44 research outputs found
Experimental Determination of the Characteristics of a Positron Source Using Channeling
Numerical simulations and `proof of principle' experiments showed clearly the
interest of using crystals as photon generators dedicated to intense positron
sources for linear colliders. An experimental investigation, using a 10 GeV
secondary electron beam, of the SPS-CERN, impinging on an axially oriented
thick tungsten crystal, has been prepared and operated between May and August
2000. After a short recall on the main features of positron sources using
channeling in oriented crystals, the experimental set-up is described. A
particular emphasis is put on the positron detector made of a drift chamber,
partially immersed in a magnetic field. The enhancement in photon and positron
production in the aligned crystal have been observed in the energy range 5 to
40 GeV, for the incident electrons, in crystals of 4 and 8 mm as in an hybrid
target. The first results concerning this experiment are presented hereafter.Comment: 3 pages, 6 figures, submitted to Linac200
Prominence-cavity regions observed using SWAP 174A filtergrams and simultaneous eclipse flash spectra
Images from the SWAP (Proba 2 mission) taken at 174A in the Fe IX/X lines are
compared to simultaneous slitless flash spectra taken during the last solar
total eclipse of July, 11th 2010. Many faint low excitation emission lines
together with the HeI and HeII Paschen Alpha chromospheric lines are recorded
on eclipse spectra where regions of limb prominences are obtained with
space-borne imagers. We consider a deep flash spectrum obtained by summing 80
individual spectra to show the intensity modulations of the continuum.
Intensity depressions are observed around the prominences in both eclipse and
SWAP images. The prominence cavities are interpreted as a relative depression
of plasma density, produced inside the corona surrounding the prominences.
Photometric measurements are shown at different scales and different,
spectrally narrow, intervals for both the prominences and the coronal
background.Comment: 22 pages, 14 figures, accepted to publish in Sol. Phy
Identification of Neutral decaying particles from T.P.C. Track Elements with Fast Simulation
Effective positron source based on coherent radiation of relativistic electrons in crystal
Radiation-damage study of a monocrystalline tungsten positron converter
The exploitation of the enhancement of positron sources by channeling effects, in particular for Linear Colliders (LC), relies on the long term resistance of the crystal to radiation damage. Such dama ge has been tested on a 0.3 mm thick tungsten monocrystal exposed during 6 months to the 30 Gev incident electron beam of the SLAC Linear Collider (SLC). The crystal was placed in the converter region , orientated in a random direction and received an integrated flux of e- (fluence) of 2 x 10^18 e-/mm^2. The crystal was analyzed before and after irradiation by X and Gamma diffractometry. No damage was observed, the mosaic spread remained unchanged during irradiation (0.4 mrad FWHM). Implications for use of orientated crystal as converter for positron sources of future LCs are discussed