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Charge-stripping foil changer with energy adjuster function
ARTICLE IN PRESS
Nuclear Instruments and Methods in Physics Research A 581 (2007) 586–588 www.elsevier.com/locate/nima
Charge-stripping foil changer with energy adjuster function H. Ryuto,1, H. Hasebe, N. Fukunishi, T. Abe, A. Goto, M. Kase, Y. Yano RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan Received 6 July 2007; received in revised form 30 July 2007; accepted 30 July 2007 Available online 12 August 2007
Abstract A charge-stripping foil changer that has an energy adjuster function was constructed. One of the 30 foils in the changer is placed at the beam position without opening the vacuum chamber. The energy of the beam behind the charge stripper is adjusted by changing the effective thickness of the foil, which is changed by tilting the foil at an angle from 01 to 601. A uranium beam was accelerated to 345 MeV/nucleon using two charge-stripping foil changers with an energy adjuster function. r 2007 Elsevier B.V. All rights reserved. PACS: 29.20.Hm; 29.25.Pj; 29.27.Eg Keywords: Charge stripper; Carbon foil; Cyclotron; Heavy-ion beam
1. Introduction The matching between the exit energy of a cyclotron and the injection energy of the following cyclotron is crucial in a heavy-ion cyclotron complex. On the other hand, it is very useful to place a charge stripper between the accelerators, because a higher charge state enables the acceleration of heavy-ion beams using a smaller accelerator. A heavy-ion beam loses a relatively large amount of kinetic energy while passing through the charge stripper in relation to its velocity and ion species. Therefore, an energy adjuster is an essential device in a heavy-ion cyclotron complex. The RIKEN RI-beam factory (RIBF) is a heavyion cyclotron complex [1] that has recently started to be used for experiments. At the RIBF, three stripper sections are used to accelerate ions from hydrogen to uranium [2]. Fig. 1 shows a schematic view of the RIBF. Ions are accelerated successively by an injector linac, the RIKEN ring cyclotron (RRC), a fixed-frequency ring cyclotron (fRC), an intermediate-stage ring cyclotron (IRC), and a superconducting ring cyclotron (SRC). The first stripper section is placed between the injector linac and the RRC. The beam energy behind the first stripper is adjusted to the Corresponding author. Tel.: +81 48 462 1111; fax: +81 48 467 4900. 1
E-mail address: [email protected] (H. Ryuto). Formerly, H. Akiyoshi.
0168-9002/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2007.07.155
injection energy of the RRC by tuning the acceleration phase and voltage of the injector linac. The second stripper section is placed between the RRC and the fRC, and the third stripper section is placed between the fRC and the IRC, namely, between two cyclotrons. It is a rather complicated task to fine-tune the extraction energy of the beam by changing the extraction radius, or fine-tune the injection energy of the following cyclotron by adjusting the injection radius. To fine-tune the beam energy easily, a charge-stripping foil changer that also has an energy adjuster function was constructed. 2. Structure and movement Fig. 2 shows a schematic view of the charge-stripping foil changer with an energy adjuster function (FCEA). A carbon foil is attached to a foil holder. The foil holder is a 0.5-mm-thick aluminum plate with a rounded rectangular hole of 28 mm 14 mm. The holders of carbon foils are attached to holder supports using leaf springs. The holder supports are placed on a pair of chain loops stretched in a cylindrical vacuum chamber. The number of holder supports is 31, and one of them is usually used to support a beam viewer, so 30 carbon foils can be set in the FCEA. A part of the chain loops is used to allow beams to pass without charge stripping, and this part is also used to
ARTICLE IN PRESS H. Ryuto et al. / Nuclear Instruments and Methods in Physics Research A 581 (2007) 586–588
determine the zero point of the loops using switches. The holders of carbon foils are exchanged at the maintenance port on the side of the cylindrical vacuum chamber. Two stepping motors are placed at one end of the cylindrical vacuum chamber. The other end is connected to a common vacuum chamber in the beam transport line. One of the stepping motors is used to change the foil at the beam position by rotating the chain loops through a biaxial feedthrough and gears. The other motor is used to tilt the foil. The distance that the beam passes through the foil, that is to say, the effective thickness of the foil, is adjusted by changing the angle between the foil and the beam. The
IRC 114 MeV/nucleon
SRC 345 MeV/nucleon
Stripper 3 86+ Ion source 35+
Stripper 1
RRC 11 MeV/nucleon
Linac 0.67 MeV/nucleon
Stripper 2 71+
fRC 51 MeV/nucleon
Fig. 1. Schematic view of RIBF. The energies at the exit of the accelerators, the charge state of uranium ions extracted from the ion source, and the charge states of uranium ions selected after the charge strippers are presented.
ions that pass through the carbon foil lose their energy approximately in proportion to the thickness of the foil; thus, the beam energy can be adjusted by tilting the foil. The maximum tilting angle is 601. The foil can be changed while maintaining the same tilting angle. 3. Application to acceleration of uranium beam A uranium beam was accelerated to 345 MeV/nucleon using two FCEAs at the second and third stripper sections. At first, 238 U35þ ions extracted from an ion source were accelerated to 11 MeV/nucleon by the injector linac and the RRC. The uranium beam bombarded a 0:3mg=cm2 -thick carbon foil attached to the FCEA at the second stripper section. The tilting angle was 01. At the second stripper section, no fine-tuning of the beam energy was performed using the FCEA for two reasons. One reason is that we chose to obtain 71þ, instead of 72þ that is the measured equilibrium charge state, using a carbon foil thinner than the equilibrium thickness, so as the foil thickness increases, the charge state fraction of 71þ decreases. The other reason is that the energy loss, 0.16 MeV/nucleon [3], is much smaller than that of the third stripper; thus, the effect of foil tilting on the beam energy is small. Then, the uranium beam was accelerated to 51 MeV/nucleon by the fRC, and bombarded a carbon foil attached to the FCEA at the third stripper section. The thickness of the carbon foil was 14 mg=cm2 , and the foil was tilted at 33 to decrease the beam energy to the incident energy of the IRC. The effective thickness of the carbon foil was thus 17 mg=cm2 . The energy loss caused by the 17 mg=cm2 thick carbon foil is 5.0 MeV/nucleon [3]. The FCEAs operated stably during the acceleration of the uranium beam.
maintenance port
beam
587
biaxial feedthrough
stepping motors
foil change
chain
foil tilt cylindrical vacuum chamber
connection to vacuum chamber in beam line leaf spring
14 mm
switch for zero point determination
holder support
beam spot 28 mm foil holder carbon foil Fig. 2. Schematic view of charge-stripping foil changer with an energy adjuster function showing side view and close-up view around the beam spot on the carbon stripper foil.
ARTICLE IN PRESS 588
H. Ryuto et al. / Nuclear Instruments and Methods in Physics Research A 581 (2007) 586–588
The FCEAs are also scheduled to be used as energy adjusters in combination with rotating charge strippers [4]. The FCEA after the RRC is also scheduled to be used as an energy adjuster improving the function of the range shifter [5] for biology experiments using heavy-ion beams.
applying the FCEAs to the acceleration of the uranium beam. This work was supported in part by the Ministry of Agriculture, Forestry and Fisheries of Japan through a fund for research projects utilizing advanced technologies in agriculture, forestry and fisheries.
4. Summary References A charge-stripping foil changer that has an energy adjuster function was constructed. One of the 30 foils in the changer can be placed at the beam position without opening the vacuum chamber. The beam energy behind the charge stripper is changed by tilting the foil. A uranium beam was accelerated to 345 MeV/nucleon using two charge-stripping foil changers with an energy adjuster function. Acknowledgments The authors thank the members of the accelerator division of RIKEN Nishina Center for their assistance in
[1] Y. Yano, in: Proceedings of the 2005 Particle Accelerator Conference, Knoxville, USA, 2005, p. 320. [2] H. Ryuto, N. Fukunishi, H. Hasebe, N. Inabe, S. Yokouchi, O. Kamigaito, A. Goto, M. Kase, Y. Yano, in: Proceedings of the 2005 Particle Accelerator Conference, Knoxville, USA, 2005, p. 3751. [3] J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Solids, Pergamon Press, New York, 1985. [4] H. Ryuto, H. Hasebe, N. Fukunishi, S. Yokouchi, A. Goto, M. Kase, Y. Yano, Nucl. Instr. and Meth. A 569 (2006) 697. [5] H. Ryuto, T. Abe, N. Fukunishi, M. Kase, Y. Yano, J. Biomed. Nanotechnol. 2 (2006) 88.
Nuclear Instruments and Methods in Physics Research A 581 (2007) 586–588 www.elsevier.com/locate/nima
Charge-stripping foil changer with energy adjuster function H. Ryuto,1, H. Hasebe, N. Fukunishi, T. Abe, A. Goto, M. Kase, Y. Yano RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan Received 6 July 2007; received in revised form 30 July 2007; accepted 30 July 2007 Available online 12 August 2007
Abstract A charge-stripping foil changer that has an energy adjuster function was constructed. One of the 30 foils in the changer is placed at the beam position without opening the vacuum chamber. The energy of the beam behind the charge stripper is adjusted by changing the effective thickness of the foil, which is changed by tilting the foil at an angle from 01 to 601. A uranium beam was accelerated to 345 MeV/nucleon using two charge-stripping foil changers with an energy adjuster function. r 2007 Elsevier B.V. All rights reserved. PACS: 29.20.Hm; 29.25.Pj; 29.27.Eg Keywords: Charge stripper; Carbon foil; Cyclotron; Heavy-ion beam
1. Introduction The matching between the exit energy of a cyclotron and the injection energy of the following cyclotron is crucial in a heavy-ion cyclotron complex. On the other hand, it is very useful to place a charge stripper between the accelerators, because a higher charge state enables the acceleration of heavy-ion beams using a smaller accelerator. A heavy-ion beam loses a relatively large amount of kinetic energy while passing through the charge stripper in relation to its velocity and ion species. Therefore, an energy adjuster is an essential device in a heavy-ion cyclotron complex. The RIKEN RI-beam factory (RIBF) is a heavyion cyclotron complex [1] that has recently started to be used for experiments. At the RIBF, three stripper sections are used to accelerate ions from hydrogen to uranium [2]. Fig. 1 shows a schematic view of the RIBF. Ions are accelerated successively by an injector linac, the RIKEN ring cyclotron (RRC), a fixed-frequency ring cyclotron (fRC), an intermediate-stage ring cyclotron (IRC), and a superconducting ring cyclotron (SRC). The first stripper section is placed between the injector linac and the RRC. The beam energy behind the first stripper is adjusted to the Corresponding author. Tel.: +81 48 462 1111; fax: +81 48 467 4900. 1
E-mail address: [email protected] (H. Ryuto). Formerly, H. Akiyoshi.
0168-9002/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2007.07.155
injection energy of the RRC by tuning the acceleration phase and voltage of the injector linac. The second stripper section is placed between the RRC and the fRC, and the third stripper section is placed between the fRC and the IRC, namely, between two cyclotrons. It is a rather complicated task to fine-tune the extraction energy of the beam by changing the extraction radius, or fine-tune the injection energy of the following cyclotron by adjusting the injection radius. To fine-tune the beam energy easily, a charge-stripping foil changer that also has an energy adjuster function was constructed. 2. Structure and movement Fig. 2 shows a schematic view of the charge-stripping foil changer with an energy adjuster function (FCEA). A carbon foil is attached to a foil holder. The foil holder is a 0.5-mm-thick aluminum plate with a rounded rectangular hole of 28 mm 14 mm. The holders of carbon foils are attached to holder supports using leaf springs. The holder supports are placed on a pair of chain loops stretched in a cylindrical vacuum chamber. The number of holder supports is 31, and one of them is usually used to support a beam viewer, so 30 carbon foils can be set in the FCEA. A part of the chain loops is used to allow beams to pass without charge stripping, and this part is also used to
ARTICLE IN PRESS H. Ryuto et al. / Nuclear Instruments and Methods in Physics Research A 581 (2007) 586–588
determine the zero point of the loops using switches. The holders of carbon foils are exchanged at the maintenance port on the side of the cylindrical vacuum chamber. Two stepping motors are placed at one end of the cylindrical vacuum chamber. The other end is connected to a common vacuum chamber in the beam transport line. One of the stepping motors is used to change the foil at the beam position by rotating the chain loops through a biaxial feedthrough and gears. The other motor is used to tilt the foil. The distance that the beam passes through the foil, that is to say, the effective thickness of the foil, is adjusted by changing the angle between the foil and the beam. The
IRC 114 MeV/nucleon
SRC 345 MeV/nucleon
Stripper 3 86+ Ion source 35+
Stripper 1
RRC 11 MeV/nucleon
Linac 0.67 MeV/nucleon
Stripper 2 71+
fRC 51 MeV/nucleon
Fig. 1. Schematic view of RIBF. The energies at the exit of the accelerators, the charge state of uranium ions extracted from the ion source, and the charge states of uranium ions selected after the charge strippers are presented.
ions that pass through the carbon foil lose their energy approximately in proportion to the thickness of the foil; thus, the beam energy can be adjusted by tilting the foil. The maximum tilting angle is 601. The foil can be changed while maintaining the same tilting angle. 3. Application to acceleration of uranium beam A uranium beam was accelerated to 345 MeV/nucleon using two FCEAs at the second and third stripper sections. At first, 238 U35þ ions extracted from an ion source were accelerated to 11 MeV/nucleon by the injector linac and the RRC. The uranium beam bombarded a 0:3mg=cm2 -thick carbon foil attached to the FCEA at the second stripper section. The tilting angle was 01. At the second stripper section, no fine-tuning of the beam energy was performed using the FCEA for two reasons. One reason is that we chose to obtain 71þ, instead of 72þ that is the measured equilibrium charge state, using a carbon foil thinner than the equilibrium thickness, so as the foil thickness increases, the charge state fraction of 71þ decreases. The other reason is that the energy loss, 0.16 MeV/nucleon [3], is much smaller than that of the third stripper; thus, the effect of foil tilting on the beam energy is small. Then, the uranium beam was accelerated to 51 MeV/nucleon by the fRC, and bombarded a carbon foil attached to the FCEA at the third stripper section. The thickness of the carbon foil was 14 mg=cm2 , and the foil was tilted at 33 to decrease the beam energy to the incident energy of the IRC. The effective thickness of the carbon foil was thus 17 mg=cm2 . The energy loss caused by the 17 mg=cm2 thick carbon foil is 5.0 MeV/nucleon [3]. The FCEAs operated stably during the acceleration of the uranium beam.
maintenance port
beam
587
biaxial feedthrough
stepping motors
foil change
chain
foil tilt cylindrical vacuum chamber
connection to vacuum chamber in beam line leaf spring
14 mm
switch for zero point determination
holder support
beam spot 28 mm foil holder carbon foil Fig. 2. Schematic view of charge-stripping foil changer with an energy adjuster function showing side view and close-up view around the beam spot on the carbon stripper foil.
ARTICLE IN PRESS 588
H. Ryuto et al. / Nuclear Instruments and Methods in Physics Research A 581 (2007) 586–588
The FCEAs are also scheduled to be used as energy adjusters in combination with rotating charge strippers [4]. The FCEA after the RRC is also scheduled to be used as an energy adjuster improving the function of the range shifter [5] for biology experiments using heavy-ion beams.
applying the FCEAs to the acceleration of the uranium beam. This work was supported in part by the Ministry of Agriculture, Forestry and Fisheries of Japan through a fund for research projects utilizing advanced technologies in agriculture, forestry and fisheries.
4. Summary References A charge-stripping foil changer that has an energy adjuster function was constructed. One of the 30 foils in the changer can be placed at the beam position without opening the vacuum chamber. The beam energy behind the charge stripper is changed by tilting the foil. A uranium beam was accelerated to 345 MeV/nucleon using two charge-stripping foil changers with an energy adjuster function. Acknowledgments The authors thank the members of the accelerator division of RIKEN Nishina Center for their assistance in
[1] Y. Yano, in: Proceedings of the 2005 Particle Accelerator Conference, Knoxville, USA, 2005, p. 320. [2] H. Ryuto, N. Fukunishi, H. Hasebe, N. Inabe, S. Yokouchi, O. Kamigaito, A. Goto, M. Kase, Y. Yano, in: Proceedings of the 2005 Particle Accelerator Conference, Knoxville, USA, 2005, p. 3751. [3] J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Solids, Pergamon Press, New York, 1985. [4] H. Ryuto, H. Hasebe, N. Fukunishi, S. Yokouchi, A. Goto, M. Kase, Y. Yano, Nucl. Instr. and Meth. A 569 (2006) 697. [5] H. Ryuto, T. Abe, N. Fukunishi, M. Kase, Y. Yano, J. Biomed. Nanotechnol. 2 (2006) 88.