Here are minutes of our meeting on Thursday -- please just reply with, or let me know, any corrections -- thanks!:
Phoning in: just me and Karun Thanjavur (UVic) this time (with regrets from Arnold Gaertner (NRC))
This telecon was just a brief chat between Karun and me (due to a convergence of people being away and it slipping others' minds). Karun has measured the output of the 2" Labsphere integrating spheres that are part of the present science light source, and his plots of the light output distributions can be found at http://projectaltair.org/public/karunfiles/IntSphCalib/June2014eps/June2014eps.html (copied over from http://astrowww.phys.uvic.ca/~karun/ALTAIR/IntSphCalib/June2014eps/ for archival purposes). If one looks at, for example, the plot http://projectaltair.org/public/karunfiles/IntSphCalib/June2014eps/TestData1_11July_cont.png , one can see that there are two blemishes on the inner surface of the sphere, one near the zenith, and one about 10 or 15 degrees away from the zenith (in addition to a couple of blemishes further away from the zenith of the inner surface). Karun consistently observes these blemishes (as one can see in the TestData2..., TestData3..., etc. files), so they are definitely real. (We discussed ways to check these blemishes by eye while the sphere is still mounted on the test stand -- with a dental mirror which we definitely have, but with which it might not be so easy to get a good look; or with a small endoscope, which we think some of our department colleagues might have and which we might possibly be able to borrow.) We have known since we took delivery of the two spheres nearly 2 years ago that their inner surfaces look far from perfect, the reason almost certainly being that the spheres are aluminum and the diffuse reflective coating on the inside surface is Duraflect (a Labsphere proprietary paint) -- when painting aluminum one should always use an "etch primer" (either an etch primer before applying the paint, or a paint which contains an etch primer) -- and Labsphere did not do this before applying the Duraflect, and thus the Duraflect in the spheres has a tendency to flake off in places. (We also believe that Labsphere only applied a single coat of Duraflect, rather than e.g. two coats.) The solution to this would be to 1) be sure to apply an etch primer to the aluminum prior to applying the diffuse reflective coating, and also apply more than one coat of the diffuse reflective paint; or 2) to not use a diffuse reflective paint at all, and instead use a material like Spectralon (a Labsphere proprietary version of expanded PTFE) as the diffuse reflector for the inner surface. We will do one (or try both) of those two approaches with future integrating spheres that we order.
Karun's plots in the links above can be compared with the NRC plots of the light output distribution from the same integrating sphere in the NRC report on pages 5-7 of http://projectaltair.org/public/files/NRC_MSS_ALTAIRReport1_16Apr2014.pdf , however the latter are 1-D plots of a single cross-section of the output of the sphere, and so likely do not precisely correspond to an axis along which either of those two blemishes are contained.
Karun is also starting to make progress on Zemax-based computational modelling, and Divya, Ryan, and Victor are making progress on Angora (FDTD open source) based computational modelling. Karun also just had the UVic machine shop finish making a useful part for laboratory source measurements. I'm working on some analytical modelling of diffuser-based light sources. For integrating sphere-based light sources, Karun et al's computational modelling with and without different baffles in place will study whether a baffle and/or a diffuser in the next set of integrating spheres will be useful for us. As soon as we have a design for a baffle or diffuser, we'll hand that to Allied Scientific Pro and World Star Tech respectively.
That's all I remember, please send things that I forgot. Next telecon as usual in two weeks, on Thursday, July 31, at 2:30 pm Eastern time.
cheers, thanks all! justin
On Wed, 16 Jul 2014 19:28:16 GMT, Justin Albert wrote:
> Hi, > > Telecon tomorrow (July 17) at our regular time of 2:30 pm Eastern time > (11:30 am Pacific, 20.30 European). Discussion items include: progress > toward new gondola and flights, goniometric and pre- and post-flight > calibration, light source modelling, nanosat and new laser module > design, computing/website, grant applications, recap of schedules. A > reminder of the CSA project timeline is attached. > > Here's the dial-in info: If you are calling in from Canada or U.S.: > 1. Dial Toll-Free Number: 866-740-1260 (U.S. & Canada) > 2. Enter 7-digit access code: 5082741 followed by the # > > If you are calling in from elsewhere: > 1. To locate International Toll-Free Numbers go to > http://www.readytalk.com/intl (enter 7-digit access code 5082741) > 2. Dial toll free number from web link > 3. Enter Passcode: Enter 7-digit ACCESS CODE: 5082741 followed by the # > > Here's the tentative agenda: > I) Construction of new gondola and payload, robustness improvements, next flights > II) Light source studies and modelling, pre- and post-flight calibration, and goniometric calibrations > III) Nanosat, new integrating spheres, and multicolour laser module designs > IV) Computing/website > V) Grant applications > VI) AOB > > Talk to you all tomorrow, > justin > > Attachments: > http://projectaltair.org/HyperNews/get/AUX/2012/11/12/18.02-43361-Schedule-20120702_hqp.pdf >
