New electron source concept for single-shot sub-100 fs electron diffraction in the 100 keV range

We present a method for producing sub-100 fs electron bunches that are suitable for single-shot ultrafast electron diffraction experiments in the 100 keV energy range. A combination of analytical results and state-of-the-art numerical simulations show that it is possible to create 100 keV, 0.1 pC, 20 fs electron bunches with a spotsize smaller than 500 micron and a transverse coherence length of 3 nm, using established technologies in a table-top set-up. The system operates in the space-charge dominated regime to produce energy-correlated bunches that are recompressed by established radio-frequency techniques. With this approach we overcome the Coulomb expansion of the bunch, providing an entirely new ultrafast electron diffraction source concept

Study of high-speed angular-contact ball bearings under dynamic load

Research program studies behavior of specific high-speed, angular-contact ball bearings. Program is aimed at detailed investigation of ball-separator behavior and lubrication surface-finish effects in a specific gyro wheel

A New Limit on the Antiproton Lifetime

Measurements of the cosmic ray pbar/p ratio are compared to predictions from an inhomogeneous disk-diffusion model of pbar production and propagation within the Galaxy, combined with a calculation of the modulation of the interstellar cosmic ray spectra as the particles propagate through the heliosphere to the Earth. The predictions agree with the observed pbar/p spectrum. Adding a finite pbar lifetime to the model, we obtain the limit tau_pbar > 0.8 Myr (90 % C.L.).Comment: 13 pages, 3 encapsulated Postscript figures, uses AASTeX; accepted by Astrophysical Journal; minor change

Compression of sub-relativistic space-charge-dominated electron bunches for single-shot femtosecond electron diffraction

We demonstrate compression of 95 keV, space-charge-dominated electron bunches to sub-100 fs durations. These bunches have sufficient charge (200 fC) and are of sufficient quality to capture a diffraction pattern with a single shot, which we demonstrate by a diffraction experiment on a polycrystalline gold foil. Compression is realized by means of velocity bunching as a result of a velocity chirp, induced by the oscillatory longitudinal electric field of a 3 GHz radio-frequency cavity. The arrival time jitter is measured to be 80 fs

Search for muonic decays of the antiproton at the Fermilab Antiproton Accumulator

A search for antiproton decay has been made at the Fermilab Antiproton Accumulator. Limits are placed on six antiproton decay modes which contain a final-state muon. At the 90% C.L. we find that tau/B(mu gamma) > 5.0 x 10^4 yr, tau/B(mu pi0) > 4.8 x 10^4 yr, tau/B(mu eta) > 7.9 x 10^3 yr, tau/B(mu gamma gamma) > 2.3 x 10^4 yr, tau/B(mu K0S > 4.3 x 10^3 yr, and tau/B(mu K0L) > 6.5 x 10^3 yr.Comment: 8 pages + 3 Postscript figure

Juvenile Finfish and Blue Crab Stock Assessment Program Bottom Trawl Survey annual data report series, volume 1991

This report presents a summary page for each tow conducted by the Virginia Institute of Marine Science, Juvenile Fish and Blue Crab Trawl Survey during 1991. The sampling methods and summarized data are presented in Bonzek et al. (1992). Data analysis and calculations of juvenile indices for selected species are presented in Colvocoresses et al. (1991). The purpose of this report is simply to provide a hard copy record of trawl results. It also provides a method to retrieve information about one or several particular trawls without consulting computerized archives. · · All data about each tow are presented, except that length data are summarized to number measured, minimum size, maximum size, mean size, and standard error. Each page contains four major subsections:: Station Data, Atmospheric and Hydrographic Data, Comments; and Catch Summa:ry Data. Each subsection is further divided into groups of related data, such as Station Identification Data or Atmospheric Data

Search for antiproton decay at the Fermilab Antiproton Accumulator

A search for antiproton decay has been made at the Fermilab Antiproton Accumulator. Limits are placed on thirteen antiproton decay modes. The results include the first explicit experimental limits on the muonic decay modes of the antiproton, and the first limits on the decay modes e- gamma gamma, and e- omega. The most stringent limit is for the decay mode pbar-> e- gamma. At 90% C.L. we find that tau/B(pbar-> e- gamma) > 7 x 10^5 yr. The most stringent limit for decay modes with a muon in the final state is for the decay pbar-> mu- gamma. At 90% C.L. we find that tau/B(pbar-> mu- gamma) > 5 x 10^4 yr.Comment: 20 pages, 8 figures. Submitted to Phys. Rev. D. Final results on 13 channels (was 15) are presente

Juvenile Finfish and Blue Crab Stock Assessment Program Bottom Trawl Survey Annual Data Summary Report Series Volume 1990

This report summarizes data collected by the Virginia Institute of Marine Science (VIMS) monthly trawl survey cruises for January through December, 1990. The trawl survey is a long term, broad scope monitoring program. Its primary goal is to produce annual indices of juvenile (young-of-year) abundance of commercially, recreationally and ecologically important marine and estuarine finfish and crustaceans. The objective is to provide indices of sufficient accuracy and precision for· both immediate resource !fianagement needs and long-term understanding of environmental influences on fishery resources. A second important product of this effort is the documentation and monitoring of habitat utilization by juveniles and smaller adults of these species. The program also provides a sound framework for the procurement of biological samples for life history studies and other concurrent scientific investigations relevant to fishery resource management. At present the program consists of a monthly random stratified design survey of the lower Chesapeake Bay initiated in 1988 (Chittenden, 1989) and fixed station mid-channel transects in each of the three major Virginia tributaries: the York, James, and Rappahannock rivers (Wojcik and Van Engel, 1988a, 1988b, 1989). The river survey is based upon a sampling program initiated in 1955 ( a random stratified design was used from 1973-79). Changes in gear type and sampling methods used over the history of the river survey are summarized in Figure 1. The following tables and figures include data for all finfish species and blue crabs caught during 1990. Data are also presented showing station locations and showing the atmospheric and hydrographic data collected at each station

Heavy quark production via leptoquarks at a neutrino factory

The proposed neutrino factory (NF) based on a muon storage ring (MSR) is an ideal place to look for heavy quark production via neutral current (NC) and charged current (CC) interactions. In this article, we address the issue of contribution coming from mediating leptoquarks (LQ) in $\nu_\mu (\bar\nu_e)-{\rm N}$ interactions leading to the production of $b(\bar b)$ at a MSR and investigate the region where LQ interactions are significant in the near-site experiments.Comment: 12 pages latex, 10 ps figures, uses axocolour.sty, Slightly revised version to appear in PR

Floquet theory of neutrino oscillations in the earth

We review the Floquet theory of linear differential equations with periodic coefficients and discuss its applications to neutrino oscillations in matter of periodically varying density. In particular, we consider parametric resonance in neutrino oscillations which can occur in such media, and discuss implications for oscillations of neutrinos traversing the earth and passing through the earth's core.Comment: LaTeX, 28 pages, 8 eps figures. Contribution to the special issue of Yad. Fiz. dedicated to the memory of A.B. Migda