Peter Sievers

A decommissioned LHC model magnet as an axion telescope

The 8.4 T, 10 m long transverse magnetic field of a twin aperture LHC bending magnet can be utilized as a macroscopic coherent solar axion-to-photon converter. Numerical calculations show that the integrated time of alignment with the Sun would be 33 days/yr with the magnet on a tracking table capable of

A Stationary Target for the CERN-Neutrino-Factory

5i in the vertical direction and

Designing and building a collimation system for the high-intensity LHC beam

40i in the horizontal direction. The existing lower bound on the axion-to-photon coupling constant can be improved by a factor between 30 and 100 in 3 yr, i.e., g !cc [9]10~11 GeV~1 for axion masses [ 1 eV. This value falls within the existing open axion mass window. The same set-up can simultaneously search for low- and high-energy celestial axions, or axion-like particles, scanning the sky as the Earth rotates and orbits the Sun. ( 1999 Elsevier Science B.V. All rights reserved.

Conducting target for pion production

Abstract As production target for Neutrino Factories, free mercury jets with high axial velocity of about 20 m / s are being studied. For the CERN-Neutrino-Factory proposal with a 4 MW beam power, but with a relatively large beam size at 2.2 GeV /c and pulsed at 50 Hz , maximum energy deposition densities of below 20 J / g and average power densities of about 1 kW / g are expected in the target. Therefore, a study has been made which discusses the feasibility and limits of a stationary target. It is proposed to use densely packed solid spheres of heavy material and with diameters in the millimeter range. These spheres are confined inside a Titanium container and cooled by an efficient water circuit or possibly by He-gas. Dynamic response, as pressure pulses and vibrations are greatly reduced in the small target granules due to relatively long beam bursts, each with a duration of 3.3 μs . The encouraging results achieved in this assessment justify to pursue further experimental tests, in particular of the cooling of the target, its lifetime under repetitive thermal cycles (4.3 Mio / day ) and of radiation damage, to validate this proposal. It is expected that the lifetime of this target will be adequate for the operation of the CERN-Neutrino-Factory, at least over its initial phase below 4 MW beam power.

Comparison of measurements of angular hadron energy spectra, induced activity and dose with FLUKA82 calculations

The Large Hadron Collider (LHC) will collide proton beams at 14 TeV c.m. with unprecedented stored intensities. The transverse energy density in the beam will be about three orders of magnitude larger than previously handled in the Tevatron or in HERA, if compared at the locations of the betatron collimators. In particular, the population in the beam halo is much above the quench level of the superconducting magnets. Two LHC insertions are dedicated to collimation with the design goals of preventing magnet quenches in regular operation and preventing damage to accelerator components in case of irregular beam loss. We discuss the challenges for designing and building a collimation system that withstands the high power LHC beam and provides the required high cleaning efficiency. Plans for future work are outlined.

A positron source using an axially oriented crystal associated to a granular amorphous converter

When particles are produced inside a magnetic field, the portrait at the end of the target depends on the nature and intensity of the field. Targets embedded in a strong solenoidal field have been up to now the reference configuration for neutrino factories and muon colliders as well. An alternative configuration consists of pulsing an axial current through the target. It is shown that a conducting target can produce a much brighter beam than a target magnetized by a solenoid for the same field intensity at the periphery of the target.

Studies of a scheme for low emittance muon beam production from positrons on target

Abstract Three experiments are described in which extended targets were bombarded with high-energy protons. The experiments were simulated using the Monte Carlo hadron cascade package FLUKA82. The measured and simulated quantities included the hadron yield around a target as a function of polar angle and energy and the two-dimensional ( r − z ) distributions of stars and energy deposition inside an aluminium cylinder. The agreement between the calculations and measurements is generally within experimental errors.

Targetry R&D for PRISM Project

A non-conventional positron source using the intense γ radiation from an axially oriented monocrystal which materializes into e + e pairs in a granular amorphous converter is described.The enhancement of photon radiation by multi-GeV electrons crossing a tungsten crystal along its axis is repo...

THE FINAL COLLIMATION SYSTEM FOR THE LHC

A new scheme to produce muon beams characterised by very low emittance, in such a way to avoid the need for cooling, using a positron beam of about 45 GeV interacting on electrons on target is being studied by our group. This scheme is challenging and innovative, and needs a full design study to be developed. In particular, one of the novel topics to be investigated is the interaction between the positron beam stored in a low emittance ring with a thin target, to be inserted directly in the ring chamber to produce muons. Produced muons will then be immediately collected at the exit of the target and transported to two

THE MECHANICAL DESIGN FOR THE LHC COLLIMATORS

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