Voltage pulsing for localized clearance measurement

Mechanical clearance is a critical parameter of the head/disk interface (HDI) for sliders flying in close proximity in hard disk drives. It depends on a variety of HDI parameters, such as the air-bearing design, disk roughness, and the disk lubricant. An experimental setup was developed to determine the mechanical clearance locally at any location on the disk. Voltage pulsing is used to add an additional force component to the complex HDI equilibrium. The applied force is attractive in character and therefore reduces the mechanical spacing between the slider and the disk. If the magnitude of the applied voltage is changed, a slight contact between the slider and the disk can be realized. Simultaneous measurement of the induced slider displacement using a laser vibrometer allows the quantification of the mechanical clearance. The effect of disk roughness and microwaviness on the mechanical clearance is investigated.     

Dynamics of transient events at the head/disk interface

Slider/disk contacts of nano and pico sliders are investigated using an acoustic emission sensor and a high bandwidth laser Doppler vibrometer (LDV). The following cases are studied: (a) influence of scratch impact on the airbearing stiffness; (b) influence of lubricant thickness on slider dynamics for single bump impacts; (c) influence of lubricant thickness on slider vertical stick–slip vibrations; (d) dynamics of take-off and landing. Linear time frequency analysis is applied to study simultaneously the impact response of the airbearing and the slider torsional and bending modes. The contact dynamics of single bump impacts is examined as a function of disk velocity and lubricant thickness. Increased slider vibrations are found for thick lubricant films both for sliding contacts as well as for single bump impacts. During the transition from sliding to flying a change of the bending mode frequency is observed.     

650-nm vertical-cavity surface-emitting lasers: laser properties and reliability investigations

650-nm AlGaInP-AlGaAs-based oxide-confined VCSELs are investigated in dependence on the current aperture size. VCSELs with small aperture (a=5 /spl mu/m) have a maximum continuous-wave (CW) output power of about 1 mW at room temperature. They reach higher operating temperatures (T/sub max/=55/spl deg/C), have narrower beam profiles, less transverse modes, and a higher side mode suppression compared to large aperture VCSELs (a>13 /spl mu/m). The latter devices emit a CW-output power P=3 mW at 20/spl deg/C. Reliability tests of 655-nm devices show at 20/spl deg/C an output power of P/spl ap/0.4 mW over more than 1000 h and at 40/spl deg/C P/spl ap/0.1 mW over 500 h.     

Holzeigenschaften von Buchen aus immissionsgeschädigten Beständen

In 30 trees from two over 100 years old, immission-damaged beech stands in the Hils, Lower Saxonia, the growth increment at breast height (1,30 m) as well as moisture content and wood density were investigated. Trees of damage class 2 with the greatest damage showed greater increment from the beginning of the 70ties and stronger variabilities in moisture content as compared with trees of damage classes 0 and 1. No immission-induced changes in wood density could be found.     

Buchbesprechungen

Ohne Zusammenfassung     

Characterization of head modulation during touchdown process using magnetic spacing sensitivity analysis

Microsystem Technologies - Recent growth in the cloud storage industry has created a massive demand for higher capacity hard disk drives (HDD). A sub-nanometer head media spacing (HMS) remains the...