1、BSI Standards PublicationProcess management for avionics Atmospheric radiation effectsPart 5: Assessment of thermal neutron fluxes and single event effects in avionics systemsBS IEC 62396-5:2014National forewordThis British Standard is the UK implementation of IEC 62396-5:2014. Itsupersedes DD IEC/T
2、S 62396-5:2008 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee GEL/107, Process management for avionics.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the
3、 necessary provisions ofa contract. Users are responsible for its correct application. The British Standards Institution 2014.Published by BSI Standards Limited 2014ISBN 978 0 580 84550 5ICS 03.100.50; 31.020; 49.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This
4、 British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 August 2014.Amendments/corrigenda issued since publicationDate Text affectedBRITISH STANDARDBS IEC 62396-5:2014IEC 62396-5 Edition 1.0 2014-08 INTERNATIONAL STANDARD Process management for avionic
5、s Atmospheric radiation effects Part 5: Assessment of thermal neutron fluxes and single event effects in avionics systems INTERNATIONAL ELECTROTECHNICAL COMMISSION S ICS 03.100.50; 31.020; 49.060 PRICE CODE ISBN 978-2-8322-1821-1 Registered trademark of the International Electrotechnical Commission
6、Warning! Make sure that you obtained this publication from an authorized distributor. colourinsideBS IEC 62396-5:2014 2 IEC 62396-5:2014 IEC 2014 CONTENTS FOREWORD . 3 1 Scope 5 2 Normative references. 5 3 Terms and definitions 5 4 Overview of thermal neutron single event rate calculation . 5 5 Ther
7、mal neutron flux inside an airliner 7 5.1 Definition of thermal neutron . 7 5.2 Overview. 7 5.3 Background on aircraft measurements . 7 5.4 Calculational approach 8 5.5 Processing of in-flight neutron flux data . 9 6 Thermal neutron SEU cross-sections . 13 6.1 Overview of the issue 13 6.2 Mechanism
8、involved 13 6.3 Thermal neutron SEU cross-sections and Ratio-2 15 7 Recommendation for devices in avionics at the present time . 17 7.1 General . 17 7.2 Ratio-1 17 7.3 Ratio-2 18 7.4 Thermal neutron upset rate . 18 8 Determining thermal neutron SEE rates for use in equipment assessments . 18 8.1 Dem
9、onstration of thermal neutron immunity to SEE 18 8.1.1 Thermal neutron test 18 8.1.2 Absence of boron 10 (B10) . 18 8.2 Determination of thermal neutron SEE where there is no evidence of thermal neutron immunity 19 8.2.1 Results from thermal neutron testing 19 8.2.2 Conservative estimation . 19 8.2.
10、3 High voltage devices 19 9 Single event burn out in high voltage devices due to thermal neutrons 19 Bibliography . 20 Figure 1 Atmospheric neutron spectra measured in four aircraft 10 Figure 2 Neutron cross-sections for boron-10 including total cross-section (red), total elastic cross-section (gree
11、n) and (n,) nuclear capture cross-section (blue) . 15 Table 1 Tabulation of the various atmospheric neutron measurements used 9 Table 2 Comparison of thermal and high energy neutron fluxes and their ratios . 11 Table 3 Calculated neutron fluxes in the Boeing 747 structure 12 Table 4 SRAM SEU cross-s
12、ections induced by thermal and high energy neutrons . 16 BS IEC 62396-5:2014IEC 62396-5:2014 IEC 2014 3 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ PROCESS MANAGEMENT FOR AVIONICS ATMOSPHERIC RADIATION EFFECTS Part 5: Assessment of thermal neutron fluxes and single event effects in avionics systems
13、FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the
14、 electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted t
15、o technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International
16、 Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each tec
17、hnical committee has representation from all interested IEC National Committees. 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Pub
18、lications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their na
19、tional and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter. 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment s
20、ervices and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by independent certification bodies. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to IEC or its directors, employees, s
21、ervants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the public
22、ation, use of, or reliance upon, this IEC Publication or any other IEC Publications. 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication. 9) Attention is drawn to the possibil
23、ity that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 62396-5 has been prepared by IEC technical committee 107: Process management for avionics. This first
24、 edition cancels and replaces the first edition of IEC/TS 62396-5 published in 2008. This edition constitutes a technical revision. This edition includes the following technical changes with respect to the previous technical specification: a) Change to title. b) Updated references and bibliography.
25、c) Subclause 6.2 expanded to consider smaller geometry devices. BS IEC 62396-5:2014 4 IEC 62396-5:2014 IEC 2014 d) Table 4 neutron cross-sections expanded to add more recent data and the ratio between thermal and high energy neutron cross-section amended to 2,42 from 2,77. e) Addition of reference s
26、ection on thermal neutron high voltage burn out. f) New clause on determination of thermal neutron SEE rates for use in equipment assessments. g) Document aligned as an IEC standard. The text of this international standard is based on the following documents: FDIS Report on voting 107/237/FDIS 107/2
27、42/RVD Full information on the voting for the approval of this international standard can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. A list of all the parts in the IEC 62396 series, published und
28、er the general title Process management for avionics Atmospheric radiation effects, can be found on the IEC website. The committee has decided that the contents of this publication will remain unchanged until the stability date indicated on the IEC web site under “http:/webstore.iec.ch“ in the data
29、related to the specific publication. At this date, the publication will be reconfirmed, withdrawn, replaced by a revised edition, or amended. A bilingual version of this publication may be issued at a later date. IMPORTANT The colour inside logo on the cover page of this publication indicates that i
30、t contains colours which are considered to be useful for the correct understanding of its contents. Users should therefore print this document using a colour printer. BS IEC 62396-5:2014IEC 62396-5:2014 IEC 2014 5 PROCESS MANAGEMENT FOR AVIONICS ATMOSPHERIC RADIATION EFFECTS Part 5: Assessment of th
31、ermal neutron fluxes and single event effects in avionics systems 1 Scope The purpose of this part of IEC 62396 is to provide a more precise definition of the threat that thermal neutrons pose to avionics as a second mechanism for inducing single event upset (SEU) in microelectronics. There are two
32、main points that will be addressed in this part of IEC 62396: a) a detailed evaluation of the existing literature on measurements of the thermal flux inside of airliners, and b) an enhanced compilation of the thermal neutron SEU cross-section in currently available SRAM devices (more than 20 differe
33、nt devices). The net result of the reviews of these two different sets of data will be two ratios that are considered to be very important for leading to the ultimate objective of how large a threat is the SEU rate from thermal neutrons compared to the SEU threat from the high energy neutrons (E 10
34、MeV). The threat from the high energy neutrons has been dealt with extensively in the literature and has been addressed by two standards (IEC 62396-1 in avionics and JESD89A 11in microelectronics on the ground). Neutrons with E 1 MeV are considered for parts with geometries below 150 nm. NOTE Refere
35、nce is made to IEC 62396-1:2012, 5.3.2, for smaller geometry parts below 150 nm which provides the neutron flux for energies above 1 MeV. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For da
36、ted references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 62396-1:2012, Process management for avionics Atmospheric radiation effects Part 1: Accommodation of atmospheric radiation effects via single
37、event effects within avionics electronic equipment IEC 62396-4, Process management for avionics Atmospheric radiation effects Part 4: Design of high voltage aircraft electronics managing potential single event effects 3 Terms and definitions For the purposes of this document, the terms and definitio
38、ns given in IEC 62396-1 apply. 4 Overview of thermal neutron single event rate calculation The two ratios that this part of IEC 62396 considers to be important are: _ 1Numbers in square brackets refer to the Bibliography. BS IEC 62396-5:2014 6 IEC 62396-5:2014 IEC 2014 a) the ratio of the thermal ne
39、utron flux inside an airliner relative to the flux of high energy ( 10 MeV) neutrons inside the airliner, and b) the ratio of the SEU cross-section due to thermal neutrons relative to that due to high energy neutrons. These ratios are considered to be important because with them, once the SEU rates
40、are defined from the high energy neutrons for an avionics box, a topic which has been dealt with extensively, such as in IEC 62396-1 and 1, then the additional SEU rate due to thermal neutrons can be obtained with these ratios. Thus, given the SEU rate from high energy neutrons, multiplying this by
41、the two ratios gives the SEU rate from the thermal neutrons. The total SEU rate will be the combination of the SEU rates from both the high energy and thermal neutrons. The process for calculating the SEU rate from the thermal neutrons is shown in the following set of equations, (1) to (5). SEU rate
42、 (Hi E2, upset/devh) = Hi(neutron flux = 6 000 n/cm2h) (Hi E, SEU X-Sctn. cm2/dev) (1) SEU rate (thermal neutron, upset/devh) ( )( )( )( )( )Sctn.-XSEUEHiSctn.-XSEUthermfluxneutronfluxneutronEHirateSEUHitherm= (2) Ratio-1 ( )( )fluxneutronfluxneutronHithermal= (3) Ratio-2 ( )( )Sctn.-XSEUEHiSctn.-XS
43、EUtherm= (4) SEU rate (thermal neutron, upset/devh) SEU rate (Hi E neutron upset/devh) Ratio-1 Ratio-2 (5) The objective of this part of IEC 62396 is to provide the values of Ratio-1, the ratio of the thermal to high energy neutron flux within an airplane, and of Ratio-2, the ratio of the SEU cross-
44、section due to thermal neutrons relative to that due to high energy neutrons. The Ratio-1 should be relatively similar in various types of commercial airliners, but it could vary significantly in other types of aircraft, such as military fighters. However, in the larger type of military aircraft, su
45、ch as AWACS (Advanced Warning and Command System, E-3, which is based on either a Boeing 707-320-B or 767) and JSTARS (Joint Surveillance Target Attack Radar System, E-8C, which is based on Boeing 707-300 airframe), the ratio should be very similar to that in airliners. With regard to the ratio of t
46、he thermal neutron SEU cross-sections, until recently, not very many such SEU cross-sections were reported in the literature. There were a few, and these were cited in 1. Due to the data that has recently become available, the number of devices in which the thermal neutron SEU cross-section has been
47、 measured has increased significantly. This additional data allows us to have good confidence on the values that have been measured and the resulting average value of the ratio. _ 2Hi E = High Energy. BS IEC 62396-5:2014IEC 62396-5:2014 IEC 2014 7 5 Thermal neutron flux inside an airliner 5.1 Defini
48、tion of thermal neutron Thermal neutrons are so called because although most atmospheric neutrons are produced at high energies following cosmic ray interactions, after a sufficient number of in-elastic collisions with the surrounding medium, the neutron velocity is reduced such that is has approxim
49、ately the same average kinetic energy as the molecules of the surrounding medium. This energy depends on the temperature of the medium, so it is called thermal energy. The thermal neutrons are therefore in thermal equilibrium with the molecules (or atoms) of the medium in which they are present. In a medium that has only a small probability of absorbing, rather than scattering, neutrons, the kinetic energies of the thermal neutrons is
