Magnetic flux with the magnetic field conductor and pinhole

The invention relates to a magnetic flux sensor (1, 21, 51) comprising a a) loop-shaped magnetic head, said - a tip (2, 22, 32, 52), which widens into a rod or a foil (3, 23, 53), - a loop-shaped part (3a, 23a, 53a) - and at least one magnetic field lines of the sample returning part (4, 24, 54 ', 54' '), having, b) SQUID (7, 27, 57), c) and a perforated plate (5, 25, 35, 55) with hole (6, 26, 36, 56), wherein the associated magnetic field lines of the sample loop back part (4, 24, 54 ', 54' ') of the loop-shaped magnetic conductor with the perforated plate (5, 25, 35, 55).