Measurements of the bunch longitudinal shape of beam particles are crucial for optimization and control of LINAC beam parameters and maximization of its integrated luminosity. The non-interceptive bunch extension monitor for the LINAC of SPIRAL2 facility is being developed at GANIL. Five bunch extension monitors will be installed at the beginning of the LINAC between superconducting cavities. The principle of operation is based on the registration of x-rays induced by ions of accelerator beam interacting with a thin tungsten wire positioned on the beam path. The monitor consists of two parts: a system for wire insertion and positioning, and an x-ray detector based on microchannel plates (MCP). A detector prototype has been developed for three years and was tested using protons and heavy ions beams. The influence of the cryomodule operation on the diagnostic measurement was also studied.