MainPage:Nuclear:Summer2013:AerogelCharacterization

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Brief description of goals

1. Identify the refractive index (n) experimentally in order to know what particles can best be detected when shot through it.

2. Test the affect of humidity on aerogel by putting it in an area of controlled humidity and then retesting for the refractive index.

Refractive Index

Using Snell's Law on the two faces of the aerogel where the light changes mediums, properties of triangles and properties of angles (which can be seen in the sketch below) we are able to find the derivation for n. (Note: Joel stepped us through this process)

Derivation of n: Media:nderivation.pdf

Notes: Beta is assumed to be 90 degrees and alpha is assumed to be 45 degrees because that is how the laser has been positioned. Gamma is the angle between the original, unrefracted beam and the final refracted beam. It is assumed that gamma can be found using the arctangent of the difference between the original beam and the refracted beam and the length between beta and where the beam hits the wall. This, though is slightly wrong unless the incidence angle is the minimum deviation because only then is the imaginary triangle that can be made by extending the normal lines where the light beam hits the face of the aerogel is the angle gamma actually under beta. Due to the fact that you are measuring from the wall where the light hits to gamma, if the angle is not directly under it, the calculations will be slightly off.

Humidity effects over Aerogel Tiles

One of our concerns for the long term use of aerogel, in the Kaon Aerogel Detector, is how the aerogel will behave. We know from papers that it is manufactured by drying silica gel. So, in principle, the tiles can absorb water again and change their densities. As their densities are directly related to their refractive indexes, it is important to understand any change we may find.

The tiles we have are coated by an hydrophobic thin layer of material, so we have a protection on them already. And the trays of the detector will be rightly stored. But studying the water absorption and its effects on the aerogel properties would be an interesting way of understanding better our detector.

The first idea would be to construct an isolated box to have one aerogel tile submitted for a long time into high humidity. From time to time, we would measure the mass and refractive index of the tile to see any change on its properties.

Materials we bought for the project:

• Humidifier - McMaster 3 Gallon
• Humidifier controller - McMaster HVAC Service
• Plastic box to create the controlled environment
• Tubes