A. De Angelis

XeCl discharge diagnostic by holographic interferometry

A direct measurement of the electron-density time evolution in the active medium of a self-sustained XeCl laser discharge has been performed by means of the holographic interferometry technique. The time and space resolved behaviour of the discharge seems to confirm that the halogen depletion instability and the hot spots developing in the cathode region are the basic mechanisms which determine the premature termination of the output laser pulse.

Design considerations on a high-power VUV FEL

We explore the feasibility conditions of a high-power EEL operating in the VUV region (below 100 nm) and exploiting a coupled oscillator triplicator configuration. A high quality beam from a linac is passed through a EEL oscillator and produces laser radiation at 240 nm. The same beam is extracted and then injected into a second undulator tuned at the third harmonic of the first. The bunching produced in the oscillator allows the start up of the laser signal in the second section which operates as an amplifier. We discuss the dynamical behavior of the system and the dependence of the output power on the characteristics of the e-beam and of the oscillator. The possibility of enhancing the output power, adding a tapered section to the second undulator, is finally analyzed. >

Above threshold operation of the ENEA free electron laser

Abstract Recent experimental results of the ENEA FEL experiment performed with a 20 MeV, 120 mA microtron and a linearly polarized pulsed electromagnetic undulator are reported.

Status of the ENEA-Dartmouth far infrared Cherenkov laser experiment

Abstract In this article we report on the design parameters and status of the experiment of the ENEA-Dartmouth Cherenkov free electron laser. A brief analysis of the spontaneous emission process is also presented.

A 100 μm Cherenkov laser experiment

Abstract The basic operating principles of far infrared Cherenkov lasers are summarized and then used as a design guide for a proposed 100 μm region oscillator experiment. A discussion of the required accelerator and resonator parameters is presented and the preliminary experimental progress is reviewed.

The FERMI FEL project at Trieste

Abstract The main features of the proposed new IR/FIR FEL user facility, FERMI, are described.

Characterization of a high-uniformity, X-ray preionized XeCl laser

SummaryThe construction and the operating characteristics of a X-ray preionized discharge XeCl laser are described. A specific laser output energy of 3.3 J/l with a pulsewidth of 150 ns and a spatial beam uniformity better than 90% in a (3.5×3.5) cm2 cross-section was achieved. Intrinsic efficiency up to 3.6% has been obtained without the use of an external prepulse circuit. A fast, high-voltage prepulse to intensify the preionization has been successfully tried out, obtaining a better energy coupling to the gas and more reliable conditions at lower working voltage.RiassuntoSi presentano le caratteristiche costruttive e operative di un laser a XeCl preionizzato a raggi X e funzionante in regime di scarica autosostenuta. Si sono ottenuti impulsi laser con energie specifiche di 3.3 J/l e durata di 150 ns. L’uniformità spaziale del fascio laser di dimensioni (3.5×3.5) cm2 è risultata migliore del 90%. La massima efficienza intrinseca raggiunta senza l’uso di un circuito esterno di preimpulso è stata del 3.6%. L’introduzione del preimpulso ad alta tensione per intensificare la preionizzazione ha consentito di migliorare l’accoppiamento in energia depositata nel mezzo attivo e di ottenere un punto di lavoro piú stabile a tensione di pompaggio piú bassa.РезюмеОписываются конструкция и характеристики рентгеновского предионизационного XeCl лазера. Были получены лазерные импульсы с удельной энергией 3.3 Дж/литр и длительностью 150 нс. Пространственная однородность лазерного пучка с размерами (3.5×3.5) см2 была лучше 90%. Была получена внутренняя эффективность вплоть до 3.6% без использования внешнего предимпульсного тока. Успешно опробовано введение предимпульса высокого напряжения для интенсификации предионизации. Получено улучшение связи энергии в активной среде и более надежные условия работы лазера при меньшем напряжении.

Status of the free electron laser experiment at the ENEA Frascati center

Abstract The status of the free electron laser experiment under realization at the ENEA Frascati center is described. The experimental results relevant to electron beam and spontaneous radiation are reported.

A far-infrared quasi-optical resonator for a Cherenkov free electron laser

Abstract A Cherenkov free electron laser experiment (Ch-FEL) employing a 5 MeV microtron electron-beam source and providing coherent radiation in the spectral range from 100 to 1000 μm is under way in our laboratories. Recent tests of a quasi-optical resonator are reported.

Design considerations for the ENEA-FEL optical resonator

Abstract The main problems connected with the design of the optical resonator for a free electron laser are briefly analyzed with respect to the optimization of the laser performance. The proper operation of the ENEA free electron laser indeed requires accurate setting and control of both mirror spacing and angular alignment. A long-path Fabry-Perot interferometer with a sensitivity of ∼ 10−6 rad developed for the control of the resonator alignment is described.