arXiv subjects

Alex Fomin

Publications and source records attributed to Alex Fomin.

4 recordsLinked to original sources

arXiv2022

HL-LHC layout for fixed-target experiments in ALICE based on crystal-assisted beam halo splitting

The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) is the world's largest and most powerful particle accelerator colliding beams of protons and lead ions at energies up to 7 ZTeV, Z is the atomic number. ALICE is one of the detector experiments optimised for heavy-ion collisions. A fixed-target experiment in ALICE is being considered to collide a portion of the beam halo, split using a bent crystal inserted in the transverse hierarchy of the LHC collimation system, with an internal target placed a few meters upstream of the existing detector. This study is carried out as a part of the Physics Beyond Collider effort at CERN. Fixed-target collisions offer many physics opportunities related to hadronic matter and the quark-gluon plasma to extend the research potential of the CERN accelerator complex. Production of physics events depends on the particle flux on target. The machine layout for the fixed-target experiment is developed to provide a flux of particles on the target high enough to exploit the full capabilities of the ALICE detector acquisition system. This paper summarises the fixed-target layout consisting of the crystal assembly, the target and downstream absorbers. We discuss the conceptual integration of these elements within the LHC ring, the impact on ring losses, and expected performance in terms of particle flux on target.

physics.acc-ph↗

arXiv2017

Radiation of a relativistic electron with non-equilibrium own Coulomb field

The condition and specific features of non-dipole regime of radiation is discussed in connection with the results of recent CERN experiment NA63 on measurement of radiation power spectrum of $149\,$GeV electrons in thin tantalum targets. The first experimental detection of logarithmic dependence of radiation yield from the target thickness is the conclusive evidence of the effect of radiation suppression in a thin layer of matter, which was predicted many years ago, and which is the direct manifestation of radiation of relativistic electron with non-equilibrium own Coulomb field. The special features of angular distribution of radiation and its polarization in a thin target at non-dipole regime are proposed for a new experimental study.

physics.acc-ph↗

arXiv2017

Multiple scattering effect on angular distribution and polarization of radiation by relativistic electrons in a thin crystal

The multiple scattering of ultra relativistic electrons in an amorphous matter leads to the suppression of the soft part of radiation spectrum (the Landau-Pomeranchuk-Migdal effect), and also can change essentially the angular distribution of the emitted photons. A similar effect must take place in a crystal for the coherent radiation of relativistic electron. The results of the theoretical investigation of angular distributions and polarization of radiation by a relativistic electron passing through a thin (in comparison with a coherence length) crystal at a small angle to the crystal axis are presented. The electron trajectories in crystal were simulated using the binary collision model which takes into account both coherent and incoherent effects at scattering. The angular distribution of radiation and polarization were calculated as a sum of radiation from each electron. It is shown that there are nontrivial angular distributions of the emitted photons and their polarization that are connected to the superposition of the coherent scattering of electrons by atomic rows ("doughnut scattering" effect) and the suppression of radiation (similar to the Landau-Pomeranchuk-Migdal effect in an amorphous matter). It is also shown that circular polarization of radiation in the considered case is identically zero.

physics.acc-ph↗

arXiv2017

Computer simulation of detecting system of compact positron-emission tomograph based on scintillator-photodiode detectors

We present the original computer code for the simulation of multi-element detection system of the compact positron-emission tomograph based on a scintillator-photodiode type of detection elements. The use of such type of detection elements allows obtaining a high spatial resolution at a relatively small total size of the tomograph. This program gives an opportunity to choose the optimal geometry of detection system depending on the parameters of its elements, and analyze the efficiency of different image reconstruction algorithms. The handy interface for the designed compact positron-emission tomograph operation has been created.

physics.med-ph↗