The development of spherical pulse ionization chambers for neutron spectroscopy on DD fusion plasmas is presented. Chambers filled with methane plus a small amount of 3He, with different aspect ratios α (i.e. the ration of outer to inner electrode radii) and with different filling pressures have been investigated. The energy resolution for the 765 keV peak from the 3He(n th, p) 3H reaction without correction of electronic noise is 3.3% and 3.1% for aspect ratios of 30 and 40, respectively. Experiments with quasimonoenergetic neutrons generated by a proton beam impinging on a solid Ti 3H target confirm these results. To determine the ion temperature from the pulse height spectrum a procedure has been developed to obtain the information by fitting an evaluated pulse height distribution to the high energy slope of the experimental spectrum. Thus ion temperatures ≥ 1 keV can be measured if a sufficient neutron flux is available. Finally, the time behaviour of the spherical chamber is investigated.