Particle production in Au+Au collisions has been measured in the PHOBOS experiment at RHIC for a range of collision energies. Three empirical observations have emerged from this dataset which require theoretical examination. First, there is clear evidence of limiting fragmentation. Namely, particle production in central Au + Au collisions, when expressed as dN/d{eta}{prime} ({eta}{prime} {triple_bond} {eta} - y{sub beam}), becomes energy independent at high energy for a broad region of {eta}{prime} around {eta}{prime} = 0. This energy-independent region grows with energy, allowing only a limited region (if any) of longitudinal boost-invariance. Second, there is a striking similarity between particle production in e{sup +}e{sup -} and Au + Au collisions (scaled by the number of participating nucleon pairs). Both the total number of produced particles and the longitudinal distribution of produced particles are approximately the same in e{sup +}e{sup -} and in scaled Au + Au. This observation was not predicted and has not been explained. Finally, particle production has been found to scale approximately with the number of participating nucleon pairs for <N{sub part}> > 65. This scaling occurs both for the total multiplicity and for high p{sub T} particles (3 < p{sub T} < 4.5 GeV/c).

The effects of opacity of the nuclei together with a blackbody type of emission along the system history are considered as a means to explain the ratio R{sub out}/R{sub sid} observed by STAR and PHENIX collaborations at RHIC. Within our model, no flow is required to explain the data trend of this ratio for large surface emissivities.

We show that an observable fraction of the measured elliptic flow may originate in classical gluon fields at the initial stage of a peripheral high-energy nuclear collision. This mechanism complements the contribution of late stage mechanisms, such as those described by hydrodynamics, to the observed elliptic flow.

The PHOBOS experiment at RHIC has measured the multiplicity of primary charged particles as a function of centrality and pseudorapidity in Au+Au collisions at {radical}(s{sub NN}) = 19.6, 130 and 200 GeV. Two observations indicate universal behavior of charged particle production in heavy ion collisions. The first is that forward particle production, over a range of energies, follows a universal limiting curve with a non-trivial centrality dependence. The second arises from comparisons with pp/{bar p}p and e{sup +}e{sup -} data. <N{sub ch}>/<N{sub part}/2> in nuclear collisions at high energy scales with {radical}s in a similar way as N{sub ch} in e{sup +}e{sup -} collisions and has a very weak centrality dependence. These features may be related to a reduction in the leading particle effect due to the multiple collisions suffered per participant in heavy ion collisions.

We have investigated the flash of light that accompanies laser damage using time-resolved spectroscopy. Damage events were initiated in the bulk of DKDP and fused silica with 355-nm, 3-ns pulsed radiation. Spectra from the accompanying flash were recorded in the 200-500 nm wavelength range with 10-ns temporal resolution. Ten ns following damage initiation, the spectra were found to be roughly blackbody with temperatures on the order of 5000-7000 K. The observed temperatures and cooling rates can be related to the size and electron density of the plasma ''fireball'' that initiates the damage event.

The PHOBOS experiment at RHIC has measured the multiplicity of primary charged particles as a function of centrality and pseudorapidity in Au+Au collisions at {radical}(s{sub NN}) = 19.6, 130 and 200 GeV. Two kinds of universal behavior are observed in charged particle production in heavy ion collisions. The first is that forward particle production, over a range of energies, follows a universal limiting curve with a non-trivial centrality dependence. The second arises from comparisons with pp/{bar p}p and e{sup +}e{sup -} data. <N{sub ch}>/<N{sub part}/2> in nuclear collisions at high energy scales with {radical}s in a similar way as N{sub ch} in e{sup +}e{sup -} collisions and has a very weak centrality dependence. This feature may be related to a reduction in the leading particle effect due to the multiple collisions suffered per participant in heavy ion collisions.

The inner-shell photo-ionization (ISPI) scheme requires photon energies at least high enough to photo-ionize the K-shell. {approx}286 eV, in the case of carbon. As a consequence of the higher cross-section, the inner-shell are selectively knocked out, leaving a hole state 1s2s{sup 2}2p{sup 2} in the singly charged carbon ion. This generates a population inversion to the radiatively connected state 1s{sup 2}2s{sup 2}2p in C+, leading to gain on the 1s-2p transition at 45 {angstrom}. The resonant character of the lasing transition in the single ionization state intrinsically allows much higher quantum efficiency compared to other schemes. Competing processes that deplete the population inversion include auto-ionization, Auger decay, and in particular collisional ionization of the outer-shell electrons by electrons generated during photo-ionization. These competing processes rapidly quench the gain. Consequently, the pump method must be capable of populating the inversion at a rate faster than the competing processes. This can be achieved by an ultra-fast, high intensity laser that is able to generate an ultra-fast, bright x-ray source. With current advances in the development of high-power, ultra-short pulse lasers it is possible to realize fast x-ray sources based that can deliver powerful pulses of light in the multiple hundred terawatt regime …

EUVE and the ROSAT WFC have left a tremendous legacy in astrophysics at EUV wavelengths. More recently, Chandra and XMM-Newton have demonstrated at X-ray wavelengths the power of high-resolution astronomical spectroscopy, which allows the identification of weak emission lines, the measurement of Doppler shifts and line profiles, and the detection of narrow absorption features. This leads to a complete understanding of the density, temperature, abundance, magnetic, and dynamic structure of astrophysical plasmas. However, the termination of the EUVE mission has left a gaping hole in spectral coverage at crucial EUV wavelengths ({approx}100-300 {angstrom}), where hot (10{sup 5}-10{sup 8} K) plasmas radiate most strongly and produce critical spectral diagnostics. CHIPS will fill this hole only partially as it is optimized for diffuse emission and has only moderate resolution (R {approx} 150). For discrete sources, we have successfully flown a follow-on instrument to the EUVE spectrometer (A{sub eff} {approx} 1 cm{sup 2}, R {approx} 400), the high-resolution spectrometer J-PEX(A{sub eff} {approx} 3 cm{sup 2}, R {approx} 3000). Here we build on the J-PEX prototype and present a strawman design for an orbiting spectroscopic observatory, APEX, a SMEX-class instrument containing a suite of 8 spectrometers that together achieve both high effective area (A{sub …

Two different cell chemistries, Gen 1 and Gen 2, were subjected to accelerated aging experiments. In Gen 1 calendar life experiments, useful cell life was strongly affected by temperature and time. Higher temperature accelerated cell performance degradation. The rates of impedance increase and power fade followed simple laws based on a power of time and Arrhenius kinetics. The data have been modeled using these two concepts, and the calculated data agree well with the experimental values. The Gen 1 calendar life increase and power fade data follow (time){sup 1/2} kinetics. This may be due to solid electrolyte interface (SEI) layer growth. From the cycle life experiments, the impedance increase data follow (time){sup 1/2} kinetics also, there is an apparent change in overall power fade mechanism, from 3% to 6% {Delta}SOC. Here, the power of time changes to a value less than 0.5 indicating that the power fade mechanism is due to factors more complex than just SEI layer growth. The Gen 2 calendar and cycle life experiments show the effect of cell chemistry on kinetics. The calendar life impedance data follow either ''linear'' or (time){sup 1/2} plus linear kinetics, depending on time and temperature.

I compute the first viscous correction to the thermal distribution function. With this correction, I calculate the effect of viscosity on spectra, elliptic flow, and HBT radii. Indicating the breakdown of hydrodynamics, viscous corrections become of order one for 1.5GeV. Viscous corrections to HBT radii are particularly large and reduce the outward and longitudinal radii. This reduction is a direct consequence of the reduction in longitudinal pressure.

The effects of opacity of the nuclei together with a blackbody type of emission along the system history are considered as a means to explain the ratio R{sub out}/R{sub sid} observed by STAR and PHENIX collaborations at RHIC. Within our model, no flow is required to explain the data trend of this ratio for large surface emissivities.