At the previous ICRC, Kruger et al. 2005, Proc. 29th ICRC, Pune, 2, 473, and 2, 477, reported on the first tests of two newly constructed calibration neutron monitors. These monitors are designed to provide an intercalibration between the 50- odd neutron monitors around the world, so that rigidity spectra can be calculated from them. In those papers we described the difference in the latitudinal (energy) dependence between the calibrator and a standard 3NM64 neutron monitor. We also reported on a larger than expected instrumental temperature effect on the calibrator, being 0.12%/ degree C. Here we summarize these results and report on new experiments on the sensitivity of the calibrator to its environment, in particular to different ground surfaces. These surface effects have to be eliminated in the calibration procedure for the stationary neutron monitors.

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 1 (SH), pages 741-744