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

Abstract

Abstract-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.

The “Environmental” Challenges: Impact of Radiation on Machine Components

“…Table 1 summarizes the level of accumulated High Energy Hadron (HEH) fluence measured during 2012 for the most critical LHC areas where electronic equipment is installed and which are relevant for the HL-LHC project, together with the expected radiation levels for nominal LHC performance (50 fb −1 y −1 ). The HEH fluence measurements are based on the RadMon reading of the Single Event Upsets (SEU) of SRAM memories whose sensitivity was extensively calibrated in various facilities [14]. The results obtained during 2012 LHC proton operation show that the measurements very well compare with previously performed FLUKA calculations and observed differences can actually be attributed to changes of operational parameters not considered in the calculations [15].…”

Single Event Effect cross section calibration and application to quasi-monoenergetic and spallation facilities

“…The CHARM R-factors were experimentally obtained using the technique of applying two different voltages on the RadMON SRAM detector [24]. As can be seen, despite the relatively large R-factor in VESUVIO and large intermediate energy neutron impact (quantified through the F HEHeq =F HEH ratio) the results for the three first environments in the table (with 10% hardness values below 400 MeV) are highly compatible with the monoenergetic HEH cross section, s à HEH .…”

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

“…So-called RadMon detectors 15,16) were used for the benchmark at the CERF facility as the RadMon provides online measurements of the Total Ionizing Dose (TID as measured with a RadFET), the 1 MeV neutron equivalent fluence (measured with a PIN-diode ) and the high-energy (> 20 MeV) hadron fluence (measured by "counting" SEUs). Each RadMon can be operated at 5 V or 3 V where the lower voltage effectively increases its Single Event Upset (SEU) sensitivity.…”

“…During the past years and in view of their high importance for the LHC, a significant effort was made in order to improve their calibration . 9) During the CERF experiment these RadMons were replaced between the different measurement positions to study their response in the various mixed radiation field which are representative for the LHC. For the same setup FLUKA simulations were performed including all relevant details (geometry, materials, source term, etc…).…”

“…The radiation fields are very stable throughout the year as the alignment of the beam has to be extremely precise. The integrated radiation levels thus scale with the integrated beam on target intensity and each test position can be calibrated just once, which is done with the dedicated monitors (RadMon) 15,16) and cross checked with activation foils and passive dosimeters, as well as successfully compared to detailed Monte Carlo calculations. A comparison for the radiation levels at the test locations between the FLUKA simulations and the measurements is shown in Table 2.…”