Testing the NASA BioSentinel Pixel Dosimeter Using Gamma-ray and Neutron Sources at the LLNL Calibration Lab.

Area of Science:

• Space Science
• Radiation Detection

Background:

• Accurate radiation dosimetry is crucial for space missions.
• The NASA BioSentinel mission requires reliable dosimeters to monitor radiation exposure.
• The Pixel Dosimeter (BPD) is a key instrument for the BioSentinel mission.

Purpose of the Study:

• To evaluate the accuracy of the ground-based NASA BioSentinel Pixel Dosimeter (BPD).
• To assess the BPD's response to gamma-ray and neutron radiation sources in a controlled laboratory setting.
• To compare BPD measurements against NIST-traceable benchmark values.

Main Methods:

• The BPD was exposed to calibrated gamma-ray (60Co, 137Cs) and neutron (252Cf) sources at the Lawrence Livermore National Laboratory Radiation Calibration Laboratory.
• Absorbed dose measurements from the BPD were compared with established benchmark values.
• Linear Energy Transfer (LET) spectra were analyzed for different radiation sources.

Main Results:

• The BPD accurately measured absorbed dose from gamma rays, with agreement within 3.8% of benchmark values.
• The BPD demonstrated insensitivity to neutrons, detecting only the gamma-ray component from the 252Cf source.
• LET spectra for 60Co and 252Cf were consistent with expectations, while the 137Cs spectrum showed substantial differences, attributed to high dose rate and low secondary electron energy, without affecting absorbed dose accuracy.

Conclusions:

• The NASA BioSentinel Pixel Dosimeter (BPD) accurately measures absorbed dose from low Linear Energy Transfer (LET) charged particles.
• The BPD's insensitivity to neutrons is not considered a limitation for the BioSentinel mission due to anticipated low neutron fluence.
• The study validates the BPD's capability for accurate radiation monitoring in space environments.