### Abstract

For a Self-Amplified Spontaneous Emission (SASE) Free-Electron Laser (FEL), the FEL pulse energy fluctuates from shot to shot, because the lasing process starts up from shot noise. When operating in the exponential growth regime, the radiation exhibits the properties of completely chaotic polarized light. Hence, the probability distribution of the FEL pulse energy follows a Gamma-distribution. Measuring such a distribution function, one can calculate the average number of "degrees of freedom" or "modes" in the radiation pulse. Measuring the FEL power gain length, one can extract the temporal duration of a single coherent spike, therefore, one can calculate the FEL pulse temporal duration. In this paper, we report experimental results at LCLS. Measurements are conducted for both nominal charge (250 pC) and low charge (40 pC and 20 pC) cases.

Original language | English (US) |
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Pages | 147-150 |

Number of pages | 4 |

State | Published - Dec 1 2010 |

Externally published | Yes |

Event | 32nd International Free Electron Laser Conference, FEL 2010 - Malmo City, Sweden Duration: Aug 23 2010 → Aug 27 2010 |

### Other

Other | 32nd International Free Electron Laser Conference, FEL 2010 |
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Country | Sweden |

City | Malmo City |

Period | 8/23/10 → 8/27/10 |

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### ASJC Scopus subject areas

- Nuclear and High Energy Physics

### Cite this

*LCLS X-RAY pulse duration measurement using the statistical fluctuation method*. 147-150. Paper presented at 32nd International Free Electron Laser Conference, FEL 2010, Malmo City, Sweden.