Harmonics in a auantum free electron laser: towards a compact, coherent γ-ray source

Short-wavelength Free Electron Lasers (FELs) which have recently produced intense hard X rays are currently based on the concept of classical Self-Amplified Spontaneous Emission (SASE) In order to extend the production of Intense coherent radiation to sub-A wavelengths then an alternative to the conventional SASE-FEL concept will be necessary as conventional SASE-FELs require long wigglers (similar to 100 m) and large accelerators (similar to km) and produce radiation which has poor temporal coherence Recently we have introduced the concept of the Quantum Free Electron laser (QFEL) The QFEL is characterised by quantised electron momentum recoil and the emission of monochromatic coherent radiation from a compact apparatus This makes It appealing for applications requiring a high degree of temporal coherence We show that a SASE-QFEL may offer the possibility to produce intense coherent gamma-rays via harmonic generation This has the potential to open up new applications e g coherent interactions involving nuclear transitions.