stability and reliability. Off-axis positioning of the sample can also give high yield of uranium ion beams but with reasonable sputtering current and source drain current, which has recently been successfully tested in RIKEN.4 Highly charged 92 Mo beams are recently requested by the users. Sputtering method was tried to produce Mo beams with SECRAL. An Ø10 mm natural Mo rod was installed and tested at 18 GHz. Since it was a natural material, with 7 isotopes mixed, the spectrum could only show the produced charges peaked between O4+ and N3+ which indicated optimum charge states of Mo21+∼22+ with a current of ∼30 eμA. Therefore, sputtering method could be used to produce intense highly charged Mo beams. An alternative solution is using a resistor oven filled with MoO3 material, which has been successfully tested to produce more than 150 eμA Mo16+ at MSU with SuSI source.5 III. OPERATION STATUS
The first beam SECRAL delivered to HIRFL accelerators was accomplished in 2007, and it was used for routine operation together with other two ion sources, i.e., 14.5 GHz Lanzhou ECR ion source No. 3 (LECR3) and an all permanent magnet source Lanzhou All Permanent ECR ion source No.1 (LAPECR1), whereas it works as the only injector of intense highly charged heavy ion beams, such as 129 Xe27+ , 209 31+∼36+ Bi , Ni19+ , 238 U32+ , 112 Sn26+ , etc. The annual operation time has been increasing over the years, from 760 h in
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02A942-3
Sun et al.
Rev. Sci. Instrum. 85, 02A942 (2014)
TABLE I. Main design parameters of SECRAL II. ωecr Binj Bext Mirror length Radial field at inner chamber wall Warmbore ID Coldmass length Plasma volume
28 GHz 3.7 T 2.2 T 420 mm 2.0 T Ø142 mm 810 mm >5 l
2007 to 3617 h in 2012. The total routine operation time till this summer maintenance shutdown is summed up to 13 230 h. The source was normally operated at 18 GHz/1.6 kW or 24 GHz/1.5 kW for the accelerators. No quenches during routine operation ever happened. IV. SECRAL II PROJECT
SECRAL II ion source is a close copy of the fully superconducting ECR ion source SECRAL. The main difference is the cryogenic system design. SECRAL design did not include the helium recondensation system to circulate the evaporated helium gas. Therefore, Liquid Helium (LHe) must be refilled when the depth inside the LHe reservoir is too low. Even after an upgrading program that designed and fabricated an external circulating system for SECRAL, the source operation is still interrupted by LHe refilling when the plasma is heated with high microwave power. SECRAL II is designed to be installed with 5 GM coolers that could possibly provide a dynamic cooling capacity of ∼5.0 W to the 4.2 K reservoir. SECRAL II is designed to be operated at 28 GHz. Table I gives the typical design parameters of the source. The magnet configuration will follow the SECRAL concept which places the sextupole coils external to the axial coils. The magnet cold mass dimension is identical to that of SECRAL. Only one type of superconducting wire is used in the design and fabrication, i.e., the Monolith type rectangular NbTi wire with insulated size of 1.2 mm × 0.83 mm supplied by WST Inc. The Cu/Sc ratio is 1.3:1. The solenoids are already available which have been tested to 115% design currents (limited by available current power supplies). Three of the six sextupole coil windings are finished, and the cold mass assembly is scheduled by the end of 2013. The schematic plot of SECRAL II is given in Fig. 2.
FIG. 2. Sectional view of SECRAL II magnet.
V. CONCLUSION
This paper gives a general introduction of the recent progress of superconducting ECR ion sources at IMP. Intense beam production such as 422 eμA Bi30+ and 396 eμA Bi31+ , and the status of on-line operation with metallic beams are discussed. For the state of the art 3rd generation ECRISs, the present metallic beam intensities are mainly limited by the techniques to produce vapor from solid materials. As long as enough stable vapor delivered to the plasma, more intense metallic beams could be achieved. In the end of the paper, an on-going SECRAL II project is briefly introduced. ACKNOWLEDGMENTS
This work is supported by the 100 Talents Program of the CAS (Grant No. Y214160BR0), NSF (Contract No. 11221064), and MOST (Contract No. 2014CB845500). 1 H.
W. Zhao, L. T. Sun, X. H. Guo et al., High Energy Phys. Nucl. Phys. 31 (Suppl. I), 8 (2007). 2 J. W. Xia, W. L. Zhan, B. W. Wei et al., Nucl. Instrum. Methods Phys. Res. A 488, 11 (2002). 3 D. Leitner, M. L. Galloway, T. J. Loew et al., Rev. Sci. Instrum. 79, 02C710 (2008). 4 Y. Higurashi, J. Ohnishi, K. Ozeki, M. Kidera, and T. Nakagawa, “Recent development of RIKEN 28 GHz SC-ECRIS,” Rev. Sci. Instrum. (these proceedings). 5 G. Machicoane, D. Cole, D. Leitner, D. Neben, and L. Tobos, “Metallic beam development for the Facility for Rare Isotope Beam (FRIB),” Rev. Sci. Instrum. (these proceedings).
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 131.217.6.7 On: Thu, 21 May 2015 08:58:02
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 131.217.6.7 On: Thu, 21 May 2015 08:58:02
REVIEW OF SCIENTIFIC INSTRUMENTS 85, 02A942 (2014)
Progress of superconducting electron cyclotron resonance ion sources at Institute of Modern Physics (IMP)a) L. Sun,1,b) W. Lu,1,2 Y. C. Feng,1 W. H. Zhang,1 X. Z. Zhang,1 Y. Cao,1 Y. Y. Zhao,2 W. Wu,1 T. J. Yang,1 B. Zhao,1 H. W. Zhao,1 L. Z. Ma,1 J. W. Xia,1 and D. Xie3 1
Institute of Modern Physics, CAS, Lanzhou 730000, China University of Chinese Academy of Sciences, Beijing 100049, China 3 Nuclear Science Division, LBNL, Berkeley, California 94720, USA 2
(Presented 11 September 2013; received 5 September 2013; accepted 24 September 2013; published online 20 December 2013) Superconducting ECR ion sources can produce intense highly charged ion beams for the application in heavy ion accelerators. Superconducting Electron Resonance ion source with Advanced Design (SECRAL) is one of the few fully superconducting ECR ion sources that has been successfully built and put into routine operation for years. With enormous efforts and R&D work, promising results have been achieved with the ion source. Heated by the microwave power from a 7 kW/24 GHz gyrotron microwave generator, very intense highly charged gaseous ion beams have been produced, such as 455 eμA Xe27+ , 236 eμA Xe30+ , and 64 eμA Xe35+ . Since heavy metallic ion beams are being more and more attractive and important for many accelerator projects globally, intensive studies have been made to produce highly charged heavy metal ion beams, such as those from bismuth and uranium. Recently, 420 eμA Bi30+ and 202 eμA U33+ have been produced with SECRAL source. This paper will present the latest results with SECRAL, and the operation status will be discussed as well. An introduction of recently started SECRAL II project will also be given in the presentation. © 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4825164] I. INTRODUCTION
SECRAL was available at IMP in 2005. This is a 3rd generation ECRIS designed to be operated at the frequency 18–28 GHz. The maximum mirror field at source injection is 3.7 T and the field at source extraction is 2.2 T. A 2.0 T radial field is measured at the Ø126 mm ID plasma chamber inner wall surface. The effective plasma chamber volume of SECRAL is 5.2 l. With a maximum of 3.0 kW 18 GHz microwave injection, ∼0.6 kW/l power density could be achieved. The preliminary test results obtained in 2006 with these source conditions mentioned above, set many recorded beam intensities at 18 GHz, some even comparable to those obtained with VENUS at 28 GHz.1 The source was removed and connected to the Heavy Ion Research Facility in Lanzhou (HIRFL) injection line in 2006 and the first beam was delivered for accelerator operation in 2007. Since then, SECRAL has become the main working horse to provide intense highly charged ion beams for the accelerators. In 2009, a GyCOM 24 GHz/7 kW gyrotron microwave generator was delivered to IMP and connected to the source instantly. The successive commissioning with the maximum microwave power of 4 kW validated the frequency scaling laws also works well with SECRAL source, for instance, Xe30+ 101 eμA/18 GHz increased to 236 eμA/24 GHz (a factor of 2.3), Xe35+ 16 eμA/18 GHz increased to 64 eμA/24 GHz (a factor of 4), which indicates that the higher the charge states, the higher the gain by frequency scaling. a) Contributed paper, published as part of the Proceedings of the 15th
International Conference on Ion Sources, Chiba, Japan, September 2013. b) Author to whom correspondence should be addressed. Electronic mail:
[email protected]. 0034-6748/2014/85(2)/02A942/3/$30.00
The HIRFL facility is now mainly composed of two cyclotrons, i.e., the K69 SFC and the K450 SSC, two radioactive beam lines RIBLL1 and RIBLL2, and two cascade storage rings, i.e., CSRm and CSRe. CSRm is the main acceleration and accumulation synchrotron ring for stable nuclei ion beams with a maximum beam intensity of 1 × 109 ppp.2 CSR cannot achieve its full performance with the present operation scheme, i.e., ECR + SFC + CSRm or ECR + SFC + SSC + CSRm, mainly because the injection beam intensity (from cyclotron) to CSRm is too weak, especially for heavier ion beams (heavier than Kr). Therefore, an upgrade project of design and fabrication of a dedicated Linac injector to CSRm is proposed at IMP. A high performance ECR ion source SECRAL II is thus funded and expected to be delivered by 2015. II. METALLIC ION BEAM PRODUCTION
Production of gaseous ion beams with ECR ion source is quite straightforward, which needs no special technical support. While for the case of solid material or metallic ion beam production, special instrument is needed to produce sufficient vapor of incident material that could be delivered and ionized by the hot ECR plasma. At IMP, sputtering, micro-oven, and MIVOC methods had been used for metallic beam production. In the case of highly charged ion beam production with SECRAL, only micro-oven and sputtering methods are used. A. Micro-oven method
Three types of micro-ovens have been designed and tested at IMP, i.e., resistor oven with the highest operating temperature of 1600 ◦ C but moderate material loading
85, 02A942-1
© 2013 AIP Publishing LLC
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02A942-2
Sun et al.
Rev. Sci. Instrum. 85, 02A942 (2014)
routine operation, an average of 40 eμA Ni19+ could be delivered from SECRAL, while more intense beam needs a higher temperature oven. A high temperature resistor oven similar to the LBNL 2000 ◦ C oven design3 is now under development at IMP. Different from the LBNL one, no cooling water is needed in the design, and therefore to lower the needed heating currents. Off-line test with the oven current around 200 A, it can provide a temperature up to 2000 ◦ C. When installed to SECRAL operating at an 18 GHz field, the oven failed to work at the current of 140 A which corresponds to a temperature of 1600 ◦ C. Later inspection of the oven found obvious damages caused by localized over-heating on the oven and strong twisting force stemmed from Lawrence force. Some R&D is now still going on to modify the structure to make the oven durable at high temperature. FIG. 1. Spectrum of intense bismuth ion beam production.
B. Sputtering method
capacity, low temperature oven with the highest operating temperature of 800 ◦ C and much larger material loading capacity, and high temperature oven that could reach the temperature of 2000 ◦ C mainly designed for refractory material ion beam production. The low temperature oven is a design incorporated with a commercial 100 W Watt-Flex Cartridge Heater and a large capacity crucible for long term uninterrupted routine operation of intense low melting point metallic ion beams, such as bismuth beams, lead beams, etc. This design works fine at IMP, especially in terms of very intense metallic ion beam production. With a maximum load of 2 g bismuth material, this oven can be used for a long term intense beam production test. The high yield production test was done with 24 GHz microwave heating. At 3.5 kW 24 GHz microwave power, a maximum beam current of 422 eμA Bi30+ was obtained. When optimized for Bi31+ , 396 eμA beam current was measured at the faraday cup (Fig. 1). A 3 h stability test with a Bi31+ beam intensity of 330 eμA showed very small variation. The average material consumption rate was estimated to be around 8.7 mg/h with an ionization efficiency of 5.2% (not counting in the transmission efficiency). During the test, the beam intensity of Bi30+ and Bi31+ did not show any tendency of saturation. Present beam intensity record was limited by the highest temperature of 800 ◦ C that could be provided by the oven. At higher oven temperature and thereby more bismuth vapor, more intense highly charged bismuth beam is possible. Intense highly charged tin ion beams were produced with resistor oven on SECRAL. At about 950 ◦ C, obvious tin ion beam peaks could be observed in the spectrum. With better source conditioning, highly charged Sn ion beams were obtained at the main yield temperature of 1100 ◦ C. Since 112 Sn isotope is an expensive material, the oven was not further pushed for more intense beam test. But 50 eμA 112 Sn27+ was easily achieved at 18 GHz with 1.2 kW rf power feeding. During the 61 days straight routine operation, 50 eμA 112 Sn26+ beams were delivered to the cyclotrons. The average material consumption rate was estimated to be 1.4 mg/h. Resistor oven has also been used to produce nickel ion beams, which needs to push the oven to work at its temperature limit 1600 ◦ C. For
For very refractory materials, such as uranium, tantalum, and so on, sputtering method is very easy and feasible method to produce highly charge ion beams with an ECR ion source. At 24 GHz, SECRAL has produced 202 eμA 238 U33+ with 18 O2 as the support gas, while 238 U33+ beam intensity saturates at 160 eμA with 16 O2 as the support gas. This indicates a significant mass effect of 18 O over 16 O. At IMP, the uranium sample was on-axis positioned which resulted in very high load current to the sputtering sample. During the test at 24 GHz, more than 10 emA drain current from the sample and 15 emA of drain current from the source were detected, which could be problematic for intense beam operation in term of stability and reliability. Off-axis positioning of the sample can also give high yield of uranium ion beams but with reasonable sputtering current and source drain current, which has recently been successfully tested in RIKEN.4 Highly charged 92 Mo beams are recently requested by the users. Sputtering method was tried to produce Mo beams with SECRAL. An Ø10 mm natural Mo rod was installed and tested at 18 GHz. Since it was a natural material, with 7 isotopes mixed, the spectrum could only show the produced charges peaked between O4+ and N3+ which indicated optimum charge states of Mo21+∼22+ with a current of ∼30 eμA. Therefore, sputtering method could be used to produce intense highly charged Mo beams. An alternative solution is using a resistor oven filled with MoO3 material, which has been successfully tested to produce more than 150 eμA Mo16+ at MSU with SuSI source.5 III. OPERATION STATUS
The first beam SECRAL delivered to HIRFL accelerators was accomplished in 2007, and it was used for routine operation together with other two ion sources, i.e., 14.5 GHz Lanzhou ECR ion source No. 3 (LECR3) and an all permanent magnet source Lanzhou All Permanent ECR ion source No.1 (LAPECR1), whereas it works as the only injector of intense highly charged heavy ion beams, such as 129 Xe27+ , 209 31+∼36+ Bi , Ni19+ , 238 U32+ , 112 Sn26+ , etc. The annual operation time has been increasing over the years, from 760 h in
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 131.217.6.7 On: Thu, 21 May 2015 08:58:02
02A942-3
Sun et al.
Rev. Sci. Instrum. 85, 02A942 (2014)
TABLE I. Main design parameters of SECRAL II. ωecr Binj Bext Mirror length Radial field at inner chamber wall Warmbore ID Coldmass length Plasma volume
28 GHz 3.7 T 2.2 T 420 mm 2.0 T Ø142 mm 810 mm >5 l
2007 to 3617 h in 2012. The total routine operation time till this summer maintenance shutdown is summed up to 13 230 h. The source was normally operated at 18 GHz/1.6 kW or 24 GHz/1.5 kW for the accelerators. No quenches during routine operation ever happened. IV. SECRAL II PROJECT
SECRAL II ion source is a close copy of the fully superconducting ECR ion source SECRAL. The main difference is the cryogenic system design. SECRAL design did not include the helium recondensation system to circulate the evaporated helium gas. Therefore, Liquid Helium (LHe) must be refilled when the depth inside the LHe reservoir is too low. Even after an upgrading program that designed and fabricated an external circulating system for SECRAL, the source operation is still interrupted by LHe refilling when the plasma is heated with high microwave power. SECRAL II is designed to be installed with 5 GM coolers that could possibly provide a dynamic cooling capacity of ∼5.0 W to the 4.2 K reservoir. SECRAL II is designed to be operated at 28 GHz. Table I gives the typical design parameters of the source. The magnet configuration will follow the SECRAL concept which places the sextupole coils external to the axial coils. The magnet cold mass dimension is identical to that of SECRAL. Only one type of superconducting wire is used in the design and fabrication, i.e., the Monolith type rectangular NbTi wire with insulated size of 1.2 mm × 0.83 mm supplied by WST Inc. The Cu/Sc ratio is 1.3:1. The solenoids are already available which have been tested to 115% design currents (limited by available current power supplies). Three of the six sextupole coil windings are finished, and the cold mass assembly is scheduled by the end of 2013. The schematic plot of SECRAL II is given in Fig. 2.
FIG. 2. Sectional view of SECRAL II magnet.
V. CONCLUSION
This paper gives a general introduction of the recent progress of superconducting ECR ion sources at IMP. Intense beam production such as 422 eμA Bi30+ and 396 eμA Bi31+ , and the status of on-line operation with metallic beams are discussed. For the state of the art 3rd generation ECRISs, the present metallic beam intensities are mainly limited by the techniques to produce vapor from solid materials. As long as enough stable vapor delivered to the plasma, more intense metallic beams could be achieved. In the end of the paper, an on-going SECRAL II project is briefly introduced. ACKNOWLEDGMENTS
This work is supported by the 100 Talents Program of the CAS (Grant No. Y214160BR0), NSF (Contract No. 11221064), and MOST (Contract No. 2014CB845500). 1 H.
W. Zhao, L. T. Sun, X. H. Guo et al., High Energy Phys. Nucl. Phys. 31 (Suppl. I), 8 (2007). 2 J. W. Xia, W. L. Zhan, B. W. Wei et al., Nucl. Instrum. Methods Phys. Res. A 488, 11 (2002). 3 D. Leitner, M. L. Galloway, T. J. Loew et al., Rev. Sci. Instrum. 79, 02C710 (2008). 4 Y. Higurashi, J. Ohnishi, K. Ozeki, M. Kidera, and T. Nakagawa, “Recent development of RIKEN 28 GHz SC-ECRIS,” Rev. Sci. Instrum. (these proceedings). 5 G. Machicoane, D. Cole, D. Leitner, D. Neben, and L. Tobos, “Metallic beam development for the Facility for Rare Isotope Beam (FRIB),” Rev. Sci. Instrum. (these proceedings).
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