Readme for C port

This C port aims to make the database easy to use in modern programming use. The library is based on the Fortran procedures, but have a few differences to note. Currently no table printing function is implemented yet.

There are a few differences that the user need to be aware:

• All calculations are done in double precision
• Data files should be put in XCOM subdirectory
• Data points on both sides of K edge is used for non-phoelectric cross sections (This may case jitter, but is not investegated yet).

Other changes are purely architectural and compatible improvements:

• Data is lazy loaded into a static table, instead of loading per output table per constituent element.
• FORM subroutine equavalent XCOM_parse_formula merges multiple occurances of same element, but still does not take braces (CH2CH2 is okay, Al2(SO4)3 is not).
• Material description is organized into structs
• Added procedures for calculating scatter part and total attenuation (but no "Total excluding coherent scatter").
• Energies are in eV cross sections are in b/atom, attenuations are in cm2/g.

Sample usage in sample.cpp

#include "XCOM.h"

#include <stdio.h>
int main()
{
	int error = 0;
	XCOM_material_info mat1;
	FILE* normal_mat1_output = 0;
	if(!normal_mat1_output) {
		error = -1;
		goto CLEANUP;
	}
	{
		XCOM_material_info info_resin = {0};
		if (!XCOM_parse_formula(&info_resin, "C6H7O2")) {
			error = -1;
			goto CLEANUP;
		}
		XCOM_material_info info_carbon = {0};
		info_carbon.element_count = 1;
		info_carbon.Z[0] = 6;
		info_carbon.weight_portion[0] = 1;

		const double rho_carbon_fiber = 1.80;
		const double rho_resin = 1.10;

		mat1 = info_resin;

		const double mat1_carbon_part = (1.4 - rho_resin) / (rho_carbon_fiber - rho_resin);

		if (!XCOM_material_mix_into(&mat1, mat1_carbon_part, &info_carbon)) {
			error = -1;
			goto CLEANUP;
		}
	}
	if (!XCOM_load_material(&mat1)) {
		error = -1;
		goto CLEANUP;
	}
	normal_mat1_output = fopen("mat1.csv", "w");
	if (!normal_mat1_output) {
		error = -1;
		goto CLEANUP;
	}
	for(int i = 1; i <= 200; ++i) {
		double energy = i *1000;
		double mat1_coherent = XCOM_material_coherent_scatter_attenuation(&mat1, energy);
		double mat1_incoherent = XCOM_material_incoherent_scatter_attenuation(&mat1, energy);
		double mat1_phot = XCOM_material_photoelectric_attenuation(&mat1, energy);
		double mat1_np = XCOM_material_nucleus_pair_production_attenuation(&mat1, energy);
		double mat1_sp = XCOM_material_shell_pair_production_attenuation(&mat1, energy);

		fprintf(normal_mat1_output, "%.6E,%.6E,%.6E,%.6E,%.6E,%.6E\n",
			energy, mat1_coherent, mat1_incoherent, mat1_phot, mat1_np, mat1_sp);
	}
CLEANUP:
	if(normal_mat1_output)
		fclose(normal_mat1_output);
	return error;
}

This prints the data for one material in csv format between 1keV to 200 keV

Original Readme

XCOM Documentation

M. J. Berger and J. H. Hubbell

A computer program and data base are presented which can be used to calculate, with a personal computer, photon cross sections for scattering, photoelectric absorbtion and pair production, as well as total attenuation coefficients, in any element, compound, or mixture, at energies from 1 keV to 100 GeV.

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Table of Contents:

I. Disclaimer II. Why you should use the Web III. Version History IV. Files for XCOM V. Setup VI. Running XCOM VII. Program Notes

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I. Disclaimer:

The National Institute of Standards and Technology (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data contained therein have been selected on the basis of sound scientific judgement. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the Database.

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II. Why you should use the Web:

Simple and convenient user interface
Graphing
Updated regularly

Check out the online version at:

http://physics.nist.gov/XCOM

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III. Version History:

Description
Version Number
Date
Programmer(s)

Programming Update
Version 3.1
June 1999
Martin J. Berger and Stephen M. Seltzer

NIST Standard Reference Database 8
Version 2.0
June 1990
Martin J. Berger and John H. Hubbell

Original Release
Version 1.2
July 1987
Martin J. Berger and John H. Hubbell

For more comprehensive version history information see the online documentation:

http://physics.nist.gov/PhysRefData/Xcom/Text/version.html

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IV. Files for XCOM:

XCOM.f Fortan Source ATWTS.DAT Atomic Weights Data File ENB.DAT Data File HASH1.DAT Data File HASH2.DAT Data File INDEX.DAT Data File MDATX3.xxx Cross Sections Data for each element where "xxx" is the atomic number

for PC only

XCOM.exe Photon Cross Sections Program makedisk.bat Application that can be used to copy the XCOM program to a floppy disk without including any extraneous files

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V. Setup:

1. Make a directory for XCOM
2. Unzip the XCOM zip into that directory

Note: PC users can skip step 3

3. Compile (and link) XCOM.f

To run the program, run XCOM and follow command line instructions

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VI. Running XCOM:

Follow comand line instructions

Note on: Format for entry from prepared input file - First, the number of energies in the list - Then, energies in MeV - All items separated by blank spaces

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VII. Program Notes:

For calculation information such as the method used see the online documentation:

http://physics.nist.gov/PhysRefData/Xcom/Text/intro.html