Parallel capable? : yes

Parameter Name | Units | Type | Default | Description |

XMAX | double | 0.0 | size of alpha | |

XS1 | double | 0.0 | inner scraper position relative to XMAX | |

XS2 | double | 0.0 | outer scraper position relative to XMAX | |

DP1 | double | -1 | inner scraper fractional momentum deviation | |

DP2 | double | 1 | outer scraper fractional momentum deviation | |

XPUCK | double | -1 | position of scraper puck | |

WIDTHPUCK | double | 0.0 | size of scraper puck | |

DX | double | 0.0 | misalignment | |

DY | double | 0.0 | misalignment | |

DZ | double | 0.0 | misalignment | |

TILT | double | 0.0 | rotation about incoming longitudinal axis | |

PART | long | `0` |
0=full, 1=first half, 2=second half | |

ORDER | long | `0` |
matrix order [1,3] | |

GROUP | string | NULL | Optionally used to assign an element to a group, with a user-defined name. Group names will appear in the parameter output file in the column ElementGroup |

This element provides a matrix-based implementation of an alpha magnet [5].
Matrices up to third order are available [4].

The parameter `XMAX` determines the size of the alpha, which is related
to the gradient in the magnet and the central momentum by

(10) |

Because an alpha magnet has large dispersion at the midplane, it is often used
for momentum filtration in addition to bunch compression. The dispersion at the
center is given by the simple relation

(11) |

To split an alpha magnet, one uses the `PART` parameter. E.g.,

! First half, with momentum filter between -5% and +2.5% AL1: ALPH,XMAX=0.11,PART=1,DP1=-0.05,DP2=0.025 ! Second half AL2: ALPH,XMAX=0.11,PART=2 AL: LINE=(AL1,AL2)

As just illustrated, the parameters `DP1` and `DP2` may be used to filter the
momentum by providing fractional momentum deviation limits. These are implemented in
a physical fashion by computing the corresopnding horizontal position deviations and
imposing these as limits on the particle coordinates. One may also do this directly
using the `XS1` and `XS2` parameters, which specify maximum acceptable deviations
from the nominal horizontal position. `XS1` is the allowed deviation on the low-energy
side while `XS2` is the allowed deviation on the high-energy side.