CATCH 1.4 User's Guide

The Monte Carlo program CATCH (Capture And Transport of CHarged particles in a crystal) for the simulation of planar channelling in bent crystals is presented. The program tracks a charged particle through the distorted-crystal lattice with the use of continuous-potential approximation and the non-diffusion approach to the processes of scattering on electrons and nuclei. The output consists of the exit angular distributions, the energy loss spectra, and the spectra of any close-encounter process of interest. The curvature variability, face twist, and various surface imperfections of the real crystal can be taken into account.Comment: 12 page

Crystal Channelling in Accelerators

Crystal lattice can trap and channel particle beams along major crystallographic directions. In a bent crystal, the channelled particles follow the bend. This makes a basis for an elegant technique of beam steering by means of bent channelling crystals, experimentally demonstrated from 3 MeV to 1 TeV. This technique was strongly developed in recent studies at CERN, FNAL, IHEP, and BNL, and can lead to interesting applications also at the LHC, such as crystal collimation making a collider cleaner by an order of magnitude. We review recent developments in the field and show outlook for the future.Comment: Invited talk at 10th European Particle Accelerator Conference (EPAC 06), Edinburgh, UK, 26-30 Jun 200

Channeling of high-energy particles in a multi-wall nanotube

Channeling of high-energy particles in straight and bent multi-wall nanotubes (MWNT) has been studied in computer simulations and compared to the channeling properties of single-wall nanotubes (SWNT) and bent crystal lattices. It is demonstrated that MWNT can efficiently channel positively-charged high-energy particles trapped between the walls of MWNT. Bending dechanneling in MWNT has been computed as a function of the particle momentum to nanotube curvature radius ratio, $pv/R$. It is found that a bent MWNT can steer a particle beam with bending capabilities similar to those of bent silicon crystal lattice and to those of best (i.e. the narrowest) SWNT. In view of channeling applications at particle accelerators, MWNT appear favored as compared to SWNT, because MWNT can be produced quite straight (and in aligned array), while SWNT is typically very curved, thus posing a severe problem for channeling applications. Therefore, we suggest that MWNT provide a better candidate for channeling than SWNT.Comment: 16 pages, 6 figures, to appear in Phys. Lett.

Simulation of the CERN-SPS crystal extraction experiment

Simulation of the CERN crystal-extraction experiments at the SPS, including the real crystal geometry and SPS parameters, as well as multiple turns and passes, has been performed. Two crystals with different geometry have been tried. We argue that in both cases the extraction experiment suffered from the crystal edge imperfection. For the experimental conditions reproduced, the efficiency of the first (twisted) crystal was found to be 12-18% (peak) in the angular range of 140-260 microrad (FWHM), depending on the vertical beam position at the crystal location. For the second (U-shaped) crystal the peak efficiency was much the same, ~19%, while the angular scan FWHM reduced to 70 microrad. These results, as well as the beam profiles, are in agreement with measurements. Finally we suggest some ways to advance this experiment.Simulation of the CERN crystal-extraction experiments at the SPS, including the real crystal geometry and SPS parameters, as well as multiple turns and passes, has been performed. Two crystals with different geometry have been tried. We argue that in both cases the extraction experiment suffered from the crystal edge imperfection. For the experimental conditions reproduced, the efficiency of the first (twisted) crystal was found to be 12-18% (peak) in the angular range of 140-260 microrad (FWHM), depending on the vertical beam position at the crystal location. For the second (U-shaped) crystal the peak efficiency was much the same, ~19%, while the angular scan FWHM reduced to 70 microrad. These results, as well as the beam profiles, are in agreement with measurements. Finally we suggest some ways to advance this experiment