The 2D "QxQy ASCII" output files of SANS data are of the format below. Based on the instrument settings, each pixel of the 2D detector data is converted into Qx and Qy. The 2D detector is a normal XY coordinate system when viewed from the neutron source. Qx and Qy both positive is a point in the upper right quadrant and both negative is a point in the lower left quadrant. What corrections have been applied to the data depend on what (if any) reduction steps were applied before exporting the file.

In each file there is a header of information describing the sample information (gleaned from the raw data file) and information about the processing steps that were taken to generate the reduced data file. The data is in a 8-column format where the 8 columns are:

Note that the VSANS output files are 9-columns, with the 9th column being the mask (0|1) where 1 means that the pixel is to be masked and 0 means that the pixel is to be used. Each VSANS detector panel is written as a separate data file. If a single output file with a unified 2D detector is desired, use the NXcanSAS 2D output format.

1. Qx (1/Angstrom)
2. Qy (1/Angstrom)
3. I(Qx,Qy) (1/cm)
4. err I(QxQy) (1/cm)
5. Qz (1/A)
6. SigmaQ Parallel (1/A)
7. SigmaQ Perpendicular (1/A)
8. fs Beamstop Shadow factor (0,1)
9. mask (0|1) (only in VSANS output files)

Note that the Q-values are set up (naturally) on an XY grid. The resolution function is most conveniently defined at each XY value in terms of the orthogonal directions - parallel to Q and perpendicular to Q.

The error on the intensity is currently calculated as the square root of the intensity. For later analysis, any error values that are zero, Inf, or NaN are set equal to the average error of the entire data set. A full error propagation through the data reduction is in progress.

(only a snippet of the file is shown here)

FILE: SILIC009.SA3_SRK_S109   CREATED: 22-JAN-2008 02:39:11
LABEL: Silica 2 pct in D2O Scatt 1.3M                              
MON CNT   LAMBDA (A)  DET_OFF(cm)   DET_DIST(m)   TRANS   THICK(cm)
7.6329e+06  6       20     1.33     0.72568     0.2
BCENT(X,Y)   A1(mm)   A2(mm)   A1A2DIST(m)   DL/L   BSTOP(mm)   DET_TYP  
106.8  64.59  50    3    5.4675    0.142    50.8    ORNL  
SAM: RAW Data File: SILIC009.SA3_SRK_S109
BGD: none
EMP: none
DIV: none
MASK: none
ABS Parameters (3-6): none
Average Choices: none

*** Data written from RAW folder and may not be a fully corrected data file ***
Data columns are Qx - Qy - I(Qx,Qy) - err(I) - Qz - SigmaQ_parall - SigmaQ_perp - fSubS(beam stop shadow)
Error wave is properly propagated through all reduction steps 8/2011
ASCII data created Fri, Jun 27, 2014 7:32:18 AM

-0.37782049	-0.22708508	121	12.034039	0.097299263	0.027318737	0.0029338649	1
-0.37470853	-0.22736368	62	8.9214897	0.09613394	0.027131699	0.0029346643	1
-0.37158513	-0.22764063	120	11.98863	0.094975442	0.026945159	0.0029354612	1
-0.36845037	-0.22791593	70	9.4113016	0.093823873	0.026759125	0.0029362559	1
-0.36530426	-0.22818954	67	9.231039	0.092679322	0.02657361	0.0029370477	1
-0.36214682	-0.22846146	91	10.578622	0.091541886	0.026388623	0.0029378361	1
-0.35897815	-0.22873165	77	9.8175964	0.090411671	0.026204174	0.0029386205	1