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The AMS system at the Shanghai Institute of Nuclear Research
298
Nuclear Instruments and Methods in Physics Research B52 (1990) 298-300 North-Holland
The AMS system at the Shanghai Institute of Nuclear Research Liu Lianfan, Sheng Shugang, Si Houzhi, Yi Weixi ‘) and Cheng Xiaowu Shanghai Institute of Nuclear Research, Academia Sinica, Shanghai, PR China ” Institute of Geochemistry, Academia Sinica, PR China
The main features of the AMS system based on the 6 MV tandem accelerator at the Shanghai Institute of Nuclear Research are described. A number of modifications of the ion source, beam optics design and sample preparation have been made. The system will be used primarily for “Be, 14C and 26Alanalysis. A similar capability should be possible for other rare isotopes. It will be applied to various fields of geology, meteoritics, oceanography and archaeology.
1. Introduction The AMS system based on the 6 MV tandem accelerator at the Shanghai Institute of Nuclear Research (SINR) will be put into operation by the end of this year. In this paper, the main features of the facility will be described. This system will be used primarily for “Be, 14C and ‘!4l analysis and applied to various fields of geology, meteoritics, oceanography and archaeology.
(10Be’60-, etc.) ions are selected by the 90° inflection magnet and injected sequentially into the accelerator. Mass-25 ions are monitored by an off-axis Faraday cup at the exit of the magnet while mass-26 ions are accelerated.
2. Description of the facility A schematic diagram of the elements of the AMS system is shown in fig. 1. The system is based on a 6 MV tandem accelerator which is built for general nuclear physics applications. A number of modifications have been made to meet the requirements of AMS. 2. I. Injector The sputtering ion source is shown in fig. 2. Its design is based on the structure of Hiconex 860 with the following modifications: (1) the insulator between the sputter target and the cesium ionizer is made of alumina ceramic with an appropriate shield instead of boron nitride to reduce boron contamination in loBe analysis; (2) the shape of the ionizer is spherical to improve beam emittance; and (3) it possesses a multi-position sample holder. Fig. 3 is a schematic diagram of the injector system. The negative beam from the ion source is focussed by an einzel lens, preaccelerated to 60 kV and passed through a three-slit system to confine the beam emittance to match the acceptance of the gas stripper. In “Be analysis, mass-25 (9Be’60-) and mass-26
Fig. 1.Schematic diagram of the SINR AMS facility.
0168-583X/90/%03.50 0 1990 - Elsevier Science Publishers B.V. (North-Holland)
299
Liu Lianfan et al. / AMS at the Shanghai Institute of Nuclear Research To valve
and pump sample wheel (18 positions)
Target
sample holder
Gate 04
z
CM
I1 1
)
(for
valve
exchanging
targets)
Fig. 2. Schematic diagram of the sputter ion source.
steerer
Faraday
cup
cs sputtering ion ScluPce
2.2. Accelerator The 6 MY tandem accelerator [l] is a vertical machine built in Shanghai. The accelerating tubes [2] are made of short tube sections bolted together. Each section consists of alumina ceramic rings bonded to titanium metal. Between adjoining sections there is a decoupling diaphragm with a 25 mm opening. Proper configuration of the diaphragm is chosen such that all secondary particles emitted from the aperture fringes can be suppressed in one section to overcome the “long tube effect”. We use a laddertron as the charge carrying unit. The original GVM will be replaced by a new one with higher precision; special care has been taken in its mechanical fabrication to minimize the relative vibration between the rotor and stator. 2.3. High-energy analysis system
Fig. 3. Schematic diagram of the injector system.
We will use 1705+ (from 9Be’70-) as the monitor beam for “Be measurement [3], as it has nearly the II. NEW & FUTURE FACILITIES
300
L+iuL.ianfan et al. / AMS at rhe Shanghai Insliiure of Nuclear Re.vearch
same velocity as “Be3+. Beam currents from the accelerator are focussed by magnetic quadrupole lenses. “Be3+ together with “OS* ions pass through the velocity selector before being analyzed by the 90° magnet. ions are detected by an off-axis At the exit, “05+ Faraday cup. The deviation of the beam spot from the central position provides an error signal to correct the terminal voltage. In the meanwhile, “Be ions are further focus& by quadrupole lenses, analyzed by a loo electrostatic analyzer and finally detected by a AE-E particle identification system which consists of an ionization chamber and a Si(Au) detector.
r705+ as a monitoring beam until the new box is installed. The AE-E detector, as well as the data acquisition system, have been built and calibrated with a, Be, B and C ions from a cyclotron. We have some troubles with our tandem accelerator. The laddertron broke down when we first raised the terminal voltage early last year. Since that happened, the structure of the laddertron bodies and nylon links has been modified. A new laddertron was built and ran satisfactorily. We plan to try the beam in May and by the end of this year we will be able to do preliminary work on AMS.
3. Present status and perspectives
Acknodedgement
The chemical processes for making Be0 samples have been settled and work well. A set of Be0 samples from the Jinlin meteorite, ocean sediment, Mn nodules and blanks have been prepared for use. BeO-, C- and B- negative ions from the sputtering ion source have been extracted and analyzed, and further work to improve the beam characteristics is in progress. Most of the elements of the AMS system have been installed and tested, except the electrostatic analyzer which is still under construction. The existing vacuum box of the 90” analyzing magnet is not wide enough at by the wall its exit, so that 9Be3+ would be intercepted when the magnetic field is adjusted for ‘“Be’+. A new one is being built to solve this problem. We will use
We thank S.Z. Zhou and G.B. Liu for their useful suggestions. This work is supported by Chinese Academy of Sciences.
References
111Zhang Zhongmu, Lai Weiquan and Jiao Souhua, Nucl. Instr. and Meth. A268 (1988) 337.
PI Lai Weiquan, Xu Senlin and Zhu Xikai, Proc. 3rd Int. Conf. on Electrostatic Accelerator Tech. (IEEE Publishing Services, 1981) p. 110. 131 R. Middleton and J, Klein, Proc. Workshop on Techniques in AMS, Oxford, UK. 1986, pp. 77-81.
Nuclear Instruments and Methods in Physics Research B52 (1990) 298-300 North-Holland
The AMS system at the Shanghai Institute of Nuclear Research Liu Lianfan, Sheng Shugang, Si Houzhi, Yi Weixi ‘) and Cheng Xiaowu Shanghai Institute of Nuclear Research, Academia Sinica, Shanghai, PR China ” Institute of Geochemistry, Academia Sinica, PR China
The main features of the AMS system based on the 6 MV tandem accelerator at the Shanghai Institute of Nuclear Research are described. A number of modifications of the ion source, beam optics design and sample preparation have been made. The system will be used primarily for “Be, 14C and 26Alanalysis. A similar capability should be possible for other rare isotopes. It will be applied to various fields of geology, meteoritics, oceanography and archaeology.
1. Introduction The AMS system based on the 6 MV tandem accelerator at the Shanghai Institute of Nuclear Research (SINR) will be put into operation by the end of this year. In this paper, the main features of the facility will be described. This system will be used primarily for “Be, 14C and ‘!4l analysis and applied to various fields of geology, meteoritics, oceanography and archaeology.
(10Be’60-, etc.) ions are selected by the 90° inflection magnet and injected sequentially into the accelerator. Mass-25 ions are monitored by an off-axis Faraday cup at the exit of the magnet while mass-26 ions are accelerated.
2. Description of the facility A schematic diagram of the elements of the AMS system is shown in fig. 1. The system is based on a 6 MV tandem accelerator which is built for general nuclear physics applications. A number of modifications have been made to meet the requirements of AMS. 2. I. Injector The sputtering ion source is shown in fig. 2. Its design is based on the structure of Hiconex 860 with the following modifications: (1) the insulator between the sputter target and the cesium ionizer is made of alumina ceramic with an appropriate shield instead of boron nitride to reduce boron contamination in loBe analysis; (2) the shape of the ionizer is spherical to improve beam emittance; and (3) it possesses a multi-position sample holder. Fig. 3 is a schematic diagram of the injector system. The negative beam from the ion source is focussed by an einzel lens, preaccelerated to 60 kV and passed through a three-slit system to confine the beam emittance to match the acceptance of the gas stripper. In “Be analysis, mass-25 (9Be’60-) and mass-26
Fig. 1.Schematic diagram of the SINR AMS facility.
0168-583X/90/%03.50 0 1990 - Elsevier Science Publishers B.V. (North-Holland)
299
Liu Lianfan et al. / AMS at the Shanghai Institute of Nuclear Research To valve
and pump sample wheel (18 positions)
Target
sample holder
Gate 04
z
CM
I1 1
)
(for
valve
exchanging
targets)
Fig. 2. Schematic diagram of the sputter ion source.
steerer
Faraday
cup
cs sputtering ion ScluPce
2.2. Accelerator The 6 MY tandem accelerator [l] is a vertical machine built in Shanghai. The accelerating tubes [2] are made of short tube sections bolted together. Each section consists of alumina ceramic rings bonded to titanium metal. Between adjoining sections there is a decoupling diaphragm with a 25 mm opening. Proper configuration of the diaphragm is chosen such that all secondary particles emitted from the aperture fringes can be suppressed in one section to overcome the “long tube effect”. We use a laddertron as the charge carrying unit. The original GVM will be replaced by a new one with higher precision; special care has been taken in its mechanical fabrication to minimize the relative vibration between the rotor and stator. 2.3. High-energy analysis system
Fig. 3. Schematic diagram of the injector system.
We will use 1705+ (from 9Be’70-) as the monitor beam for “Be measurement [3], as it has nearly the II. NEW & FUTURE FACILITIES
300
L+iuL.ianfan et al. / AMS at rhe Shanghai Insliiure of Nuclear Re.vearch
same velocity as “Be3+. Beam currents from the accelerator are focussed by magnetic quadrupole lenses. “Be3+ together with “OS* ions pass through the velocity selector before being analyzed by the 90° magnet. ions are detected by an off-axis At the exit, “05+ Faraday cup. The deviation of the beam spot from the central position provides an error signal to correct the terminal voltage. In the meanwhile, “Be ions are further focus& by quadrupole lenses, analyzed by a loo electrostatic analyzer and finally detected by a AE-E particle identification system which consists of an ionization chamber and a Si(Au) detector.
r705+ as a monitoring beam until the new box is installed. The AE-E detector, as well as the data acquisition system, have been built and calibrated with a, Be, B and C ions from a cyclotron. We have some troubles with our tandem accelerator. The laddertron broke down when we first raised the terminal voltage early last year. Since that happened, the structure of the laddertron bodies and nylon links has been modified. A new laddertron was built and ran satisfactorily. We plan to try the beam in May and by the end of this year we will be able to do preliminary work on AMS.
3. Present status and perspectives
Acknodedgement
The chemical processes for making Be0 samples have been settled and work well. A set of Be0 samples from the Jinlin meteorite, ocean sediment, Mn nodules and blanks have been prepared for use. BeO-, C- and B- negative ions from the sputtering ion source have been extracted and analyzed, and further work to improve the beam characteristics is in progress. Most of the elements of the AMS system have been installed and tested, except the electrostatic analyzer which is still under construction. The existing vacuum box of the 90” analyzing magnet is not wide enough at by the wall its exit, so that 9Be3+ would be intercepted when the magnetic field is adjusted for ‘“Be’+. A new one is being built to solve this problem. We will use
We thank S.Z. Zhou and G.B. Liu for their useful suggestions. This work is supported by Chinese Academy of Sciences.
References
111Zhang Zhongmu, Lai Weiquan and Jiao Souhua, Nucl. Instr. and Meth. A268 (1988) 337.
PI Lai Weiquan, Xu Senlin and Zhu Xikai, Proc. 3rd Int. Conf. on Electrostatic Accelerator Tech. (IEEE Publishing Services, 1981) p. 110. 131 R. Middleton and J, Klein, Proc. Workshop on Techniques in AMS, Oxford, UK. 1986, pp. 77-81.