Publications
Publication Information
| Title | Polarized Fusion and Potential in situ Tests of Fuel Polarization Survival in a Tokamak Plasma |
| Authors | Andrew Sandorfi, L. Baylor, A. Deur, N. Eidietis, W. Heidbrink, G. Jackson, J. Liu, M. Lowry, G. Miller, D. Pace, S.P. Smith, S. Tafti, K. Wei, X. Wei |
| JLAB number | JLAB-PHY-22-3693 |
| LANL number | (None) |
| Other number | DOE/OR/23177-5582 |
| Document Type(s) | (Journal Article) |
| Associated with EIC: | No |
| Supported by Jefferson Lab LDRD Funding: | No |
| Funding Source: | Nuclear Physics (NP) |
| Other Funding: | DOE-FES General Atomics R&D funds U VA Initiative Fund |
|
Journal Compiled for Nuclear Fusion Volume 63 Page(s) 076009 Refereed | |
| Publication Abstract: | The use of spin-polarized fusion fuels would provide a significant boost towards the ignition of a burning plasma. The cross section for the primary fusion fuel in a tokamak reactor, D+T /rightarrow ?+n, would be increased by a factor of 1.5 if the fuels were spin polarized parallel to the local field, rather than randomly oriented. Furthermore, our simulations show that additional non-linear gains in power would accompany this increase in large-scale machines such as ITER, due to increased alpha heating. The potential realization of such benefits rests on the crucial question of the survival of spin polarizations for periods comparable to the particle confinement time. During an initial peak of interest in such options during the 1980s, calculations predicted that polarizations could in fact survive a plasma environment, although concerns persisted regarding the cumulative impacts of wall recycling. In that era, the technical challenges of preparing and handling polarized materials prevented direct tests in research tokamaks and left the large scale fueling of a power reactor beyond reach. Over the last several decades, this situation has dramatically changed. Detailed simulations of the ITER plasma have predicted negligible wall recycling in a high-power reactor, and recent advances in laser-driven sources have projected the capability of producing nearly 100% polarized D and T in the quantities that would be needed to fuel a fusion reactor. What remains is the crucial step of verifying the expected gains from polarized fuel through an in-situ demonstration of polarization survival in a plasma. We outline how such a measurement is now possible using the isospin-mirror reaction, D+3He /rightarrow ?+p. The use of polarized 3He avoids the complexities of handling tritium, while encompassing the same nuclear reaction spin-physics. Drawing upon advances in polarized material technologies, we evaluate two methods of delivering deuterium, using dynamically polarized Lithium-Deuteride (with deuteron vector polarization P_V^D of 70%) or frozen-spin Hydrogen-Deuteride (with P_V^D of 40%), together with a method of injecting optically-pumped 3He (with 65% polarization). Once prepared for cryogenic injection, pellets of these material all have quite long polarization decay times (~ 6 minutes for LiD at 2 K, ~ 2 months for HD at 2 K, and ~3 days for 3He at 77 K), all far greater than the duration of a plasma shot in a research tokamak such as DIII-D. Both species can be propelled from a single dedicated injection gun, with cooling stages at 2 K for polarized D, and ~80 K for polarized 3He. Straight, vertical injection is preferred to maximize efficiency and plasma penetration. Signals of ~15 MeV protons provide an essentially background free signature of D+3He fusion. In a selection of shots with similar plasma characteristics, the expected ratios of yields from shots with fuel spins parallel and antiparallel range from 1.3 (HD + 3He) to 1.6 (LiD + 3He). Detailed tracking simulations for a high ion-temperature hydrogen plasma in the DIII-D tokamak confirm that this large signal should persist over a wide range of poloidal angles. |
| Experiment Numbers: | other |
| Group: | Hall B |
| Document: | |
| DOI: | https://doi.org/10.1088/1741-4326/acc3ae |
| Accepted Manuscript: | Baylor_2023_Nucl._Fusion_63_076009.pdf |
| Supporting Documents: | |
| Supporting Datasets: | |