IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 61, NO. 4, AUGUST 2014 1663 An SRAM Based Monitor for Mixed-Field Radiation Environments G. Tsiligiannis, L. Dilillo, A. Bosio, P. Girard, S. Pravossoudovitch, A. Todri, A. Virazel, J. Mekki, M. Brugger, F. Wrobel, and F. Saigné Abstract—CERN hosts a large number of electronic devices and equipment, functioning over its different particle accelerators. In certain areas, they operate in harsh radiation environments. In order to assure their proper functionality, the equipment or some of their sensitive components undergo several tests in experimental test areas representative of the LHC radiation fields, while special- ized monitors constantly record the respective radiation levels. The purpose of this study is to evaluate the use of monitors using re- cent technology nodes (90 nm) in order to have a better estimation of the expected error rate of the devices. The H4IRRAD experi- mental test area has been specifically designed to reproduce the radiation field that is present within the LHC tunnel and shielded areas. It has been used to test our custom SRAM based monitors. The monitors have been exposed to a maximum dose and high en- ergy hadron fluence of about 76 Gy and cm respec- tively. The results show that the total ionizing dose (TID) effect does not impact the bit cross section of our devices. Moreover the Single Event occurrence is coherent to the beam intensity fluctu- ations, proving that these devices are appropriate for SEU moni- toring under mixed particle fields. Index Terms—H4IRRAD, mixed particle fields, monitor, particle accelerators, radmon, SEU, SRAM. I. INTRODUCTION V ARIOUS types of accelerators and particle colliders op- erate at CERN, establishing a harsh and complex radi- ation environment for the installed electronic devices. Proper functioning of the equipment operating at mixed-field radiation areas is essential, and thus the error rate estimation of each de- vice is of significant importance. Since each equipment is com- Manuscript received September 30, 2013; revised December 09, 2013; ac- cepted December 31, 2013. Date of publication February 28, 2014; date of cur- rent version August 14, 2014. This work was supported by the French “Agence National pour la Recherche” (ANR) under the framework of the HAMLET project (ANR-09-BLAN-0155-01). G. Tsiligiannis, L. Dilillo, A. Bosio, P. Girard, S. Pravossoudovitch, A. Todri, and A. Virazel are with the Laboratoire d’Informatique, de Robotique et de Microelectronique de Montpellier (LIRMM) Universite de Montpellier II/CNRS, 34095 Montpellier Cedex 5, France (e-mail: tsiligiann@lirmm.fr; dilillo@lirmm.fr; bosio@lirmm.fr; girard@lirmm.fr; Serge.Pravossoudovitch@lirmm.fr; todri@lirmm.fr; virazel@lirmm.fr). J. Mekki and M. Brugger are with CERN, 1211 Geneva 23, Switzerland (e-mail: julien.mekki@cern.ch; markus.brugger@cern.ch). F. Wrobel is with the Institut d’Electronique du Sud, Universite Montpellier II/CNRS, UMR-CNRS 5214, France, and also with the Institut Universitaire de France (e-mail: frederic.wrobel@ies.univ-montp2.fr). F. Saigné is with the Institut d’Electronique du Sud, Universite Montpel- lier II/CNRS, UMR-CNRS 5214, France (e-mail: frederic.saigne@ies.univ- montp2.fr). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TNS.2014.2299733 posed of numerous of different components and of different technology, their testing and evaluation is performed in several levels and using various methods. Testing electronic devices under radiation is typically requir ed when they are meant to be used for safety-critical applica- tions such as nuclear, space and avionics. Depending on the na- ture of the application the devices will be used, they are sub- jected under different sources of radiation for testing. For ex- ample, heavy ions are mostly used for the testing of devices in- tegrated at space applications. Protons are also used to test ICs for space applications and evaluate the degradation of the device as a result of the received Total Ionizing Dose (TID). In [1] the impact of TID to the Single Event Upset (SEU) hardness of a de- vice has been studied when irradiated with gamma rays, low-en- ergy x-rays and protons under different voltage and temperature setups. Neutrons and alpha particles are also a common source of radiation for testing the devices’ sensitivity to Single Event Effects (SEE), usually when terrestrial applications are consid- ered. [2] reviews in detail the accelerated and life testing of de- vices under neutrons and alpha particles. Studies like the ones mentioned, reveal the response of a device when subjected to specific particle source types. However, when it comes to com- plex mixed particle fields such as the ones encountered within particle accelerators, the radiation environments are composed by several particle types spanning over a large energy range (from thermal energies to several GeVs). The use of Commer- cial Off The Shelf (COTS) ICs in certain electronic systems op- erating in these accelerators makes the testing under such envi- ronments a necessity. It is important to note that for the atmo- spheric spectra, particles yield similar energies and thus com- parable concerns for specific energy dependent effects such as latch-up [3]. The mixed particle type and energy field encountered at the LHC is composed of charged and neutral hadrons (protons, pions, kaons and neutrons), photons, electrons and muons ranging from thermal energies up to the GeV range. This com- plex field has been extensively simulated by the FLUKA Monte Carlo code benchmarked in detail for radiation damage issues at the LHC [4], [5]. The radiation is due to particles generated by proton-proton (or ion-ion) collisions in the experimental areas, distributed beam losses (protons, ions) around the accel- erator, and to beam interacting with the residual gas inside the beam pipe. The proportion of the different particle species in the field depends on the distance and on the angle with respect to the interaction point, as well as on the amount (if any) of installed shielding material. In this environment, electronic components and systems exposed to a mixed radiation field will 0018-9499 © 2014 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.