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Level Set Interface Extinction Index Interpolation Method
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   Level Set Interface Extinction Index Interpolation Method = {char_string}

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**Description / Usage**
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This specifies the interpolation method of the level set properties for Extinction Index

Possible choiches for char_string:

LINEAR 
   Default linear interpolation :math:`p = (1-H({\phi})) p_- + H({\phi}) p_+`

LOG
   Log interpolation :math:`p = p_-^{(1-H({\phi}))} p_+^{H({\phi})}`


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**Examples**
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The following is a usage example for this card:

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   Level Set Interface Extinction Index Interpolation Method = LOG


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**Technical Discussion**
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The log interpolation has been found to behave better in some cases where
material property differences are large.