K.-I. Nogami

Response from piezoelectric elements appearing immediately after collisions with silver particles

Ferroelectric lead zirconate titanate (PZT) elements were studied by directly bombarding them with hypervelocity silver particles. The mass and velocity of these hypervelocity silver particles ranged from 1to80pg and 2to6km∕s, respectively. This report examines the pulsed signals observed immediately after collision. The first cycle of the pulse is discussed because the information on impact is presumably recorded on the wave form. The experimental data were analyzed using the wave form that was generated immediately after collision. Consequently, the following conclusions were made: (1) the sensitivity of the element is independent of the thickness of element, (2) the pulse height is proportional to the particle momentum over the measured range, and (3) the wave form is not explicitly related to the velocity of the particles at the time of collision. The potential of a single PZT element acts as a real-time detector for hypervelocity microparticles is discussed.

Measurement of temperature after hypervelocity collision of microparticles in the range from 10 to 40 km/s

The temperature recorded immediately after hypervelocity collision of microparticles comprising iron and nickel with a silver-coated piezoelectric plate was analyzed using photomultipliers of different spectral response characteristics. The conversion rate between the velocity and temperature is estimated to be ∼900 K/km∕s in the velocity range of 10–40 km/s. This rate is greater than that reported earlier.

Position Sensitive Element for Hypervelocity Microparticles Using a Piezoelectric Plate

The propagation of transverse waves generated acoustically in a piezoelectric element by colliding it with hypervelocity microparticles was studied. The propagation times were measured by a set of multiple electrodes on the surface of the element. The coordinates that the particles struck were determined by combining the propagation times and the velocity of the waves. By using the position-sensitive element, significant deviations between the prior indicated and actually measured orbits were observed. The potential of the present element as part of a steering system is discussed.

Measurement of incident position of hypervelocity particles on piezoelectric lead zirconate titanate detector

A cosmic dust detector for use onboard a satellite is currently being developed by using piezoelectric lead zirconate titanate (PZT). The characteristics of the PZT detector have been studied by bombarding it with hypervelocity iron (Fe) particles supplied by a Van de Graaff accelerator. One central electrode and four peripheral electrodes were placed on the front surface of the PZT detector to measure the impact positions of the incident Fe particles. It was demonstrated that the point of impact on the PZT detector could be identified by using information on the time at which the first peak of the output signal obtained from each electrode appeared.

A future observational plan of dust particles around the Moon by LDM (Lunar Dust Monitor) onboard the orbiter of the next Japanese lunar mission

This paper describes our future observation of the dust environment around the Moon by the Lunar Dust Monitor (LDM) to increase our knowledge regarding how the dust inflow and outflow contribute to lunar surface materials. Dust observation in lunar orbit is of great significance to better understand the source of supply of lunar materials, the evolution of lunar regolith, ejecta escaped from the Moons gravitational sphere, and the inflow dust related to meteor streams. Although there have been several past missions of dust observation around the Moon, the origins of the observed dust particles in those missions could not be identified due to low statistics of dust flux or low accuracy of determining their arrival directions. To quantitatively study dust particles around the Moon, we need further data for improved statistics. In a feasibility study, we propose the instrumentation of a LDM that can measure the mass and speed of dust particles with a large detection area of 0.04 m2. With this LDM, we aim at quantitatively studying dust particles around the Moon, inclusive of interplanetary dust, β meteoroids, interstellar dust, and possibly lunar dust that originate from the surface materials of the Moon. In this paper, we summarize the significance of dust particles around the Moon and report an overview of our instrument proposed for the next Japanese lunar mission SELENE-2.