The fourth international LTE opacity workshop and code comparison study, WorkOp-IV, was held in Madrid in 1997. Results of this workshop are summarized with a focus on iron opacities. In particular, the astrophysically important photon absorption region between 50 and 80 eV is emphasized for a sequence of iron plasmas at densities and temperatures that produce nearly the same average ionization stage (Z* {approximately} 8.6). Experimental data that addressed this spectral region is also reviewed.

The performance of transparent optics in high fluence applications is often dominated by inhomogeneities in the first few hundred nanometers of material. Defects undetectable with optical methods can cause catastrophic failures when used in critical applications where high strength, chemical or mechanical resistance or extreme smoothness is required. Not only are these defects substantially smaller than the wavelength of visible light, they are often concealed below a layer of glass-like material deposited during the polishing process. In high quality glass, the chemical and material properties of the outermost layer are modified by the grinding, lapping and polishing processes used in fabrication. Each succeeding step in a process is designed to remote damage from the previous operation. However, any force against the surface, no matter how slight will leave evidence of this damage. These processes invariably create dislocations, cracks and plastic deformation in the subsurface region.

Horizontal orbit errors at the sextuples in the Advanced Photon Source (APS) storage ring can cause changes in tune and modulation of the beta functions around the ring. To determine the significance of these effects requires knowing the orbit relative to the magnetic center of the sextuples. The method considered here to determine the horizontal beam position in a given sextupole is to measure the tune shift caused by a change in the sextupole strength. The tune shift and a beta function for the same plane uniquely determine the horizontal beam position in the sextupole. The beta function at the sextupole was determined by propagating the beta functions measured at nearby quadrupoles to the sextupole location. This method was used to measure the sextupole magnetic center offset relative to an adjacent beam position monitor (BPM) at a number of sextupole locations. We report on the successes and problems of the method as well as an improved method.

Synchrotron radiation interacting with the vacuum chamber walls in a storage ring produce photoelectrons that can be accelerated by the beam, acquiring sufficient energy to produce secondary electrons in collisions with the walls. If the secondary-electron yield (SEY) coefficient of the wall material is greater than one, as is the case with the aluminum chambers in the Advanced Photon Source (APS) storage ring, a runaway condition can develop. As the electron cloud builds up along a train of stored positron or electron bunches, the possibility exists that a transverse perturbation of the head bunch will be communicated to trailing bunches due to interaction with the cloud. In order to characterize the electron cloud, a special vacuum chamber was built and inserted into the ring. The chamber contains 10 rudimentary electron-energy analyzers, as well as three targets coated with different materials. Measurements show that the intensity and electron energy distribution are highly dependent on the temporal spacing between adjacent bunches and the amount of current contained in each bunch. Furthermore, measurements using the different targets are consistent with what would be expected based on the SEY of the coatings. Data for both positron and electron beams are presented.

The muon collider requires intense, cooled muon bunches to reach the required luminosity. Due to the limited life-time of the muon, the cooling process must take place very rapidly. Ionization cooling seems to be our only option, given the large emittances of the muon beam from pion decay. However, this ionization cooling method has been found quite difficult to implement in practice. We describe a scheme based on the use of liquid hydrogen absorbers fol-lowed by r.f. cavities (�pillbox� or �open iris� type), em-bedded in a transport lattice based on high field solenoids. These solenoidal fields are reversed periodically in order to suppress the growth of the canonical angular momentum. This channel has been simulated in detail with independent codes, featuring conventional tracking in e.m. fields and de-tailed simulation of multiple scattering and straggling in the the absorbers and windows. These calculations show that the 15 Tesla lattice cools in 6-Dphase space by a factor {approx} 2 over a distance of 20 m.

We present preliminary results on various aspects of charm baryon studies at the 1996-1997 fixed target experiment of Fermilab studying charm produced from incident {Sigma}{sup -}, proton, and {pi}{sub -} beams at 600 GeV. First results include the comparison of hadroproduction asymmetries for {Lambda}{sub c}{sup +} production from the 3 beams as well xF distributions and the first observation of the Cabbibo-suppressed decay {Xi}{sub c}{sup +} {yields} pK{sup -}{pi}{sup +}. The relative branching fraction of the Cabbibo-suppressed mode to the 3-body Cabbibo-favored modes is also presented.

Chromaticity control in the Fermilab Main Injector will be important both in accelerating protons and antiprotons from 8 GeV to 150 GeV (or 120 GeV) and in decelerating recycled 150 GeV antiprotons to 8 GeV for storage in the Recycler Ring. The Main Injector has two families of sextupoles to control the chromaticity. In addition to the natural chromaticity, they must correct for sextupole fields from ramp-rate-dependent eddy currents in the dipole beampipes and current-dependent sextupole fields in the dipole magnets. The horizontal sextupole family is required to operate in a bipolar mode below the transition energy of 20 GeV. We describe methods used to control chromaticities in the Fermilab Main Injector. Emphasis is given to the software implementation of the operator interface to the front-end ramp controllers. Results of chromaticity measurements and their comparison with the design model will be presented.

BTeV is a collider experiment at Fermilab designed for precision studies of CP violation and mixing. Unlike most collider experiments, the BTeV detector has a forward geometry that is optimized for the measurement of B and charm decays in a high-rate environment. While the rate of B production gives BTeV an advantage of almost four orders of magnitude over e{sup +} e{sup {minus}} B factories, the BTeV Level 1 trigger must be able to accept data at a rate of 100 Gigabytes per second, reconstruct tracks and vertices, trigger on B events with high efficiency, and reject minimum bias events by a factor of 100:1. An overview of the Level 1 trigger will be presented.

We describe methods used to measure and control tunes in the Fermilab Main Injector (FMI). Emphasis is given to software implementation of the operator interface, to the front-end embedded computer system, and handling of hysteresis of main dipole and quadrupole magnets. Techniques are developed to permit control of tune of the Main Injector through several acceleration cycles: from 8.9 GeV/c to 120 GeV/c, from 8.9 GeV/c to 150 GeV/c, and from 150 GeV/c to 8.9 GeV/c. Systems which automate the complex interactions between tune measurement and the variety of ramping options are described. Some results of tune measurements and their comparison with the design model are presented.

As a way to lower the cost of plastic scintillation detectors, commercially available polystyrene pellets have been used in the production of scintillating materials that can be extruded into different profiles. The selection of the raw materials is discussed. Two techniques to add wavelength shifting dopants to polystyrene pellets and to extrude plastic scintillating strips are described. Data on light yield and transmittance measurements are presented.

Measurements of the top quark mass and the t{bar t} production cross section, obtained by CDF and D0 Collaborations at the Tevatron, are presented. The methodology of analyses and their underlying assumptions are summarized. The CDF and D0 top mass averages, based on {approx}100 pb{sup -1} of data collected by each experiment in Run-I, and obtained from a set of selected measurements in several channels are M{sub t} = 176:0 {plus_minus} 4:0(stat) {plus_minus} 5:1(syst) GeV/c{sup 2} and M{sub t} = 172:1 {plus_minus} 5:2(stat) {plus_minus} 4:9(syst) GeV/c{sup 2} , respectively. The combined Tevatron top quark mass is M{sub t} = 174:3 {plus_minus}3:2(stat) {plus_minus}4:0(syst) GeV/c}sup 2} , where the correlations between CDF and D0 averages were taken into account. The CDF measurement of the t{bar t} cross section (assuming M{sub t} = 175 GeV/c{sup 2} ) is {sigma}{sub tt} = 7.6{sup 1.8}{sub 1.5} pb, and the D0 value (assuming M{sub t} = 172.1 GeV/c{sup 2} ) is {sigma}{sub tt} = 5:9 {plus_minus} 1:7 pb. In anticipation of the much increased statistics in Run-II, the fact that top quark physics is one of the best windows to new physics beyond the Standard Model is emphasized.

For physicists and engineers involved in the design and analysis of beamlines (transfer lines or insertions) the lattice function matching problem is central and can be time-consuming because it involves constrained nonlinear optimization. For such problems convergence can be difficult to obtain in general without expert human intervention. Over the years, powerful codes have been developed to assist beamline designers. The canonical example is MAD (Methodical Accelerator Design) developed at CERN by Christophe Iselin. MAD, through a specialized command language, allows one to solve a wide variety of problems, including matching problems. Although in principle, the MAD command interpreter can be run interactively, in practice the solution of a matching problem involves a sequence of independent trial runs. Unfortunately, but perhaps not surprisingly, there still exists relatively few tools exploiting the resources offered by modern environments to assist lattice designer with this routine and repetitive task. In this paper, we describe a fully interactive lattice matching program, written in C++ and assembled using freely available software components. An important feature of the code is that the evolution of the lattice functions during the nonlinear iterative process can be graphically monitored in real time; the user can dynamically interrupt the iterations …

A search for long-lived charged massive particles in CDF's Run1b data sample is presented. The search looks for highly ionizing tracks which would result from slowly moving massive particles. We search for strongly produced particles using a stable color triplet quark as a reference model, and a separate search was performed for weakly produced particles using long-lived sleptons in Gauge- Mediated Supersymmetry Breaking as a reference model. No excess over background was observed, and we derive limits on the cross-sections for production of these particles. Prospects for RunII are also discussed.