Neutron beam contamination

hugh50935

Hi all,

It appears that I have some contamination from the monochromator in my 2.95A fixed wavelength neutron beam, which is causing small reflections to appear at 1/3 positions (i.e. a Lamda/3 harmonic contamination).

Does anyone know if it is possible to create an emission profile for a fixed-wavelength neutron beam which incorporates a constant fraction of the Lamda/3 beam?

I started off trying to use this:

neutron_data
lam
	ymin_on_ymax  1
	la 0.5 lo 2.946878 lh 0.1
	la 0.5 lo 0.982293 lh 0.1

But it only fits the peaks from the main (2.95A) wavelength. Ideas?

I figure I could always make a 'dummy' phase the same as the primary phase but with 3X the lattice parameters then treat it like multiple phases, but I don't think this is a very elegant solution.

Thanks for your help!

Cheers,
Hugh

alancoelho

Best to use another str with its own lam.

lam can be str dependent as well as xdd dependent:

xdd...
lam... ' define your normal lam

str... ' define your normal str

str... ' define another str with the harmonic lam
lam... ' ' the harmonic lam

for strs {
' put common str stuff here
}

hugh50935

Hi Alan,

Thanks for the response. Everything is working perfectly (so far)!

Cheers,
Hugh

hugh50935

Hi Alan,

Actually, perhaps this isn't solved as I originally thought. I have multiple phases as well as the beam contamination. Since the whole material is subjected to the beam contamination, I'm assuming that all the structural information goes into the "for strs {}" section. This works for a single phase, but what if I have more than one which need to be in separate strs and therefore can't be in the common "for strs {}"?

Thanks for your help.

Cheers,
Hugh

alancoelho

Hi Hugh

If you have more than one str then you can either list them twice each with their own appropriate lam or use for strs n1 to n2 {}; ie.

xdd...

str... ' 1st str
lam... ' 1st lam

str... ' 1st str
lam... ' 2nd lam

str... ' 2nd str
lam... ' 1st lam

str... ' 2nd str
lam... ' 2nd lam

for strs 1 to 2 {
' put 1st str stuff here and dont use the @ sign
}

for strs 3 to 4 {
' put 2nd str stuff here and dont use the @ sign
}