University:
Swansea University
Course:
PM134 | Microbiology
Academic year:

2023
Views:

322

Pages:

3
Author:

Sanjeev KG

Vacuum System Inside of the & optical system and the specimen chamber must be kept at high vacuum of 10-3to10-4 pa. → Diffusion Rump does this. Mostly weed : turbo moleculca pump. →A Specimen pre-evacuation chamber (airlock chomber) While keeping a high vacuum in the. Specimen Chamber. Working SEM uses electrons instead of light to form an image → A beam of es is produced at the top of the microscope by heating of a metallic filament. 1 The I beam follows a vertical path through the column of the microscope. It make its way through electromagnete lena which focus and divert the beam down towcords the sample. → Once. It hits the Sampla, other tes, (backscattered/20) are ejected from the sample. Detectors wlled the 2° Or backscattered is, and convert them to a signal that is Sent to a viewing Screen. Image formation 'beam is foussed into a fine Probe, which is Setbord scanned across the surface of the specimen u the help of scanning wils. Each Pont on the specimen that is struck by the accelerated electron emits signal in the form of electromag rodiation Selected Portion of this radiation, usually sccundary (1 and/or back'srattered Es (BSE), are collected by a deti Resulting Signal & amplified and displayed on a TV Sover Lamputer monitor 2° electron When the incident è beam enters the specimen; 2° Electron are produced from the emission of the valence is of the constituent atome in the specimen. → Since the energy of 2 electron is very small, those generated at a deep region are quickly absorbed by the Spoumen. → only those generated ad the top suryare cof the specimen are amitted Outside of core the specimen. The means that 2° electrone very sensitive. to the swyare 12 electron is used to observe the topography of the specimen Swyare