Value chain · CLM-1118
In plain terms
In 1977 five radiation-damaged cells were healed with a laser or an electron gun, getting back between a fifth and a half of what they had lost; the electron gun did better and the laser missed parts of the cells. It was a first try, and everyone said so.
The claim as recorded
The first SPS annealing test, Simulation Physics for Boeing (15 March 1977), irradiated silicon cells with protons and annealed them with a pulsed Nd:YAG laser and a DC electron beam: of the maximum power lost to irradiation, the laser restored 21, 20 and 40 per cent on three cells and the electron beam 44 and 54 per cent on two, with the unirradiated controls unchanged (0) or slightly worse (-7 per cent, attributed to the anti-reflection coating); the laser's "nonsymmetrical" spot did not cover the whole cell (raw word, render reading of the clause), so more recovery was expected from full coverage; Boeing summarised the result as "About 50 percent of the lost capacity was restored" and the subcontractor called it "extremely promising".
Evidence behind this: T3-NASA contractor report, not peer reviewed: a subcontractor's feasibility test on seven cells with the measured I-V figures tabulated; a short-scope test the authors call preliminary.
Scope and limits
FIVE IRRADIATED CELLS, ONE TEST EACH, AND THE PROTON FLUENCE CARRIES A SUSPECTED TRANSCRIPTION ERROR: read at zoom 6 to 8, the test description (PDF 161) prints "5 x 10^12 1 MeV protons/cm2" and the I-V figure captions (PDF 168) "After 5 x 10^12 protons/cm2", while Table I's header and notes (PDF 167) print "After 2x10^15 1 MeV Protons" and "2 x 10^15 1 MeV Protons cm-2"; one irradiation is described, the two figures differ by 400, and the table's figure is the suspected slip; Boeing's summary (PDF 49) gives the damage as "the equivalent of 10^16 one-MeV electrons", a different unit that does not decide it. Bench annealing of bare cells at 25 C; no glass cover, no blanket, no repeated cycles, no in-orbit method. The "about 50 percent" is the electron-beam pair; the laser cells recovered 20 to 40.
What it assumes
Pmax in mW per cell as tabulated; the "% Recovered" definition as (after anneal - after irradiation) / (initial - after irradiation), which the recomputation confirms.
Where it comes from
PDF 167 / printed 162, Table I render read, "Summary of Electron and Laser Beam Annealing of Proton Irradiated Solar Cells", columns Initial, "After 2x10^15 1 MeV Protons", After Beam Anneal, "% Recovered" (Voc, Isc, Pmax): pulsed Nd:YAG laser, 8E Violet 75.8 / 30.5 / 39.8 mW, 36 / 18 / 21; 9C Hybrid B 66.1 / 24.7 / 32.8, 41 / 26 / 20; 12E Violet 73.0 / 34.4 / 49.8, 53 / 45 / 40; 55 Violet control 68.2 / no irradiation / 68.2, 0 / 0 / 0; DC electron beam, 8C Hybrid B 64.6 / 33.2 / 46.9, 49 / 47 / 44; 9G conventional 52.2 (the second digit damaged on the scan) / 24.8 / 39.4, 98 / 52 / 54; 67 Violet control 66.7 / no irradiation / 62.3, 0 / -6.0 / -7.0; notes "All data AMO", "Initial & After 2 x 10^15 1 MeV Protons cm-2 - Boeing 30 C" and "After Anneal - SPI 25 C". PDF 161 / printed 156, render read at zoom 6: "The cells had been irradiated to 5 x 10^12 1 MeV protons/cm2. Cells did not have protective coverglasses." PDF 166 / printed 161, normalised: "Significant recovery of cell performance was accomplished using both the scanned electron beam and pulsed laser". PDF 168 / printed 163, normalised: "The directed energy anneal feasibility test results are considered to be extremely promising"; the "nonsymmetrical" spot (raw) and its incomplete coverage, and the control cell's AR-coating explanation, as render readings. PDF 49 / printed 45, normalised: "About 50 percent of the lost capacity was restored"; "had been severely damaged by the equivalent of 10" ^16 one-MeV electrons. Recomputed from Table I: (39.8 - 30.5) / (75.8 - 30.5) = 20.5 per cent; (32.8 - 24.7) / (66.1 - 24.7) = 19.6; (49.8 - 34.4) / (73.0 - 34.4) = 39.9; (46.9 - 33.2) / (64.6 - 33.2) = 43.6; (39.4 - 24.8) / (52.2 - 24.8) = 53.3 (55.3 if the damaged digit is a 1); each within a point of the printed 21, 20, 40, 44, 54.
Basis: per cent of lost maximum power recovered; mV and mA per cell at AM0
Cite this
energyaperture.com/c/clm-1118
CLM-1118, Energy Aperture, as of 1977-03.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-475
- CLM-1114The 1977 silicon design assumed an 18 per cent cell that did not yet exist, doubled the sunlight on it with cheap plastic mirrors, and got...CLM-1115Mirrors that doubled the light only added 40 per cent to the output, because the cells ran hot and the mirrors were not flat; after thirty...CLM-1116Thirty years of radiation behind a hair-thin glass cover was expected to take a third of the cell's power; a cover three times thicker...CLM-1117The 1977 study found the cheapest way to keep a silicon satellite at full power was to heal the radiation damage in place rather than build...CLM-1120In 1977 the gallium arsenide option rested on a 20 per cent cell nobody had made, an assumption that it would still be near 20 per cent...CLM-1121Half a kilogram per square metre for the working blanket, about half of it the silicon itself; per kilowatt delivered on the ground the...CLM-1468The basic idea, a solar power satellite climbing to its final orbit on electric engines run by solar panels it carries, with no separate...