Photomultiplier tube with dynode modulation for photon-counting
View Patent ↗In a photomultiplier tube (PMT) device having a plurality of dynodes provided between a cathode and an anode, a cancellation circuit provides two different modulation signals to the PMT to cancel the effects of the modulation signals upon the output of the PMT. For one embodiment, a cancellation circuit includes an input to receive an input modulation signal, a first output to provide a first output modulation signal to a first dynode, and a second output to provide a second output modulation signal to a second dynode, wherein the first and second output modulation signals are 180 degrees out-of-phase. For another embodiment, the cancellation circuit provides the input modulation signal to one of the PMT's dynodes, and also subtracts the input modulation signal from the PMT's output signal.
1. A circuit, comprising:
a circuit component for modulating a gain of a photomultiplier tube in association with one or more dynodes of the photomultiplier tube, utilizing a modulation signal;
a circuit component for generating a matched signal matched to the modulation signal; and
a circuit component for combining the matched signal with an anode signal at an anode of the photomultiplier tube to generate a combination signal with a photon pulse amplitude that is preserved;
wherein the modulating, the generating, and the combining are performed for photon-counting.
2. A method, comprising:
modulating a gain of a photomultiplier tube in association with one or more dynodes of the photomultiplier tube, utilizing a modulation signal;
generating a matched signal matched to the modulation signal; and
combining the matched signal with an anode signal at an anode of the photomultiplier tube to generate a combination signal with a photon pulse amplitude that is preserved;
wherein the modulating, the generating, and the combining are performed for photon-counting.
3. The method of claim 2 , wherein the modulation signal is generated utilizing a cancellation circuit.
4. The method of claim 3 , and further comprising a voltage divider circuit having a plurality of resistor stages, each resistor stage coupled to one of the dynodes of the photomultiplier tube.
5. The method of claim 3 , wherein the cancellation circuit includes a first output coupled to a first of the dynodes and a second output connected to a second of the dynodes.
6. An apparatus, comprising:
a photomultiplier tube including a cathode, an anode, and one or more dynodes; and
a photon-counting circuit coupled to the photomultiplier tube, the circuit for generating a first modulation signal and a second modulation signal 180-degrees out-of-phase with the first modulation signal.
7. The apparatus of claim 6 , wherein the circuit includes a cancellation circuit.
8. The apparatus of claim 7 , and further comprising a voltage divider circuit having a plurality of resistor stages, each resistor stage coupled to one of the dynodes of the photomultiplier tube.
9. The apparatus of claim 7 , wherein the cancellation circuit includes a first output coupled to a first of the dynodes and a second output connected to a second of the dynodes.
10. The apparatus of claim 6 , wherein superimposition of a modulation signal upon an output signal of the photomultiplier tube is cancelled.
11. The apparatus of claim 6 , wherein the first modulation signal and the second modulation signal are applied to adjacent dynodes of the photomultiplier tube.
12. The apparatus of claim 6 , wherein a level of at least one of the first modulation signal and the second modulation signal is adjusted for minimizing a net AC modulation voltage at the anode of the photomultiplier tube.
13. A method, comprising:
providing a photomultiplier tube including a cathode, an anode, and one or more dynodes; and
generating a first modulation signal and a second modulation signal 180-degrees out-of-phase with the first modulation signal, for photon-counting.
14. An apparatus, comprising:
a photomultiplier tube including a cathode, an anode, and one or more dynodes including a first dynode with a first modulation signal applied thereto;
a photon-counting circuit coupled to the photomultiplier tube, the circuit for attenuating the first modulation signal, and subtracting the attenuated modulation signal from an anode signal at the anode of the photomultiplier tube;
wherein a path length of the attenuated modulation signal is matched.
15. The apparatus of claim 14 , wherein the attenuated modulation signal is capacitively-coupled.
16. The apparatus of claim 14 , wherein the circuit includes a cancellation circuit.
17. A method, comprising:
providing a photomultiplier tube including a cathode, an anode, and one or more dynodes including a first dynode with a first modulation signal applied thereto;
attenuating the first modulation signal; and
subtracting the attenuated modulation signal from as anode signal at the anode of the photomultiplier tube;
wherein the attenuating and the subtracting are performed for photon-counting, and a path length of the attenuated modulation signal is matched.