The effects of electron and proton radiation on GaSb infrared solar cells

Gallium antimonide (GaSb) infrared solar cells were exposed to 1 MeV electrons and protons up to fluences of 1 times 10(exp 15) cm (-2) and 1 times 10(exp 12) cm (-2) respectively. In between exposures, current voltage and spectral response curves were taken. The GaSb cells were found to degrade slightly less than typical GaAs cells under electron irradiation, and calculations from spectral response curves showed that the damage coefficient for the minority carrier diffusion length was 3.5 times 10(exp 8). The cells degraded faster than GaAs cells under proton irradiation. However, researchers expect the top cell and coverglass to protect the GaSb cell from most damaging protons. Some annealing of proton damage was observed at low temperatures (80 to 160 C)

Design comparison of cesium and potassium vapor turbine-generator units for space power

Design comparison of cesium and potassium vapor turbogenerator units for space power plant

Tandem concentrator solar cells with 30 percent (AMO) power conversion efficiency

Very high efficiency concentrator solar panels are envisioned as economical and reliable electrical power subsystems for space based platforms of the future. GaAs concentrator cells with very high efficiencies and good sub-bandgap transmissions can be fabricated on standard wafers. GaSb booster cell development is progressing very well; performance characteristics are still improving dramatically. Consistent GaAs/GaSb stacked cell AMO efficiencies greater than 30 percent are expected

The decay law can have an irregular character

Within a well-known decay model describing a particle confined initially within a spherical $\delta$ potential shell, we consider the situation when the undecayed state has an unusual energy distribution decaying slowly as $k\to\infty$; the simplest example corresponds to a wave function constant within the shell. We show that the non-decay probability as a function of time behaves then in a highly irregular, most likely fractal way.Comment: 4 pages, 3 eps figure

Advanced photovoltaic power systems using tandem GaAs/GaSb concentrator modules

In 1989, Boeing announced the fabrication of a tandem gallium concentrator solar cell with an energy conversion efficiency of 30 percent. This research breakthrough has now led to panels which are significantly smaller, lighter, more radiation resistant, and potentially less expensive than the traditional silicon flat plate electric power supply. The new Boeing tandem concentrator (BTC) module uses an array of lightweight silicone Fresnel lenses mounted on the front side of a light weight aluminum honeycomb structure to focus sunlight onto small area solar cells mounted on a thin back plane. This module design is shown schematically. The tandem solar cell in this new module consists of a gallium arsenide light sensitive cell with a 24 percent energy conversion efficiency stacked on top of a gallium antimonide infrared sensitive cell with a conversion efficiency of 6 percent. This gives a total efficiency 30 percent for the cell-stack. The lens optical efficiency is typically 85 percent. Discounting for efficiency losses associated with lens packing, cell wiring, and cell operating temperature still allows for a module efficiency of 22 percent which leads to a module power density of 300 Watts/sq. m. This performance provides more than twice the power density available from a single crystal silicon flat plate module and at least four times the power density available from amorphous silicon modules. The fact that the lenses are only 0.010 ft. thick and the aluminum foil back plane is only 0.003 ft. thick leads to a very lightweight module. Although the cells are an easy to handle thickness of 0.020 ft., the fact that they are small, occupying one-twenty-fifth of the module area, means that they add little to the module weight. After summing all the module weights and given the high module power, we find that we are able to fabricate BTC modules with specific power of 100 watts/kg

Probing coherent charmonium photoproduction off light nuclei at medium energies

We demonstrate how the elementary amplitudes $\gamma N\to \Psi N$, the amplitude of the nondiagonal $J/\psi N\Leftrightarrow \psi' N$ transition, and the total $J/\psi N$ and $\psi' N$ cross sections can be determined from measurements of the coherent $J/\psi$ and $\psi'$ photoproduction off light nuclei at moderate energies. For this purpose we provide a detailed numerical analysis of the coherent charmonium photoproduction off silicon within the generalized vector dominance model (GVDM) adjusted to account for the physics of charmonium models and color transparency phenomenon.Comment: 8 pages, 5 figures (color

Diffractive production and the total cross section in deep inelastic scattering

We explore the consequences for diffractive production, gamma* p --> X p, in deep inelastic scattering at low values of x\sim Q^2/W^2 <<1 that follow from our recent representation of the total photoabsorption cross section, sigma_{gamma* p}, in the generalized vector dominance/ color dipole picture(GVD/CDP) that is based on the generic structure of the two-gluon-exchange from QCD. Sum rules are derived that relate the transverse and the longitudinal (virtual) photoabsorption cross section to diffractive forward production of q q-bar states that carry photon quantum numbers ("elastic diffraction"). Agreement with experiment in the W^2 and Q^2 dependence is found for M_X^2/Q^2<<1, where M_X is the mass of the produced system X. An additional component ("inelastic diffraction"), not actively contributing to the forward Compton amplitude, is needed for diffractive production at high values of M_X. Our previous theoretical representation of the total photoabsorption cross section sigma_{gamma* p}=sigma_{gamma* p}(eta), in terms of the scaling variable eta=(Q^2+m_0^2)/Lambda^2(W^2) is extended to include the entire kinematic domain, x==0, where scaling in eta holds experimentally.Comment: 19 pages with 4 figures,(eps and ps files), Late

Signals for black body limit in coherent ultraperipheral heavy ion collisions

We argue that study of total cross section of photoabsorption and coherent photoproduction of $\rho,\rho^{\prime}$-mesons in ultraperipheral heavy ion collisions (UPC) is effective method to probe onset of black body limit(BBL) in the soft and hard QCD interactions. We illustrate the expected features of the onset of BBL using generalized vector dominance model. We show that this model describes very well $\rho$-meson coherent photoproduction at $6 \leq E_{\gamma} \leq 10 GeV$. In the case of $\rho$-meson production we find a UPC cross section which is a factor $\sim 1.5$ larger than the one found by Klein and Nystrand. The advantages of the process of coherent dijet production to probe onset of BBL in hard scattering regime where decomposition over the twists becomes inapplicable are explained and relative importance of the $\gamma +Pomeron$ and $\gamma +\gamma$ mechanisms is estimated.Comment: 17 pages, 7 figure

The Pomeron In Exclusive Vector Meson Production

An earlier developed model for vector meson photoproduction, based on a dipole Pomeron exchange, is extended to electroproduction. Universality of the non linear Pomeron trajectory is tested by fitting the model to ZEUS and H1 data as well as to CDF data on $\bar pp$ elastic scattering.Comment: 12 pages, 13 figure

Deep inelastic scattering and "elastic" diffraction

We examine the total cross section of virtual photons on protons, $\sigma_{\gamma^* p}(W^2,Q^2)$, at low $x \cong Q^2/W^2 \ll 1$ and its connection with ``elastic'' diffractive production $\gamma^*_{T,L}p \to X^{J=1}_{T,L} p$ in the two-gluon exchange dynamics for the virtual forward Compton scattering amplitude. Solely based on the generic structure of two-gluon exchange, we establish that the cross section is described by the (imaginary part of the) amplitude for forward scattering of $q \bar q$ vector states, $(q \bar q)^{J=1}_{T,L} p \to (q \bar q)^ {J=1}_{T,L} p$. The generalized vector dominance/color dipole picture (GVD/CDP) is accordingly established to only rest on the two-gluon-exchange generic structure. This is explicitly seen by the sum rules that allow one to directly relate the total cross section to the cross section for elastic diffractive forward production, $\gamma^*_{T,L} p\to (q \bar q)^{J=1}_{T,L} p$, of vector states.Comment: 24 pages, latex file with three eps figures. BI-TP 2002/2