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Analysis and manufacturing of ShenGuangIII facility target chamber
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Analysis and manufacturing of ShenGuangIII facility target chamber Mingzhi Zhu a , Xiaojuan Chen a , Yuanli Xu a,∗ , Haiying Gao a , Xinghua Que a , Wenkai Wu a , Huilin Liu b , Yong Xiang c a b c
Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 621900, Sichuan, PR China China Erzhong Group Co., Ltd., Deyang 618000, Sichuan, PR China Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, Sichuan, PR China
a r t i c l e
i n f o
Article history: Received 8 September 2013 Received in revised form 17 February 2014 Accepted 17 March 2014 Available online xxx Keywords: ShenGuangIII Target chamber Fabrication and testing
a b s t r a c t This paper will present a summary of the ShenGuangIII facility target chamber. During the machining the sphericity tolerances were addressed in forming process and numerical control vertical lathe for the individual plates. Procedure was developed for weld groove and welding of individual plates. The two hemispheric shells of the target chamber were welded in China Erzhong Group Co., Ltd. and sent to a temporary enclosure near the target bay for welding together. A drilling machine that can be accurately positioned on the sphere shell was used to bore the holes for the ports. After construction, the target chamber was lifted and placed on the support pedestal. The adjustment system and the precision surveyors with laser trackers were used to accurately position the target chamber on the pedestal support. The helium spray probe was used for the leak testing of the vacuum target chamber. Leak testing and repair of discovered leaks were performed to insure the vacuum integrity of the target chamber. A complete survey of the port flanges and custom contour machining of spacer plates were completed to insure that the devices attached to these port flanges meet the alignment requirement. The target shooting experiment of the sixth bundles of ShenGuangIII facility has shown that the target chamber satisfied the stability and precision criteria. © 2014 Published by Elsevier B.V.
1. Introduction The requirement of the ShenGuangIII target chamber included the synchronization of laser beams arriving at the target simultaneously, fixed focal plane distances from the final optics to the targets, stringent vibration stability, and space constraints. The result is that the target chamber, the largest single piece of equipment for ShenGuangIII facility, is a 30,000 kg sphere made of aluminum alloy 5052. The alloy is formable and weldable. It also has low activation from neutrons and gamma rays formed in the destruction of the targets. It has an internal diameter of 6 m and a wall thickness of 8 cm. The target chamber provides ∼148 holes including: 48 laser beam ports, 89 diagnostic ports, a port for fast ignition, and four ports for the target positioners and alignment assemblies. There are about 400 removable protection panels that were fastened on the racks welded on the target chamber’s interior surface. The protection panels are use as both the first wall and beam dumps. The target chamber has a vertical maintenance
∗ Corresponding author. Tel.: +86 816 2482264. E-mail address: [email protected] (Y. Xu).
access port which is located inside the support pedestal [1,2]. The main parameters of the target chamber are in Table 1. The target chamber, as shown in Fig. 1, has been fabricated and moved into the target area building. This paper will present a summary of the ShenGuangIII target chamber.
2. Analyses The target chamber is located in the center of the target bay. The height of the target chamber center is 15.1 m. The target chamber is supported in vertical direction on a thick concrete pedestal and laterally with eight passive friction dampers and support structure from the target bay floor near the equatorial plan. The required target chamber shell plate thickness was initially determined, considering the final optics assemblies, to produce a target chamber that would not buckle and maintain appropriate buckling coefficient under normal operating conditions. The required minimum safety factor for the target chamber static analysis is 2. An 8 cm wall thickness met the requirement. The static analysis showed that the maximum displacement is 0.95 mm, the maximum equivalent stress is 21.5 MPa, and the factor of safety is 3 considering the dead weight. The maximum displacement is 1 mm, the
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Table 1 Main parameters of the target chamber. Material Total mass Inner diameter Nominally wall thickness Ports of FOAs (diameters) Ports for physical diagnostic instruments Ports for target positioning (diameters) Ports for target alignment (diameters) Port for fast ignition (diameters)
Aluminum alloy 5052 About 30,000 kg 6m 80 cm 48 (540 mm) 89 (460 mm or 300 mm) 2 (600 mm) 2 (400 mm) 1 (1000 mm)
maximum equivalent stress is 21.8 MPa, and the factor of safety is 2.8 considering both the dead weight and atmospheric pressure. Evacuating the chamber causes a deformation of 0.2 mm. Global finite element model was used to evaluate the dynamic behaviors of the target area structures under broadband ambient random vibration based on modal superposition method [3,4]. The broadband ambient random vibration input motion is specified as the power spectral density (acceleration amplitude 10−10 g2 /Hz, 1 Hz–100 Hz) in X–Z direction. Fig. 2 is the target area finite element model and target chamber responses under broadband ambient random vibration. The maximum displacement of the target chamber is 2.8 m. The maximum displacement of the target is 3.4 m. The maximum rotation of the port flanges is 2.1 rad. The passive friction dampers effectively minimize vibration induced motion. The seismic responses analysis of the target chamber was done considering the interaction with the building and supports. The maximum displacement is 1.26 mm, the maximum equivalent stress is 21.9 MPa, and the factor of safety is 2.97. 3. Fabrication 3.1. Machining and construction Due to the allowance for thinning, the aluminum plates with 100 mm thickness were adopted for the forming process. The plate layout pattern of the target chamber is an expanded cube (6 sides) with 2 plated per side (12 plates total). As manufactured, the 12 aluminum plates measure 4.5 m by 2.5 m and weigh about 2 tons each.
Fig. 1. Schematic of the ShenGuangIII target chamber.
Fig. 2. Target area finite element model and target chamber responses under broadband ambient random vibration.
The aluminum plates were warm formed in two dish shaped dies to a calculated radius of curvature that would allow for weld shrinkage. A template was made for curvature inspection and errors are within 5 mm. The inner spherical surface excess material of these plates was removed in a numerical control vertical lathe with a special design fixture. The edges were precisely machined to the proper dimensions with the required weld groove configuration in a numerical control boring machine. The plates were inspected for dimensional accuracy that were found to be acceptable [5,6]. The hemispheric shells, as shown in Fig. 3, of the target chamber were welded in China Erzhong Group Co., Ltd. The plates that formed the hemispheric shell were fit together without welding on the pre-assembled support structure. The hemispheric shell geometry was checked by precision survey with a laser tracker to verify the proper sphericity prior to welding. The hemispheric shell welding was done using the gas metal arc welding process. During the welding process the hemispheric shell sphericities were re-checked to assure the requisite shape was maintained. The two hemispheric shells were sent to a temporary enclosure near the ShenGuangIII target bay. The upper and down hemispheric shells were welded together. In the temporary enclosure the sphere shell was supported on a rotate mechanism, as shown in Fig. 4. The laser tracker was used to perform a precision survey of the interior surface. The survey verified the sphericity and established the bestfit center of the sphere. The laser tracker was used to accurately mark all the holes for the ports and the protection panel racks. A drilling machine that can be accurately positioned on the sphere
Please cite this article in press as: M. Zhu, et al., Analysis and manufacturing of ShenGuangIII facility target chamber, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.040
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Fig. 3. Hemispheric shell during fabrication process. Six pieces were welded to form each hemisphere.
shell was used to bore the holes for the ports, as shown in Fig. 5. The diameter of the hole is not more than 0.5 mm larger than the outside diameter of the specific port designated for that location. This was done to minimize the potential that the subsequent welding of the port to the sphere shell causes the port to fall outside its prescribed location tolerances. Fig. 6 is the target chamber with holes. Special designed fixture was used to accurately position the ports in the holes for welding. Fig. 7 is the target chamber with ports.
Fig. 5. Boring the port hole. Each port was 540 cm in diameter.
3.2. Target chamber placement and alignment The support pedestal was checked for elevation error by precision survey with the laser tracker. After the welding of all ports the target chamber was lift from the temporary enclosure and set in the target bay on its support pedestal by a 300 tons crawler crane. The eight passive friction dampers were installed without locking. An adjustment system was developed that could elevate, translate and rotate the target chamber in small incremental moves. The adjustment system was supported through embedments in the target chamber pedestal support and attached to the target chamber connection structure. The precision surveyors using laser trackers were performed to determine the current target chamber best-fit center based on evaluating the most critical target chamber components, which include the location of the 48 laser beam ports, ports for the target positioners and alignment assemblies. At the same time, the relationship between the best-fit center and the critical ports were
Fig. 4. ShenGuangIII target chamber in temporary enclosure.
Fig. 6. Target chamber with holes.
Fig. 7. Target chamber with ports.
Please cite this article in press as: M. Zhu, et al., Analysis and manufacturing of ShenGuangIII facility target chamber, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.040
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Fig. 8. Target chamber bagged to verify the vacuum integrity.
confirmed for the target chamber to be accurately positioned on the support pedestal. The four perpendicular jacks of the adjustment system were used to establish the proper position, elevation, and tilt of the target chamber. The two opposite jacks of the adjustment system were used to establish the proper azimuth. Once in position the actual gaps between the top of the pedestal and the base of the target chamber were measured. The custom pad irons were machined and installed to lock the target chamber in position. Then the target chamber and the eight passive friction dampers were locked and the adjustment system was moved. The height error of the target chamber is less than ±0.12 mm, the position error is less than ±0.18 mm, and the azimuth error is less than 50 rad. 4. Testing
Fig. 9. ShenGuangIII target chamber in target bay. In additions to the beam ports, the chamber has 89 diagnostic ports.
4.1. Vacuum leak testing The target chamber is designed to provide a vacuum environment down to 5 × 10−4 Pa. After all of the welding the target chamber’s interior surface were hand smoothed with fine grit flapper wheels to approximate the mill finish. The target chamber was thoroughly rinsed with a high-pressure water spray. O-rings were installed in all flanged joints on the target chamber. The section of o-rings slightly larger than the standard section were chosen to eliminate the adverse effect brought from the weld plane distortion of the flanges. The helium spray probe was used for the leak testing of the vacuum target chamber. The testing was proceeded with the repeated cycles of pumping down – leak testing – venting to repair leaks. Smaller leaks not visible at higher pressure were identified and corrected. Each successive pump down cycle resulted in an improved base pressure. The source of the leaks was about equally split between the weld leaks in the ports and the o-ring leaks. The required leak rates of each port and o-ring are less than 1 × 10−12 Pa m3 /s. After all leaks were eliminated, the target chamber was bagged, as shown in Fig. 8, to verify the vacuum integrity of all sphere shell butt welds and port welds. The results showed that the integrated leak rate of the target chamber is less than 1 × 10−10 Pa m3 /s which is acceptable for operation. 4.2. Laser beam port spacers The final positions of the target chamber, port flanges for laser beams, and port flanges for the target positioners and alignment assemblies were accurately surveyed with the laser tracker when the target bay is environmentally controlled and the variation in temperature allow measurement with necessary degree of
accuracy. When the plane and location of the flange surfaces were established, custom-machine spacers were made for each of these ports. The flange position errors are 0.1–0.6 mm for the final optics assemblies that mounts to the ports. The flange position errors are 0.28–0.32 mm for the target positioners and alignment assemblies [7].
5. Discussion In order to satisfy the stability requirement, the target chamber’s supports included the vertical concrete pedestal and the lateral passive friction dampers and support structures from the building floor near the equatorial plan. These connectors also serve as seismic and torsional supports. After the upper and down hemispheric shells are welded together, the laser tracker is used to perform the precision survey of the interior surface and established the best-fit center of the sphere. The tracker is then used to accurately mark all port locations referenced from the best-fit center. When the target bay is environmentally controlled and the variation in temperature allow measurement with sufficient accuracy, the laser tracker is used to establish the planes and locations of the flange surfaces. The custom-machined spacers are used to correct the plane. To provide a vacuum environment, the target chamber’s interior surface is hand smoothed to approximate the mill finish. The section of o-rings slightly larger than the standard section are chosen to eliminate the adverse effect brought from the weld plane distortion of the flanges.
Please cite this article in press as: M. Zhu, et al., Analysis and manufacturing of ShenGuangIII facility target chamber, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.040
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6. Conclusion The fabrication and installation of the ShenGuangIII target chamber was accomplished, and is ready to accept the final optics assemblies, utilities, and diagnostics, as shown in Fig. 9. In the ShenGuangIII facility, the 5th and 6th bundles of the beam transport system have been accomplished. The target shooting experiments with the sixth bundle has been done, and results show that the stability and precision requirements have been satisfied. Acknowledgements Financial supports are acknowledged from the Science and Technology Development Foundation of China Academy of Engineering Physics (No. 2012B0203021). The authors of this paper are thankful to Qiang Du, Jiaquan Feng, Xueqian Chen of Institute of System Engineering of China Academy of Engineering Physics for their valuable contributions. The authors would like to express our
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particular appreciation to the SGIII target area group of Research Center of Laser Fusion of China Academy of Engineering Physics. References [1] Y.L. Xu, H.Y. Gao, Engineering Design of Target Chamber of SG-III Facility, in: Report S031.4.1, 2007, ISE. [2] Y.L. Xu, W.K. Wu, X.Q. Chen, The Research of the Technology of Design and Fabrication of SGIII facilities Target Chamber, in: Report GF-A0161143M, 2012, ISE. [3] Q. Du, W.K. Wu, Y.L. Xu, Structural Design and Stability Analyses for the Target Area of the SG-III Facility, in: Report GF-A0060980G, 2003, ISE. [4] M.Z. Zhu, X.J. Chen, M.C. Wang, W.K. Wu, Y.L. Xu, G. Chen, et al., Target area structural design of ShenGuangIII, Fusion Eng. Des. 88 (2013) 165–169. [5] Y.L. Xu, H.L. Liu, W.K. Wu, M.Z. Zhu, Fabrication and construction of large scale aluminum target chamber for SGIII, Adv. Mater. Res. 472–475 (2012) 1957–1962. [6] Y.L. Xu, X.Q. Chen, H.Y. Gao, X.H. Que, W.K. Wu, H.L. Liu, et al., Development of vacuum target chamber component in ShenGuang-III laser facility, High Power Laser and Particle Beams 24 (2012) 2623–2626. [7] M.Z. Zhu, W.K. Wu, X.J. Chen, M.C. Wang, Y.L. Chen, G. Chen, et al., Verification Research on Design Method and Capability of ICF Facility General Structure, in: Report 05010309. 1, 2012, ISE.
Please cite this article in press as: M. Zhu, et al., Analysis and manufacturing of ShenGuangIII facility target chamber, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.040
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Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Analysis and manufacturing of ShenGuangIII facility target chamber Mingzhi Zhu a , Xiaojuan Chen a , Yuanli Xu a,∗ , Haiying Gao a , Xinghua Que a , Wenkai Wu a , Huilin Liu b , Yong Xiang c a b c
Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 621900, Sichuan, PR China China Erzhong Group Co., Ltd., Deyang 618000, Sichuan, PR China Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, Sichuan, PR China
a r t i c l e
i n f o
Article history: Received 8 September 2013 Received in revised form 17 February 2014 Accepted 17 March 2014 Available online xxx Keywords: ShenGuangIII Target chamber Fabrication and testing
a b s t r a c t This paper will present a summary of the ShenGuangIII facility target chamber. During the machining the sphericity tolerances were addressed in forming process and numerical control vertical lathe for the individual plates. Procedure was developed for weld groove and welding of individual plates. The two hemispheric shells of the target chamber were welded in China Erzhong Group Co., Ltd. and sent to a temporary enclosure near the target bay for welding together. A drilling machine that can be accurately positioned on the sphere shell was used to bore the holes for the ports. After construction, the target chamber was lifted and placed on the support pedestal. The adjustment system and the precision surveyors with laser trackers were used to accurately position the target chamber on the pedestal support. The helium spray probe was used for the leak testing of the vacuum target chamber. Leak testing and repair of discovered leaks were performed to insure the vacuum integrity of the target chamber. A complete survey of the port flanges and custom contour machining of spacer plates were completed to insure that the devices attached to these port flanges meet the alignment requirement. The target shooting experiment of the sixth bundles of ShenGuangIII facility has shown that the target chamber satisfied the stability and precision criteria. © 2014 Published by Elsevier B.V.
1. Introduction The requirement of the ShenGuangIII target chamber included the synchronization of laser beams arriving at the target simultaneously, fixed focal plane distances from the final optics to the targets, stringent vibration stability, and space constraints. The result is that the target chamber, the largest single piece of equipment for ShenGuangIII facility, is a 30,000 kg sphere made of aluminum alloy 5052. The alloy is formable and weldable. It also has low activation from neutrons and gamma rays formed in the destruction of the targets. It has an internal diameter of 6 m and a wall thickness of 8 cm. The target chamber provides ∼148 holes including: 48 laser beam ports, 89 diagnostic ports, a port for fast ignition, and four ports for the target positioners and alignment assemblies. There are about 400 removable protection panels that were fastened on the racks welded on the target chamber’s interior surface. The protection panels are use as both the first wall and beam dumps. The target chamber has a vertical maintenance
∗ Corresponding author. Tel.: +86 816 2482264. E-mail address: [email protected] (Y. Xu).
access port which is located inside the support pedestal [1,2]. The main parameters of the target chamber are in Table 1. The target chamber, as shown in Fig. 1, has been fabricated and moved into the target area building. This paper will present a summary of the ShenGuangIII target chamber.
2. Analyses The target chamber is located in the center of the target bay. The height of the target chamber center is 15.1 m. The target chamber is supported in vertical direction on a thick concrete pedestal and laterally with eight passive friction dampers and support structure from the target bay floor near the equatorial plan. The required target chamber shell plate thickness was initially determined, considering the final optics assemblies, to produce a target chamber that would not buckle and maintain appropriate buckling coefficient under normal operating conditions. The required minimum safety factor for the target chamber static analysis is 2. An 8 cm wall thickness met the requirement. The static analysis showed that the maximum displacement is 0.95 mm, the maximum equivalent stress is 21.5 MPa, and the factor of safety is 3 considering the dead weight. The maximum displacement is 1 mm, the
http://dx.doi.org/10.1016/j.fusengdes.2014.03.040 0920-3796/© 2014 Published by Elsevier B.V.
Please cite this article in press as: M. Zhu, et al., Analysis and manufacturing of ShenGuangIII facility target chamber, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.040
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Table 1 Main parameters of the target chamber. Material Total mass Inner diameter Nominally wall thickness Ports of FOAs (diameters) Ports for physical diagnostic instruments Ports for target positioning (diameters) Ports for target alignment (diameters) Port for fast ignition (diameters)
Aluminum alloy 5052 About 30,000 kg 6m 80 cm 48 (540 mm) 89 (460 mm or 300 mm) 2 (600 mm) 2 (400 mm) 1 (1000 mm)
maximum equivalent stress is 21.8 MPa, and the factor of safety is 2.8 considering both the dead weight and atmospheric pressure. Evacuating the chamber causes a deformation of 0.2 mm. Global finite element model was used to evaluate the dynamic behaviors of the target area structures under broadband ambient random vibration based on modal superposition method [3,4]. The broadband ambient random vibration input motion is specified as the power spectral density (acceleration amplitude 10−10 g2 /Hz, 1 Hz–100 Hz) in X–Z direction. Fig. 2 is the target area finite element model and target chamber responses under broadband ambient random vibration. The maximum displacement of the target chamber is 2.8 m. The maximum displacement of the target is 3.4 m. The maximum rotation of the port flanges is 2.1 rad. The passive friction dampers effectively minimize vibration induced motion. The seismic responses analysis of the target chamber was done considering the interaction with the building and supports. The maximum displacement is 1.26 mm, the maximum equivalent stress is 21.9 MPa, and the factor of safety is 2.97. 3. Fabrication 3.1. Machining and construction Due to the allowance for thinning, the aluminum plates with 100 mm thickness were adopted for the forming process. The plate layout pattern of the target chamber is an expanded cube (6 sides) with 2 plated per side (12 plates total). As manufactured, the 12 aluminum plates measure 4.5 m by 2.5 m and weigh about 2 tons each.
Fig. 1. Schematic of the ShenGuangIII target chamber.
Fig. 2. Target area finite element model and target chamber responses under broadband ambient random vibration.
The aluminum plates were warm formed in two dish shaped dies to a calculated radius of curvature that would allow for weld shrinkage. A template was made for curvature inspection and errors are within 5 mm. The inner spherical surface excess material of these plates was removed in a numerical control vertical lathe with a special design fixture. The edges were precisely machined to the proper dimensions with the required weld groove configuration in a numerical control boring machine. The plates were inspected for dimensional accuracy that were found to be acceptable [5,6]. The hemispheric shells, as shown in Fig. 3, of the target chamber were welded in China Erzhong Group Co., Ltd. The plates that formed the hemispheric shell were fit together without welding on the pre-assembled support structure. The hemispheric shell geometry was checked by precision survey with a laser tracker to verify the proper sphericity prior to welding. The hemispheric shell welding was done using the gas metal arc welding process. During the welding process the hemispheric shell sphericities were re-checked to assure the requisite shape was maintained. The two hemispheric shells were sent to a temporary enclosure near the ShenGuangIII target bay. The upper and down hemispheric shells were welded together. In the temporary enclosure the sphere shell was supported on a rotate mechanism, as shown in Fig. 4. The laser tracker was used to perform a precision survey of the interior surface. The survey verified the sphericity and established the bestfit center of the sphere. The laser tracker was used to accurately mark all the holes for the ports and the protection panel racks. A drilling machine that can be accurately positioned on the sphere
Please cite this article in press as: M. Zhu, et al., Analysis and manufacturing of ShenGuangIII facility target chamber, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.040
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Fig. 3. Hemispheric shell during fabrication process. Six pieces were welded to form each hemisphere.
shell was used to bore the holes for the ports, as shown in Fig. 5. The diameter of the hole is not more than 0.5 mm larger than the outside diameter of the specific port designated for that location. This was done to minimize the potential that the subsequent welding of the port to the sphere shell causes the port to fall outside its prescribed location tolerances. Fig. 6 is the target chamber with holes. Special designed fixture was used to accurately position the ports in the holes for welding. Fig. 7 is the target chamber with ports.
Fig. 5. Boring the port hole. Each port was 540 cm in diameter.
3.2. Target chamber placement and alignment The support pedestal was checked for elevation error by precision survey with the laser tracker. After the welding of all ports the target chamber was lift from the temporary enclosure and set in the target bay on its support pedestal by a 300 tons crawler crane. The eight passive friction dampers were installed without locking. An adjustment system was developed that could elevate, translate and rotate the target chamber in small incremental moves. The adjustment system was supported through embedments in the target chamber pedestal support and attached to the target chamber connection structure. The precision surveyors using laser trackers were performed to determine the current target chamber best-fit center based on evaluating the most critical target chamber components, which include the location of the 48 laser beam ports, ports for the target positioners and alignment assemblies. At the same time, the relationship between the best-fit center and the critical ports were
Fig. 4. ShenGuangIII target chamber in temporary enclosure.
Fig. 6. Target chamber with holes.
Fig. 7. Target chamber with ports.
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Fig. 8. Target chamber bagged to verify the vacuum integrity.
confirmed for the target chamber to be accurately positioned on the support pedestal. The four perpendicular jacks of the adjustment system were used to establish the proper position, elevation, and tilt of the target chamber. The two opposite jacks of the adjustment system were used to establish the proper azimuth. Once in position the actual gaps between the top of the pedestal and the base of the target chamber were measured. The custom pad irons were machined and installed to lock the target chamber in position. Then the target chamber and the eight passive friction dampers were locked and the adjustment system was moved. The height error of the target chamber is less than ±0.12 mm, the position error is less than ±0.18 mm, and the azimuth error is less than 50 rad. 4. Testing
Fig. 9. ShenGuangIII target chamber in target bay. In additions to the beam ports, the chamber has 89 diagnostic ports.
4.1. Vacuum leak testing The target chamber is designed to provide a vacuum environment down to 5 × 10−4 Pa. After all of the welding the target chamber’s interior surface were hand smoothed with fine grit flapper wheels to approximate the mill finish. The target chamber was thoroughly rinsed with a high-pressure water spray. O-rings were installed in all flanged joints on the target chamber. The section of o-rings slightly larger than the standard section were chosen to eliminate the adverse effect brought from the weld plane distortion of the flanges. The helium spray probe was used for the leak testing of the vacuum target chamber. The testing was proceeded with the repeated cycles of pumping down – leak testing – venting to repair leaks. Smaller leaks not visible at higher pressure were identified and corrected. Each successive pump down cycle resulted in an improved base pressure. The source of the leaks was about equally split between the weld leaks in the ports and the o-ring leaks. The required leak rates of each port and o-ring are less than 1 × 10−12 Pa m3 /s. After all leaks were eliminated, the target chamber was bagged, as shown in Fig. 8, to verify the vacuum integrity of all sphere shell butt welds and port welds. The results showed that the integrated leak rate of the target chamber is less than 1 × 10−10 Pa m3 /s which is acceptable for operation. 4.2. Laser beam port spacers The final positions of the target chamber, port flanges for laser beams, and port flanges for the target positioners and alignment assemblies were accurately surveyed with the laser tracker when the target bay is environmentally controlled and the variation in temperature allow measurement with necessary degree of
accuracy. When the plane and location of the flange surfaces were established, custom-machine spacers were made for each of these ports. The flange position errors are 0.1–0.6 mm for the final optics assemblies that mounts to the ports. The flange position errors are 0.28–0.32 mm for the target positioners and alignment assemblies [7].
5. Discussion In order to satisfy the stability requirement, the target chamber’s supports included the vertical concrete pedestal and the lateral passive friction dampers and support structures from the building floor near the equatorial plan. These connectors also serve as seismic and torsional supports. After the upper and down hemispheric shells are welded together, the laser tracker is used to perform the precision survey of the interior surface and established the best-fit center of the sphere. The tracker is then used to accurately mark all port locations referenced from the best-fit center. When the target bay is environmentally controlled and the variation in temperature allow measurement with sufficient accuracy, the laser tracker is used to establish the planes and locations of the flange surfaces. The custom-machined spacers are used to correct the plane. To provide a vacuum environment, the target chamber’s interior surface is hand smoothed to approximate the mill finish. The section of o-rings slightly larger than the standard section are chosen to eliminate the adverse effect brought from the weld plane distortion of the flanges.
Please cite this article in press as: M. Zhu, et al., Analysis and manufacturing of ShenGuangIII facility target chamber, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.040
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6. Conclusion The fabrication and installation of the ShenGuangIII target chamber was accomplished, and is ready to accept the final optics assemblies, utilities, and diagnostics, as shown in Fig. 9. In the ShenGuangIII facility, the 5th and 6th bundles of the beam transport system have been accomplished. The target shooting experiments with the sixth bundle has been done, and results show that the stability and precision requirements have been satisfied. Acknowledgements Financial supports are acknowledged from the Science and Technology Development Foundation of China Academy of Engineering Physics (No. 2012B0203021). The authors of this paper are thankful to Qiang Du, Jiaquan Feng, Xueqian Chen of Institute of System Engineering of China Academy of Engineering Physics for their valuable contributions. The authors would like to express our
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particular appreciation to the SGIII target area group of Research Center of Laser Fusion of China Academy of Engineering Physics. References [1] Y.L. Xu, H.Y. Gao, Engineering Design of Target Chamber of SG-III Facility, in: Report S031.4.1, 2007, ISE. [2] Y.L. Xu, W.K. Wu, X.Q. Chen, The Research of the Technology of Design and Fabrication of SGIII facilities Target Chamber, in: Report GF-A0161143M, 2012, ISE. [3] Q. Du, W.K. Wu, Y.L. Xu, Structural Design and Stability Analyses for the Target Area of the SG-III Facility, in: Report GF-A0060980G, 2003, ISE. [4] M.Z. Zhu, X.J. Chen, M.C. Wang, W.K. Wu, Y.L. Xu, G. Chen, et al., Target area structural design of ShenGuangIII, Fusion Eng. Des. 88 (2013) 165–169. [5] Y.L. Xu, H.L. Liu, W.K. Wu, M.Z. Zhu, Fabrication and construction of large scale aluminum target chamber for SGIII, Adv. Mater. Res. 472–475 (2012) 1957–1962. [6] Y.L. Xu, X.Q. Chen, H.Y. Gao, X.H. Que, W.K. Wu, H.L. Liu, et al., Development of vacuum target chamber component in ShenGuang-III laser facility, High Power Laser and Particle Beams 24 (2012) 2623–2626. [7] M.Z. Zhu, W.K. Wu, X.J. Chen, M.C. Wang, Y.L. Chen, G. Chen, et al., Verification Research on Design Method and Capability of ICF Facility General Structure, in: Report 05010309. 1, 2012, ISE.
Please cite this article in press as: M. Zhu, et al., Analysis and manufacturing of ShenGuangIII facility target chamber, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.040