A cytometer includes an avalanche photodiode, a switching power supply, a filter, and voltage adjustment circuitry. The switching power supply includes a feedback loop. The filter is electrically connected between the switching power supply and the avalanche photodiode. The voltage adjustment circuitry adjusts a voltage on the feedback loop based at least in part on a voltage measured between the filter and the avalanche photodiode.

A multi-channel photomultiplier tube (PMT) detector assembly includes a photocathode. The detector assembly includes a first dynode channel including a first set of dynode pathways. The first set of dynode pathways include a plurality of dynode stages configured to receive a first portion of the photoelectrons and direct a first amplified photoelectron current onto a first anode. The detector assembly includes an additional dynode channel including an additional set of dynode pathways. The additional set of dynode pathways includes a plurality of dynode stages configured to receive an additional portion of the photoelectrons and direct an additional amplified photoelectron current onto an additional anode. The detector assembly includes a grid configured to direct the first portion of the photoelectrons to one or more of the first set of pathways and an additional portion of the photoelectrons to one or more of the additional set of pathways.

A system, apparatus and method of improved measurement of the SPF factor of sunscreen compositions. In one embodiment, a method of measuring the protection of a sunscreen composition includes exposing skin to a known intensity of light, measuring the amount of remitted light from the skin, applying sunscreen to the skin, exposing the skin to which the sunscreen has been applied the known intensity of emitted light of the spectrum of light from which the sunscreen is intended to protect the skin, measuring the amount of light remitted from the skin, and calculating a UltraViolet-A Protection Factor (UVA-PF) of the sunscreen by comparing the amount of light remitted from the skin with the sunscreen to the amount of light remitted from the skin without the sunscreen.

A cytometer includes an avalanche photodiode, a switching power supply, a filter, and voltage adjustment circuitry. The switching power supply includes a feedback loop. The filter is electrically connected between the switching power supply and the avalanche photodiode. The voltage adjustment circuitry adjusts a voltage on the feedback loop based at least in part on a voltage measured between the filter and the avalanche photodiode.

An electron tube includes a housing having a window having an electromagnetic wave transmitting property, an electron emission plate disposed inside the housing, the electron emission plate emitting electrons, and a holding member disposed inside the housing and configured to hold the electron emission plate and to apply a voltage to the electron emission plate. The electron emission plate has a first main surface and a second main surface facing each other. The holding member has a base portion being in contact with the first main surface, and a plurality of electron emission plate biasing portions which are in contact with an edge of the second main surface and are configured to elastically bias the electron emission plate to the base portion. The holding member is electrically connected to the second main surface through the plurality of electron emission plate biasing portions.

The photomultiplier includes a set of macrocells, each comprising at least two microcells, each being connected to an output node according to an OR diagram, and achieving great energy efficiency upon deactivating each of the microcells when these are activated almost simultaneously, and that otherwise would have been masked by the OR diagram. To this end, each of the microcells comprises an active quenching and recharge circuit; an avalanche diode; a first deactivation transistor with its gate connected to an external processor, and its drain and source associated with the active quenching and recharge circuit; a second deactivation transistor with its gate connected to an external processor, and its source associated with the active quenching and recharge circuit.

Aspects of the present disclosure include systems for detecting light from a particle in a flow stream by spectral discrimination. Light detection systems according to certain embodiments include a wavelength separator component configured to propagate light between a first set of linear variable optical filters and a second set of linear variable optical filters where each set of linear variable optical filters is configured to pass light having predetermined sub-spectral ranges and a plurality of photodetectors positioned to detect light from each sub-spectral range across the linear variable optical filters. Systems having a light source for irradiating a particle in a flow stream and a photodetector modulator component for binning data signals generated in a plurality of photodetector channels of the light detection system are also described. Methods for detecting light with the subject systems and kits having one or more components for detecting light according to the subject methods are also provided.

A system, apparatus and method of improved measurement of the SPF factor of sunscreen compositions. In one embodiment, a method of measuring the protection of a sunscreen composition includes exposing skin to a known intensity of light, measuring the amount of remitted light from the skin, applying sunscreen to the skin, exposing the skin to which the sunscreen has been applied the known intensity of emitted light of the spectrum of light from which the sunscreen is intended to protect the skin, measuring the amount of light remitted from the skin, and calculating a UltraViolet-A Protection Factor (UVA-PF) of the sunscreen by comparing the amount of light remitted from the skin with the sunscreen to the amount of light remitted from the skin without the sunscreen.

An example circuit includes a light detector and a biasing capacitor having (i) a first terminal that applies to the light detector an output voltage that can either bias or debias the light detector and (ii) a second terminal for controlling the output voltage. The circuit includes a first transistor connected to the second terminal of the biasing capacitor and configured to drive the output voltage to a first voltage level above a biasing threshold of the light detector and thereby biasing the light detector. The circuit includes a second transistor connected to the second terminal of the biasing capacitor and configured to drive the output voltage to a second voltage level below the biasing threshold of the light detector and thereby debiasing the light detector. The second voltage is a non-zero voltage that corresponds to a charge level of the biasing capacitor.

A cytometer includes an avalanche photodiode, a switching power supply, a filter, and voltage adjustment circuitry. The switching power supply includes a feedback loop. The filter is electrically connected between the switching power supply and the avalanche photodiode. The voltage adjustment circuitry adjusts a voltage on the feedback loop based at least in part on a voltage measured between the filter and the avalanche photodiode.