Using optical correlation to measure leak rates in sealed packages.
An optical correlation technique has been shown to accurately measure leak conduction rates from 10(-1) to 10(-6) atm cc/sec. Using hybrid microcircuit packages with glass capillary leakers, dimensional changes were detected as the packages were exposed to a small increase in external pressure. The rate at which the package returns to its original dimensions is measured and used, along with the internal free volume, to compute the leak rate. Because of its several advantages, the technique has the potential to become a useful nondestructive quality-control technique.
Rapid evaluation of hermetic seals in microelectronic packages using shearography
One possible failure of microelectronic devices is due to leakage resulted from imperfect hermetical seal in microchips and microelectronic packages. This paper presents an optical technique for rapid evaluation of hermetics seals. It is based on measuring package deformation with shearography. The package under test is stressed by an external pressure change and the deformation of the test package's lid is measured with shearography. With the pressure change maintained, the lid of a perfectly sealed package will remain deformed while a leaky package will not hold the deformation that can be monitored by shearography. The proposed process of leaking testing is very fast and practical.
Reduction of Surface Flashover of the Beam Screen of the LHC Injection Kickers
The LHC injection kicker magnets include beam screens to shield the ferrite yokes against wake fields resulting from the high intensity beam. The screening is provided by conductors lodged in the inner wall of a ceramic support tube. Operation with increasingly higher bunch intensity, and narrow bunches, now requires improved ferrite screening. This will be implemented by additional conductors; however the good high-voltage behaviour of the kicker magnets must not be compromised by the supplementary screening. Extensive studies and optimisations have been carried out, to better satisfy the often conflicting requirements for low beam coupling impedance, fast magnetic field rise-time, high vacuum and good high voltage behaviour. A new configuration is proposed which reduces significantly the electric field associated with the screen conductors and the secondary electron yield of the surface of the ceramic tube. Results of high voltage test results are also presented.