Search results for "Collimated light"

Focal Length Measuring Technique Using The Talbot Effect

1987

The Talbot effect - or self-imaging phenomenon - is applied to the measurement of focal lengths. The technique only requires axial distances to be measured and is suitable for both converging and diverging thick lenses.

Collimation for CLIC

2003

The collimation system of the Compact Linear Collider (CLIC) must fulfil a number of conflicting requirements, namely it should (1) remove beam halo to reduce the detector background, (2) provide a minimum distance between collimators and collision point for muon suppression, (3) ensure collimator survival and machine protection against errand beam pulses, (4) not be excessively long, and (5) not amplify incoming trajectory fluctuations via the collimator wake fields. Two optical systems have been designed — the first linear, the second non‐linear —, which promise to meet all these requirements for the design beam energy of 1.5 TeV. We decribe the various design criteria, a preliminary perf…

Improved determination of the β−ν¯e angular correlation coefficient a in free neutron decay with the aSPECT spectrometer

2020

We report on a precise measurement of the electron-antineutrino angular correlation ($a$ coefficient) in free neutron beta-decay from the $a$SPECT experiment. The $a$ coefficient is inferred from the recoil energy spectrum of the protons which are detected in 4$\pi$ by the $a$SPECT spectrometer using magnetic adiabatic collimation with an electrostatic filter. Data are presented from a 100 days run at the Institut Laue Langevin in 2013. The sources of systematic errors are considered and included in the final result. We obtain $a = -0.10430(84)$ which is the most precise measurement of the neutron $a$ coefficient to date. From this, the ratio of axial-vector to vector coupling constants is …

A large proportional drift chamber with two-dimensional read-out

1976

Abstract The construction and performance of a large drift chamber are described, which has a sensitive area of 5 m2 and an average chamber thickness of 0.55 × 10−3 radiation lengths. Simultaneous sense wire- and high voltage read-out gives a good time correlation with ajitter of 2.0 ns fwhm. Measurements with a collimated radioactive α-sources resulted in a time resolution of 4.3 ns fwhm corresponding to a space resolution of 0.20 mm fwhm at the sense wire. The space resolution at the high voltage plane is about 25 mm fwhm.

Collimation of Target Induced Halo Following MAGIX at MESA

2019

The Mainz Energy-recovering Superconducting Accelerator (MESA) will be an electron accelerator allowing operation in energy-recovery linac (ERL) mode. It provides the opportunity to operate scattering experiments at energies of ~100 MeV with thin gas-targets. The MESA Internal Gas Target Experiment (MAGIX) aims to operate windowless jet targets and different gases up to Xenon to search for possible dark photon interactions, to precisely measure the magnetic proton radius and astrophysical S-factors. Investigations on the impact of the target on beam dynamics and beam losses are required for machine safety and to examine limits to ERL operation. The goal of this work is to understand target …

On the Origin of the X-Ray Emission in Protostellar Jets Close to the Launching Site

2019

Observations of stellar jets show evidence of X-ray emitting shocks close to the launching site. In some cases, the shocked features appear to be stationary (e.g. HH 154 and DG Tau). We aim at investigating the origin of X-ray emission and the effect of perturbations in X-ray emitting stationary shocks in stellar jets. We performed a set of 2.5-dimensional MHD numerical simulations modelling supersonic pulsed jets ramming into a magnetized medium, exploring different parameters for the model. We consider two cases: a jet less dense than the ambient medium (HH 154), and a jet denser than the ambient (DG Tau). In both cases, we found that the jet is collimated by the magnetic field forming a …

Numerical study of emission and dynamics from a TDE-powered jet

2012

A transient event Swift J1644+57 is thought to be caused by the emission from a collimated relativistic jet. The jet, powered by the sudden onset of accretion onto a supermassive black hole following the tidal disruption of a star, collides with the gaseous circumnuclear medium and produces forward and reverse shocks which emit synchrotron radiation. We perform 1D and 2D relativistic hydrodynamic simulations using the MRGENESIS code. The aim of the simulations is to study the dynamics of a jet thought to exist in transient events such as Swift J1644+57, as discussed in recent literature. We discuss 1D and 2D jet evolution, on-axis radio light curves and differences between 1D and 2D jet dyn…

Dielectric Collimators for Beam Delivery Systems*

2012

Abstract Wakefield generation by the collimation system is known to be a critical linear collider design issue. Optimization of the collimators represents a tradeoff between beam quality (halo reduction) and luminosity reduction. The primary objective is to reduce both short range (resonant) and long range (resistive) deflecting wakefields from collimators that reduce the luminosity of the machine. We consider the CLIC BDS (beam delivery system) and examine the potential for using dielectric rather than highly conducting materials for collimation. We present some examples of the flexibility gained by having control over the permittivity and conductivity of the collimator. We discuss simulation …

2017

Accretion dynamics in the formation of young stars is still a matter of debate because of limitations in observations and modeling. Through scaled laboratory experiments of collimated plasma accretion onto a solid in the presence of a magnetic field, we open a first window on this phenomenon by tracking, with spatial and temporal resolution, the dynamics of the system and simultaneously measuring multiband emissions. We observe in these experiments that matter, upon impact, is ejected laterally from the solid surface and then refocused by the magnetic field toward the incoming stream. This ejected matter forms a plasma shell that envelops the shocked core, reducing escaped x-ray emission. T…

Enhancement of the linear polarization of coherent bremsstrahlung by collimation of the photon beam

1998

A method is described to precisely predict the relative intensities and degrees of linear polarization of coherent bremsstrahlung from diamond crystals, taking into account the collimation of the photon beam and the lateral distribution and angular divergence of the electron beam in addition to the properties of the crystal. It is confirmed that the increase of the degree of linear polarization through collimation of the photon beam is a sizable effect. Compared to previous approaches considerable progress has been made in reproducing the experimentally observed relative intensities of collimated coherent bremsstrahlung, by taking into account the angular distribution of coherent bremsstrah…