atten_coeff v3.3
07-OCT-94 MJF
23-JAN-96 MJF
03-MAR-99 MJF

    produce data files on attenuation and transmission for a material

example:

	atten_coeff << EOF
	min_keV max_keV dkeV
	N_materials
	mat_file thickness(cm)
	mat_file thickness(cm)
	.
	.
	EOF

directories/links:
        _materials: path to directory of material files
        _database: path to database directory

arguments:
	min_keV: 	minimum energy for tables
	max_keV: 	maximum energy for tables
	dkeV: 		energy increment for tables 
        N_materials: 	the number of material slabs considered
        mat_file:  	file name for a specific material descriptor
        thickness: 	material thickness in cm
 
associated files:
 
        read: none  (other than database and material files)

	write: "mat_file".atn
		   ascii file with table of energy(keV) , cm-1, cm2/gm, 
		   transmission for each material listed.	

		"trans.dat" 
		   ascii file with table of energy(kev) and total 
		   transmission through all materials listed.

method:
	The photoelectric cross sections are obtained from
	Biggs as used in the Tiger codes, Biggs F and Lighthill,
	Analytical Approximations of X-ray Cross Sections II,
	Technical Report SC-RR-710507, 1971.

	The incoherent (Compton, see sinc.doc) and coherent(see scoh.doc)
	cross sections are taken from
	McMaster, Del Grande, Kerr, Mallett, Husbell, Compilation of
	X-Ray Cross-Sections, UCRL-50174, 1970.

	The cross sections are converted to attenuation coefficients using
	the material information in the material files.

	The total cross section reported includes the coherent scattering
	cross section.

