Development of Cosmic Dust
Detectors Onboard Spacecrafts
H.Shibata1, H.Ohashi2, T.Hirai2, K.Nogami3, T.Iwai4, S.Sasaki5,S.Hasegawa6, M.Fujii7, T.Miyachi7, S.Takechi8, S.Minami8,
R.Srama9 and E.Grün9
1Kyoto University,Japan
2Tokyo University of Marine Science and Technology,Japan
3Dokkyo Medical University,Japan
4The University of Tokyo,Japan
5National Astronomical Observatory,Japan
6Japan Aerospace Exploration Agency (JAXA) ,Japan
7Waseda University, Tokyo, Japan
8Osaka City University, Osaka, Japan
9Max-Planck-Institute for Nuclear Physics, Germany

Introduction
Cosmic dust composed of small (submicron- ~ micronsized) solid particles pervades interstellar space.
In order to investigate the flux, mass, velocity and chemicalcomponent of cosmic dusts, we have been developing
three types of cosmic dust detectors for in situ
measurement onboard spacecrafts.
1. IID (Impact Ionization dust/debris Detector)
2. Piezoelectric (PZT) impact detector
3. TOF (Time of Flight) mass spectrometer with IID or PZT
These instruments are calibrated by ground based
experiments using with Electrostatic Dust Accelerators.

Dust Accelerator (HIT, Univ. Tokyo)
Target (Al, Mo, Au)
CSADeflector

CSA

1601.5mm
Detector

Beam Monitor

3.75 MV Vande Graaff
Accelerator

MicroParticle
Beam Monitor

Chamber

Van deGraaff
Accelerator

Max-Planck-Insitut fürKernphysik
Heidelberg, Germany
2MV Van de Graff
accelerator

Beam line

Target chamber

1. IID(Impact Ionization dust/debris Detector)• Gold plated metaltarget• Double entrancegrids• Large impact area
(20cm x 20cm)• Light weightPrinciple of Impact Ionization
Dust Detector

Charge Signal

t = c gv

Particle Mass , Velocity

a±Q /m = c rvbt : Rise time v: Velocity
Q : Charge
m： Mass
Cg , Cr , α , β : Constants[D.K.Bedford, 1970]

V→Q (Charge)
Qtt

Impact point

Impact velocity vs Rise timet = c gva

Impact velocity vs Charge/mass±Q /m = c rvb

2. Piezoelectric Impact Detector
MDM (Mercury Dust Monitor)
PZT (piezoelectric lead zirconate titanate)element as an impact target
Measurements of dust particle1) Number of incoming dust particle with
crude direction
2) Momentum or velocity of particle

MDM (Mercury Dust Monitor)

DustParticles5.5 km/s
28 pg

Slow

25 km/s
29f g

High speed
7.2 km/s
5.5pg

9.7 km/s
1.2 pgMedium3. TOF-MS with IID or PZT• Impact Induced Plasma (Particle mass and velocity)• Chemical Analysis (Secondary ion mass analysis)– TOF (Time of Flight) mass spectrometer

TargetMetal plate

Signal analysis
Mass, velocity

FeatureModerate signal

PZT

Mass, velocity

Velocity fromwaveform

MicroPZT

Mass, velocity

Large signal

Reflectron (Prototype)Protective Tube

Target ( 800 – 1200 V )Effective Area : 18×18 mm

Detector (MSP)Effective Area ~ 57 mm2(Diameter = 8.5 mm)

Reflection Plate( 1000 – 2500 V)

Reflecting Region( Potential Ring )Curved Potential TOF-MS
Linear Type

TargetParallel Potential TypeI

Detector

Impact Point :Y = ± 4 mm
Initial Energy ： 0.1 eVCurved Potential Type

TargetTargetDetector

DetectorSchematics of target setup+ HV
CSA+Positive ions accelerated
into filed free region for
TOF analysis

Au Plated Piezo Ceramic Element

Micro Piezoelectric Element
PZT

Electrode

Plastic moldMicro-PZT 25micron square, 250micron high