Value chain · CLM-1119
In plain terms
Two years on, a laser could put back about half the radiation damage in a paper-thin cell in a few seconds, and an oven could put back nearly all of it in twenty minutes; but nobody could yet put a glass cover on such a cell that survived the heat, so the thing the satellite would actually carry had not been annealed.
The claim as recorded
Boeing's 1979 annealing test on 50-micron silicon cells found that a CO2 laser at "POWER DENSITY - 42 W/cm2" for about a second per pulse, with exposure times of two to ten seconds at 500 C, gave "average 50% recovery from charged particle irradiation damage with 5-10 seconds exposure", against "Thermal bulk annealing in an oven for 20 minutes has shown 90-100% recovery", a difference that "suggests a time dependance for more complete annealing"; "All cells tested without breakage showed some recovery" and the laser energy needed was "less than earlier estimates by about a factor of 5"; but the test could not anneal a glassed cell because "a suitable method of glassing was not found": Schott's electron-beam evaporated 75 um covers were "full of bubbles" and the cells "curled up like potato chips", RF sputtering was too slow, ion sputtering gave good coatings on cells then broken in handling, and the thermally matched Corning 7070 glass "is not commercially available at this time in" 50 to 75 um.
Evidence behind this: T3-NASA contractor test report, not peer reviewed, with the recovery, exposure and temperature stated and the sample losses admitted; ten cells, six tested.
Scope and limits
SIX BARE CELLS, ONE OR TWO CYCLES, NO COVER GLASS, NO BLANKET; the 90-100 per cent oven figure is cited from prior work, not measured here; the deposition rates (2 um/hr ion-beam, 100 um/hr electron-beam) are the test's, not a production method's. 1.9 MeV protons at 10^12/cm2 is a different damage state from CLM-1118's. The 500 C anneal is the silicon requirement Rockwell contrasted with GaAs's 125 C (CLM-1085).
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF 4 / printed 1, render read: "Laser annealing tests were conducted on ten 50-micron cells" (raw); "These showed no loss in output due to exposure to the laser"; "Two cells were broken in handling"; "Six cells were successfully tested" (all raw; the control-cell sentence between them a render reading); normalised: "All cells tested without breakage showed some recovery"; "Exposure times ranged from two to ten seconds at 500" C; "Resulting energy requirements are less than earlier estimates by about a factor of 5"; raw: "a suitable method of glassing was not found"; the Schott, RF and ion-sputtering sentences as render readings ("full of bubbles", "curled up like potato chips"). PDF 43 / printed 40, normalised: irradiated with "1.9 MeV protons to a fluence of" 1 x 10^12 protons/cm2, with cells 18, 19, 31 and 32 under-irradiated by a source malfunction (render reading); PDF 44, Figure 45, raw: "POWER DENSITY - 42 W/cm2", "TIME - 1.020 SEC". PDF 50 / printed 47, render read, normalised spans: "average 50% recovery from charged particle irradiation damage with 5-10 seconds exposure"; "Thermal bulk annealing in an oven for 20 minutes has shown 90-100% recovery"; "This difference in recovery suggests a time dependance for more complete annealing"; "Corning 7070 glass has thermal expansion characteristics that are very closely matched to silicon"; raw: "is not commercially available at this time in" 50 um to 75 um thickness. PDF 51 / printed 48: recommendations for "a statistically significant number of samples", tests on glassed cells once a glassing technique exists (render reading), and "20-30 anneal cycles" (normalised).
Basis: per cent recovery of irradiation damage; seconds of exposure at degrees C; W/cm2 of laser power density; um of cell and cover
Cite this
energyaperture.com/c/clm-1119
CLM-1119, Energy Aperture, as of 1979-04.