Pulse duration

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

A new high intensity and short-pulse molecular beam valve

Abstract: In this paper, we report on the design and performance of a new home-built pulsed gas valve, which we refer to as the Nijmegen Pulsed Valve (NPV). The main output characteristics include a short pulse width (as short as 20 μs) combined with operating rates up to 30 Hz. The operation principle of the NPV is based on the Lorentz force created by a pulsed current passing through an aluminum strip located within a magnetic field, which opens the nozzle periodically. The amplitude of displacement of the opening mechanism is sufficient to allow the use of nozzles with up to 1.0 mm diameter. To investigate the performance of the valve, several characterizations were performed with different experimental methods. First, a fast ionization gauge was used to measure the beam intensity of the free jet emanating from the NPV. We compare free jets from the NPV with those from several other pulsed valves in current use in our laboratory. Results showed that a high intensity and short pulse-length beam could be generated by the new valve. Second, the NPV was tested in combination with a skimmer, where resonance enhanced multiphoton ionization combined with velocity map imaging was used to show that the NPV was able to produce a pulsed molecular beam with short pulse duration (∼20 μs using 0.1% NO/He at 6 bars) and low rotational temperature (∼1 K using 0.5% NO/Ar at 6 bars). Third, a novel two-point pump-probe method was employed which we label double delay scan. This method allows a full kinematic characterization of the molecular beam, including accurate speed ratios at different temporal positions. It was found that the speed ratio was maximum (S = 50 using 0.1% NO/He at 3 bars) at the peak position of the molecular beam and decreased when it was on the leading or falling edge.

100 T magnet developed in Osaka

Abstract: A non-destructive pulsed magnet for 100 T has been developed to carry out precise magnetic measurements at extremely low temperatures and under high pressures Our record magnet has generated 803 T in a 10 mm bore with 7 ms pulse duration and then is called a 80 T magnet The 80 T magnet consists of inner and outer coils, both of these are made by winding with Cu–Ag wire and reinforced by maraging steel The inner coil is a single-layer coil backed up with a thin maraging pipe and the outer coil is made with nine layers reinforced by a thick maraging ring Magnetization and magnetoresistance measurements at 13 K have been carried out up to 70 T in the 80 T magnet The outer coil of the 80 T magnet has an 18 mm bore and can generate 713 T as a record and then is called a 70 T magnet The 18 mm bore of the 70 T magnet is a useful space for introducing an extremely low temperature into high magnetic field; this was used to carry out both magnetization and magnetoresistance measurements at 80 mK up to 60 T We have examined the lifetime of the 70 T magnet at various maximum fields in ordinary use The results show that about 100 shots can be made with 60 T and 500 shots at 55 T We have developed another 70 T magnet with longer pulse duration of about 20 ms for magnetization measurements under high pressure up to 10 kbar The 70 T magnet for high-pressure experiments has an 18 mm bore and an inductance of about 3 mH The magnet consists of an inner five-layer coil backed up with a thick maraging steel pipe and the outer has 11 layers and a maraging ring As the pressure cell used for the measurement is made of Be–Cu, a longer pulse is necessary to allow penetration of the pulsed field into the cell Magnetization measurements under high pressure have been carried out successfully up to 55 T although the pulse duration is not long enough to keep the temperatures very low A new pulsed magnet with higher field and longer pulse duration is proposed

High-power subnanosecond beams of runaway electrons and volume discharge formation in gases at atmospheric pressure

Abstract: A non-local criterion for runaway electrons generation is proposed, which is a universal two-valued dependence of the critical voltage U cr on pd for a certain gas (where p is the pressure and d is the interelectrode distance). This dependence subdivides the (U, pd) plane into an area of efficient electron multiplication and an area in which electrons leave the gas gap without multiplication. Electron beams of subnanosecond pulse duration and an amplitude of hundreds of amperes are generated at atmospheric pressure in various gases. A volume nanosecond discharge with a high specific excitation power was realized without the pre-ionization of the discharge gap by using an additional external source. The role of the electron avalanches propagating from the cathode to the anode in a dense gas was considered.

Digital circuit for control of gradual turn on of electrical tissue stimulators

Abstract: A circuit for causing the gradual turn-on of electrical tissue stimulation in a digitally controlled stimulator is disclosed. A stimulation pulse counter and a pulses per step memory circuit are connected to a decoder to provide an amplitude incrementing signal after a presettable count of stimulation pulses. An amplitude counter receives the incrementing signal to increment the amplitude of the stimulation output pulse through a digital to analog converter circuit and to reset the pulse counter. A maximum amplitude memory circuit and decoder operate in conjunction with the amplitude counter to latch the counter when a preset pulse amplitude is obtained. At the end of a stimulation interval, the amplitude counter is reset and stimulation pulses begin at the minimum amplitude at the start of the next stimulation interval.