**1. NAME AND TITLE**

NX1-NX2: Code System to Calculate Excitation Functions for (n,charged particle) Reactions.

**2. CONTRIBUTORS**

Institute of Atomic Energy, Beijing, China, through the International Atomic Energy Agency, Vienna, Austria, and the NEA Data Bank, Gif-Sur-Yvette, Cedex, France.

**3. CODING LANGUAGE AND COMPUTER**

Fortran 77; VAX family.

**4. NATURE OF PROBLEM SOLVED**

NX1 calculates excitation functions for (n,p) and (n,alpha) reactions. NX2 calculates excitation functions for (n,d) and (n,3He) reactions.

**5. METHOD OF SOLUTION**

The formulas for the excitation functions are analytical expressions. Therefore, no numerical techniques are required. They have been derived based on an evaporation model considering pre-equilibrium emission. Some primary approximations are:

1. Pre-equilibrium emission only occurs at the state of exciton number n = 3.

2. There is only one competing reaction of (n,n').

3. The (n,pn) and (n,alphan) reactions are primary channels for secondary particle emission.

4. A complex particle such as d, t, 3He, or alpha is regarded as an exciton which is previously formed in the target nucleus with a probability P(g).

5. The penetration factor of a rectangular-well potential is used to describe the effects of Coulomb barrier.

6. The energy level density of the compound nucleus is taken in the form of constant temperature.

**6. RESTRICTIONS OR LIMITATIONS**

The incident neutron energy must be less than or equal to 20 MeV. The target mass number is between 23 and 197.

**7. TYPICAL RUNNING TIME**

The sample input took only a few seconds on a VAX 6000 under the VAX/VMS operating system.

**8. COMPUTER HARDWARE REQUIREMENTS**

The code will run on the VAX family of computers.

**9. COMPUTER SOFTWARE REQUIREMENTS**

The code was written in Fortran 77 and uses the VAX/VMS Fortran compiler.

**10. REFERENCE**

ZHAO Zhixiang and ZHOU Delin, *Systematics of Excitation Function for (n,charged particle)
Reactions*, INDC(CPR)-8/L (June 1986).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one DS/HD (1.2 Mb) 5.25 inch diskette, including source files and sample cases.

**12. DATE OF ABSTRACT**

January 1992.

**KEYWORDS: ** NEUTRON; NUCLEAR MODELS