PVDF copolymer dust detectors: particle response and penetration characteristics

Abstract

Experiments using glass impactors with diameters in the range ∼ 10–200 μm and impact velocities in the range 0.9–14.4 km/s were carried out to measure the signal characteristics, velocity loss and degree of fragmentation for particles penetrating single and multiple polyvinylidene fluoride (PVDF) copolymer sensors with thicknesses 1.5–3.5 μm. Pure PVDF sensors were also studied for comparison. Up to three sensors were placed in a time-of-flight (TOF) telescope arrangement which was followed by capture cell devices. The experimental results showed that PVDF copolymer sensors are xcellent dust detectors and have a response to dust impacts 30% higher than that of pure PVDF sensors. For impactors having velocities > 9 km/s and diameters s ≈ 40 μm, the particles vaporize upon single sensor penetration. For larger particles, ∼ 50% are totally vaporized and ∼ 50% provide TOF information but result in little or no debris in the capture cells. For impact velocities < 9.0 km/s, ∼ 75% of the impactors suffer mild fragmentation, or no fragmentation, following single sensor penetration, with fractional velocity losses which range from < 0.5% for larger particles to ∼ 15% for smaller particles. For impactors with diameter greater than ∼ 10 times the sensor thickness, the diameter of the penetration hole in the sensor is less than 20% larger than the impactor diameter, and fragment spray angles of single and double sensor penetration are small (∼ 2.5°) . The results for combined PVDF trajectory-capture cell systems established that, for ∼ 75% of the impactors with velocities < ∼ 8 km/s, thin sensor trajectory systems satisfy the requirements of velocity/trajectory determination, of identification of the location of particle fragments in capture cells, and of sufficient fragment mass following penetration of the trajectory sensors for successful capture and subsequent chemical and isotopic analysis.