Q1D needs more data

[mantid-builder]

Original Reporter: Steve Williams

Correct Q1D to what Richard says here:
Q1D NEEDS

Cross section = Sum{ counts at w in pixel } / sum{ M(w)eta(w)T(w)omega(pixel) }

NOT the present

Cross section = Sum{ counts/M(w)eta(w)T(w)} /Sum{ omega(pixel) }

w is wavelength, “sum� is over all pixels and time channels contributing to given Q, M(w) is monitor, eta(w) direct beam efficiency ratio, T(w) is the experimentally measured sample transmission, omega is pixel solid angle times some possible flood source correction factor.

Sorry this does not fit neatly into object oriented code, which was why we compromised in the first place, though it does make the error calculation simpler as the actual number of neutrons is kept in the numerator and you can just take its square root. I have ignored the sample volume rescaling above.

These means Q1D requires counts as function of wavelength with no pixel, or bin (wavelength) dependent corrections done to it. Other corrections, that effect all data equally are possible, for example correction by sample volume, before or after Q1D.

All pixel and bin dependent corrections must be done within Q1D so Q1D needs the monitor spectrum, transmission spectrum, detector efficency correction and flood (flat cell) file.

For each output value of Q the numerator and denominator of Richrd's Colette question above is formed as a sum. Once the two sums are complete the division takes place.

This will agree with what is here: http://www.mantidproject.org/Q1D

[mantid-builder]

This issue was originally trac ticket 3105