**1. NAME AND TITLE**

STRAGL: Calculation of Energy Loss Straggling of Heavy Charged Particles.

**2. CONTRIBUTORS**

Los Alamos National Laboratory, Los Alamos, New Mexico.

Lawrence Berkeley Laboratory, Berkeley, California.

**3. CODING LANGUAGE AND COMPUTER**

FORTRAN IV; CDC 6600.

**4. NATURE OF PROBLEM SOLVED**

STRAGL calculates the energy-loss distribution (straggling) of a monoenergetic beam of
charged particles, heavier than electrons, after it has passed through a thin absorber.

**5. METHOD OF SOLUTION**

The energy-loss distribution is calculated using Vavilov's formulas with the modification
developed by Shulek et al. which includes the effects of bound electrons. The calculation extends
and corrects the older regions of the Landau distribution and the gaussian straggling distribution.
The mean ionization potential of the absorber can either be supplied or will be calculated by the
program. The output listing provides various parameters of interest used in the calculation, the
mean energy loss, most probable energy loss, and the fwhm of the energy distribution. The
distribution is then plotted on the listing directly, and a table is printed that lists the values of the
distribution directly in probability per unit energy versus the energy loss.

**6. RESTRICTIONS OR LIMITATIONS**

The beam is assumed to be monoenergetic and heavier than electrons. There is no high energy
limit. The low energy and the large thickness limits are determined by the restriction that the mean
energy loss should not be more than 10 to 20% of the initial particle energy. For very thin
absorbers (for example, a few keV energy loss), the calculation also fails.

**7. TYPICAL RUNNING TIME**

The compile time is about 5 seconds and a typical case takes about 10 seconds on the CDC
6600 computer.

**8. COMPUTER HARDWARE REQUIREMENTS**

The code is operable on the CDC 6600 computer.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A FORTRAN IV compiler is required.

**10. REFERENCES**

a. Included in the documentation:

R. G. Clarkson and N. Jarmie, "Energy-Loss Straggling of Heavy Charged Particles,"
*Computer Physics Communications*, 2(7) (1971) 433-442.

H. Bichsel, "Straggling of Heavy Charged Particles: Comparison of Born Hydrogenic-Wave-Function Approximation with Free-Electron Approximation," *Phys. Rev. B* 1(7) (April 1970).

H. Bichsel, "Straggling and Particle Identification in Silicon Detectors," *Nucl. Inst. Meth.*, 78
(1970) 277-284.

b. Background information:

P. V. Vavilov, *Soviet Phys. JETP 5* (1957) 749.

P. Shulek, B. M. Golovin, L. A. Kulyukina, S. V. Medved and P. Pavlovich, *Soviet J. Nucl.
Phys.* 4 (1967) 400.

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents (10.a) and one (1.2MB) DOS diskette which contains
the source code and sample problem input and output.

**12. DATE OF ABSTRACT**

May 1975.

**KEYWORDS: ** CHARGED PARTICLES