1 Cosmic Radiation Effects on High-Temperature Superconductors for Deep Space Habitat Shielding¹Lorne M. Forsythe, ¹John Reisel, Ph.D., ²Prasenjit Guptasarma, Ph.D. ¹Mechanical Engineering, University of Wisconsin-Milwaukee, WI, USA ²Physics, University of Wisconsin-Milwaukee, WI, USA
2 Cosmic Radiation Radiation exposure remains one of the most challenging problems facing long-term, deep-space, human exploration missions including travel to Mars [1]. The hazards associated with long-term or chronic exposure to Galactic Cosmic Radiation (GCR) and acute exposure from Solar Particle Events (SPEs) [1] constitutes one of the most important barriers impeding plans for interplanetary travel by crewed spacecraft [2]. Figure 1: The interplanetary space environment [2].
3 Radiobiology Effects Figure 1: The interplanetary space environment [2]. Figure 2: Relative abundance of GCR nuclei from hydrogen (Z = 1) to iron (Z = 26) and individual ion contribution to total annual dose equivalent with neutrons at Z = 0 [1,2] Figure 3: Select health effects due to space radiation exposures [2].
4 Disadvantages of Passive ShieldingPassive radiation shielding consists of placing a physical material between a person and a radiation source. An in-depth analysis was performed by NASA [4] on four typical passive shielding materials to assess their impact on the length of time an astronaut can stay in deep space and not exceed a design basis radiation exposure of 150 mSv. The Mars Design Reference Mission Architecture 5.0 [5] has that a proposed Mars mission would consist of a 200 day transit from Earth to Mars, a 200 day transit from Mars to Earth, and a 500 day stay on the surface [4]. To enable a Mars round-trip transit time of 400 days while remaining below the 150 mSv exposure limit would require 24 heavy lift launches of pure polyethylene material [4]. NASA has concluded that vehicle mass cannot be the sole shielding mechanism for long duration, deep-space missions [4]. Figure 4: Number of days to the 150 mSv exposure per mission for various shielding materials [4].
5 Advantages of Active Radiation Shielding (ARS)Figure 5: NASA’s proposed ARS design. Six expandable coils and one compensator coil are wrapped around the crew module for radiation Protection [6]. Figure 6: Magnetic flux density distribution for a complete shielding coil assembly [3,6].
6 Advantages of Active Radiation Shielding (ARS)Surrounding a spaceship with large volumes of magnetic fields can accordingly protect the habitat of a spaceship and enable extended missions of human beings for the exploration of the solar system and in the far future of intergalactic space [1,6]. One promising solution is the use of active radiation shielding (ARS) designs that harness the Lorentz force to divert harmful charged particle radiation away from the crew, as shown in Figure 7. The most important advantage to using ARS designs is that they have the potential to reduce radiation exposure to acceptable levels using a significantly lower mass penalty [1,7]. Figure 7: Lorentz force allows for charged particle deflection away from the habitat [1].
7 High Temperature Superconductors (HTS)The ability of a magnetic field to deflect incident cosmic radiation away from the crew is a function of both the magnetic field’s strength and size [7]. Superconducting materials exhibit no, or negligible, electrical resistivity below a critical temperature, Tc, thus enabling the construction of powerful magnetic fields which are not constrained by the high power requirements and resistance losses associated with standard electromagnets [7]. High temperature superconducting (HTS) materials like YBa2Cu3O7-δ (YBCO) ribbon, enable the construction of powerful magnetic fields that are relatively lightweight and can feasibly fit into conventional launch systems [6].
8 HTS YBa2Cu3O7-δ (YBCO) Figure 8: Example YBCO tape. The superconductor itself is layered or imbedded within stabilizer and substrate materials [7]. Figure 9: Advanced 2nd Generation (2G) conductor from American Superconductor [6].
9 Prior YBCO Radiation Damage AnalysesFew materials with a functional crystal structure have ever been studied in the space radiation environment; Previous YBCO irradiation studies have been performed at relatively low energies, focused on accelerator applications [8], ways to increase critical current densities [9], or understand structure damage mechanisms [10]; Ultimately, previous studies are largely irrelevant with respect to studying the effects of damaging cosmic radiation or applications to active shielding designs as they have not been performed at the correct energies (~10 MeV·n-1 to ~1012 MeV·n-1) or with relevant GCR particles. Our study aims to rectify this problem.
10 Project Overview & TestingOur experimental study will look at complex materials like YBCO where the crystal structure is integral to its function and study the effects of exposure to various heavy-ion beams with energies more characteristic of actual space radiation (~10 MeV·n-1 to ~1012 MeV·n-1) using terrestrial particle accelerators.
11 Project Overview & TestingKey materials engineering & technology questions we plan to shed light on are: What materials & thicknesses are required to make an active shielding design possible? What material technology should be applied to HTS tape to mitigate radiation damage and make it work for full and/or repetitive missions, thus extending its life? To do this, we need to better understand how structure changes at necessarily high energies and what the root causes are? What energies cause the biggest problems? We also intend to perform functional testing of a scalable YBCO solenoid while exposed to an operating beam-line (i.e. simulated cosmic radiation exposure) and examine shielding efficiency for alternative magnet geometries
12 Project Overview & TestingMaterial structure will be analyzed before and after irradiation using a Quantum Design Physical Property Measurement System (PPMS®) at Dr. Guptasarma’s laboratory. This information will then be used to inform mission designers about superconductor suitability in the space radiation environment and how to design radiation protection for the resultant magnet systems, thus allowing for extended human presence in deep-space. Figure 10: Quantum Design PPMS® [11].
13 Project Status & Future GoalsWork on this project has only recently begun. To date we are working on synthesizing HTS YBCO superconductor material in our lab that can be used for preliminary structural and superconducting characterization & analysis. In the near future, YBCO samples grown in our lab will be subjected to low-yield gamma radiation to study the before & after effects of radiation damage on the material. This work will guide us in future experiments, characterization, and analysis involving more expensive 2G YBCO tape and sample irradiation involving particle accelerators. Preliminary design concepts for experiments that will test functional YBCO solenoids while being subjected to accelerator beams is also being examined. Figure 11: ATLAS Heavy-ion LINAC at Argonne National Laboratory, Lemont, Illinois.
14 References Washburn, S.A., Blattnig, S.R., Singleterry, R.C., Westover, S.C., Analytical-HZETRN model for rapid assessment of active magnetic radiation shielding. Adv. Space Res. 53, 8-17. Chancellor, J.C., Scott, G.B.I., Sutton, J.P., Space Radiation: The number one risk to astronaut health beyond low Earth orbit. Life 4, Battiston, R., Burger, W.J., Calvelli, V., Musenich, R., Choutko, V., Datskov, V.I., Della Torre, A., Venditti, F., Gargiulo, C., Laurenti, G., Lucidi, S., Harrison, S., Meinke, R., Active Radiation Shield for Space Exploration Missions (ARSSEM) report. European Space Agency (ESA), Singleterry, R.C., Radiation engineering analysis of shielding materials to assess their ability to protect astronauts in deep space from energetic particle radiation. Acta Astro. 91, National Aeronautics and Space Administration (NASA), Human Exploration of Mars, Design Reference Architecture 5.0. NASA-SP National Aeronautics and Space Administration (NASA), Magnet Architectures and Active Radiation Shielding Study (MAARS). NASA Technical Report TP Washburn, S.A., Blattnig, S.R., Singleterry, R.C., Westover, S.C., Active magnetic radiation shielding system analysis and key technologies. Life Sci. in Spa. Res. 4, Greene, G.A., Gupta, R.C., Sampson, W.B., Snead, Jr., C.L., The Effect of Proton Irradiaiton on the Critical Current of Commercially Produced YBCO Conductors. IEEE Tran. On App. Sup. 19 (3), Zhao, Y.J., Liu, J.R., Meng, R.L., Chu, W.K., Thermal neutron irradiation of 6Li doped Y1Ba2Cu3O7-δ and flux pinning enhancement. Physica C 198, Jackson, E.M., Weaver, B.D., G.P. Summers, Shapiro, P., Burke, E.A., Radiation-Induced Tc Reduction and Pair Breaking in High-Tc Superconductors. Phy. Rev. Lett. 74 (15), Source:
15 Acknowledgement We would like to thank Dr. Robert Singleterry (NASA, Langley Research Center, VA) and Scott Washburn (University of Colorado Boulder) for their expertise and guidance on this project.
16 QUESTIONS?