This is test dataset taken by a CERN@school Timepix detector in Comma Separated Value (CSV) format. It consists of the frame data for three 256x256 pixel frames, with each frame's data in a separate file. The original binary format data may be found at the figshare link below.
The data themselves are the readings from the pixels (X, Y, number of counts) caused by particles incident on the Timepix detector's silicon sensor element when exposed to a potassium chloride source. Three frames were taken with an acquisition time of 60 seconds.
Further information may be found on the CERN@school website. A simple frame display (written in Python, with matplotlib) may be found in the Github repository linked to below.