Powder dictionary (pdCIF) version 1.0.1
Length of the specimen that is illuminated by the radiation source (in millimetres). Use _pd_instr_cons_illum_len for instruments where the illumination length does not vary with 2\q, by adjustment of the divergence slits (sometimes known as \q-compensated slits). Use _pd_instr_var_illum_len for instruments where the illuminated length of the specimen has been characterized as a function of 2\q, most commonly true with a fixed divergence slit.
The permitted range is 0.0 -> infinity