Submitted by Anonymous on Sat, 06/02/2007 - 05:59
Forums
Greenland Ice Studies

Mrs. Dodd, the students really enjoyed the live webinar yesterday! we had a lively discussion about your experiences afterwards. These are a few questions they still wanted to as:

Caroline: How big is the fiber optic camera and how is it transported to the sites?

Audrey/Micarah: What is a snow chamber experiement?

Angelina: What is a photomultiplier tube?

Thanks again for answering all of their questions! Lollie/Redd School/Houston

Wed, 06/06/2007 - 13:46

Jo Dodds

Hi Lollie.  I asked Katrine Gorham and Barry Lefer to answer your students' questions and I will copy their replies to you.  Thanks for all of your interest.Caroline: How big is the fiber optic camera and how is it transported to the sites?
Caroline, the fiber optic camera is only a little bit bigger than a digital camera, but we also have a fiber switch that changes which fiber is connected to the camera.  The fiber switch and the PC to record the data and control the fiber switch are much bigger.   In addition I have a fairly larger heater in there to keep everything warm, so the whole thing is about 3 ft x 3 ft x 3 ft on skis.  Here is an attached photo.

Audrey/Micarah: What is a snow chamber experiement?

Augrey and Micarah:  Katrine Gorham (from University of California - Irvine) is going to answer your question, since she is doing all the snow sampling.
 The snow chamber that I am using at Summit consists of a quartz tube that is packed with snow. Before leaving the lab in California I prepared a mixture of gasses. I flow these gasses through the chamber and then let the chamber sit in the sun and "bake" for predetermined length of time. After letting the chamber bake, I collect the chamber air into a stainless steel canister. The canister is then shipped back to California where the contents will be analyzed using gas chromatography. By looking at ratios of different hydrocarbons in the snow I will be able to estimate radical concentrations.
Hopefully this answers the question. If you (or the students) have any more questions, just let me know.
Take care, Katrine
Angelina: What is a photomultiplier tube?

Angelina: Photomultiplier tubes ( or PMTs for short) are very sensitive detectors of light.  PMTs multiply the signal produced by light by as much as 100 million times.    PMTs are constructed from a glass vacuum tube which houses both positive and negatively charged plates. When a photon hits the special plate, it makes electron (kind of like what happens in a solar panel). In the vacuum tube the electrons move very quickly towards a series of more positively charged plates.  We carefully measure the electric current produced by these electrons. This allows us to measure very low levels of light in the snow.
Hope this helps.  Please feel free to ask me more questions. Barry