The neutron dose equivalent rate measurements by R3DR/R2 spectrometers on the international space station.

The data from two Bulgarian-German instruments with the basic name "Radiation Risk Radiometer-Dosimeter" (R3D) are discussed. The R3DR instrument worked inside the ESA EXPOSE-R facility (2009-2010), while R3DR2 worked inside the ESA EXPOSE-R2 facility (2014-2016). Both were outside the Russian Zvezda module on the International Space Station (ISS). The data from both instruments were used for calculation of the neutron dose equivalent rate. Similar data, obtained by the Russian "BTNNEUTRON" instrument on the ISS are used to benchmark the R3DR/R2 neutron dose equivalent rate. The analisys reveals that the "BTNNEUTRON" and R3DR/R2 values are comparable both in the equatorial and in the South Atlantic Anomaly (SAA) regions. The R3DR/R2 values are smaller than the "BTNNEUTRON" values in the high latitude regions. The comparison with the Monte Carlo simulations of the secondary galactic cosmic rays (GCR) neutron ambient dose equivalent rates (El-Jaby and Richardson, 2015, 2016) also shows a good coincidence with the R3DR/R2 spectrometer data obtained in the equatorial and high latitude regions.