# Neutron diffraction

1. Jan 18, 2012

### v_pino

1. The problem statement, all variables and given/known data
In an experimental setup (shown in attachment) like this for neutron diffraction, how do I find the wavelength of the neutron. It should be around 2nm.

2. Relevant equations

$$\lambda = \frac{h}{mv}=\frac{396}{v}$$

3. The attempt at a solution

I am having trouble with finding v of the neutron. Does it have to do with the total length of the tube?

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2. Jan 19, 2012

### technician

The only speed information in your diagrams states that the neutrons are 'thermal' neutrons. This means that they are in thermal equilibrium with the moderator.
In an online reference site I read that neutrons have a range of speeds but the accepted speed for thermal neutrons is 2200 m/s.
In the absence of any other information I would use this and at least get some sort of answer.