DWJ's+10.22-26

This is a type of electron microscope capable of producing high-resolution images of a sample surface. Also I am researching STM which means a non-optical microscope that scans an electrical probe over a surface to be imaged to detect a weak electric current flowing between the tip and the surface. ||  ||
 * 10/22/07 Monday ||  ||
 * Today, I am chosen to do SEM. SEM means **scanning electron microscope**.

SEM images have a characteristic three-dimensional apprearance and are useful for judging the surface structure of the sample. ||
 * 10/23/07 Tuesday ||
 * Today, I have searched SEM images.
 * [[image:bwidow.gif caption="bwidow.gif"]]

Magnification: X 500 The Black Widow is a cobweb spider. Their cobwebs are built in dark, out of the way places. The claw has three hooks, the middle one used to work the silk. ||


 * 10/24/07 Wednesday

I also searched about SEM's history. The SEM was pioneered by Manfred von Ardenne in the 1930s. The instrument was further developed by Charles Oatley and first commercialized by Cambridge Instruments. The development of the SEM in the early 1950's brought with it new areas of study in the medical and physical sciences because it allowed examination of a great variety of specimens.



The first scanning electron microscope - At this time, elecron gun was huge. Also vacuum and pump were big too. ||


 * 10/25/07 Thursday ||
 * Since I am going to ND tomorrow, I found some research information about how SEM works. The SEM uses electrons instead of light to form an image. A beam of electrons is produced at the top of the microscope by heating of a metallic filament. The electron beam follows a vertical path through the column of the microscope. It makes its way through electromagnetic lenses which focus and direct the beam down towards the sample. Once it hits the sample, other electrons are ejected from the sample. Detectors collect the secondary or backscattered electrons, and convert them to a signal that is sent to a viewing screen similar to the one in an ordinary television, producing an image.

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And I and Brighid Corcoran (studying Ph.D in Chemistry) have observed Kosher salt and Table salt using SEM. SEM that I used in ND was pretty much looks like a modern SEM. ||
 * 10/26/07 Friday ||
 * Today, I went to the ND to search what SEM really looks like, what SEM does and how it works.