Fifty-one full-length major histocompatibility complex class II alleles in the olive baboon (Papio anubis).

Here we report 51 novel major histocompatibility complex (MHC) class II alleles in a group of related olive baboons.

Novel DRA alleles extracted from seven macaque cohorts.

In this document, we report the detection of 37 DRA alleles in macaque cohorts.

Compression of subrelativistic space-charge-dominated electron bunches for single-shot femtosecond electron diffraction.

We demonstrate the 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 by inverting the positive space-charge-induced velocity chirp. This inversion is induced by the oscillatory longitudinal electric field of a 3 GHz radio-frequency cavity. The arrival time jitter is measured to be 80 fs.

Laser wakefield acceleration: the injection issue. Overview and latest results.

External injection of electron bunches into laser-driven plasma waves so far has not resulted in 'controlled' acceleration, i.e. production of bunches with well-defined energy spread. Recent simulations, however, predict that narrow distributions can be achieved, provided the conditions for properly trapping the injected electrons are met. Under these conditions, injected bunch lengths of one to several plasma wavelengths are acceptable. This paper first describes current efforts to demonstrate this experimentally, using state-of-the-art radio frequency technology. The expected charge accelerated, however, is still low for most applications. In the second part, the paper addresses a number of novel concepts for significant enhancement of photo-injector brightness. Simulations predict that, once these concepts are realized, external injection into a wakefield accelerator will lead to accelerated bunch specs comparable to those of recent 'laser-into-gasjet' experiments, without the present irreproducibility of charge and final energy of the latter.

How to realize uniform three-dimensional ellipsoidal electron bunches.

Uniform three-dimensional ellipsoidal distributions of charge are the ultimate goal in charged particle accelerator physics because of their linear internal force fields. Such bunches remain ellipsoidal with perfectly linear position-momentum phase space correlations in any linear transport system. We present a method, based on photoemission by radially shaped femtosecond laser pulses, to actually produce such bunches.

Nonlinear electrostatic emittance compensation in kA, fs electron bunches.

Nonlinear space-charge effects play an important role in emittance growth in the production of kA electron bunches with a bunch length much smaller than the bunch diameter. We propose a scheme employing the radial third-order component of an electrostatic acceleration field, to fully compensate the nonlinear space-charge effects. This results in minimal transverse root-mean-square emittance. The principle is demonstrated using our design simulations of a device for the production of high-quality, high-current, subpicosecond electron bunches using electrostatic acceleration in a 1 GV/m field. Simulations using the GPT code produce a bunch of 100 pC and 73 fs full width at half maximum pulse width, resulting in a peak current of about 1.2 kA at an energy of 2 MeV. The compensation scheme reduces the root-mean-square emittance by 34% to 0.4pi mm mrad.

Small-angle approximation in the description of radiative collective effects within an ultrarelativistic electron bunch.

The problem of the evaluation of radiative collective effects accompanying accelerated motion of a short ultrarelativistic electron bunch in vacuum is considered within the framework of the small-angle approximation; second order expansion in the transverse velocity of electrons is performed in order to obtain an analytical expression for energy spread within the bunch. Comparison with earlier results by other authors shows good agreement.

Structure of nickel layers in ni-C multilayer coatings: influence of annealing.

The structure of Ni-C multilayer and single nickel layer samples has been analyzed before and after annealing, using two techniques: fluorescence EXAFS (F1EXAFS) at the Ni-K. edge and CuKα reflection. Annealing at a temperature of 450°C resulted in a change in the structure of the nickel layers from amorphous like to crystalline like. A reduction of the Bragg reflectivity by a factor of 7 was also found. Comparison between the EXAFS data of the annealed sample and of a nickel foil show a difference in the amplitude of the EXAFS. This is ascribed to a non-Gaussian atomic distribution of the backscattering atoms in the annealed sample around their average positions, whereas the atomic distribution in the (polycrystalline) Ni foil is a Gaussian one. From the annealing experiments we conclude that no irreversible changes take place in the structure of the nickel layers at temperatures below 200°C.

Characterization of a Multilayer Coated Laminar Reflection Grating at λ = 0.154 nm.

A laminar grating of 1200 1/mm was coated with an x-ray reflecting multilayer coating. The multilayer coating consisted of 41 alternating layers of ReW and C having a period of 2.3 nm. In this paper we report on diffraction measurements of the coated grating at the CuKα emission line. We describe its reflection behavior using a simple theoretical model and derive two diffraction conditions, corresponding to the grating relation and the Bragg law, for which peak intensities are to be observed. We find that grating order efficiencies are modulated by the multilayer reflection.

Soft X-Ray Emission of Laser-Produced Plasmas: Comparison for 30-ps and 20-ns Laser Pulses.

Soft x-ray emission spectra (250-875 eV) are presented for plasmas, produced by picosecond and nanosecond frequency-doubled Nd:YAG-glass laser pulses incident on 14 different target materials. The emitted spectra have been corrected for various apparatus functions which enables a direct comparison between plasmas produced by pico- and nanosecond laser pulses. The relative integrated emission intensity as a function of Z number, obtained from the corrected spectra, shows an oscillatory behavior, with distinct maxima for those elements exhibiting a dominant line emission in our photon energy window. We found for our two pulse lengths an approximately equal conversion efficiency from laser light into x-ray photons. General suggestions are given as to what target material should be used for different applications using the laser plasma as x-ray source in the energy range Studied.