Known-answer NaCl (rock salt, a=5.6402 A) powder pattern in Q-space on the exact convention of the 150K deCIFer reference (q 1.92-29.16 A^-1, step 0.02, 1363 points, decaying curved baseline, ~8-12% multiplicative noise, FWHM 0.22 A^-1). Intensities from pymatgen XRDCalculator (lambda=0.4312 A so the full Q grid is covered; Debye-Waller B_Na=3.0, B_Cl=2.0 giving measured-like 220/200 ratio). Validated: all peaks with I>=8.7% detected at positions within 0.022 A^-1 and relative intensities within ~1%. Replaces truncated control b938a76e (which only covered q<=5.77).