Optical detectors and methods of using them
Certain embodiments described herein are directed to optical detector and optical systems. In some examples, the optical detector can include a plurality of dynodes, in which one or more of the dynodes are coupled to an electrometer. In other configurations, each dynode can be coupled to a respective electrometer. Methods using the optical detectors are also described.
1. A method of detecting optical emission, the method comprising:
simultaneously detecting an input current signal at each dynode of a plurality of dynodes of a photomultiplier configured to receive photons, in which each dynode is electrically coupled to a processor; and
using the processor to average the detected input current signals at each dynode that comprises a measured current input signal above a noise current input signal and below a saturation current input signal to determine a mean input current.
2. The method of claim 1 , further comprising terminating signal amplification at a dynode where a saturation current is measured.
3. The method of claim 2 , further comprising altering the voltage at a downstream dynode adjacent to the dynode where the saturation current is measured to terminate the signal amplification.
4. The method of claim 1 , further comprising determining the mean input current by:
calculating the input currents at all dynodes and discarding calculated input currents below the noise current input signal and above the saturation current input signal;
scaling each non-discarded calculated input current by its respective gain; and
averaging the scaled input currents to determine the mean input current.
5. The method of claim 1 , further comprising providing a floating voltage to each dynode of the plurality of dynodes.
6. The method of claim 1 , further comprising controlling the voltage at each dynode independently of voltage at the other dynodes of the plurality of dynodes.
7. The method of claim 1 , further comprising measuring the photons without adjusting the gain.
8. The method of claim 1 , further comprising measuring optical emission from a plurality of samples comprising different concentrations without adjusting the gain of the photomultiplier.
9. The method of claim 1 , further comprising measuring optical emission from a plurality of samples comprising different concentrations without adjusting entry slit width of the photomultiplier.
10. The method of claim 1 , further comprising calculating a sample concentration from the determined mean input current.
11. A method of detecting optical emission, the method comprising:
simultaneously detecting an input current signal of at least two internal dynodes of a photomultiplier configured to receive photons, in which the at least two internal dynodes are electrically coupled to a processor; and
using the processor to average the detected input current signals at each of the at least two internal dynodes comprising a measured current input signal above a noise current input signal and below a saturation current input signal to determine a mean input current.
12. The method of claim 11 , further comprising terminating signal amplification at a dynode where a saturation current is measured.
13. The method of claim 11 , further comprising simultaneously detecting an input current signal at every other internal dynode of the plurality of dynodes.
14. The method of claim 11 , further comprising simultaneously detecting an input current signal at every third internal dynode of the plurality of dynodes.
15. The method of claim 14 , further comprising terminating signal amplification at a dynode where a saturation current is measured.
16. The method of claim 11 , further comprising providing a floating voltage at each detected dynode of the plurality of dynodes.
17. The method of claim 11 , further comprising controlling the voltage at each dynode independently of voltage at the other dynodes of the plurality of dynodes.
18. The method of claim 11 , further comprising measuring optical emission from a plurality of samples comprising different concentrations without adjusting the voltage of the photomultiplier.
19. The method of claim 11 , further comprising measuring optical emission from a plurality of samples comprising different concentrations without adjusting entry slit width of the photomultiplier.
20. The method of claim 11 , further comprising calculating sample concentration from the determined mean input current.