- Email: [email protected]
Technical Aspects of Delivering Simultaneous Dual and Triple Ion Beams to a Target at the Michigan Ion Beam Laboratory
Available online at www.sciencedirect.com
ScienceDirect Physics Procedia 90 (2017) 385 – 390
Conference on the Application of Accelerators in Research and Industry, CAARI 2016, 30 October – 4 November 2016, Ft. Worth, TX, USA
Technical Aspects of Delivering Simultaneous Dual and Triple Ion Beams to a Target at the Michigan Ion Beam Laboratory O. Toadera*, F. Naaba, E. Ubersedera, T. Kubleya, S. Tallera and G. Wasa a
Nuclear Engineering and Radiological Sciences, University of Michigan, 2600 Draper Dr. Ann Arbor MI 48109, USA
Abstract
The Michigan Ion Beam Laboratory (MIBL) at the University of Michigan in Ann Arbor, Michigan, USA, plays a significant role in supporting the mission of the U.S. DOE Office of Nuclear Energy. MIBL is a charter laboratory of the NSUF (National Scientific User Facility – US DoE) and hosts users worldwide. The laboratory has evolved from a single accelerator laboratory to a highly versatile facility with three accelerators (3 MV Tandem, a 400 kV Ion Implanter and a 1.7 MV Tandem), seven beam lines and five target chambers that together, provide unique capabilities to capture the extreme environment experienced by materials in reactor systems. This capability now includes simultaneous multiple (dual, triple) ion irradiations, an irradiation accelerated corrosion cell, and soon, in-situ dual beam irradiation in a transmission electron microscope (TEM) for the study of radiation damage coupled with injection of transmutation elements. The two beam lines that will connect to the 300 kV FEI Tecnai G2 F30 microscope are expected to be operational by the end of 2017. Multiple simultaneous ion beam experiments involving light and heavy ions are already in progress. This paper will outline the current equipment and will focus on the new capability of running dual and triple ion beam experiments. 2017The The Authors. Published by Elsevier ©©2017 Authors. Published by Elsevier B.V.B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Scientific Committee of the Conference on the Application of Accelerators in Research Peer-review under responsibility of the Scientific Committee of the Conference on the Application of Accelerators in Research and Industry and Industry. Keywords: ion beams irradiations, dual beams, triple beam,ion source
* Corresponding author. Tel.: 1-734-936-0166; fax: 1-734-936-8820. E-mail address: [email protected]
1875-3892 © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Scientific Committee of the Conference on the Application of Accelerators in Research and Industry doi:10.1016/j.phpro.2017.09.039
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O. Toader et al. / Physics Procedia 90 (2017) 385 – 390
1.
Introduction
Ion irradiation is being considered as a surrogate for simulating nuclear reactor irradiations in the development of new materials for application in nuclear reactor cores. Light and heavy ions can play complementary roles in such studies when employed either sequentially or simultaneously. There are a number of laboratories in the world that are currently using a multiple ion beam setup to study these effects, such as TIARA – Japan and JANNUSFrance, to name only a couple and they generate a wide range of research in the field [1-5]. Michigan Ion Beam Laboratory (MIBL – Fig 1a) was established in 1986 and went through a major upgrade in 2014, when a third accelerator was added. After the accelerator installation, four new additional beamlines and three new ion sources were added, significantly boosting the experimental range capabilities. With the installation of the 3 MV Pelletron, and the setting up of a chamber connected to all three particle accelerators, the scientists are now equipped with tools that allow them to conduct simultaneous dual and triple ion beam irradiation experiments. The main mission of MIBL is to help better understand ion irradiation versus neutron irradiation in materials [6]. In this way, scientists hope to reduce the cost of producing irradiated materials for the scope of identifying novel materials capable to withstand large radiation doses and at the same time to understand failure under extreme radiation conditions. The same tools can be employed to better understand the mechanism by which irradiation accelerates corrosion and explore microstructure evolution at very high doses and dose rates.
Figure 1: MIBL: (a) accelerator room overhead view and (b) 3-D drawing including the target rooms.
2.
Major Equipment
2.1 Particle accelerators The lab is equipped with three particle accelerators. The largest is a 3 MV Pelletron (Wolverine – Fig 2a), built by National Electrostatics Corporation (NEC), and is capable of delivering either a focused ion beam with 2.5 mm full-width-half-max (FWHM) near the target (or rastered for up to 2 cm / 2 cm), or a defocused ion beam with great uniformity over the irradiated area. The Pelletron is also capable of accelerating a variety of ion species with multiple charge states, from 1 MeV to 6 MeV for protons and 9 MeV or higher for heavier ions. The 1.7 MV accelerator (Maize – Fig 2b) is a solid state, gas insulated device manufactured by High Voltage Engineering Europa (HVEE) capable of operation between 0.4 and 1.7 MV. Maize can deliver protons up to 3.2 MeV and heavier ions at 5 MeV and higher, depending on the charge state. The 400 kV ion implanter (Blue – Fig 2c) operates with a positive ion source and can, in principle, deliver any ion with a Z from 1 to 92. It was made by NEC and is equipped with a Danfysik ion source and a HVEE implant chamber. The operational energy range is 10 – 400 kV with
O. Toader et al. / Physics Procedia 90 (2017) 385 – 390
currents exceeding 100s of μA for some elements, and a terminal chamber capable of implants from LN2 temperature to 8000C. 2.2 Ion Sources Wolverine can operate with three different ion sources: a Torvis ion source (NEC – Fig 3a) that can produce intense beams of protons and deuterons, an Alphatross ion source (NEC- Fig 3b) with Rb charge exchange that delivers negative He beam, and a PS120 (Peabody Scientific– Fig 3c) sputter type ion source that can deliver beams from solid targets by Cs sputtering (e.g. Fe, Ni, Au, W, Si, etc). Maize is equipped with two ion sources: an electron cyclotron resonance (ECR) type ion source, model M100 (Pantechnik–Fig 3d) delivering negative He ion beam through a charge exchange canal, and a MultiCathode SNICS ion source (NEC–Fig 3e) that delivers a wide range of beams from solid targets by Cs sputtering. Blue is equipped with a versatile positive ion source Model 921, produced by Danfysik (Fig 3f) that can operate in three modes based on the state of the target material: gas, liquid and solid target.
Figure 2: (a) Wolverine (Pelletron accelerator), (b) Maize (Tandetron accelerator), (c) Blue (ion implanter) and (d) FEI Tecnai 300 kV TEM.
Figure 3: MIBL ion sources: (a) Torvis, (b) Alphatross, (c) PS120, (d) M100, (e) MC-SNICS and (f) Model 921 and MBC (g)
2.3 Beamlines There are seven active beamlines in the laboratory (Fig 1b- top right) and two in development that connect to five target chambers in the target rooms. The North Target Room (NTR) hosts: beamline 1 (BL1) that delivers ions used in surface analysis, and beamline 2 (BL2) that is used for ion irradiation experiments. Most single ion radiation damage experiments take place in BL2 chamber. The South Target Room (STR) (bottom right Fig 1b) hosts five beamlines. Beamline 3 (BL3) delivers ions to a water cell used in Irradiation Assisted Corrosion (IAC) experiments. Here, a thin sample of thickness 30-100 μm is bombarded from one side with protons up to 5.4 MeV energy. The other side is exposed to high temperature, high pressure water up to 320°C and 2000 psi, acting as both the window between the high vacuum beamline and the water cell, and the sample. This novel capability is used to determine the behavior of materials when simultaneously subjected to both corrosion and irradiation. Beamline 4 (BL4) is connected to the multi-beam chamber (MBC – Fig 3g-right) and can be used as a separate single ion irradiation beamline or as part of the dual and triple ion beam experiments. The first part of beamline 5 (BL5) terminates in an implantation chamber. Beyond this chamber, BL5 continues to the MBC as the third line of the triple ion beam arrangement (MBC – Fig 3g, middle). Due to the fact that the ion source of Blue can deliver
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multiple ionization states of heavy ions, the energy of gas ion beams such as Xe and Kr could be increased to more than 1.5 MeV on target. Beamline 7 (BL7) delivers ions from Maize to the MBC (MBC – Fig 3g, left), either independently or as part of the dual or triple beam arrangement. Beamline 9 (BL9) is used in surface analysis experiments. Beamline 6 (BL6) and beamline 8 (BL8) are being built to connect Blue and Maize to a 300 kV FEI Tecnai TEM (Fig 2d). This project is expected to be completed during the 2017 calendar year. This setup will allow in-situ observation of radiation damage and gas injection in real time. 3.
Setting up dual and triple beam experiments
3.1 Challenges The laboratory consists of two rooms (Fig 1b): the accelerator room (AR) and the target rooms (south - STR and north - NTR). The first major challenge of setting up the new capabilities, was a four foot thick wall between the two rooms that needed to accommodate up to nine separate holes. The location of three of them (BL4, BL5 and BL7), leading to the MBC, was critical to delivering triple ion beams to one target. In addition to the wall, there was a 1.5 feet drop between the AR and the TR. Due to the wall, there was no direct line of sight between the high energy (HE) magnets of the accelerators and the future location of the MBC. A good deal of engineering and surveying was contracted to produce the holes in the correct location. The next significant challenge was the fact that the centerline for Blue had a 12 inch difference in height compared to the centerline of Maize and Wolverine. That was corrected with a set of magnetic deflectors installed in the AR, which brought BL5 to the same level as BL4 and BL7. One last, but not insignificant challenge, was the lack of an overhead crane in the target rooms. Portable cranes and lifts were employed to set up quadrupole magnets for BL2, BL4 and BL7 and other beamline components. 3.2 The alignment of BL4, BL5 and BL7 To accomplish the physical alignment of the three beamlines through which simultaneous dual and triple ion beams could be delivered, a specially designed end-station stage was employed (Fig 4a). On top of this stage was mounted a piece of scintillating ceramic material with a grid drawn every 2 mm. Each ion beam through each beamline involved, was first focused (Fig 4b-top) then centered on the ceramic piece (Fig 4c). Next, a beam rastering device was used to enlarge the beam, to a size close to the maximum size that could be accommodated on the stage (Fig 4d). Finally, the beam and the alignment lasers were overlapped (Fig 4e). The procedure was repeated for each beamline and as the last step, all beams and lasers from BL4, BL5 and BL7 were overlapped to confirm the common center point to within 0.5 mm.
Figure 4 : (a) Alignment stage (b) BPM profile, (c) Focused beam on stage (d) Rastered beam on stage and (e) Laser and beam overlapped
3.3 Dual and triple ion beam experiments The MBC setup (Fig 5a) enables scientists to run experiments either in single beam mode, dual beam mode or triple beam mode (Fig 5b). In either case, the same stage (Fig 4a) is used. The samples to be irradiated are
O. Toader et al. / Physics Procedia 90 (2017) 385 – 390
mounted on the stage (Fig 5c-top) and then laser alignment is conducted to locate the actual position of the beam(s). In the case of dual beam experiments, the heavy ion beam is defocused (Fig 4b-bottom – BPM view) and profiled on the target area (Fig 5d, x and y directions) until a flat beam density (+/-10%) over the irradiated area is achieved. The light ion beams (He and H - Fig 5b) could be passed through a rotatable degrader foil to ensure uniform implantation within the irradiation area and at the depth up to where the heavy ions (Fe) reach. The movement of the degrader is programed for the purpose of uniform implantations. If the path of the ions through the foil increases (higher angles from the normal), the energy of the emerging ions decreases, implanting the ions closer to the surface of the target. The foil thickness is chosen such that for the normal incidence to the maximum desired penetration depth is reached.
Figure 5 (a,b) Triple beamline setup, dual beam setup, (c) experimental stage and laser alignment and (d) defocussed beam profiling (x and y).
The helium beam (and H if needed) is co-injected along the damage curve of the Fe ions with a pre-determined dose of heavy ions/light ions established within the purpose of the experiment. The He/Fe ion current ratio is maintained to achieve the target amount of He deposited per displaced atom, as calculated from simulation software SRIM (www.srim.org). In the case of a triple ion beam experiment, the same procedures are followed, with the addition of an extra ion beam, H+ that is delivered from the Blue accelerator, with sufficient energy to have the same penetration depth as the other ion beams (Fe and He). If desired, this ion beam could also be passed through an energy degrader. The experiments are well controlled [6], as evidenced by the following: 1) the vacuum in the implantation chamber is in the ultra-high vacuum range (UHV or mid to low 10-8 torr); 2) the target temperature is controlled within ±5-7°C of the desired range, through simultaneous heating and cooling of the stage from the backside; 3) the sample temperature is monitored in real time with a high spatial resolution thermal imager (FLIR A600 series); 4) the dose is monitored with high precision charge integrators; and 5) the beam delivery mode can be either raster-scanned or defocussed, depending on the experiment. 4. Remote control of experiments and future plans As part of the recent MIBL upgrade, the laboratory was given full remote control capabilities. Analog signals are digitized using embedded hardware, and all laboratory equipment can be utilized and monitored from the control room (CR - Fig. 6a) over the internet protocol (IP). Each accelerator in MIBL has a single control computer (three in total) for its entire set of components from ion source to target, and a single large monitor gives an overview of the laboratory's systems. This remote control method does not limit control and monitoring to a single location. When properly secured, the systems can be operated from anywhere in the world. The digitization of the signals also allows selected signals to be logged in a database for future recall or displayed in real time. Considering future plans, it is worth noted that during the calendar year 2017, it is expected that BL6 will be built as a branch of BL5 and would connect with the 300 keV FEI TEM (Fig 6b). At the same time, a short version of BL8 will also be built, and would connect an Aphatross ion source (Fig 3b) to a second port of the TEM. Delivering ion beams through these new beamlines, would enable the scientists to simultaneously produce and observe radiation damage, either from one ion beam or two ion beams. Also for the first time at MIBL, a holder for TEM discs was designed (Fig 6c) that would be mounted on the regular experimental stage (Fig 4a) to allow for proton or heavy ion
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irradiation of TEM discs. The thermal imager (FLIR) that is mounted on all experimental chambers in tandem with the spot-welded thermocouples, would allow for real time monitoring of the temperature of the TEM discs during irradiations (Fig 6d).
Figure 6. (a) Control room and (b) 3-D view of the BL6 and BL8
4. Summary MIBL can now conduct single ion irradiation experiments, simultaneous dual and triple ion beam experiments in either raster-scanned or defocused beam mode. The experimental conditions are controlled to within very tight specifications. The lab can conduct irradiations with very large beam fluences, in UHV chambers and beamlines and with fully remote control of irradiation conditions. The setting up of dual and triple beam experiments enabled MIBL to expand the range of capabilities offered to its users. Currently, there are ongoing collaborations with groups from three continents and multiple countries, as well as numerous universities, national laboratories and companies. In addition to these capabilities, in the near future (end of 2017), the laboratory will be able to offer in-situ ion irradiation experiments with the addition of a 300 kV Tecnai TEM connected to two new beamlines. Acknowledgements The expansion and the new capabilities of MIBL were made possible with support from DOE – Nuclear Energy Program, Electric Power Research Institute (EPRI), TerraPower Inc., Oak Ridge National Laboratory, the University of Michigan’s College of Engineering (CoE) and the University of Michigan’s Nuclear Engineering and Radiological Sciences (NERS) department. References [1] C.–L. Chen, A. Richter, R. Kogler, 2014, The effect of dual Fe+/He+ ion beam irradiation on microstructural changes in FeCrAl ODS alloys. Journal of Alloys and Compounds, 586 S173-S179 [2] M. Roldan, P. Fernandez, R. Vila, A. Gomez-Herrero, F.J. Sanchez, 2016, The effect of triple ion beam irradiation on cavity formation on pure EFDA iron. , Journal of Nuclear Materials, 479, 100-111. [3] D. Brimbal, B. Decamps, J. Henry, E. Meslin , A. Barbu, (2014) Single- and dual-beam in situ irradiations of high purity iron in a transmission electron microscope: Effects of heavy ions irradiation and helium injection. Acta Materialia, 64, 391-401 [4] Y. Kupriiyanova, V. Bryk, O. Borodin, A. Kalchenko, V. Voyevodin, G. Tolstolutskaya, F. Garner, (2016) Use of double and triple ion irradiation to study the influence of high levels of helium and hydrogen on void swelling of 8-12% Cr ferritic martensitic steels, Journal of Nuclear Materials, 468, 264-273 [5] S. Pellegrino, P. Trocellier, S. Miro, Y. Serryus, E. Bordas, H. Martin, N. Chaabane, S. Vaubaillon, J. Gallien, L. Beck, (2012) The JANNUS Saclay facility: A new platform for materials irradiation, implantation and ion beam analysis, Nuclear Instruments and Methods in Physics Research B, 273, 213-217 [6] F. Naab, E. West, O. Toader, G. Was, 2011, Conducting well-controlled ion irradiations to understand neutron irradiation effects in materials, AIP Conference proceedings, CAARI, 2010. [7] S. Raiman, A. Flick, O. Toader, P. Wang, N. Samad, Z. Jiao and G. Was (2014) A facility for studying irradiation accelerated corrosion in high temperature water, Journal of Nuclear Materials, Vol. 451, Issues 1-3, August 2014
ScienceDirect Physics Procedia 90 (2017) 385 – 390
Conference on the Application of Accelerators in Research and Industry, CAARI 2016, 30 October – 4 November 2016, Ft. Worth, TX, USA
Technical Aspects of Delivering Simultaneous Dual and Triple Ion Beams to a Target at the Michigan Ion Beam Laboratory O. Toadera*, F. Naaba, E. Ubersedera, T. Kubleya, S. Tallera and G. Wasa a
Nuclear Engineering and Radiological Sciences, University of Michigan, 2600 Draper Dr. Ann Arbor MI 48109, USA
Abstract
The Michigan Ion Beam Laboratory (MIBL) at the University of Michigan in Ann Arbor, Michigan, USA, plays a significant role in supporting the mission of the U.S. DOE Office of Nuclear Energy. MIBL is a charter laboratory of the NSUF (National Scientific User Facility – US DoE) and hosts users worldwide. The laboratory has evolved from a single accelerator laboratory to a highly versatile facility with three accelerators (3 MV Tandem, a 400 kV Ion Implanter and a 1.7 MV Tandem), seven beam lines and five target chambers that together, provide unique capabilities to capture the extreme environment experienced by materials in reactor systems. This capability now includes simultaneous multiple (dual, triple) ion irradiations, an irradiation accelerated corrosion cell, and soon, in-situ dual beam irradiation in a transmission electron microscope (TEM) for the study of radiation damage coupled with injection of transmutation elements. The two beam lines that will connect to the 300 kV FEI Tecnai G2 F30 microscope are expected to be operational by the end of 2017. Multiple simultaneous ion beam experiments involving light and heavy ions are already in progress. This paper will outline the current equipment and will focus on the new capability of running dual and triple ion beam experiments. 2017The The Authors. Published by Elsevier ©©2017 Authors. Published by Elsevier B.V.B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Scientific Committee of the Conference on the Application of Accelerators in Research Peer-review under responsibility of the Scientific Committee of the Conference on the Application of Accelerators in Research and Industry and Industry. Keywords: ion beams irradiations, dual beams, triple beam,ion source
* Corresponding author. Tel.: 1-734-936-0166; fax: 1-734-936-8820. E-mail address: [email protected]
1875-3892 © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Scientific Committee of the Conference on the Application of Accelerators in Research and Industry doi:10.1016/j.phpro.2017.09.039
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O. Toader et al. / Physics Procedia 90 (2017) 385 – 390
1.
Introduction
Ion irradiation is being considered as a surrogate for simulating nuclear reactor irradiations in the development of new materials for application in nuclear reactor cores. Light and heavy ions can play complementary roles in such studies when employed either sequentially or simultaneously. There are a number of laboratories in the world that are currently using a multiple ion beam setup to study these effects, such as TIARA – Japan and JANNUSFrance, to name only a couple and they generate a wide range of research in the field [1-5]. Michigan Ion Beam Laboratory (MIBL – Fig 1a) was established in 1986 and went through a major upgrade in 2014, when a third accelerator was added. After the accelerator installation, four new additional beamlines and three new ion sources were added, significantly boosting the experimental range capabilities. With the installation of the 3 MV Pelletron, and the setting up of a chamber connected to all three particle accelerators, the scientists are now equipped with tools that allow them to conduct simultaneous dual and triple ion beam irradiation experiments. The main mission of MIBL is to help better understand ion irradiation versus neutron irradiation in materials [6]. In this way, scientists hope to reduce the cost of producing irradiated materials for the scope of identifying novel materials capable to withstand large radiation doses and at the same time to understand failure under extreme radiation conditions. The same tools can be employed to better understand the mechanism by which irradiation accelerates corrosion and explore microstructure evolution at very high doses and dose rates.
Figure 1: MIBL: (a) accelerator room overhead view and (b) 3-D drawing including the target rooms.
2.
Major Equipment
2.1 Particle accelerators The lab is equipped with three particle accelerators. The largest is a 3 MV Pelletron (Wolverine – Fig 2a), built by National Electrostatics Corporation (NEC), and is capable of delivering either a focused ion beam with 2.5 mm full-width-half-max (FWHM) near the target (or rastered for up to 2 cm / 2 cm), or a defocused ion beam with great uniformity over the irradiated area. The Pelletron is also capable of accelerating a variety of ion species with multiple charge states, from 1 MeV to 6 MeV for protons and 9 MeV or higher for heavier ions. The 1.7 MV accelerator (Maize – Fig 2b) is a solid state, gas insulated device manufactured by High Voltage Engineering Europa (HVEE) capable of operation between 0.4 and 1.7 MV. Maize can deliver protons up to 3.2 MeV and heavier ions at 5 MeV and higher, depending on the charge state. The 400 kV ion implanter (Blue – Fig 2c) operates with a positive ion source and can, in principle, deliver any ion with a Z from 1 to 92. It was made by NEC and is equipped with a Danfysik ion source and a HVEE implant chamber. The operational energy range is 10 – 400 kV with
O. Toader et al. / Physics Procedia 90 (2017) 385 – 390
currents exceeding 100s of μA for some elements, and a terminal chamber capable of implants from LN2 temperature to 8000C. 2.2 Ion Sources Wolverine can operate with three different ion sources: a Torvis ion source (NEC – Fig 3a) that can produce intense beams of protons and deuterons, an Alphatross ion source (NEC- Fig 3b) with Rb charge exchange that delivers negative He beam, and a PS120 (Peabody Scientific– Fig 3c) sputter type ion source that can deliver beams from solid targets by Cs sputtering (e.g. Fe, Ni, Au, W, Si, etc). Maize is equipped with two ion sources: an electron cyclotron resonance (ECR) type ion source, model M100 (Pantechnik–Fig 3d) delivering negative He ion beam through a charge exchange canal, and a MultiCathode SNICS ion source (NEC–Fig 3e) that delivers a wide range of beams from solid targets by Cs sputtering. Blue is equipped with a versatile positive ion source Model 921, produced by Danfysik (Fig 3f) that can operate in three modes based on the state of the target material: gas, liquid and solid target.
Figure 2: (a) Wolverine (Pelletron accelerator), (b) Maize (Tandetron accelerator), (c) Blue (ion implanter) and (d) FEI Tecnai 300 kV TEM.
Figure 3: MIBL ion sources: (a) Torvis, (b) Alphatross, (c) PS120, (d) M100, (e) MC-SNICS and (f) Model 921 and MBC (g)
2.3 Beamlines There are seven active beamlines in the laboratory (Fig 1b- top right) and two in development that connect to five target chambers in the target rooms. The North Target Room (NTR) hosts: beamline 1 (BL1) that delivers ions used in surface analysis, and beamline 2 (BL2) that is used for ion irradiation experiments. Most single ion radiation damage experiments take place in BL2 chamber. The South Target Room (STR) (bottom right Fig 1b) hosts five beamlines. Beamline 3 (BL3) delivers ions to a water cell used in Irradiation Assisted Corrosion (IAC) experiments. Here, a thin sample of thickness 30-100 μm is bombarded from one side with protons up to 5.4 MeV energy. The other side is exposed to high temperature, high pressure water up to 320°C and 2000 psi, acting as both the window between the high vacuum beamline and the water cell, and the sample. This novel capability is used to determine the behavior of materials when simultaneously subjected to both corrosion and irradiation. Beamline 4 (BL4) is connected to the multi-beam chamber (MBC – Fig 3g-right) and can be used as a separate single ion irradiation beamline or as part of the dual and triple ion beam experiments. The first part of beamline 5 (BL5) terminates in an implantation chamber. Beyond this chamber, BL5 continues to the MBC as the third line of the triple ion beam arrangement (MBC – Fig 3g, middle). Due to the fact that the ion source of Blue can deliver
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multiple ionization states of heavy ions, the energy of gas ion beams such as Xe and Kr could be increased to more than 1.5 MeV on target. Beamline 7 (BL7) delivers ions from Maize to the MBC (MBC – Fig 3g, left), either independently or as part of the dual or triple beam arrangement. Beamline 9 (BL9) is used in surface analysis experiments. Beamline 6 (BL6) and beamline 8 (BL8) are being built to connect Blue and Maize to a 300 kV FEI Tecnai TEM (Fig 2d). This project is expected to be completed during the 2017 calendar year. This setup will allow in-situ observation of radiation damage and gas injection in real time. 3.
Setting up dual and triple beam experiments
3.1 Challenges The laboratory consists of two rooms (Fig 1b): the accelerator room (AR) and the target rooms (south - STR and north - NTR). The first major challenge of setting up the new capabilities, was a four foot thick wall between the two rooms that needed to accommodate up to nine separate holes. The location of three of them (BL4, BL5 and BL7), leading to the MBC, was critical to delivering triple ion beams to one target. In addition to the wall, there was a 1.5 feet drop between the AR and the TR. Due to the wall, there was no direct line of sight between the high energy (HE) magnets of the accelerators and the future location of the MBC. A good deal of engineering and surveying was contracted to produce the holes in the correct location. The next significant challenge was the fact that the centerline for Blue had a 12 inch difference in height compared to the centerline of Maize and Wolverine. That was corrected with a set of magnetic deflectors installed in the AR, which brought BL5 to the same level as BL4 and BL7. One last, but not insignificant challenge, was the lack of an overhead crane in the target rooms. Portable cranes and lifts were employed to set up quadrupole magnets for BL2, BL4 and BL7 and other beamline components. 3.2 The alignment of BL4, BL5 and BL7 To accomplish the physical alignment of the three beamlines through which simultaneous dual and triple ion beams could be delivered, a specially designed end-station stage was employed (Fig 4a). On top of this stage was mounted a piece of scintillating ceramic material with a grid drawn every 2 mm. Each ion beam through each beamline involved, was first focused (Fig 4b-top) then centered on the ceramic piece (Fig 4c). Next, a beam rastering device was used to enlarge the beam, to a size close to the maximum size that could be accommodated on the stage (Fig 4d). Finally, the beam and the alignment lasers were overlapped (Fig 4e). The procedure was repeated for each beamline and as the last step, all beams and lasers from BL4, BL5 and BL7 were overlapped to confirm the common center point to within 0.5 mm.
Figure 4 : (a) Alignment stage (b) BPM profile, (c) Focused beam on stage (d) Rastered beam on stage and (e) Laser and beam overlapped
3.3 Dual and triple ion beam experiments The MBC setup (Fig 5a) enables scientists to run experiments either in single beam mode, dual beam mode or triple beam mode (Fig 5b). In either case, the same stage (Fig 4a) is used. The samples to be irradiated are
O. Toader et al. / Physics Procedia 90 (2017) 385 – 390
mounted on the stage (Fig 5c-top) and then laser alignment is conducted to locate the actual position of the beam(s). In the case of dual beam experiments, the heavy ion beam is defocused (Fig 4b-bottom – BPM view) and profiled on the target area (Fig 5d, x and y directions) until a flat beam density (+/-10%) over the irradiated area is achieved. The light ion beams (He and H - Fig 5b) could be passed through a rotatable degrader foil to ensure uniform implantation within the irradiation area and at the depth up to where the heavy ions (Fe) reach. The movement of the degrader is programed for the purpose of uniform implantations. If the path of the ions through the foil increases (higher angles from the normal), the energy of the emerging ions decreases, implanting the ions closer to the surface of the target. The foil thickness is chosen such that for the normal incidence to the maximum desired penetration depth is reached.
Figure 5 (a,b) Triple beamline setup, dual beam setup, (c) experimental stage and laser alignment and (d) defocussed beam profiling (x and y).
The helium beam (and H if needed) is co-injected along the damage curve of the Fe ions with a pre-determined dose of heavy ions/light ions established within the purpose of the experiment. The He/Fe ion current ratio is maintained to achieve the target amount of He deposited per displaced atom, as calculated from simulation software SRIM (www.srim.org). In the case of a triple ion beam experiment, the same procedures are followed, with the addition of an extra ion beam, H+ that is delivered from the Blue accelerator, with sufficient energy to have the same penetration depth as the other ion beams (Fe and He). If desired, this ion beam could also be passed through an energy degrader. The experiments are well controlled [6], as evidenced by the following: 1) the vacuum in the implantation chamber is in the ultra-high vacuum range (UHV or mid to low 10-8 torr); 2) the target temperature is controlled within ±5-7°C of the desired range, through simultaneous heating and cooling of the stage from the backside; 3) the sample temperature is monitored in real time with a high spatial resolution thermal imager (FLIR A600 series); 4) the dose is monitored with high precision charge integrators; and 5) the beam delivery mode can be either raster-scanned or defocussed, depending on the experiment. 4. Remote control of experiments and future plans As part of the recent MIBL upgrade, the laboratory was given full remote control capabilities. Analog signals are digitized using embedded hardware, and all laboratory equipment can be utilized and monitored from the control room (CR - Fig. 6a) over the internet protocol (IP). Each accelerator in MIBL has a single control computer (three in total) for its entire set of components from ion source to target, and a single large monitor gives an overview of the laboratory's systems. This remote control method does not limit control and monitoring to a single location. When properly secured, the systems can be operated from anywhere in the world. The digitization of the signals also allows selected signals to be logged in a database for future recall or displayed in real time. Considering future plans, it is worth noted that during the calendar year 2017, it is expected that BL6 will be built as a branch of BL5 and would connect with the 300 keV FEI TEM (Fig 6b). At the same time, a short version of BL8 will also be built, and would connect an Aphatross ion source (Fig 3b) to a second port of the TEM. Delivering ion beams through these new beamlines, would enable the scientists to simultaneously produce and observe radiation damage, either from one ion beam or two ion beams. Also for the first time at MIBL, a holder for TEM discs was designed (Fig 6c) that would be mounted on the regular experimental stage (Fig 4a) to allow for proton or heavy ion
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irradiation of TEM discs. The thermal imager (FLIR) that is mounted on all experimental chambers in tandem with the spot-welded thermocouples, would allow for real time monitoring of the temperature of the TEM discs during irradiations (Fig 6d).
Figure 6. (a) Control room and (b) 3-D view of the BL6 and BL8
4. Summary MIBL can now conduct single ion irradiation experiments, simultaneous dual and triple ion beam experiments in either raster-scanned or defocused beam mode. The experimental conditions are controlled to within very tight specifications. The lab can conduct irradiations with very large beam fluences, in UHV chambers and beamlines and with fully remote control of irradiation conditions. The setting up of dual and triple beam experiments enabled MIBL to expand the range of capabilities offered to its users. Currently, there are ongoing collaborations with groups from three continents and multiple countries, as well as numerous universities, national laboratories and companies. In addition to these capabilities, in the near future (end of 2017), the laboratory will be able to offer in-situ ion irradiation experiments with the addition of a 300 kV Tecnai TEM connected to two new beamlines. Acknowledgements The expansion and the new capabilities of MIBL were made possible with support from DOE – Nuclear Energy Program, Electric Power Research Institute (EPRI), TerraPower Inc., Oak Ridge National Laboratory, the University of Michigan’s College of Engineering (CoE) and the University of Michigan’s Nuclear Engineering and Radiological Sciences (NERS) department. References [1] C.–L. Chen, A. Richter, R. Kogler, 2014, The effect of dual Fe+/He+ ion beam irradiation on microstructural changes in FeCrAl ODS alloys. Journal of Alloys and Compounds, 586 S173-S179 [2] M. Roldan, P. Fernandez, R. Vila, A. Gomez-Herrero, F.J. Sanchez, 2016, The effect of triple ion beam irradiation on cavity formation on pure EFDA iron. , Journal of Nuclear Materials, 479, 100-111. [3] D. Brimbal, B. Decamps, J. Henry, E. Meslin , A. Barbu, (2014) Single- and dual-beam in situ irradiations of high purity iron in a transmission electron microscope: Effects of heavy ions irradiation and helium injection. Acta Materialia, 64, 391-401 [4] Y. Kupriiyanova, V. Bryk, O. Borodin, A. Kalchenko, V. Voyevodin, G. Tolstolutskaya, F. Garner, (2016) Use of double and triple ion irradiation to study the influence of high levels of helium and hydrogen on void swelling of 8-12% Cr ferritic martensitic steels, Journal of Nuclear Materials, 468, 264-273 [5] S. Pellegrino, P. Trocellier, S. Miro, Y. Serryus, E. Bordas, H. Martin, N. Chaabane, S. Vaubaillon, J. Gallien, L. Beck, (2012) The JANNUS Saclay facility: A new platform for materials irradiation, implantation and ion beam analysis, Nuclear Instruments and Methods in Physics Research B, 273, 213-217 [6] F. Naab, E. West, O. Toader, G. Was, 2011, Conducting well-controlled ion irradiations to understand neutron irradiation effects in materials, AIP Conference proceedings, CAARI, 2010. [7] S. Raiman, A. Flick, O. Toader, P. Wang, N. Samad, Z. Jiao and G. Was (2014) A facility for studying irradiation accelerated corrosion in high temperature water, Journal of Nuclear Materials, Vol. 451, Issues 1-3, August 2014