Giovanni Spiezia

Digital Integrator for Fast Accurate Measurement of Magnetic Flux by Rotating Coils

A fast digital integrator (FDI) with dynamic accuracy and a trigger frequency higher than those of a portable digital integrator (PDI), which is a state-of-the-art instrument for magnetic measurements based on rotating coils, was developed for analyzing superconducting magnets in particle accelerators. Results of static and dynamic metrological characterization show how the FDI prototype is already capable of overcoming the dynamic performance of PDI as well as covering operating regions that used to be inaccessible

Design of a Linear Variable Differential Transformer With High Rejection to External Interfering Magnetic Field

The sensitivity of linear variable differential transformer (LVDT) position sensors to external slowly varying magnetic fields represents a critical issue when these sensors are installed close to high-current cables or electrical motors with significant fringe fields. The resulting position error can reach several hundreds of micrometers against a specified uncertainty normally below a few micrometers. In this paper, the design of a LVDT position sensor with high rejection to external constant or slowly varying magnetic fields is addressed by exploiting the finite element method (FEM) simulator FLUX. A shield, isolated from the sensors magnetic circuit, has been considered to reduce the effect of magnetic fields on the secondary voltages of the LVDT. In addition, a dc current is used in order to polarize the magnetic circuit to reduce the sensitivity of the sensor to external interferences.

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.

LHC RadMon SRAM Detectors Used at Different Voltages to Determine the Thermal Neutron to High Energy Hadron Fluence Ratio

The thermal neutron SEU cross-section of the Toshiba SRAM memory used in the LHC RadMon system was measured at different voltages. A method using the difference in its response compared to mixed particle energy field is proposed to be used as a discriminator between thermal neutron and high-energy hadron fluences. For test purposes, the proposed method was used at the CNGS and CERF facilities to estimate the field composition by counting SEUs at two different voltages and the results were compared to simulations.

Automatic Test Bench for Measurement of Magnetic Interference on LVDTs

This paper proposes an automatic test bench, based on a rigorous and repeatable measurement procedure, for the analysis of a position sensor linear variable differential transformer (LVDT). The test bench allows complete characterization of an LVDT sensor working in an interfering magnetic field by evaluating the uncertainty and nonlinearity of the sensor. This issue is addressed in neither the sensor datasheet nor the scientific literature. The potential of the method and the performance of the automated test bench are proven by measuring the main sensor characteristics such as nonlinearity and uncertainty, and the error of a position reading due to external magnetic interference on two commercial LVDTs. The sensors are based on two different reading techniques, and both are analyzed using current and voltage excitations. In fact, the test bench permits to study the robustness of the sensor with respect to external magnetic fields by comparing position drifts due to interference at varying source excitations and reading techniques.

SEU Measurements and Simulations in a Mixed Field Environment

Single Event Upset (SEU) measurements were performed using the European Space Agencys (ESA) Standard SEU Monitor in the H4 Irradiation mixed-field test area at CERN. The results, tightly correlated with the radiation environment, are compared with those obtained with the CERN Radiation Monitors (RadMons) as well as with the Monte Carlo simulation of the experimental setup using the FLUKA Monte Carlo transport code. In addition, the SEU cross section of the device for particles and energies not available in standard testing (such as charged pions or GeV-energy hadrons) are simulated and discussed, showing an increase of over a factor 2 for nucleons in the 200 MeV-3 GeV range. A monoenergetic SEU cross section measurement at 120 GeV is included in the analysis.

A New RadMon Version for the LHC and its Injection Lines

A system to monitor the radiation levels is required in the Large Hadron Collider (LHC) and its injection lines in order to quantify the radiation effects on electronics. Thus, the RadMons were installed in critical areas where equipment is or will be placed. The first years of operation, successive test campaigns and new requirements, raised the need for a new design of the monitor. The architecture of the new RadMon, the radiation reliability and the design strategy adopted for the sensors, used for monitoring the mixed radiation field of the LHC accelerator, are described highlighting the achieved improvements in terms of radiation robustness and measurement accuracy of a device which is of interest for many other research institutes.

The LHC Radiation Monitoring System - RadMon

Julien Mekki, Sergio Batuca, Markus Brugger, Marco Calviani, Alfredo Ferrari, Daniel Kramer, Roberto Losito, Alessandro Masi, Anna Nyul, Paul Peronnard, Christian Pignard, Ketil Roeed, Thijs Wijnands CERN CERN CH-1211, Geneve 23, Switzerland E-mail:; Julien.Mekki@cern.ch; Sergio.batuca@cern.ch; Markus.Brugger@cern.ch; Marco.Calviani@cern.ch, Alfredo.Ferrari@cern.ch; Daniel.kramer@cern.ch; Roberto.Losito@cern.ch; Alessandro.Masi@cern.ch; Ana.Nyul@cern.ch; Paul.Peronnard@cern.ch; Christian.Pignard@cern.ch; Ketil.Roeed@cern.ch; Thijs.Wijnands@cern.ch

Mixed Particle Field Influence on RadFET Responses Using Co-60 Calibration

RadFET sensors are used for Total Ionizing Dose (TID) monitoring inside CERN accelerators. While RadFET sensors are typically well characterized with a Co-60 gamma source, their radiation response can be affected when they are used in high-energy mixed particle fields. This paper presents experimental results and corresponding discussions on the effect of CERN accelerator-like environments on the dose measured by 100 nm, 400 nm and 1000 nm thick oxide RadFETs. Simulations of the radiation environment at the CERN test areas have also been performed to investigate the contribution of each particle type to the deposited dose and are used as a tool to understand the observed effects.

A Fast Digital Integrator for Magnetic Field Measurements at Cern

A self-calibrating digital instrument for flux measurements on magnets for accelerators used in basic research on subnuclear particles is proposed. The instrument acquires voltage arising from rotating coils transducers with a theoretical resolution of 10 ppt and a maximum sampling frequency of 800 kS/s. Then, samples are integrated on-line and suitably processed in order to improve time resolution and flux accuracy. This allows the limits of state-of-the-art digital fluximeters, related mainly to new-generation rotating coils, with trigger rate of 20 kHz and coils speed of 10 rps, to be overcome. The instrument has been prototyped at magnetic measurement and testing (MTM) group of European Laboratory for Nuclear Research (CERN), under a framework of cooperation with the University of Sannio. Details on hardware and firmware conception, as well as on experimental results of the instrument principle validation, and of the preliminary metrological characterization of the prototype, are provided