The data in here were obtained in 2011 from a Vulcan TAP experiment dedicated to measure magnetic fields at the rear of plastic targets using optical polarimetry. Details are given in the paper titled "Micron-scale mapping of megagauss magnetic fields using optical polarimetry to probe hot electron transport in petawatt-class laser-solid interactions" DOI : 10.1038/s41598-017-08619-1, SREP-16-47342. The data in here contain the raw CCD images that were used to generate the magnetic field profiles in Fig.2 in the publication. These are the measurements of the three Stokes parameters (I0 - the total transmission, I1, the parallel polarization component and I2, the perpendicular polarization component) of the reflected light from the target rear. Measurements were done with 3 calibrated optical CCD cameras. The camera settings are provided in the excel sheet. The method of calculating magnetic fields from the Stokes parameters is mentioned in the document. A matlab code developed internally was used for computations. The files here contain the Stoke parameters at three delays: (1) a negative delay where the reflected probe comes before the pump pulse, (2) probe incident 5 ps after the pump and (3) probe incident 10 ps after the pump. The files are named as "120701_5ps_I0", "120803_10ps_I1" etc, where "5ps", "10ps" etc. denote the time-delay (and therefore correspond to Fig. 2b, Fig. 2c etc. in the manuscript respectively) and I0, I1 etc denote the Stokes' components (as described in the Methods section). It was confirmed that I1^2+I2^2+I3^2=I0^2. Pixel-by-pixel calculation of the ellipticity was performed, detailed in the Methods section, and the magnetic field was calculated as described in "Magnetic field measurements.pdf".EPSRC-Fusion Doctoral Training Network EP/J003832/1 MiUR PRIN-2012AY5LEL STFC (CLF) Newton-Bhabha Funds