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The detection of star-to-star chemical variations in star clusters older than2 Gyr has changed the traditional view of star clusters as canonical examplesof "simple stellar populations" (SSPs) into the so-called "multiple stellarpopulations" (MPs). Although the significance of MPs seems to correlate withcluster total mass, it seems that the presence of MPs is determined by clusterage, however. In this article, we use deep photometry from the Hubble SpaceTelescope to investigate whether the FG-type dwarfs in the $\sim$1.7 Gyr-oldcluster NGC 1846, have helium spread. By comparing the observation with thesynthetic stellar populations, we estimate a helium spread of$\Delta{Y}\sim0.01\pm0.01$ among the main-sequence stars in NGC 1846. Themaximum helium spread would not exceed $\Delta{Y}\sim0.02$, depending on theadopted fraction of helium-enriched stars. To mask the color variation causedby such a helium enrichment, a nitrogen enrichment of at least $\Delta{\rm[N/Fe]}$=0.8 dex is required, which is excluded by previous analyses of thered-giant branch in this cluster. We find that our result is consistent withthe $\Delta{Y}$--mass relationship for Galactic globular clusters. To examinewhether or not NGC 1846 harbors MPs, higher photometric accuracy is required.We conclude that under the adopted photometric quality, there is no extremehelium variation among NGC 1846 dwarfs.

Multiple stellar populations at less evolved stages-II: no evidence of significant helium spread among NGC 1846 dwarfs