NOTESTesting the NASA BioSentinel Pixel Dosimeter Using Gamma-ray and Neutron Sources at the LLNL Calibration LabHoman, J.1; Lusby, T. C.1; Ricco, A. J.1; Mintz, J. L.2; Braby, L. A.3; Straume, T.∗,1Author Information 1NASA Ames Research Center, Moffett Field, CA 2Lawrence Livermore National Lab, Livermore, CA 3Texas A&M University, College Station, TX. The authors declare no conflicts of interest. ∗For correspondence, contact: Tore Straume, NASA Ames Research Center, Mail Stop 236-7, Moffett Field, CA 94035, USA. (Manuscript accepted 21 July 2021) Health Physics: February 2022 - Volume 122 - Issue 2 - p 344-348 doi: 10.1097/HP.0000000000001502 Buy Metrics Abstract The objective of this paper is to evaluate the accuracy of the NASA BioSentinel Pixel Dosimeter (BPD) using gamma-ray and neutron sources in a standard calibration lab. The dosimeter tested here is the ground-based version of the BPD that will be onboard the BioSentinel mission. The BPD was exposed to radiation from 60Co, 137Cs, and 252Cf at selected distances (dose rates) at the Lawrence Livermore National Laboratory (LLNL) Radiation Calibration Laboratory (RCL), and the results were compared with NIST traceable benchmark values. It is recognized that these sources are not analogs for the space environment but do provide direct comparisons between BPD response and well characterized calibration lab values. For gamma rays, the BPD measured absorbed dose agrees to ≤ 3.8% compared with RCL benchmark values. For neutrons, the results show that the BPD is insensitive, i.e., the BPD detected only the gamma-ray dose component from 252Cf. The LET spectra obtained for gamma rays from 60Co and 252Cf are consistent with expectations for these gamma-ray energies, but the LET spectrum from the 137Cs gamma rays differs substantially. The potential causes for this difference are the high dose rate from 137Cs and the lower secondary electron energy produced by 137Cs gamma rays. However, neither of these results in errors in the absorbed dose. Based on comparisons with NIST-traceable standards, it is evident that the BPD can measure absorbed dose accurately from low LET charged particles. The sensor’s insensitivity to neutrons is unlikely to be a limitation for the BioSentinel mission due to the expected low secondary neutron fluence. Written work prepared by employees of the Federal Government as part of their official duties is, under the U.S. Copyright Act, a "work of the United States Government" for which copyright protection under Title 17 of the United States Code is not available. As such, copyright does not extend to the contributions of employees of the Federal Government.