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Let us chose the point O in plasma at the distance h from the probe surface where electric field of the probe is negligible while each electron of plasma passing this point could reach the probe surface without collisions with plasma components : \ lambda_D \ ll \ lambda _ , \ lambda_D is Debye length and \ lambda _ is the electron free path calculated for its total cross section with plasma components .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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