Isao Ueno

New Method for Estimating Impact Strength of Solder-Ball-Bonded Interfaces in Semiconductor Packages

A method for estimating the impact strength of a solder ball junction in encapsulated semiconductor packages was developed. This method reveals the impact force in a solder ball unit and the time required for a solder ball to break. The bombardment absorbed energy required for the ball to break is evaluated as impact strength. This method can be used to quantitatively evaluate the impact strength of solder ball junctions, which is difficult to do using conventional shear and tensile strength estimation methods.

Sequences of neutron and X-ray flashes during a long-lasting current in a plasma focus device

The possibility of increasing the neutron yield of a dense plasma focus by several focus events during a single discharge of an energy store is discussed. On a small focus device supplied with a long-lasting current pulse from an inductive energy store, experiments were carried out where several radiation flashes in rapid succession during one discharge could be observed. By the time-of-flight method the generation of fast neutrons was proved.

Neutron Yield in a Repetitive Dense Plasma Focus

A first, preliminary result of the neutron yield from a repetitively produced dense plasma focus is reported, where the repetitive focalization of plasma is performed at the top end of the inner electrode of the plasma focus device. The number of repetitions of plasma was elected to be more than 10 in a single discharge of the capacitor bank. In the case of a small repetition number of plasma production, the scaling law of neutron yield seems to be the standard one for a single focus event in a single discharge of the capacitor bank.

Comparative Study of Various Models of Energetic Ion Generation from Plasma Focus

Various simple models are developed to derive a scaling law for the kinetic energy of fast ions generated from plasma focus devices. Various electric fields are considered as the driving source; those induced by rapidly-increasing plasma inductance, those induced by enhanced resistivity, and these induced by macro- and microscopic plasma instabilities. The electric field and the kinetic ion energy are shown to be represented by a universal analytical scaling law. The results are also compared with experimental observations.

Ablation Accelerator (ABLAC) as Driver for Impact Fusion

This paper presents considerations on the design both of an ablation accelerator suitable as a driver for impact fusion, and a projectile to be accelerated by the accelerator. We argue that the proposed approach offers an attractive option for accelerating an iron projectile to hypervelocities suitable for fusion applications.

Behavior of Thin Arc Plasma in a Self-Crowbar Air Gap

The measurement of the drift speed of an arc plasma in a self-crowbar air gap is reported, the speed being measured during the growth phase of the current in the device. The drift speed is concluded to be constant with time during this phase, although the force from the magnetic pressure is not constant during current start-up. This makes possible the design of a practical self-crowbar air gap switch. The possibility of designing a self-crowbar rotary air gap switch (SCRAGS), in which the rotary motion of the arc would dramatically lower the heat load on the electrode material, is also pointed out.

Sheath Potential Generated by a Relativistic Electron Beam

It is reported that a new sheath structure is formed in a plasma where a relativistic electron beam is injected. An application of this new sheath to the pinched-plasma ion beam source is described in order to avoid the electron bombardment on the electrode.