Coherence limits and chirp control in long pulse free electron laser oscillator

Y. Socol*, A. Gover, A. Eliran, M. Volshonok, Y. Pinhasi, B. Kapilevich, A. Yahalom, Y. Lurie, M. Kanter, M. Einat, B. Litvak

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We report experimental studies of the spectral linewidth and chirp characteristics of the mm-wave rf radiation of the Israeli Electrostatic- Accelerator free electron laser (EA-FEL), along with theory and numerical simulations. The simulations, matching the experimental data, were carried out using a space-frequency-domain model. EA-FELs have the capacity to generate long pulses of tens microseconds and more, that in principle can be elongated indefinitely (cw operation). Since a cold beam FEL is by nature a "homogeneously broadened laser," EA-FEL can operate, unlike other kinds of FELs, at a single longitudinal mode (single frequency). This allows the generation of very coherent radiation. The current status of the Israeli Tandem Electrostatic-Accelerator FEL, which is based on an electrostatic Van de Graaff accelerator, allows the generation of pulses of tens microseconds duration. It has been operated recently past saturation, and produced single-mode coherent radiation of record narrow inherent relative linewidth ∼Δf / f = 10-6 at frequencies near 100 GHz. A frequency chirp was observed during the pulses of tens of microseconds (0.3-0.5 MHz/ms). This is essentially a drifting "frequency-pulling effect," associated with the accelerator voltage drop during the pulse. Additionally, damped relaxation of the FEL oscillator was experimentally measured at the beginning and the end of the lasing pulse, in good correspondence to our theory and numerical simulations. We propose using the chirped signal of the pulsed EA-FEL for single pulse sweep spectroscopy of very fine resolution. The characteristics of this application are analyzed based on the experimental data.

Original languageEnglish
Article number080701
Pages (from-to)1-9
Number of pages9
JournalPhysical Review Special Topics - Accelerators and Beams
Issue number8
StatePublished - 31 Aug 2005


Dive into the research topics of 'Coherence limits and chirp control in long pulse free electron laser oscillator'. Together they form a unique fingerprint.

Cite this