THE BEGINNING
DESIGNING COLLECTORS FOR CATCHING
ATOMS
The solar wind consists of atomic nuclei spewed out by the Sun at high energies. These high energy nuclei, upon striking a collector surface, become imbedded up to 100 nm below the surface. By far, the most numerous solar wind particles are hydrogen nuclei, followed by helium. Other elements are much scarcer and require very pure materials, so that solar atoms can be precisely measured.
| 13C diamond |
| silicon carbide |
| diamond-like carbon |
| aluminum |
| silicon, Czochralski grown |
| silicon, float zone |
| silicon on sapphire |
| germanium |
| gold on sapphire |
| sapphire |
| carbon+cobalt+gold on sapphire |
| bulk metallic glass |
| aluminum alloy |
| gold foil |
| molybdenum (outside on canister in spacecraft lid) |
The concept was simply to expose ultrapure materials to the solar wind at the Earth-Sun L1 point and bring them back to Earth for laboratory analysis.
Fifteen materials were chosen for bulk purity, surface cleanliness, and ability to retain the captured solar wind under space conditions.
The science canister, which housed the collectors mounted on arrays, was designed so that most of the collectors were exposed to solar wind when the canister was open, but a subset were deployed only at specific times to capture solar wind during coronal mass ejections or high speed wind or the low speed interstream wind. One decision made during collector design turned out to be crucial - the collectors were made of different thicknesses for each regime of the solar wind collected. Even tiny shards of collector materials dislodged from arrays during recovery impact can be assigned to a solar wind regime simply by measuring the thickness.
|
|
An array of hexagonal collectors to capture bulk Solar Wind |
| Solar Wind Regime | Collector Thickness, µm |
|---|---|
| Bulk | 700 |
| Transient Solar Wind Associated with Coronal Mass Ejections |
650 |
| High-Speed Solar Wind from Coronal Holes |
600 |
| Low-Speed Interstream Solar Wind | 550 |
Excellent reference: Jurewicz A. J. G. et al. (2002) The Genesis Solar-Wind Collector Materials, Spa. Sci. Rev., 105, 535-560 (2003)
