| 1. |
|
|
| 2. |
- Bettoni, S., et al.
(författare)
-
Impact of laser stacking and photocathode materials on microbunching stability in photoinjectors
- 2020
-
Ingår i: Physical Review Accelerators and Beams. - : AMER PHYSICAL SOC. - 2469-9888. ; 23:2
-
Tidskriftsartikel (refereegranskat)abstract
- Microbunching instability is a well-known phenomenon that may deteriorate the performance of accelerators. The instability may be triggered by a shot-noise mechanism or by some initial intensity modulations at the generation of the electron bunch (or both) and can be amplified all along the machine. At SwissFEL, the free-electron laser (FEL) facility operating at the Paul Scherrer Institute (PSI), the initial design stipulated a shaping of the photocathode laser output to obtain a flat-top longitudinal profile. This scheme is attractive in terms of the uniformity of the beam properties along the bunch. The drawback of this approach is that some unavoidable modulations are generated along the laser pulse. We investigate, both experimentally and by numerical simulations, the longitudinal dynamics of a beam obtained illuminating a copper cathode with a laser profile shaped by the stacking technique. We repeat the analysis for several compression factors and initial laser profile modulations. We find that the microbunching instability gain renders the use of the stacking technique not efficient to run a free-electron laser facility using as photocathode a material with a short response time. We experimentally demonstrate that the use of a material with a longer response time efficiently damps the structures originating from the laser profile obtained with stacking, and helps to improve the performance of the facility. In general, this is an approach to minimize the microbunching instability at any FEL (also not using stacking) or at least reduce the use of other countermeasures, which, such as the laser heater, may degrade the final FEL performance.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Osvay, Karoly, et al.
(författare)
-
Angular dispersion and temporal change of femtosecond pulses from misaligned pulse compressors
- 2004
-
Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1077-260X. ; 10:1, s. 213-220
-
Tidskriftsartikel (refereegranskat)abstract
- A misaligned stretcher or compressor in a chirped pulse amplification laser introduces residual angular dispersion into the beam, resulting in temporal distortion of the pulse. We demonstrate that an imaging spectrograph is capable for Measuring the angular dispersion of a laser beam by an accuracy of 0.2 murad/min. Using this technique, the analytical expressions of residual angular dispersion of misaligned prism and grating compressors are experimentally proved. Temporal degradations of short pulses due to angular dispersion are studied by measuring the, temporal stretch of 16-fs pulses, while the issues of contrast deterioration are also discussed. It is proved that the simultaneous; measurement of angular dispersion and pulse duration offers the most precise alignment procedure of prismatic and grating compressors.
|
|
| 8. |
- Osvay, Karoly, et al.
(författare)
-
On the temporal contrast of high intensity femtosecond laser pulses
- 2005
-
Ingår i: Laser and Particle Beams. - 0263-0346. ; 23:3, s. 327-332
-
Tidskriftsartikel (refereegranskat)abstract
- The temporal contrast is classified into two main regimes, the nanosecond-scale and the picosecond-scale contrast prior to the main pulse. The Lund terawatt laser system is shown to be improved on the nano- and picosecond-scale by a factor of 10 and 50, respectively, when it was optimized for contrast but not for energy. Calculations are also presented to emphasize the role of angular dispersion on the picosecond contrast. Finally we show a compromise between the duration and contrast of femtosecond laser pulses amplified in an optical parametric (chirped pulse) amplifier.
|
|
| 9. |
|
|
