Multi-channel system for truck and cargo scanning using impulse radiation sources
A multi-channel system for truck scanning, includes an impulse radiation source; and a plurality of detection circuits, each detection circuit comprising a scintillator, a photodiode, a supplemental circuit, an integrator and an ADC, connected in series. A current of the photodiode is proportional to radiation from the impulse radiation source. A data storage device stores outputs of the ADCs and provides the outputs to a computer that converts them to a shadow image of the scanned truck. The supplemental circuit isolates a capacitance of the photodiode from the integrator, filters out low frequency signals from the photodiode, amplifies the signal from the photodiode and reduces a bandwidth of the photodiode seen by the integrator. The supplemental circuit reduces an influence of capacitance of the photodiode on system noise, increases a signal-to-noise ratio of the system, and reduces an influence of photodiode temperature changes on a quality of the scanned image.
1. A multi-channel system for truck scanning, comprising:
an impulse radiation source;
a plurality of detection circuits, each detection circuit comprising a scintillator, a photodiode, a supplemental circuit, an integrator and an Analog to Digital Converter (ADC), connected in series,
wherein a current of the photodiode is proportional to impulse gamma radiation from the impulse radiation source;
a data storage device storing outputs of the ADCs and providing the stored outputs to a computer that converts the outputs to a shadow image of the scanned truck,
wherein the supplemental circuit isolates a capacitance of the photodiode from the integrator, filters out low frequency signals from the photodiode, amplifies the signal from the photodiode and reduces a bandwidth of the photodiode seen by the integrator, and
wherein the supplemental circuit includes a low noise amplifier to reduce an influence of capacitance of the photodiode on system noise.
2. The system of claim 1 , wherein the supplemental circuit reduces an influence of photodiode temperature changes on a quality of the scanned truck image.
3. The system of claim 1 , wherein the impulse radiation source is a betatron.
4. The system of claim 1 , wherein the impulse radiation source generates pulses of about 2 microsecond duration.
5. A multi-channel system for truck scanning, comprising:
an impulse radiation source;
a plurality of detection circuits, each detection circuit comprising a scintillator, a photodiode, a supplemental circuit, an integrator and an Analog to Digital Converter (ADC), connected in series,
wherein a current of the photodiode is proportional to impulse gamma radiation from the impulse radiation source;
a data storage device storing outputs of the ADCs and providing the stored outputs to a computer that converts the outputs to a shadow image of the scanned truck,
wherein the supplemental circuit isolates a capacitance of the photodiode from the integrator, filters out low frequency signals from the photodiode, amplifies the signal from the photodiode and reduces a bandwidth of the photodiode seen by the integrator,
wherein the supplemental circuit includes a low noise amplifier to increase a signal-to-noise ratio of the system.
6. A multi-channel system for truck scanning, comprising:
an impulse radiation source;
a plurality of detection circuits, each detection circuit comprising a scintillator, a photodiode, a supplemental circuit, an integrator and an Analog to Digital Converter (ADC), connected in series,
wherein a current of the photodiode is proportional to impulse gamma radiation from the impulse radiation source;
a data storage device storing outputs of the ADCs and providing the stored outputs to a computer that converts the outputs to a shadow image of the scanned truck,
wherein the supplemental circuit comprises:
a low-noise operational amplifier,
wherein an output of the photodiode is connected to an inverting input of the amplifier, and a non-inverting input of the low-noise operational amplifier is connected to ground,
a first resistor and a first capacitor, connected in parallel between an output of the low-noise operational amplifier and the inverting input of the low-noise operational amplifier,
a second resistor, a third resistor and a blocking capacitor, connected in series between the output of the low-noise operational amplifier and an output of the supplemental circuit, and
a second capacitor connected between the ground and a point between the second and third resistors.
7. The system of claim 6 , wherein the first resistor is at least 2 MΩ.
8. The system of claim 6 , wherein the second resistor is 100 KΩ-600 KΩ.
9. The system of claim 6 , wherein the third resistor is 100 KΩ-600 KΩ.
10. The system of claim 6 , wherein the first capacitor is 15-30 pF.
11. The system of claim 6 , wherein the second capacitor is 200-240 pF.
12. The system of claim 6 , wherein the blocking capacitor is 1200-3000 pF.
13. The system of claim 6 , wherein the low-noise operational amplifier has a bias voltage of up to 100 μV and a bias current of up to 10 pA.
14. A multi-channel system for object scanning, comprising:
an impulse radiation source;
a plurality of detection circuits, each detection circuit comprising a scintillator, a photodiode, a supplemental circuit, an integrator and an Analog to Digital Converter (ADC), connected in series,
wherein the photodiode produces an output that is proportional to radiation from the impulse radiation source;
a computer that converts the outputs of the photodiodes to a shadow image of the scanned truck,
wherein the supplemental circuit isolates a capacitance of the photodiode from the integrator, amplifies the signal from the photodiode and reduces a bandwidth of the photodiode seen by the integrator, and
wherein the supplemental circuit includes a low noise amplifier to reduce an influence of photodiode temperature changes on a quality of the scanned object image.
15. The system of claim 14 , wherein the supplemental circuit filters out low frequency signals from the photodiode.
16. The system of claim 14 , wherein the supplemental circuit reduces an influence of photodiode temperature changes on a quality of the scanned image.
17. The system of claim 14 , wherein the supplemental circuit comprises an operational amplifier, wherein an output of the photodiode is connected to an inverting input of the amplifier, and a non-inverting input of the operational amplifier is connected to ground,
a first resistor and a first capacitor, connected in parallel between an output of the operational amplifier and the inverting input of the operational amplifier,
a second resistor, a third resistor and a blocking capacitor, connected in series between the output of the operational amplifier and an output of the supplemental circuit, and
a second capacitor connected between the ground and a point between the second and third resistors.