Error in Calculation of absolute Flux (Source_flux) ???

[Dr. Georg Artus]

Hello,

> Ok. I have modified the Monitor component to create a Monitor_flux
> component that does exactly this. It takes two extra input parameters:
> the lower and upper limit of the wavelength range to consider (eg.  lmin
> = sqrt(81.81/(E+dE)), lmax = sqrt(81.81/(E-dE)) in your case). I think
> that letting the user supply the wavelength range is more general than
> just taking the values from the source component (ie. what happens if
> another source component with no dE is used?).

Thank you very much! This will help a lot. Yesterday we have started
several jobs and up to now all fits well! May be you are right that it
is better to let the user supply the limits. 

> The unit for lmin and lmax of the Monitor_flux component is AA and the
> output is in n/cm**2/AA, which is what you need, I think. There is
> starting to be a lot of inconsistency between using neutron energies in
> meV and neutron wavelengths in AA in the different components, but that
> I something I have to sort out in some way. One idea I have is to build
> in knowledge about common units in McStas so that the user can just say
> "20 [meV]" or "4 [AA]" or "2000 [m/s]" and McStas will sort it out by
> itself, but that is for the future.

Yes, the two units, AA and meV, don't make things easier. Your solution
seems good to me. Depending on the instrument one is either used to AA
or eV. I have programmed the calculation from AA to meV in the
INITIALIZE section. 

I have another suggestion: All instruments are built in vacuum, which
normally is not the case. It would be helpful if you had a chance to
say, that you have e.g. 2m He, 5mm Al and 6m Air in the beam. In a first
approximation the location of teh material in the beam is not important.
This is just to get an estimate for the loss due to absorption by
materials. Other materials like Mg, PG, Be, Glass... could also be
interesting. To realize this with the Filter component is possible, but
still affords calculating many things by hand.


Best wishes,

Georg
-- 
*********************************************

Dr. Georg Artus
Technische Universitaet Muenchen
FRM-II Reaktorstation
D-85747 Garching

Tel: +49 (0)89/289-14675
Fax: +49 (0)89/289-14666 or 12112
E-mail: gartus at ph.tum.de