Foster, You have raised an interesting possibility. I have been out of the loop for 25 years, so my info may be dated. However, the cerium was included in the melt, with the quantity a djusted for the optimum UV absorption for the coverslide thickness.
Use of a doped layer rather than the bulk could possibly provide some improved optical matching in the "STACK". It would have to be tested for stability during the thermal cycles. If the surface doping (by dipping or by ion implantation) is a reliable process, this might be worth mentioning it to the appropriate people (who I no longer know). Andrew ---------- Forwarded message --------- From: MSF <foster...@protonmail.com> Date: Tue, Dec 20, 2022 at 1:23 PM Subject: Re: [Vo]:Solar cell lifetime in space To: <vortex-l@eskimo.com> I guess this is getting off into the weeds a bit, but is the quartz layer doped with cerium in the mass? Or is the cerium diffused into the surface by immersion in a molten cerium compound? ------- Original Message ------- On Tuesday, December 20th, 2022 at 2:26 AM, Andrew Meulenberg < mules...@gmail.com> wrote: Robin, The whole deal is a set of tradeoffs that depends on the environment to be encountered. At some altitudes, the Van Allen Belts have too much penetrating radiation to allow solar cells to be used for long-term missions. Addition of coverslides makes the solarcell assembly vulnerable to solar ultra-violet radiation. It is necessary to use high-purity fused silica for the coverslides to prevent themselves from being damaged by the UV. But these coverslides allow the UV to damage the adhesive that holds them to the solar cells. Thus, it is necessary to put a UV filter on these coverslides. The UV filters can be damaged by the trapped-proton environment if there is a manufacturing error. Cerium-doped microsheet (CMS) is generally used for coverslides because it does not transmit the UV that can damage the special adhesives (flexible conformal coatings) that can function through the thermal excursions experienced when the spacecraft enters and exits the Earth's shadow. However, the CMS cutting out the damaging UV also lowers the starting efficiency of the solar arrays that can derive energy from the UV. It is a tradeoff that must even recognize the possibility of solar flares that, when extreme and aimed at the earth, can cause more damage (in days) than all of the other sources of degradation over the rest of the mission. The tradeoff is further complicated by the variety of cells and materials (filters and coverslides) available. There is also the mission variables that are sometimes of greatest concern. Sometimes it is more important to have max power at the beginning of a mission; sometimes at the end. It was a portion of my job for nearly 30 years. Andrew _ _ _ On Mon, Dec 19, 2022 at 12:41 PM Robin <mixent...@aussiebroadband.com.au> wrote > In reply to Andrew Meulenberg's message of Mon, 19 Dec 2022 00:25:20 -0600: > Hi Andrew, > > I'm sure it does, however the high energy particles from other sources are > also present, so it seems to be fairly > effective against them too? Otherwise surely it would have been noticed > that cells in space deteriorate rapidly? > > > >Robin, > > > >This thickness of coverslide stops the low-energy trapped protons of the > >Van Allen belts that would cut the cell efficiency by ~30% in not too many > >months. > > > >Andrew > [snip] > Cloud storage:- > > Unsafe, Slow, Expensive > > ...pick any three. > >
