Observation Of Self-amplified Spontaneous Emission Research Articles

Stable Operation of a Free-Electron Laser Driven by a Plasma Accelerator.

The breakthrough provided by plasma-based accelerators enabled unprecedented accelerating fields by boosting electron beams to gigaelectronvolt energies within a few centimeters [1-4]. This, in turn, allows the realization of ultracompact light sources based on free-electron lasers (FELs) [5], as demonstrated by two pioneering experiments that reported the observation of self-amplified spontaneous emission (SASE) driven by plasma-accelerated beams [6,7]. However, the lack of stability and reproducibility due to the intrinsic nature of the SASE process (whose amplification starts from the shot noise of the electron beam) may hinder their effective implementation for user purposes. Here, we report a proof-of-principle experiment using plasma-accelerated beams to generate stable and reproducible FEL light seeded by an external laser. FEL radiation is emitted in the infrared range, showing the typical exponential growth of its energy over six consecutive undulators. Compared to SASE, the seeded FEL pulses have energies 2 orders of magnitude larger and stability that is 3 times higher.

Observation of SASE and amplified seed of the DUV-FEL at BNL

The Deep Ultra Violet FEL (DUV-FEL) experiment is being commissioned in the Source Development Laboratory at NSLS in Brookhaven National Laboratory. The goal of the project is to produce coherent radiation below 100nm wavelength using High-Gain Harmonic Generation utilizing a seed laser. As a first step of this experiment, self-amplified spontaneous emission (SASE) has been achieved at 400 and 266nm with electron beam energies at 140 and 171.7MeV. As an intermediate stage of the experiment, direct seeding with the 266nm laser also has been accomplished. We report the measurements of the SASE and direct seeding. We measure the FEL properties for various electron beam conditions and discuss the performance of the FEL.

Photon diagnostics for the study of electron beam properties of a VUV SASE-FEL

A single-pass free-electron laser operating in the self-amplified spontaneous-emission (SASE) mode at around 100 nm is currently under test at the TESLA Test Facility at DESY. After first observation of SASE in February 2000, the photon beam has been characterized by different techniques. We present the methods of VUV photon diagnostics that were used to measure the spectral and angular distribution of the photon beam and how these properties are affected by the electron beam energy and orbit in the undulator.

Observation of self-amplified spontaneous emission in the wavelength range from 80 to 180 nm at the TESLA test facility FEL at DESY

The first observation of Self-Amplified Spontaneous Emission (SASE) in a free-electron laser (FEL) in the Vacuum Ultraviolet range between 80 and 180 nm wavelength is presented. The observed FEL gain (typically above 1000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width and intensity fluctuations are discussed. Some accelerator issues are covered, and the future plans for the TESLA Test Facility (TTF) FEL are mentioned.

First observation of self-amplified spontaneous emission in a free-electron laser at 109 nm wavelength

We present the first observation of self-amplified spontaneous emission (SASE) in a free-electron laser (FEL) in the vacuum ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron laser gain (approximately 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width, and intensity fluctuations, are all consistent with the present models for SASE FELs.

Observation of self-amplified spontaneous emission and exponential growth at 530 nm

Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator.

Observation of self-amplified spontaneous emission in the near-infrared and visible wavelengths

We report evidence of self-amplified spontaneous emission (SASE) at 1064 and 633 nm. To our knowledge, these are the first measurements of SASE at such a short wavelength and employ the smallest period wiggler, 8.8 mm, used to date in a successful SASE experiment. The experiments were performed with the MIT microwiggler at the Accelerator Test Facility at BNL. Single-pass, on-axis microwiggler emissions within a 25 nm bandwidth have been recorded as a function of beam charge and show a clear enhancement over spontaneous emission. For the measurement at 1064 nm, a single micropulse at 34 MeV with a variable charge of 0--1 nC and less than 5 ps full width at half maximum bunch length was passed through the microwiggler and emissions into a limited solid angle and bandwidth, selected by an aperture and interference filter, were focused onto a silicon photodiode. Enhancement of the emissions, from 2 to 6 times the spontaneous emission level, was observed at the highest charges. In addition, we observed SASE gain at a wavelength of 633 nm at a beam energy of 48 MeV, without detailed measurements.

First observation of self-amplified spontaneous emission at 1.064 μm

We report evidence of self-amplified spontaneous emission at 1064 nm. Single pass, on-axis microwiggler emissions into a 25 nm bandwidth have been recorded as a function of beam charge, and show a clear enhancement over spontaneous emission after threshold. These are the first measurements of SASE at such a short wavelength, and employ the smallest period wiggler used to date in a successful SASE experiment. The experiment has been performed with the MIT microwiggler at the Accelerator Test Facility at BNL. A single micropulse at 34 MeV with a variable charge of 0–1 nC and <5 ps bunch length is passed through the microwiggler and emissions into a limited solid angle and bandwidth, selected by an aperture and interference filter, are focused onto a silicon photodiode. Enhancement of the emissions from 2 to 6 times the spontaneous emission level is observed at the highest charges.

Observation of self-amplified spontaneous emission in the infrared free electron laser “CLIO”

A solution has been proposed about ten years ago to reach the X-ray range: the principle is to operate the FEL in the Self-Amplified Spontaneous Emission (SASE) configuration. In the high gain regime, the spontaneous emission is amplified along the undulator in a single pass configuration and without optical cavity. We report here the observation of SASE at the shortest wavelength, the mid-infrared range. A spectral analysis of the SASE has been carried-out in the start-up regime of SASE, far from the saturation level.

Observation of Self-Amplified Spontaneous Emission in the Mid-Infrared in a Free-Electron Laser

We have produced and analyzed self-amplified spontaneous emission emitted by a relativistic electron beam passing through an undulator for the first time in the mid-infrared. The spectral behavior of the line exhibits an unexpected growth at the start-up of the process.

Observation of SASE at 47 μm

Abstract Coherent, far-infrared undulator radiation from sub-picosecond electron pulses has been observed at the Stanford SUNSHINE facility. Measured intensities exceed theoretical prediction for spontaneous radiation by more than an order of magnitude. The forward-radiated energy from a 16 MeV electron beam travelling in a single pass through an undulator with a strength parameter K = 0.6 grows exponentially and is consistent with predictions of Self-Amplified Spontaneous Emission (SASE) with a gain length of 45.4 cm or 5.9 undulator periods.