Small Corrections to the Tunneling Phase Time Formulation

After reexamining the above barrier diffusion problem where we notice that the wave packet collision implies the existence of {\em multiple} reflected and transmitted wave packets, we analyze the way of obtaining phase times for tunneling/reflecting particles in a particular colliding configuration where the idea of multiple peak decomposition is recovered. To partially overcome the analytical incongruities which frequently rise up when the stationary phase method is adopted for computing the (tunneling) phase time expressions, we present a theoretical exercise involving a symmetrical collision between two identical wave packets and a unidimensional squared potential barrier where the scattered wave packets can be recomposed by summing the amplitudes of simultaneously reflected and transmitted wave components so that the conditions for applying the stationary phase principle are totally recovered. Lessons concerning the use of the stationary phase method are drawn.Comment: 14 pages, 3 figure

Simulations of Modulation of the Current in a Field Emitter Caused by a CW or Pulsed Laser

Solutions of the time-dependent Schrödinger equation show that the tunneling current in a field emitter may be modulated by means of a laser. The steady-state response is calculated with Floquet methods, and the transient response is determined with a product formulation that does not require the use of absorbing boundary conditions or wave packets. The steady-state response contains a series of resonances, but when the full distribution of energies in a metal is considered the resulting effect is a broad peak that is typically centered in the blue end of the visible spectrum, but may be shifted by varying the applied static field. The transient solutions show that the response of the electrons to the optical fields is delayed by the semiclassical tunneling time, which is defined as the time for traversing the inverted barrier

Measurements of Modulation of the Current in a Field Emitter caused by a Laser

Numerical simulations suggest that laser illumination of a field emitter increases the tunneling curent due to a resonant interaction in which tunneling electrons exchange quanta with the laser. Thus, a laser may be used as a gate, and a time-varying current is produced if the laser is amplitude modulated. We have measured an RF tunneling current of 0.4 nA when the tungsten tip of a sealed field emitter tube is illuminated with a laser diode that is amplitude modulated at 1 MHz, and the DC curent is 5µA. The laser diode increases the DC curent by 270 nA, which is attributed to tip heating. However, the RF current (0.4 nA) has a period less than estimates of the thermal relaxation time

Absolute measurement of the DT primary neutron yield on the National Ignition Facility

The measurement of the absolute neutron yield produced in inertial confinement fusion target experiments conducted on the National Ignition Facility (NIF) is essential in benchmarking progress towards the goal of achieving ignition on this facility. This paper describes three independent diagnostic techniques that have been developed to make accurate and precise DT neutron yield measurements on the NIF

Absolute measurement of the DT primary neutron yield on the National Ignition Facility

The measurement of the absolute neutron yield produced in inertial confinement fusion target experiments conducted on the National Ignition Facility (NIF) is essential in benchmarking progress towards the goal of achieving ignition on this facility. This paper describes three independent diagnostic techniques that have been developed to make accurate and precise DT neutron yield measurements on the NIF