[en] ArDM is a new-generation WIMP detector which will measure simultaneously light and charge from scintillation and ionization of liquid argon. Our goal is to construct, characterize and operate a 1 ton liquid argon (LAr) underground detector. The project relies on the read out of the VUV scintillation light and on the extraction of the electrons produced by ionization from the liquid into the gas phase of the detector. The light has to be converted with wavelength shifters such as TetraPhenyl Butadiene in order to be detected by photomultipliers with bialkali photocathodes. I describe the light readout system and the tests of the prototype with liquid argon in the full size detector.

[en] ArDM is a new-generation WIMP detector which will measure simultaneously light and charge from scintillation and ionization of liquid argon. Our goal is to construct, characterize and operate a 1 ton liquid argon underground detector. The project relies on the possibility to extract the electrons produced by ionization from the liquid into the gas phase of the detector, to amplify and read out with Large Electron Multipliers detectors. Argon VUV scintillation light has to be converted with wavelength shifters such as TetraPhenyl Butadiene in order to be detected by photomultipliers with bialkali photocathodes. We describe the status of the LEM based charge readout and light readout system R and D and the first light readout tests with warm and cold argon gas in the full size detector.

[en] The outstanding features of the existing CERN n-TOF neutron beam are the very high instantaneous neutron flux, excellent n-TOF resolution, low intrinsic backgrounds and coverage of a wide range of neutron energies, from thermal to a few GeV. These characteristics provide a unique possibility to perform neutron-induced cross-section and angular distribution measurements for applications such as nuclear astrophysics, nuclear reactor technology and basic nuclear physics. This paper presents in detail all the characteristics of the present neutron beam in the different available configurations, which correspond to two different collimation systems and two choices of neutron moderator. The features include shape and intensity of the neutron flux, beam spatial profile, in-beam background components and the energy resolution broadening. The description of these features is based upon both dedicated measurements as well as Monte Carlo simulations, and includes an estimation of the systematic uncertainties in the mentioned quantities. The overall efficiency of the experimental program and the range of possible measurements will be expanded in the near future with the construction of a second experimental area (EAR-2), vertically located 20 m on top of the present n-TOF spallation target. This upgrade, which will benefit from a neutron flux 25 times higher than the existing one, will provide a substantial improvement in measurement sensitivities and will open the possibility to measure neutron cross-section of isotopes with very short half-lives or available in very small quantities. The technical study for the construction of this new neutron beam will be presented, highlighting the main advantages compared to the presently existing Experimental Area (EAR-1). (author)

[en] The neutron time-of-flight facility n-TOF, operating at CERN since 2001, features a neutron beam that covers the energy range from thermal to 1 GeV. Its most outstanding characteristics are its long flight path (185 m) and the high instantaneous intensity (0.5-12·10⁶ neutrons/pulse depending on the collimator configuration). The ambitious program carried out in the last decade includes a large number of experiments in the fields of nuclear energy technologies, astrophysics, basic physics, detector development and medical applications. Within the field of nuclear energy technologies most measurements are focused on determining, for the first time and/or with unprecedented accuracies, the capture and fission cross sections of actinides, both at low (resolved resonance region) and high (keV-GeV) neutron energies. This paper present a summary of all the measurements carried out since 2001 at n-TOF, including some details for several of these experiments. (author)

[en] The radiation field generated by a high energy and intensity accelerator is of concern in terms of element functionality threat, component damage, electronics reliability, and material activation, but also provides signatures that allow actual operating conditions to be monitored. The shower initiated by an energetic hadron involves many different physical processes, down to slow neutron interactions and fragment de-excitation, which need to be accurately described for design purposes and to interpret operation events. The experience with the transport and interaction Monte Carlo code FLUKA at the Large Hadron Collider (LHC), operating at CERN with 4 TeV proton beams (and equivalent magnetic rigidity Pb beams) and approaching nominal luminosity and energy, is presented. Design, operation and upgrade challenges are reviewed in the context of beam-machine interaction account and relevant benchmarking examples based on radiation monitor measurements are shown

[en] The influence of air contamination on the VUV scintillation yield in gaseous argon at atmospheric pressure is investigated. We determine with a radioactive α-source the photon yield for various partial air pressures and different reflectors and wavelength shifters. We find that the time constant of the slow scintillation component depends on gas purity and is a good indicator for the total VUV light yield, while the fast component is not affected. This dependence is attributed to impurities destroying the long-lived triplet argon excimer state. The population ratio between the slow and the fast decaying excimer states is determined for α-particles to be 5.5 ± 0.6 in argon gas at 1100 mbar and room temperature. The measured decay time constant of the slow component is 3.140 ± 0.067 μs at a partial air pressure of 2 x 10^-6 mbar

[en] Silicon microstrip detectors will provide the forward tracking in the TOTEM experiment at the LHC. To allow efficient tracking closest to the beam (∼1 mm) these detectors should be sensitive up to their physical edge (i.e. edgeless). Edgeless (without guard rings) microstrip planar detectors can be operated at cryogenic temperatures (about 130 deg. K) where leakage currents due to the active edge are drastically reduced. A silicon microstrip prototype, cut perpendicular to the strips, has been tested with a pion beam at CERN to study its efficiency close to the edge by using reference tracks from a simple silicon telescope. Results indicate that the detector measures tracks with good efficiency up to the physical edge of the silicon

[en] One source of experimental background in the LHC is showers induced by particles hitting the upstream collimators or particles that have been scattered on the residual gas. We estimate the flux and distribution of particles entering the ATLAS and CMS detectors through FLUKA simulations starting either in the tertiary collimators or with inelastic beam-gas interactions. Comparisons to MARS15 results are also presented. Our results can be used as a source term for further simulations of the machine-induced background in the experimental detectors. To ensure optimal performance of the LHC experimental detectors, it is important to understand the background, which can come fromseveral sources. In this article we discuss machine-induced background, caused either by nearby beam losses or interactions between beam particles and the residual gas inside the vacuum pipe. Beam losses outside the experimental interaction regions (IRs) are unavoidable during collider operation. The halo is continuously repopulated and has to be cleaned by the collimation system, so that the losses in the cold magnets are kept at a safe level. The collimation system is located in two dedicated insertions (IR3 and IR7) but a small leakage of secondary and tertiary halo is expected to escape. Some particles make it to the experimental IRs, where they are intercepted by tertiary collimators (TCTs) that are installed in order to protect the inner triplet magnets. Some parts of the induced high-energy shower can escape and propagate into the detectors. Another source of background is beam-gas interactions. Beam protons can scatter elastically or inelastically on residual gas molecules. If an inelastic interaction occurs close to the detector, it causes a shower that could reach the detector. Elastic interactions can scatter protons directly onto the TCTs without passing IR7, which has to be treated separately from the beam-halo losses discussed above. Machine-induced background can also originate from a cross-talk between different IPs. In this article we focus on beam-halo losses and inelastic beam-gas interactions two LHC experiments: ATLAS in IR1 and CMS in IR5. We compare also to previous results. We simulate the machine-induced showers propagating through the interaction region up to an interface plane between the machine and the detector, which is defined to be at 22.6m from the interaction point (IP) along the beam direction. The coordinates and momenta of the particles crossing this plane are recorded and can be used as a source term for further simulations of the detector itself. The interface plane extends to 30 m radially, although 99% of the total energy was found within a 2.5 m radius in the simulations.

[en] One source of experimental background in the CERN Large Hadron Collider (LHC) is particles entering the detectors from the machine. These particles are created in cascades, caused by upstream interactions of beam protons with residual gas molecules or collimators. We estimate the losses on the collimators with SixTrack and simulate the showers with FLUKA and MARS to obtain the flux and distribution of particles entering the ATLAS and CMS detectors. We consider some machine configurations used in the first LHC run, with focus on 3.5 TeV operation as in 2011. Results from FLUKA and MARS are compared and a very good agreement is found. An analysis of logged LHC data provides, for different processes, absolute beam loss rates, which are used together with further simulations of vacuum conditions to normalize the results to rates of particles entering the detectors. We assess the relative importance of background from elastic and inelastic beam–gas interactions, and the leakage out of the LHC collimation system, and show that beam–gas interactions are the dominating source of machine-induced background for the studied machine scenarios. Our results serve as a starting point for the experiments to perform further simulations in order to estimate the resulting signals in the detectors. -- Highlights: •We simulate sources of machine-induced experimental background at the CERN LHC. •We focus on the ATLAS and CMS experiments. •The LHC machine conditions are analyzed to normalize the simulation results. •Beam–gas interactions is found to be the dominating source of particles entering the detectors

[en] Beam Intercepting Devices (BID) are designed to operate in a harsh radioactive environment and are highly loaded from a thermo-structural point of view. Moreover, modern particle accelerators, storing unprecedented energy, may be exposed to severe accidental events triggered by direct beam impacts. In this context, impulse has been given to the development of novel materials for advanced thermal management with high thermal shock resistance like metal-diamond and metal-graphite composites on top of refractory metals such as molybdenum, tungsten and copper alloys. This paper presents the results of a first-of-its-kind experiment which exploited 440 GeV proton beams at different intensities to impact samples of the aforementioned materials. Effects of thermally induced shockwaves were acquired via high speed acquisition system including strain gauges, laser Doppler vibrometer and high speed camera. Preliminary information of beam induced damages on materials were also collected. State-of-the-art hydrodynamic codes (like Autodyn®), relying on complex material models including equation of state (EOS), strength and failure models, have been used for the simulation of the experiment. Preliminary results confirm the effectiveness and reliability of these numerical methods when material constitutive models are completely available (W and Cu alloys). For novel composite materials a reverse engineering approach will be used to build appropriate constitutive models, thus allowing a realistic representation of these complex phenomena. These results are of paramount importance for understanding and predicting the response of novel advanced composites to beam impacts in modern particle accelerators