Graham Roger Stevenson

A comparison of FLUKA simulations with measurements of fluence and dose in calorimeter structures

Abstract Measurements have been recently published of the spatial variation of hadron and low-energy neutron fluence and of absorbed dose in the cascades induce

Energy dependence of hadronic activity

Two features of high-energy hadronic cascades have long been known to shielding specialists: a) in a high-energy hadronic cascade in a given material (incident E ≳ 10 GeV), the relative abundance and spectrum of each hadronic species responsible for most of the energy deposition is independent of the energy or species of the incident hadron, and b) because π0 production bleeds off more and more energy into the electromagnetic sector as the energy of the incident hadron increases, the absolute level of this low-energy hadronic activity (E ≲ 1 GeV) rises less rapidly than the incident energy, and in fact rises very nearly as a power of the incident energy. Both features are of great importance in hadron calorimetry, where it is the “universal spectrum” which makes possible the definition of an intrinsic eh, and the increasing fraction of the energy going into π0s which leads to the energy dependence of eπ. We present evidence for the “universal spectrum,” and use an induction argument and simulation results to demonstrate that the low-energy activity ss Em, with 0.80 ≲ m ≲ 0.85. The hadronic activity produced by incident pions is 15–20% less than that initiated by protons.

The Large Hadron Collider (LHC) in the LEP tunnel

After the remarkable start-up of LEP, the installation of a Large Hadron Collider, LHC, in the LEP tunnel will open a new era for the High Energy Physics. This report summarizes the main LHC parameters and subsytems and describes the more recent studies and developments.

A simple procedure for the estimation of neutron skyshine from proton accelerators.

Recent calculations of neutron diffusion at an air/ground interface have enabled the establishment of a very simple procedure for estimating neutron dose equivalent at large distances from proton accelerators in the energy range 10 MeV to several tens of GeV.

The radiation field in and around Hadron collider detectors

The origin and composition of the intense radiation field to be expected in parts of the detector systems for the coming generation of multi-TeV proton-proton colliders are described. Energy spectra and flux levels of the different radiation components are given, based on Monte-Carlo computer simulations of the high-energy p-p collisions and of the development of the cascades generated in the detector. Evidence is presented for the experimental justification of these cascade simulations. The effect of detector design on the expected flux levels is demonstrated. >

A Tiny Telescope of Si-Detectors for High Energy Muon Flux Measurement with Electron Rejection

With very small (1 mm2) silicon detectors and a 30 MHz amplifier chain one can measure flux profiles of high energy muons inside a shield up to a density of 5 × 108 cm-2s-1. A telescope structure with several detectors and lead absorber plates enables elimination of both the low and high energy electrons which accompany the muons. Some results obtained in the CERN neutrino beam muon shield and in the North Area muon beam are presented.

On the prediction of radiation levels in LHC experiments

Abstract This paper is a summary of how recent results from the ROSTI and FLUKA collaborations have given more confidence in estimates of neutron fluences and doses to be expected in LHC and SSC detectors.

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

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.

The estimation of dose equivalent from the activation of plastic scintillators

It is shown that the dose equivalent to be attributed to the fluence measured by the activation of 11C in a plastic scintillator when exposed outside the shielding of a high-energy proton accelerator is close to the value of 28 fSv m2 in current use at the European Organization for Nuclear Research (CERN) when the neutron component of the field alone is considered. However the presence of significant numbers of pions and protons in stray fields would raise this conversion factor to approx. 45 fSv m2.

Transport of high energy muons in a soil shield

Abstract An experiment is described in which measurements were made of the fluence of muons as a function of radial distance at a depth of about 350 m in a soil shield irradiated by a beam of muons at 200, 240 and 280 GeV/ c . Three measurement techniques were employed: a scintillator telescope, a semiconductor detector telescope, and nuclear emulsions. The data recorded by the different techniques show agreement among themselves. They are compared with transport calculations based on the Fermi-Eyges model and on Monte Carlo calculations. The differences between the observed data and the calculations are discussed, but there is general agreement between data and calculations to better than a factor of two over a range of four orders of magnitude in fluence per incident muon.