Abstract
According to the continuous development of metal-oxide semiconductor (MOS) fabrication technology, transistors have naturally become more radiation-tolerant through steadily decreasing gate-oxide thickness, increasing the tunneling probability between gate-oxide and channel. Unfortunately, despite this radiation-hardened property of developed transistors, the field of nuclear power plants (NPPs) requires even higher radiation hardness levels. Particularly, total ionizing dose (TID) of approximately 1 Mrad could be required for readout circuitry under severe accident conditions with 100 Mrad around a reactor in-core required. In harsh radiating environments such as NPPs, sensors such as micro-pocket-fission detectors (MPFD) would be a promising technology to be operated for detecting neutrons in reactor cores. For those sensors, readout circuits should be fundamentally placed close to sensing devices for minimizing signal interferences and white noise. Therefore, radiation hardening ability is necessary for the circuits under high radiation environments. This paper presents various integrated circuit designs for a radiation hardened charge-sensitive amplifier (CSA) by using SiGe 130 nm and Si 180 nm fabrication processes with different channel widths and transistor types of complementary metal-oxide-semiconductor (CMOS) and bipolar CMOS (BiCMOS). These circuits were tested under γ–ray environment with Cobalt-60 of high level activity: 490 kCi. The experiment results indicate amplitude degradation of 2.85%–34.3%, fall time increase of 201–1730 ns, as well as a signal-to-noise ratio (SNR) of 0.07–11.6 dB decrease with irradiation dose increase. These results can provide design guidelines for radiation hardening operational amplifiers in terms of transistor sizes and structures.
Highlights
Radiation detectors have been widely used in nuclear power plants (NPPs)
This paper provides the radiation-hardened designs of a charge-sensitive amplifier (CSA) operating in harsh radiating environments such as NPPs by using channel width optimization of complementary metal-oxide-semiconductor (CMOS) and bipolar CMOS (BiCMOS)
When radiation is injected into a metal-oxide semiconductor field effect transistor (MOSFET) and bipolar junction transistor (BJT), electron hole pairs (EHP) are formed along most of the radiation path, including the oxide layer
Summary
Radiation detectors have been widely used in nuclear power plants (NPPs). For instance, measuring neutron flux in a reactor core of a NPP delivers critical information for safety operations. A containment building in NPPs presents a relatively high total dose and dose rate, 108 –109 krad and 103 –106 krad/h, unlike the outer space field with 103 –104 krad total dose and 10−4 –10−2 krad/h dose rate, respectively [2] For this harsh environment, readout circuits should be radiation hardened and installed as close as possible near the sensor to minimize voltage degradation and signal interferences caused by long coaxial cables. One major architecture of preamplifiers is a charge-sensitive amplifier (CSA), which consists of an operational amplifier (OP-Amp), a feedback capacitor, and a feedback resistor [18,19] It could be considered as a front-end readout circuit in a wide range of applications using detectors, since this circuit converts collected charges from a detector into voltage pulses with excellent converting linearity despite temperature, DC bias voltage, and gain variations [20]. In order to clear the effect of numerous control variables on the circuit level, experimental results for amplitude change, fall time variation, and electrical noise are presented within a dose rate range corresponding to NPP environments
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