Theoretical and material studies on thin-film electroluminescent devices

A theoretical study of resonant tunneling in multilayered heterostructures is presented based on an exact solution of the Schroedinger equation under the application of a constant electric field. By use of the transfer matrix approach, the transmissivity of the structure is determined as a function of the incident electron energy. The approach presented is easily extended to many layer structures where it is more accurate than other existing transfer matrix or WKB models. The transmission resonances are compared to the bound state energies calculated for a finite square well under bias using either an asymmetric square well model or the exact solution of an infinite square well under the application of an electric field. The results show good agreement with other existing models as well as with the bound state energies. The calculations were then applied to a new superlattice structure, the variablly spaced superlattice energy filter, (VSSEP) which is designed such that under bias the spatial quantization levels fully align. Based on these calculations, a new class of resonant tunneling superlattice devices can be designed

Using Multiple RISC CPUs in Parallel to Study Charm Quarks

We have integrated a system of 16 RISC CPUs to help reconstruct and analyze a 1.3 Terabyte data set of 400 million high energy physics interactions. These new CPUs provided an affordable means of processing a very large data set. The data was generated using a hadron beam and a fixed target at Fermilab Experiment 769. Signals were recorded on tape from particles created in or decaying near the target and passing though a magnetic spectrometer. Because all the interactions were independent, each CPU could completely reconstruct any interaction without reference to other CPUs. Problems of this sort are ideal for multiple processors. In the offline reconstuction system, we used Exabyte 8mm video tape drives with an I/O capacity of 7 Terabytes per year and a storage capacity of 2.3 Gigabytes per tape. This reduced tape mounts to one or two per day rather than one or two per hour as would be the case with 9-track tapes. The ETHERNET network used to link the CPUs and has an I/O capacity of 15 Terabytes per year. The RISC CPUs came in the form of commercially supported workstations with little memory and no graphics to minimize cost. Each 25 MHz MIPS R3000 RISC CPU processed data 20 times faster than 16MHz Motorola 68020 CPUs that were also used. About 8000 hours of processing was needed to reconstruct the data set. A sample of thousands of fully reconstructed particles containing a charm quark has been produced.Comment: 19 pages, 3 figures, LaTe

Theoretical and material studies on thin-film electroluminescent devices

During this report period work was performed on the modeling of High Field Electronic Transport in Bulk ZnS and ZnSe, and also on the surface cleaning of Si for MBE growth. Some MBE growth runs have also been performed in the Varian GEN II System. A brief outline of the experimental work is given. A complete summary will be done at the end of the next reporting period at the completion of the investigation. The theoretical studies are included

Sensitivity of 8B breakup cross section to projectile structure in CDCC calculations

Given the Astrophysical interest of $^7$Be$(p,\gamma)^8$B, there have been several experiments applying the Coulomb dissociation method for extracting the capture rate. Measurements at Michigan State are dominated by $E1$ contributions but have a small $E2$ component. On the other hand, a lower energy measurement at Notre Dame has a much stronger $E2$ contribution. The expectation was that the two measurements would tie down the $E2$ and thus allow for an accurate extraction of the $E1$ relevant for the capture process. The aim of this brief report is to show that the $E2$ factor in breakup reactions does not translate into a scaling of the $E2$ contribution in the corresponding capture reaction. We show that changes to the $^8$B single particle parameters, which are directly related to the $E2$ component in the capture reaction, do not effect the corresponding breakup reactions, using the present reaction theory.Comment: 4 pages, 6 figures, revtex

Transonic wind-tunnel tests of an F-8 airplane model equipped with 12 and 14-percent thick oblique wings

An experimental investigation was conducted in the Ames 14-foot transonic wind tunnel to study the aerodynamic performance and stability characteristics of a 0.087-scale model of an F-8 airplane fitted with an oblique wing. Two elliptical planform (axis ratio = 8:1) wings, each having a maximum thickness of 12 and 14 percent, were tested. Longitudinal stability data were obtained with no wing and with each of the two wings set at sweep angles of 0, 45, and 60 deg. Lateral directional stability data were obtained for the 12 percent wing only. Test Mach numbers ranged from 0.6 to 1.2 in the unit Reynolds number range from 11.2 to 13.1 million per meter. Angles of attack were between -6 and 22 deg at zero sideslip. Angles of sideslip were between -6 and +6 deg for two angles of attack, depending upon the wing configuration