Iron Projectiles Research Articles

Response of high resolution drift tubes to relativistic heavy ions

Abstract We report the results of various tests undertaken in a program to develop a drift tube hodoscope for a cosmic ray balloon experiment intended to search for extragalactic antimatter. Included are studies of mechanical integrity, electron drift velocity, tube gain, space charge saturation effects as measured for relativistic iron nuclei, and delta ray backgrounds associated with signals from iron projectiles. Implications of the results of these studies with regard to the use of drift tubes on baloon borne experiments are discussed. It is found that a spatial resolution of σ ∼ 300 μ m can be achieved over a dynamic range from Z = 20 to 30 with little degradation from delta ray effects for suitably chosen tube gains and discriminator threshold settings.

First calibration measurements with the dust impact detector DIDSY-IPM

The IPM detector consists of two separate impact ionization detectors, one of them covered by a 2.5 μm thick plastic film and a piezoelectric sensor mounted to the back of the joint impact plate. First impact tests, with iron projectiles in the mass range 10 −15 to 10 −9 g and in the speed range 1 km/s to 70 km/s, were performed with the calibration (FS) and the flight (F) model of this detector. The charge yield at 69 km/s impact speed (flyby speed of GIOTTO) has been extrapolated from the data and amounts to 400 Coulombs per gram. This corresponds to a preliminary sensitivity threshold for the impact ionization detector of about 6×10 −17 g. The penetration limit introduced by the plastic film is about 10 −14 g for iron particles. Only the biggest particles used for the test produced signals at the piezoelectric sensor. If one assumes an energy dependence of the piozoelectric signal, a preliminary sensitivity threshold of about 10 −13 g at 69 km/s can be established.

The penetration limit of thin films

One sensor of the Helios micrometeoroid experiment is covered by a thin film consisting of 3000 Å parylene and 750 Å aluminium. Micrometeoroids must penetrate this film before they are detected. In order to study the effects of the film on the detection of micrometeoroids simulation experiments were performed with iron, aluminium, glass and polyphenylene projectiles in the mass range of 5 × 10 −13g < m < 2 × 10 −10g and in the speed range of 1.5 km/ sec < ν < 13 km/ sec. The bulk densities of the projectiles ranged from 1.25 g/cm 3 (polyphenylene) to 7.9 g/cm 3 (iron). By measuring the speed of the projectiles before and after the film penetration the speed loss Δν caused by the film was determined. The angle of incidence was varied in three steps (0°, 30° and 60°). This deceleration strongly depends on the projectiles' densities: Vertically impacting iron projectiles of m = 10 −11 g and ν 1 = 3 km/ sec were subject to a relative speed loss of Δν/ ν 1 = 4%, aluminium projectiles of the same mass and speed showed Δν/ ν 1 = 8%, glass projectiles Δν/ ν 1 = 9% and polyphenylene projectiles Δν/ ν 1 = 14%. The total charge of the plasma produced upon impact on a gold target of a projectile which had penetrated the film before that was compared with the plasma produced by a projectile without a penetration. For iron projectiles these two signals did not differ significantly even at an angle of incidence of 60°. Whereas polyphenylene projectiles showed an attenuation of the charge signal by a factor of 10 after the penetration already at an angle of incidence of 0°. Polyphenylene projectiles impacting the film at an angle of incidence of 60° could no longer be detected behind the film. This experiment defined the penetration limit of the Helios film. Comparison with other penetration data yielded a penetration formula which is applicable to projectiles with diameters in the submicron to centimeter range. This penetration formula gives the penetration limit of a film as a function of the projectile's mass, speed and density.

Collisional Processes of Iron and Steel Projectiles on Targets of Different Densities

Cratering experiments for μm- and mm-sized iron- and steel-projectiles on various target materials show that crater depths and the ratios of crater diameter to crater depth D/T depend on the densities of the projectile- and target-material and on the ductility of the target material. Cratering experiments into low density material (Saffile ρ = 0.28 g/cm3) have produced elongated impact “craters”. For low target densities the “crater” depth is up to 100 times the projectile diameter, depending on its impact speed. This impact process leads to a complete accretion of the projectile mass within the target.

Microcraters formed in glass by projectiles of various densities

An experiment was conducted investigating the effect of projectile density on the structure and size of craters in soda lime glass and fused quartz. The projectiles were spheres of polystyrene-divinylbenzene (PS-DVB), aluminum, and iron with velocities between 0.5 and 15 km/sec and diameters between 0.4 and 5 microns. The projectile densities spanned the range expected for primary and secondary particles of micrometer size at the lunar surface, and the velocities spanned the lower range of micrometeoroid velocities and the upper range of secondary projectile velocities. There are changes in crater morphology as the impact velocity increases, and the transitions occur at lower velocities for the projectiles of higher density. The sequence of morphological features of the craters found for PS-DVB impacting soda lime glass for increasing impact velocity, described in a previous work (Mandeville and Vedder, 1971), also occurs in fused quartz and in both targets with the more dense aluminum and iron projectiles. Each transition in morphology occurs at impact velocities generating a certain pressure in the target. High density projectiles require a lower velocity than low-density projectiles to generate a given shock pressure.

Hypervelocity impact heating of porous aluminum

Based on experimental shock data of Al'tschuler, Anderson, and Kormer, an equation of state from Zel'dovich is used to estimate thermodynamic characteristics of a porous aluminum target, after impact by iron or aluminum projectiles, in the impact velocity range ∼8–20 km s−1, which produces shock pressures in the range 0.4–8Mbar. The initial target distention, m=ρ0/ρ00, is varied from 1 to 3. It is found that projectile and target pressures and the projectile thermal energy are monotonically decreasing functions of m. The thermal energy E′ retained in the relaxed target is a monotonically increasing function of m. The electronic fraction of thermal pressure ranges from a few percent for a nonporous target at 8 km s−1 up to 20% at 20 km s−1 and m=3. Within the ranges of target density, ρ0i, and target distention, m, considered in this study, and in the impact velocity range Vi=8–16 km s−1, the relative effectiveness of these parameters in producing target heat E′ (erg/g) can be roughly characterized by the relation E′∝ lim ∼ρ0i0.47 m1.49 Vi2.13. The minimum velocity that will produce significant target vaporization in aluminum-aluminum impact decreases from 18.4 to 7.9 km s−1 as m is changed from 1 to 3, whereas that for iron-aluminum impact drops from 14.0 to 7.4 km s−1.

Studies of plasma production at hypervelocity microparticle impact

This paper is concerned with an investigation of the plasma generated during the impact of hypervelocity microparticles with a metal target. A laboratory source of hypervelocity micron-sized iron particles is first described which utilizes a 2 MV Van de Graaff generator, followed by a discussion of the techniques used to determine the mass and velocity of the particles. On impact of the iron projectiles on a slatted molybdenum target, charge is generated, extracted from the region of impact by suitably biasing a gridded electrode, and subsequently detected using a conventional wideband electronic amplifier or an electron multiplier. It is shown statistically that during impact equal numbers of electrons and positive ions are produced - indicating plasma generation - and that the total charge released (Q) may be described empirically in terms of the mass (m) and velocity (v) of the particle by a simple power law relationship of the kind Qαmαvβ, with β = 3·2 ± 0·1 over the complete velocity range investigated (0·05 to 10 km s−1) and with α = 0·85 for v>1 km s−1 and 1·33 for v<1 km s−1. It is also shown that the charge extracted from the plasma reaches a maximum a few microseconds after impact and subsequently decays exponentially with a time constant of several micro-seconds.A crude mass analysis of the positive ions generated during the impact using a simple time-of-flight mass spectrometer has indicated that, over the velocity range investigated, the dominant ions in the spectrum are characteristic of the projectile and not the target material. From considerations of the relative abundance of the metal ions in the spectra, together with the known relative metal atom concentrations in the iron projectiles, the temperatures of the plasmas have been estimated (from Saha equilibrium considerations) to be of the order of several thousands of degrees Kelvin.In a detailed discussion, attempts are made to consider how the kinetic energy of the projectile is dissipated - eventually producing plasma - in terms of available theoretical models of hypervelocity impact. It is shown that the most satisfactory model of this very complex interaction appears to be one in which the relative importance of shock-wave propagation into the projectile and target materials is considered. Finally, a discussion of the properties and the temporal behaviour of the impact-produced plasma is presented in order to assess the relative importance of diffusion and recombination processes, thus to assist in the interpretation of the experimental results obtained in this study.

XIV. On the resistance of the air to the motion of elongated projectiles having variously formed heads

The famous theory of the parabolic motion of projectiles was at an early period found to give results not in accordance with practice. Manifestly, then, the air must offer a very sensible resistance to a body which is moving through it with a high velocity. This resistance will depend upon the form of the moving body, and upon the velocity with which it is moving. Hence, before the path of a projectile can be calculated, it will be necessary to determine experimentally the resistance opposed by the air to the motion of the projectile, corresponding to various velocities. According to Newton’s law, the resistance of the air varies as the square of the velocity. But the velocities were low in the experiments made under his direction. In 1719 John Bernoulli gave equations for finding by the method of Quadratures the path &amp;c. of a projectile, when the resistance of the air was supposed to vary according to any power of the velocity. But in spite of grave doubts respecting the accuracy of Newton’s law, it has been adopted by most of the eminent mathematicians who have written on the subject, such as Euler (1753), Lambert (1765), Borda (1769), Bezout (1789), Tempelhof (1788-9), d’Ehrenmalm (1788), Lombard (1796), and Poisson. The first good experiments made with a view to determine the resistance of the air to the motion of projectiles were those of Robins in 1742. The projectiles used were leaden bullets of small size. When we consider the great density of the material used, its liability to change its form in the barrel of the gun, and the smallness of the solid projectiles, it is truly wonderful that Robins was able to accomplish so much with his ballistic pendulum. Afterwards Hutton carried on Robins’ system of experimenting both with the whirling machine and ballistic pendulum, introducing additional precautions, and using iron projectiles of greater size. In recent times MM. Didion, Morin, and Piobert have carried on experiments in France with heavier spherical projectiles, by the help of an improved ballistic pendulum; but they have done little more than confirm the results of Robins and Hutton, and extend them to spherical projectiles of larger diameter.

On the Conversion and Rifling of Cast-Iron Ordnance, and on Chilled White Iron Projectiles

On the Conversion and Rifling of Cast-Iron Ordnance, and on Chilled White Iron Projectiles