Determination of the modes in two types of closed circuits with quantum tunneling

Others have solved the Schr\"odinger equation for a one-dimensional model having a square potential barrier in free-space by requiring an incident and a reflected wave in the semi-infinite pre-barrier region, two opposing waves in the square barrier, and a transmitted wave in the semi-infinite post-barrier region. Now we model a pre-barrier region having finite length that is shunted by the barrier to form a closed circuit. We use the boundary condition that the wavefunction and its derivative are continuous at the both ends of this model to obtain a homogeneous matrix equation. Thus, the determinant must be zero for a non-trivial solution. All but one of the following four parameters are specified and the remaining one is varied to bring the determinant to zero for a solution: (1) the electron energy, (2) the barrier length, (3) the barrier height, and (4) the pre-barrier length. The solutions with a square barrier are sets of non-intersecting S-shaped lines in the four-parameter space. The solutions with a triangular barrier have the product of the propagation constant and the length of the pre-barrier region as integer multiples of two-pi radians. Only static solutions are considered, but this method could be applied to time-dependent cases under quasistatic conditions. Suggestions are given for the design and testing of prototypes.Comment: 11 pages, 2 tables, no figure

Apparatus for measuring high frequency currents

An apparatus for measuring high frequency currents includes a non-ferrous core current probe that is coupled to a wide-band transimpedance amplifier. The current probe has a secondary winding with a winding resistance that is substantially smaller than the reactance of the winding. The sensitivity of the current probe is substantially flat over a wide band of frequencies. The apparatus is particularly useful for measuring exposure of humans to radio frequency currents

An Algorithm for the Electromagnetic Scattering Due to an Axially Symmetric Body with an Impedance Boundary Condition

Let B be a body in R3, and let S denote the boundary of B. The surface S is described by S = {(x, y, z): (x2 + Y2)½= ƒ(z), -1≤ z ≤ I}, where ƒ analytic function that is real and positive on (-1, 1) and ƒ(±1) = 0. An algorithm is described for computing the scattered field due to a plane wave incident field, under Leontovich boundary conditions. The Galerkin method of solution used here leads to a block diagonal matrix involving 2M + 1 blocks, each block being of order 2(2N + 1). If, e.g., N = O(M2), the computed scattered field is accurate to within an error bounded by Ce-cN1 2 depending only on ƒ

A broadband THz receiver for low background space applications

We have developed a sensitive bolometric receiver for low background space applications. In a 10 percent bandwidth at 1 THz, this receiver is approximately 100 times more sensitive than a quantum limited heterodyne receiver with a 1 GHz IF bandwidth. This receiver is designed to be used for the long wavelength band (200-700 microns) in the MIPS instrument on NASA's SIRTF satellite. The bolometers are cooled to 100 mK by an adiabatic demagnetization refrigerator. Roughly 60 g of cesium chrome alum salt is partially demagnetized to 100 mK, followed by a slow regulated downramp to compensate for the heat leak. The hold time of the ADR system is about 18 hours with a temperature stability of delta T(sub rms) approx. equals 10 micro-K. The composite bolometers have electrical responsivities of 10(exp 9)V/W and electrical NEP's of about 3x10(exp -17) W/square root of Hz. The bolometer signals are read out by JFET preamplifiers located on the helium plate and operated at 120 K. We have addressed a number of space qualification issues, such as the development of an analog magnet controller, construction of a cryogenic shake-table for bolometers and selection of the paramagnetic salt CCA which can survive a bakeout at 50 C. The receiver is scheduled to be flown in the spring of 1992 on a balloon telescope. This flight has a dual purpose. One is to provide realistic test of the capabilities of the new receiver. The other is to search for anisotropies in the cosmic microwave background on scales of a few degrees