Ni-62(n,gamma) and Ni-63(n,gamma) cross sections measured at the n_TOF facility at CERN

The cross section of the Ni-62(n,gamma) reaction was measured with the time-of-flight technique at the neutron time-of-flight facility n_TOF at CERN. Capture kernels of 42 resonances were analyzed up to 200 keV neutron energy and Maxwellian averaged cross sections (MACS) from kT = 5-100 keV were calculated. With a total uncertainty of 4.5%, the stellar cross section is in excellent agreement with the the KADoNiS compilation at kT = 30 keV, while being systematically lower up to a factor of 1.6 at higher stellar temperatures. The cross section of the Ni-63(n,gamma) reaction was measured for the first time at n_TOF. We determined unresolved cross sections from 10 to 270 keV with a systematic uncertainty of 17%. These results provide fundamental constraints on s-process production of heavier species, especially the production of Cu in massive stars, which serve as the dominant source of Cu in the solar system.Peer reviewedFinal Accepted Versio

Surface Laser Scanning Measurements for the n_TOF spallation target

The n_TOF spallation target is made of pure lead immersed into cooling water. The target was operating normally from 2001 until august 2004, when an increased transfer of radioactive products from the spallation target to the cooling circuit has been observed. The target was considered damaged by the safety commission (SC/RP), and an investigation campaign started to verify the actual status of the target. According to FLUKA and Ansys calculations the target was working in the elastoplastic regime of the lead material, therefore a deformation might be expected. The present paper describes a laser photographic method and the results of a possible such deformation. The target had a surface activity of the order of 20 mSv/h, therefore we were forced to perform the measurement from distance. The used method, is based on a linelaser and a high resolution digital camera for retrieving the 3D position of the surface of the lead target. Similar methods are used in the film industry and animation studios for scanning 3D figures

East Area Irradiation Test Facility: Preliminary FLUKA calculations

In the framework of the Radiation to Electronics (R2E) mitigation project, the testing of electronic equipment in a radiation field similar to the one occurring in the LHC tunnel and shielded areas to study its sensitivity to single even upsets (SEU) is one of the main topics. Adequate irradiation test facilities are therefore required, and one installation is under consideration in the framework of the PS East area renovation activity. FLUKA Monte Carlo calculations were performed in order to estimate the radiation field which could be obtained in a mixed field facility using the slowly extracted 24 GeV/c proton beam from the PS. The prompt ambient dose equivalent as well as the equivalent residual dose rate after operation was also studied and results of simulations are presented in this report

Measurements and simulations of the BLM response to a radiation field inside the CERF target area

The CERN-EU high-energy reference field (CERF) facility is installed in one of the secondary beam lines (H6) of the Super Proton Synchrotron (SPS), in the North Experimental Area at CERN. This facility is used as a reference for testing, inter-comparing and calibrating passive and active instruments. In May 2009, the SPS provided a mixed hadron beam (protons, pions and kaons) during a few days, in order to perform several measurements with different devices such as the Radiation Protection Monitor used for residual dose rates due to Induced Radioactivity in the LHC (PMI), the Secondary Emission Monitor used for high beam losses (SEM), the Radiation Monitor for electronics (RadMon), and the Beam Loss Monitor for the LHC (BLM). This report focuses on the measurements of the BLM response during this year’s operation at CERF. The measurements evaluate the sensitivity of the BLM signal to the particle energy spectrum, with special attention to the contribution coming from thermal neutrons. For this purpose, measurements are performed at various calibrated positions with different fields, as well as by using a Cd layer which is wrapped around the detector. The fields the BLM detector is exposed to are representative for the LHC and range from fields typical to the LHC tunnel, up to radiation fields encountered in shielded areas close to the LHC tunnel. For all configurations, detailed FLUKA simulations were performed to benchmark i n detail the reproducibility of the BLM signal. In addition, to evaluate the BLM response in terms of energy deposition and particles spectra, dedicated calibration calculations were performed to provide energy and particle dependent response functions of the BLM detector. This allowed calculating the contribution of the main particles to the BLM signal and their respective energy range. This successful benchmark shows not only the high accuracy which can be achieved when performing radiation field estimates of LHC like spectra with the FLUKA Monte-Carlo code, but also clarifies the possible issue of low-energy neutrons seen by the BLM detector

FLUKA Simulations for SEE Studies of Critical LHC Underground Areas

FLUKA Monte Carlo simulations have been performed to identify particle energy spectra and fluences relevant for evaluating the risk of single event effects in electronics installed in critical LHC underground areas. Since these simulations are associated with significant uncertainties, the results will compared with an online monitoring system installed to evaluate radiation levels at the location of the electronics. This comparison approach have been benchmarked in a mixed field reference facility and for a preliminary LHC monitoring case study

Neutron induced reactions for the s process, and the case of Fe and Ni isotopes

Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.Neutron capture cross sections are the key nuclear physics input to understand nucleosynthesis of the slow neutron capture process (s process). At the neutron time of flight facility n-TOF at CERN neutron capture cross sections of astrophysical interest are measured over a wide energy range. A measurement campaign to determine the stellar (n,γ) cross sections of Fe and Ni isotopes is currently being pursued. First results on the stellar cross section of Ni(n,γ) confirm previous experimental results. The cross section of the radioactive s-process branching Ni was measured for the first time at stellar energies and is about a factor of 2 higher than theoretical predictions. Future facilities and upgrades will allow to access a number of other radioactive nuclides which are crucial for understanding physical conditions of s-process environmentsPeer reviewe

Commissioning and Operation of the H4IRRAD Mixed-Field Test Area

This note reports on the commissioning and operation period of the H4IRRAD Test Area in which well characterised mixed-fields are provided for LHC equipment users. In benchmark simulations the mixed-field components were estimated and measured with the H4IRRAD beam and radiation monitoring systems. The radiation monitors, the “RadMons” and beam-loss monitors (BLMs) are the same detector types used for monitoring radiation fluences in the underground areas of the LHC. In the first two irradiation periods various equipment was exposed to irradiation produced by a secondary proton beam of 280 GeV impacting on the H4IRRAD copper target. Measurements compared to simulations are presented that quantify the high energy hadron, thermal neutron and Si 1 MeV neutron equivalent fluences at the given test locations. A crucial part was to calibrate the beam monitoring systems to measure the number of protons, p.o.t., which is outlined using different techniques. In addition, cross-checks of p.o.t. measurements are presented using the beam-loss-monitors which agree well within uncertainties

Application benchmark and comparison of the LHC Radiation Monitor and FLUKA Monte Carlo simulations in IR7

At the LHC various underground areas are partly equipped with commercial electronic devices not specifically designed to be radiation tolerant. A major concern is therefore radiation induced failures in particular due to Single Event Upsets (SEU). To ensure safe and acceptable operation of the LHC electronics a combination of both FLUKA Monte Carlo simulations and dedicated online monitoring is applied to determine the expected radiation levels in critical areas. The LHC Radiation Monitor (RadMon) which is used for this purpose has already been extensively calibrated for its radiation response in various irradiation facilities. It is nevertheless of high importance to also provide a real LHC application benchmark to validate the approach of combined simulations and montoring to correctly measure and predict radiation levels. This report therefore presents a comparison between FLUKA Monte Carlo simulations and measurements results using the RadMon in the LHC collimation region IR7. The work is carried out within the frame work of the R2E project

Layout and machine optimisation for the SPL at CERN

During the past 2 years the Superconducting Proton Linac (SPL) study has grown into an international collaboration with the goal of optimising the architecture of a pulsed superconducting (SC) high-power proton linac. This effort includes the study and prototyping of major technical components, such as SC high-gradient cavities, power couplers, the RF distribution system, HOM couplers, cryo-modules, focusing elements, etc. Even though the effort is driven by CERN’s specific needs, the established design principles are valid for a range of SC linac projects. In this paper we report on the latest decisions concerning the machine architecture and on the ongoing R&D effort for technical components

FLUKA Capabilities and CERN Applications for the Study of Radiation Damage to Electronics at High-Energy Hadron Accelerators

The assessment of radiation damage to electronics is a complex process and requires a detailed description of the full particle energy spectra, as well as a clear characterization of the quantities used to predict radiation damage. FLUKA, a multi-purpose particle interaction and transport code, is capable of calculating proton-proton and heavy ion collisions at LHC energies and beyond. It correctly describes the entire hadronic and electromagnetic particle cascade initiated by secondary particles from TeV energies down to thermal neutrons, and provides direct scoring capabilities essential to estimate in detail the possible risk of radiation damage to electronics. This paper presents the FLUKA capabilities for applications related to radiation damage to electronics, providing benchmarking examples and showing the practical applications of FLUKA at CERN facilities such as CNGS and LHC. Related applications range from the study of device effects, the detailed characterization of the radiation field and radiation monitor calibration, to the input requirements for important mitigation studies including shielding, relocation or other options