Angular response of ‘pin-hole’ imaging structure measured by collimated β source

The pitch-angle distribution of energetic particles is important for space physics studies on magnetic storm and particle acceleration. A ‘pin-hole’ imaging structure is built with the ‘pin-hole’ technique and a position sensitive detector, which can be used to measure the pitch angle distribution of energetic particles. To calibrate the angular response of the ‘pin-hole’ imaging structure, special experiment facilities are needed, such as the particle accelerator with special design. The features of this kind of particle accelerator are: 1) The energy range of the outgoing particles should be mid-energy particles (tens keV to several hundred keV); 2) the particle flux should be consistent in time-scale; 3) the directions of the outgoing particles should be the same and 4) the particle number within the spot should be low enough. In this paper, a method to calibrate the angular response of the ‘pin-hole’ imaging structure by the 90Sr/90Y β source with a collimator is introduced and simulated by Geant4 software. The result of the calibration with the collimated β source is in accord with the Geant4 simulations, which verifies the validity of this method.