Pulse duration

About: Pulse duration is a research topic. Over the lifetime, 19429 publications have been published within this topic receiving 286507 citations.

Progress of the Development of the IPP RF Negative Ion Source for the ITER Neutral Beam System

Abstract: IPP Garching has successfully developed a RF driven negative ion source for the ITER neutral beam injection system. The RF source is now an interesting alternative to the reference design with filamented sources due to its in principle maintenance-free operation. Current densities of 330 A/m 2 and 230 A/m 2 have been achieved for hydrogen and deuterium, respectively, at a pressure of 0.3 Pa and an electron/ion ratio of 1 for a small extraction area (7.0x10 -3 m 2 ) and short pulses (< 4 s). Reliable deuterium operation with more than 150 pulses in the required parameter range was obtained by an improved cesium operation utilizing a control of all source temperatures (grid as well as source body) and monitoring the amount of cesium in the source. The de- velopment concentrates now on extending the pulse length to up to 1 hour and extending the size of the source. The long pulse test bed went into operation last year; pulses of up to some 100 seconds with more or less stable conditions in terms of extracted currents and Cs dynamics have been achieved with current densities in the range of 150 - 200 A/m 2 in hydrogen operation. The pulse length, however, is still limited by non-sufficient cooling of some parts of the source and the RF circuit. The commissioning of the so-called "half-size" source test facility started recently with the first plasma pulses; this large RF source with the width and half the height of the ITER NNBI source is dedicated to the demonstration of the homogeneity of a large RF plasma — extraction is fore- seen in a latter phase — and the tests of an ITER-relevant RF circuit.

Pulse dynamics of dissipative soliton resonance with large duration-tuning range in a fiber ring laser

Abstract: The pulse dynamics operating in dissipative soliton resonance (DSR) region is experimentally investigated in a fiber ring laser. With the increase of pump power, the pulse profile transit from sech-like to rectangular shape was observed. The generated pulse in DSR region exhibits the conventional soliton spectrum with sideband generation. The duration-tuning range of the rectangular pulse is up to the cavity roundtrip time. Particularly, during the process of pulse duration broadening it was found that the rectangular pulse would trap a weak pulse generated from cw background. The obtained results may be useful for better understanding the DSR phenomenon.

Specular reflectivity of plasma mirrors as a function of intensity, pulse duration, and angle of incidence

Abstract: The specular reflectivity of plasma mirrors formed by subpicosecond pulses from a titanium:sapphire laser has been measured for different angles of incidence and for two different pulse lengths as a function of the laser intensity Laser pulses with energies up to 250 mJ and pulse durations of 90 and 500 fs were focused onto a fused silica substrate For angles of incidence between 6° and 45° the specular reflectivity increases to values of about 80% for intensities above a certain threshold intensity The threshold intensity varies with the pulse length but is nearly independent of the angle of incidence For very high intensities the specular reflectivity drops again to values of only a few percent

Direct measurement of transient pulses induced by laser and heavy ion irradiation in deca-nanometer devices

Abstract: This paper investigates the transient response of 50-nm gate length fully and partially depleted SOI and bulk devices to pulsed laser and heavy ion microbeam irradiations. The measured transient signals on 50-nm fully depleted devices are very short, and the collected charge is small compared to older 0.25-/spl mu/m generation SOI and bulk devices. We analyze in detail the influence of the SOI architecture (fully or partially depleted) on the pulse duration and the amount of bipolar amplification. For bulk devices, the doping engineering is shown to have large effects on the duration of the transient signals and on the charge collection efficiency.

Ultra-short pulse laser ablation of copper, silver and tungsten: experimental data and two-temperature model simulations

Abstract: Experimental results of femtosecond laser ablation of the metals copper, silver and tungsten are compared to simulations based on the two-temperature model. The comparison provides new information about the laser-heating process: For the noble metals (Cu, Ag), the energy transport via ballistic electrons must be included, while this effect is negligible for a transition metal (W). The comparison provides values for the range of ballistic electrons in the noble metals. The model calculation is also employed to investigate the dependence of the threshold fluence and melting depth on pulse duration. It is observed that for pulses shorter than approximately 1 ps the threshold fluence and melting depth are independent of the pulse duration, while they increase as τ 0.47 and τ 0.51, respectively, for pulses longer than ∼40 ps, in good agreement with approximate analytical expressions predicting a $\sqrt{\tau}$ dependence.