Expert: Index the field's value without an Analyzer, and also disable the storing of norms.. Note that you can also separately enable/disable norms by calling SetOmitNorms(bool). No norms means that index-time field and document boosting and field length normalization are disabled. The benfit is less memory ysage as norms take up one byte of RAM per indexed field for every document in the index, during searching. Note that once you index a given field with norms enabled, disabling norms will have no effect. In other words, for this to have the above described effect on a field, all instances of that field must be indexed with NOT_ANALYZED_NO_NORMS from the beginning.
Field.Index Class | Lucene.Net.Documents Namespace