Note that there is a possibility the saprophytic fungus (like Aspergillus, Penicillium, Mucor, etc.) will also grow on your samples. In this step, you may observe several fungi grow in your samples. (In terms of identification, you need a microscope to observe the morphology or even need molecular identification to designate the species). But please note, it is not "identification", it is a kind of preliminary screening. (3) You can determine what kind of fungus grows in your samples visually by color or sporulation characteristics. (2) Then you need to incubate in the petri dish with wet cotton or paper till sporulation. If there is any entomopathogenic in your soil, it will cause mortality. It's a common method, you can easily find articles regarding this matter. So many people have used such schemes as yours over several decades that even the vendors of PMTs (Hamamatsu, Philips, Burle, and (formerly) many others) must know, if you can't find any of the hundreds, if not thousands, of publications on the subject.You can use the "bait method" to isolate entomopathogenic fungus from the soil by making contact with insects and the soil (1). Channeltrons and MCPs have picosecond pulses, probably good enough for your fast timing. Here the electrons (after amplification) hit a phosphor surface and produce an image that a CCD camera can see. The next step was the miniaturization of the channels into a dense array ("microchannelplate" MCP), which is also at the heart of night-vison devices. Open PMTs were largely succeeded by channel electron multipliers ("channeltron") in which a funnel at the entrance of a thin glass tube provides a target for photons, electrons, or ions, and an electric field moves the (external) photoelectrons into and along the inside of the tube to initiate a sequence of secondary electron avalanches (all inside high vacuum). Then you also have to provide a vacuum for the device to work. In the old days, "open" PMTs were produced in the laboratory by cutting open the bulb, which of course makes you lose the photocathode. Usually PMTs carry their own vacuum inside their bulb (glass or quartz) envelope, with the photocathode on the inside of the "window". Practically all PMTs work in vacuum, since they are photo-electron multipliers that imply amplification via electron avalanches between the dynode stages.
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