PHOTON COUNTING IN LASER INDUCED BREAKDOWN SPECTROSCOPY
A compact, low cost device for laser induced breakdown spectroscopy (LIBS) makes use of a silicon photomultiplier detector and a photon counting method.
1 . An instrument for determining an elemental concentration of an element in a test object using laser induced breakdown spectroscopy (LIBS), the instrument comprising:
a photon detector configured to receive photons and to produce photon pulse signals, each of the photon pulse signals corresponding to a one of the photons; and,
a photon counter configured to receive the photon pulse signals and to count a total photon count.
2 . The instrument of claim 1 further comprising a laser configured to emit laser pulses of laser power to a surface of the test object, each laser pulse having a trigger time, the laser emitting a total laser pulse number of pulses during a measurement time, the laser power causing emission of the photons from atoms of the test object.
3 . The instrument of claim 2 further comprising a wavelength dispersive spectrometer configured to receive the photons and to spatially disperse the photons according to a wavelength of each photon, thereby forming a wavelength dispersed spectrum of the photons.
4 . The instrument of claim 3 further comprising a wavelength selector configured to transmit selected photons having a selected wavelength portion of the wavelength dispersed spectrum, wherein the selected wavelength portion substantially corresponds to a characteristic wavelength of the element.
5 . The instrument of claim 4 wherein the photon detector is configured to receive the selected photons and each of the photon pulse signals corresponds to a one of the selected photons.
6 . The instrument of claim 1 wherein the photon detector is a silicon photomultiplier.
7 . The instrument of claim 2 wherein the total photon count is an accumulated number of photon pulse signals received by the photon counter during the measurement time.
8 . The instrument of claim 7 wherein the measurement time is a laser pulse time, wherein the laser pulse time is a time for the laser to emit a predetermined number of pulses.
9 . The instrument of claim 8 wherein the total photon count is proportional to the elemental concentration.
10 . The instrument of claim 7 wherein the measurement time is a photon count time, wherein the photon count time is a time for the photon counter to count a predetermined total photon count.
11 . The instrument of claim 10 wherein the total laser pulse number is proportional to the elemental concentration.
12 . The instrument of claim 1 wherein the instrument is a portable instrument.
13 . A method of determining an elemental concentration of an element in a test object using laser induced breakdown spectroscopy (LIBS), the method comprising the steps of:
detecting photons with a photon detector configured to receive the photons and to produce photon pulse signals, each of the photon pulse signals corresponding to a one of the selected photons; and,
counting a total photon count with a photon counter.
14 . The method of claim 13 further comprising the step of emitting laser pulses of laser power to a surface of the test object, each laser pulse having a trigger time, the laser emitting a total laser pulse number of pulses during a measurement time, the laser power causing emission of the photons from atoms of the test object.
15 . The method of claim 14 further comprising the step of receiving the photons at a wavelength dispersive spectrometer configured to spatially disperse the photons according to a wavelength of each photon, thereby forming a wavelength dispersed spectrum of the photons.
16 . The method of claim 15 further comprising the step of transmitting selected photons having a selected wavelength portion of the wavelength dispersed spectrum, wherein the selected wavelength portion substantially corresponds to a characteristic wavelength of the element.
17 . The method of claim 16 wherein the photon detector is configured to receive the selected photons and each of the photon pulse signals corresponds to a one of the selected photons.
18 . The method of claim 13 wherein the photon detector is a silicon photomultiplier.
19 . The method of claim 14 wherein the total photon count is an accumulated number of photon pulse signals received by the photon counter during the measurement time.
20 . The method of claim 19 wherein the measurement time is a laser pulse time, wherein the laser pulse time is a time for the laser to emit a predetermined number of pulses.
21 . The method of claim 20 wherein the total photon count is proportional to the elemental concentration.
22 . The method of claim 19 wherein the measurement time is a photon count time, wherein the photon count time is a time for the photon counter to count a predetermined total photon count.
23 . The method of claim 22 wherein the total laser pulse number is proportional to the elemental concentration.
24 . The method of claim 16 wherein the instrument is a portable instrument.