DWJ's+11.05-11.09


 * **11/05/07 Monday**

Today, I finally got to put my pictures that have taken by SEM at Notre Dame. Brighid has been working on SEM and she had very interesting facts from looking at Kosher salt and table salt. Kosher salt is bigger than table salt and it is randomly shaped. In other hand, Table salt is EXACTLY squared and this is the salt we mostly use.

This is **Kosher Salt**

Closer!

It is really bumpy!

This is **Table Salt

It is exact spare ! It is not smooth as it was shown in previous one ** It is really bumpy.

There is **SEM which is located at ND.** It was making lots of noisies when we turned on SEM. We could hear all the sound that cooler which was located in back side. There are a lot of pressure in Blue box ( vacuum) ( in the picture ).

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 * **11/06/07 Tuesday**

Today I am going to research for some limitation of SEM and what the vacuum is. So, I found that there is limitation of SEM. First, samples must be **solid** and they must fit into the microscope chamber. However recently, there are some SEM that you can put some wet stuff to research. Maximum size in horizontal dimensions is usually on the order of 10 cm, vertical dimensions are generally much more limited and rarely exceed 40 mm.

Now, I have found what the vacuum is and what vacuum does. When a SEM is used, the column and sample must always be at vacuum. A vacuum environment means that most of the air molecules have been removed from the inside of the microscope. You can think of vacuum as a density; there are a certain number of gas molecules in a given space. If you think of the total number of people in the United States (240 million) as representing normal atmospheric pressure, then the density of gas molecules in a typical SEM is roughly equivalent to having only one person inhabit the entire United States! Also, there are many reasons for requiring a vacuum in an SEM. If the filament were surrounded by air, it would quickly burn out, like a light bulb. If the column were full of air, the electrons would collide with the gas molecules and never reach the sample. If gas molecules react with the sample different compounds could form and condense on the sample. This can lower the quality of the image. ||
 * **11/07/07 Wednesday
 * **11/07/07 Wednesday

I was abscent because of sickness. :(** ||


 * **11/08/07 Thursday**

Career Day ||


 * **11/09/07 Friday**

No school.

We had no school, but I have read the Notre Dame SEM text book that Brighid gave to me at home. I read heading and two chapters that she assigned to me. I also have several lectures ( video) of ND professor speaking. I listened one lecture of showing SEM muchine and Professor explaining for about an hour. ||