Question: how do you use crystals as an amplifier?

Susana Teixeira answered on 25 Jun 2013:

Lets think about what is a crystal first. In a crystal you have a 3D repeat of many copies of the same molecule, all aligned in the same orientation. In a solution, on the other hand, what you have is molecules moving around in a liquid, each in a random orientation.

So if you put a crystal in an X-ray beam like I do, each molecule interacts with the beam in a way that adds up to the neighbouring molecules, creating an amplifying effect. In other words, the interaction is strong enough that I can measure it, and relate that to what the molecules inside are.
If you put a liquid solution of those molecules in the beam, that does not happen because they are moving around and in different orientations. The interaction would be too weak for me to use.

Let’s think of a silly comparison. Imagine a crowd of people who are all perfect twins and they have a message for you. Some are sitting, some are standing, some have their backs at you, and you are a bit far away. They start telling you the message but they are not synchronised. No big surprise, you won’t understand what they are saying.
Now let us crystallise all these twins. Lets imagine they are all lined up facing you, and they tell you their message by all speaking at the same time, in the same tone. It all adds up and amplifies the message to something you can hear 😉