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Significance and Use
The neutron spectrum in a test (simulation) environment must be known in order to use a measured device response in the test environment to predict the device performance in an operational environment (see Practice E1854). Typically, neutron spectra are determined by use of a set of sensors that have response functions that are sensitive over the neutron energy region to which the device under test (DUT) responds (see Guide E721). In particular, for silicon bipolar devices exposed in reactor neutron spectra, this effective energy range is between 0.01 and 10 MeV. A typical set of activation reactions that lack fission reactions from nuclides such as 235U, 237Np, or 239Pu, will have very poor sensitivity to the spectrum between 0.01 and 2 MeV. For a pool-type reactor spectrum, 70 % of the DUT electronic damage response may lie in this range. Often, fission foils are not included in the sensor set for spectrum determinations because their use must be licensed, and they require special handling for health physics considerations. The silicon transistors provide the needed response to define the spectrum in this critical range.
If fission foils are a part of the sensor set, the silicon sensor provides confirmation of the spectrum shape.
Bipolar transistors, such as type 2N2222A, are inexpensive, are smaller than fission foils contained in a boron ball, and are sensitive to a part of the neutron spectrum important to the damage of modern silicon electronics. They also can be used directly in arrays to map 1-MeV(Si) equivalent fluence. The proper set of steps to take in reading the transistor-gain degradation is the primary subject of this test method.
1.1 This test method covers the use of 2N2222A silicon bipolar transistors as dosimetry sensors in the determination of neutron energy spectra, and as silicon 1-MeV(Si) equivalent displacement damage fluence monitors.
1.2 The neutron displacement damage is especially valuable as a neutron spectrum sensor in the range 0.1 to 2.0 MeV when fission foils are not available. It has been applied in the fluence range between 2 × 10 12 n/cm2 and 1 × 1014 n/cm2 and should be useful up to 1015 n/cm2. This test method details the steps for the acquisition and use of silicon 1-MeV equivalent fluence information (in a manner similar to the use of activation foil data) for the determination of neutron spectra.
1.3 In addition, this sensor can provide important confirmation of neutron spectra determined with other sensors, and yields a direct measurement of the silicon 1-MeV fluence by the transfer technique.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
E170 Terminology Relating to Radiation Measurements and Dosimetry
E261 Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
E265 Test Method for Measuring Reaction Rates and Fast-Neutron Fluences by Radioactivation of Sulfur-32
E720 Guide for Selection and Use of Neutron Sensors for Determining Neutron Spectra Employed in Radiation-Hardness Testing of Electronics
E721 Guide for Determining Neutron Energy Spectra from Neutron Sensors for Radiation-Hardness Testing of Electronics
E722 Practice for Characterizing Neutron Fluence Spectra in Terms of an Equivalent Monoenergetic Neutron Fluence for Radiation-Hardness Testing of Electronics
E844 Guide for Sensor Set Design and Irradiation for Reactor Surveillance, E 706 (IIC)
E944 Guide for Application of Neutron Spectrum Adjustment Methods in Reactor Surveillance, E 706 (IIA)
E1854 Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic Parts
E2005 Guide for Benchmark Testing of Reactor Dosimetry in Standard and Reference Neutron Fields
E2450 Practice for Application of CaF2(Mn) Thermoluminescence Dosimeters in Mixed Neutron-Photon Environments
ICS Number Code 31.200 (Integrated circuits. Microelectronics)
UNSPSC Code 32111613(Bipolar or radio frequency bipolar transistor)