The energy spectrum of cosmic rays in the region 2.1016-4.1017 eV

The four triggering detectors of the Haverah Park array impose a well defined threshold energy of 2.1017 eV (rho(600) = 0.3 m-2). To investigate the spectrum at lower energies an inner group of detectors, spaced at 150 m, has been used to generate a separate trigger and data recorded over a period of almost two years have now been analysed. The most directly determined ground parameter for such showers is the density at 150 m from the axis (rho(150)) and conversion to a primary energy spectrum has assumed a constant ratio of rho(150)/rho(600). Comparison is made with the Chacaltaya experiment at similar energies. (orig.)