Muon Shield Research Articles

Sub-GeV dark matter search at ILC beam dumps

Light dark matter particles may be produced in electron and positron beam dumps of the International Linear Collider (ILC). We propose an experimental setup to search for such events, the Beam-Dump eXperiment at the ILC (ILC-BDX). The setup consists of a muon shield placed behind the beam dump, followed by a multi-layer tracker and an electromagnetic calorimeter. The calorimeter can detect electron recoils due to elastic scattering of dark matter particles produced in the dump, while the tracker is sensitive to decays of excited dark-sector states into the dark matter particle. We study the production, decay and scattering of sub-GeV dark matter particles in this setup in several models with a dark photon mediator. Taking into account beam-related backgrounds due to neutrinos produced in the beam dump as well as the cosmic-ray background, we evaluate the sensitivity reach of the ILC-BDX experiment. We find that the ILC-BDX will be able to probe interesting regions of the model parameter space and, in many cases, reach well below the relic target.

Multi-parameter detector optimization: SHiP case

SHiP (Search for Hidden Particles) and the associated SPS Beam Dump Facility is a new general-purpose experiment proposed at the SPS to search for "hidden" particles as predicted by a very large number of recently elaborated models of Hidden Sectors which are capable of accommodating dark matter, neutrino oscillations, and the origin of the full baryon asymmetry in the Universe. SHiP is declared as an experiment with zero background. The Muon Shield is the key element to do this. So on the one hand it has to provide a good background suppression, on the other hand it has not be too heavy. In this paper we present the results of obtaining the new Muon Shield shape using the Bayesian Optimization. This allowed to reduce the background rate by the factor of 2.5, while keeping the weight of the shield at the same level.

Gamma Radioactivity Detection Limits and Associated Radionuclide Intakes Study in Artificial Human Urine Using Sodium-iodide and High-purity Germanium Detectors.

The performance of several gamma detectors was investigated for emergency urine bioassay screening of two radionuclides of concern: 131 I and 137 Cs. Unspiked artificial urine samples were measured for 10 min each on four different gamma detectors: 80% relative efficiency high-purity Ge detector in standard shielding, 102% low-background high-purity Ge detector equipped with top muon shield, 78% high-purity Ge well detector in standard shielding, and 4″ × 4″ NaI well detector in standard shielding. The measured gamma spectra were analyzed in two ways: (1) for the 364-keV peak region of 131 I and 662-keV peak region of 137 Cs and (2) for the total counts in the full energy spectrum (50-2,048 keV). The results were analyzed using the principles of signal detection theory according to the Currie's formalism extended by a complete uncertainty propagation. This enabled calculation of the detection capability in terms of detection limit (Bq L -1 ) of urine, the latter referred to as minimum detectable activity. The NaI well detector had the lowest minimum detectable activities for total spectra, whereas the high-purity Ge well detector had the lowest peak minimum detectable activity values. Minimum detectable inhalation and ingestion intakes from urine bioassay were calculated from the minimum detectable activity values for urine collection 1 d, 1 wk, and 1 mo past the initial intake. The calculated intakes were compared with annual limits on intake. The results are interpreted with respect to a large-scale radiological emergency response.

Optimising the Active Muon Shield for the SHiP Experiment at CERN

The SHiP experiment is designed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. The critical challenge for this experiment is to keep the Standard Model background level negligible. In the beam dump, around 1011 muons will be produced per second. The muon rate in the spectrometer has to be reduced by at least four orders of magnitude to avoid muoninduced backgrounds. It is demonstrated that new improved active muon shield may be used to magnetically deflect the muons out of the acceptance of the spectrometer.

The active muon shield in the SHiP experiment

The SHiP experiment is designed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. An essential task for the experiment is to keep the Standard Model background level to less than 0.1 event after 2× 1020 protons on target. In the beam dump, around 1011 muons will be produced per second. The muon rate in the spectrometer has to be reduced by at least four orders of magnitude to avoid muon-induced combinatorial background. A novel active muon shield is used to magnetically deflect the muons out of the acceptance of the spectrometer. This paper describes the basic principle of such a shield, its optimization and its performance.

Shielding assessment of high field (QED) experiments at the ELI-NP 10 PW laser system

High field quantum electrodynamics experiments will be conducted in the E6 experimental area of the Extreme Light Infrastructure-Nuclear Physics building. Here electrons and protons will be accelerated up to relativistic energies by multi-petawatt laser beam—target interactions. In this respect, the requirements for radiological safety measures are similar to those associated with the operation of conventional high energy accelerators. The paper presents a FLUKA simulation approach to the shielding assessment of the individual experiments. Updated source terms were used in order to compute ambient dose equivalent rates throughout E6 and neighbouring areas and check the compliance of the results with legal dose constraints. We investigated the effectiveness of an ‘all-purpose’ beam dump at E6 and the practicality of local muon shielding.

The Sandwich spectrometer for ultra low-level γ-ray spectrometry

The technical details and performance of the newly developed Sandwich spectrometer for ultra low-level γ-ray spectrometry are presented. The spectrometer, which consists of two HPGe detectors, an active muon shield and a lead/copper shield with a convenient and rapid opening mechanism, is located in an underground laboratory at a depth of 500 m water equivalent. The data is collected in list mode, which enables off-line data analysis to identify muon-induced events and possible Ge detector crosstalk due to Compton scattering. The background count-rate from 40 to 2700 keV normalised to the mass of the Ge crystals is 220 day −1 kg −1.

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.

Search for massive, long-lived, fractionally charged particles produced by 300-GeV protons

A search has been made for massive, long-lived, weakly interacting particles of fractional charge that could be produced by 300-GeV protons striking an aluminum target. The search was most sensitive to particles with a lifetime of about 100 \ensuremath{\mu}sec. These particles would have come to rest in the Caltech neutrino detector that was located halfway down the muon shield, and if they were massive enough and decayed into at least 5 GeV of visible energy in the calorimeter, they could have been detected. None were found. The 90%-confidence-level upper limit to the invariant cross section (times branching ratio $R$), $\mathrm{RE}\frac{{d}^{3}\ensuremath{\sigma}}{d{p}^{3}}$ [${\mathrm{cm}}^{2}$/${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$], is 4 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}39}$ (5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}38}$) for charge $(\frac{2}{3})e$ ($(\frac{1}{3})e$).

Muon shielding around high-energy electron accelerators: Part I. Theory

The production of muons from a high-energy electron linac is calculated using the latest cross section theory. The shielding of these muons is calculated using the Fermi-Eyges multiple scattering formulation. The effect of various approximations in the calculations is discussed. A comparison is made between theory and experiment, and reasonable agreement is obtained in the forward direction. The experiment gives a significantly higher value for the absorbed dose, as compared to theory, for locations off the production axis. This is believed to be due to a background component in the total dose measured, and suggests the need for further experimentation with emphasis on fluence (as well as absorbed dose) measurements at distances far from the axis.

Protection from muons in high energy proton accelerators

A generalization of the works on muon shielding in proton accelerators is carried out. Coulomb scattering of muons, energy losses in ionization and excitation of atoms, bremsstrahlung, direct pair formation, and nuclear interaction are taken into consideration in the computations. Coefficients obtained from recent experimental data are used in the double differential distribution of pions in p-nuclear interaction. Results of computations of muon shielding in a 1000 Ge Vaccelerator are presented. Results obtained for a. 200 GeV proton accelerator are compared with the computations of other authors.

Muon Shielding for a 500-GeV Neutrino Facility

The explicit problem considered is the amount and shape of muon shielding required for a neutrino experimental area operated with a primary proton beam of energy up to 500-GeV. Muon transport programs have been developed for NAL1 which permit the calculation of muon intensities within a semi-infinite homogeneous medium. Results of such a calculation for a neutrino facility indicate that an earth shield 1100 meters in length and 7 meters in radius is required to permit the use of a bubble chamber detector with a primary beam energy of 500-GeV. A new calculational method using only available programs is proposed which permits the quantitative estimation of the effect of a magnetized-iron deflector. Results from this technique show that a magnetized-iron block 1.5 meters in radius and capable of deflecting the highest energy muons by 22 mrad may permit the use of a shield which is adequate for bubble chamber operation but only 550 meters of earth in length at 500-GeV.

Radiation Problems with High-Energy Proton Accelerators

We shall restrict the discussion to proton accelerators in the multi-GeV energy range and of the alternating-gradient synchrotron type, with special attention given to the existing 30-GeV and the proposed 200-to 300-GeV machines. Radiation problems can be divided into two broad groups: those produced by the accelerator while it is running and those associated with the shut-down machine. The expense and difficulty of coping with these radiation problems influence the choice of design beam intensity. The problems while the machine is running are penetration of radiation through the shielding, muon shielding, penetration of radiation through ducts and labyrinths, skyshine, diffusion of radioactive air, and radiation damage to components. Some results of an LRL-CERN-Rutherford shielding experiment on the CERN-PS are presented. Problems of the shut-down accelerator include induced activity in the machine components and enclosure walls. These radiation fields affect maintenance procedures and require appropriate handling tools and shielded vehicles.