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.
Van der Lugt optical correlation for use in the improvement of hermetically sealed microstimulator technology
As neuroprostheses become smaller, the need for superior quality control becomes vital. For such devices, Van der Lugt optical correlation (VLOC) techniques, involving Fourier transform holography, offer the potential of superseding conventional leak testing methodologies -- in that working with light is cleaner, faster, more sensitive, and eliminates the disadvantages of tracer gas introduced through backfilling or `bombing.' Current leak testing methods often prove inadequate for very small and delicate devices, as they sometimes involve inordinate stress on the package, or introduce undesirable results due to chemical considerations. In the case of very small packages, gross leaks are often missed by conventional means, since minute quantities of tracer gas introduced into the package may have disappeared by the time the test is run. VLOC techniques have been shown to overcome many of these limitations. The preliminary studies reported here indicate that VLOC techniques are capable of detecting leaks in the range of 10-6 and above in large aluminum-enclosed electronic packages. Furthermore, the method has been proven capable of automation through the use of a thermoplastic recording camera.
A technique for large-field, superficial electron therapy.
The application of electron beams to radiation therapy has received increased attention in recent years. This interest stems largely from the special characteristics of the electron depth-dose distribution; the fall-off in depth dose near the end of the range of the electrons is particularly rapid for electron beams having energies less than about 10 Mev. Such an electron beam is suitable for the treatment of widespread, superficial lesions, where it is desirable to minimize the dose to deep tissues. All the common sources of super-voltage x-rays, apart from radioactive substances, are inherently capable of producing an external beam of electrons, though with varying degrees of complexity. Electrons of about the energy suitable for superficial therapy (several Mev) may be used to produce an x-ray beam which is sufficiently penetrating for the treatment of even the deepest lesions. The Stanford medical linear accelerator was designed to provide both x-rays and electron beams. The accelerator and its applic...