| Paper | Title | Page |
|---|---|---|
| TUPMS040 | Development of a THz Seed Source for FEL Microbunching Experiment at the Neptune Laboratory | 1275 |
|
||
|
Funding: This work is supported by US Department of Energy Grant No. DE-FG03-92ER40727
Seeded FEL/IFEL techniques can be used for modulation of a relativistic electron beam longitudinally on the radiation wavelength. However, in the 1-10 THz range, which is of particular importance for matched injection of prebunched electrons into a laser-driven plasma accelerating structure, a suitable radiation source is not available. At the UCLA Neptune Laboratory we have built and fully characterized a radiation source tunable in the range of 1-3 THz. The THz pulse is produced by mixing two CO2 laser lines in a noncollinear phase-matched GaAs crystal at room temperature. The crystal is pumped by 200 ns pulses of a dual beam TEA CO2 laser running at 1 Hz. A grating placed in each lasing section allowed to cover the spectral range for the difference frequency from 0.5-4.5 THz with a step of 30-40 GHz. The achieved narrow bandwidth of ~10-5 and the output power of 2kW are sufficient for seeding a single-pass, waveguide FEL amplifier-prebuncher*. These pulses were used to measure the coupling efficiency and the attenuation for different types of THz waveguides and the results will be reported.
* C. Sung et al. "Seeded FEL/IFEL techniques for radiation amplification and electron microbunching in the terahertz range" Phys. Rev. STAB, 2006 (to be published) |
||
| THPMS026 | The UCLA Helical Permanent-Magnet Inverse Free Electron Laser | 3055 |
|
||
| The Inverse Free Electron Laser (IFEL) is capable, in principle, of reaching accelerating gradients of up to 1 GV/m making it a prospective accelerator scheme for linear colliders. The Neptune IFEL at UCLA utilizes a 15 MeV Photoinjector-generated electron beam of 0.5 nC and a CO2 laser with peak energy of up to 100 J, and will be able to accelerate electrons to 100 MeV over an 80 cm long, novel helical permanent-magnet undulator. Past IFELs have been limited in their average accelerating gradient due to the Gouy phase shift caused by tight focusing of the drive laser. Here, laser guiding is implemented via an innovative Open Iris-Loaded Waveguide Structure scheme which ensures that the laser mode size and wave front are conserved through the undulator. The results of the first phase of the experiment are discussed in this paper, including the design and construction of a short micro-bunching undulator, testing of the OILS waveguide, as well as the results of corresponding simulations. |