lines

Table of Contents

1. Beam Lines
- 1.1. Simple Beam Lines
- 1.2. Sub-lines

1. Beam Lines

The accelerator to be studied is known to OPAL as a sequence of physical elements called a beam line. A beam line is built from simpler beam lines whose definitions can be nested to any level. A powerful syntax allows to repeat or to reflect pieces of beam lines. Formally a beam line is defined by a LINE command:

label:LINE=(member,...,member);

label see Section [label] gives a name to the beam line for later reference.

Each member may be one of the following:

An element label,
A beam line label,
A sub-line, enclosed in parentheses,

Beam lines can be nested to any level.

1.1. Simple Beam Lines

The simplest beam line consists of single elements:

label:LINE=(member,...,member);

Example:

L:LINE=(A,B,C,D,A,D);

ORIGIN: Position vector of the origin of the line. All elements in this line that are placed using ELEMEDGE use this position as reference.
ORIENTATION: Vector of Tait-Bryan angles [bib:tait-bryan] of the orientation of the line at the origin.

1.2. Sub-lines

Instead of referring to an element, a beam line member can refer to another beam line defined in a separate command. This provides a shorthand notation for sub-lines which occur several times in a beam line. Lines and sub-lines can be entered in any order, but when a line is used, all its sub-lines must be known.

Example:

L:LINE=(A,B,S,B,A,S,A,B);
S:LINE=(C,D,E);

This example produces the following expansion steps:

Replace sub-line S:
```
(A,B,(C,D,E),B,A,(C,D,E),A,B)
```
Omit parentheses:
```
A,B,C,D,E,B,A,C,D,E,A,B
```

valuated to constants immediately.