A high-voltage pulse-slicer unit with variable pulse duration has been developed and integrated with a 7 MeV linear electron accelerator (LINAC) for pulse radiolysis investigation. The pulse-slicer unit provides switching voltage from 1 kV to 10 kV with rise time better than 5 ns. Two MOSFET based 10 kV switches were configured in differential mode to get variable duration pulses. The high-voltage pulse has been applied to the deflecting plates of the LINAC for slicing of electron beam of 2 μs duration. The duration of the electron beam has been varied from 30 ns to 2 μs with the optimized pulse amplitude of 7 kV to get corresponding radiation doses from 6 Gy to 167 Gy.
A high-voltage pulse generator based on a self-matched transmission line with variable pulse amplitude and duration is developed. Two avalanche transistor stacks are used as switches. The pulse width is varied by adjusting the delay in triggering two switches whereas amplitude is adjusted by adjusting load resistance. A pulse with amplitude of 800 V to 3.8 kV and width of 5 ns to 38 ns can be obtained using this circuit.
Investigation of a monochromatic point X-ray source of photon energy $5 keV has been carried out. The source was set up using a laser produced aluminium plasma as a cathode and a point-tip titanium anode. Optimum parameters of the diode were determined from experimental measurements of X-ray intensity dependence on laser pulse energy, applied accelerating voltage, and distance between target (cathode) and anode, using Nd:glass laser pulses (FWHM 30 ns) of 2 mJ to 4 J energy. Electron temperature characterization of the target plasma was also performed from the XUV emission spectrum (5 to 80Ð). Parameters of X-ray radiation in Ti K-shells are 1) spectral brightness of $ 10 20 photons/cm 2 -sec-sr-keV, 2) spatial size $ 300 microns, and 3) X-ray pulse duration less than 20 ns.
A high voltage pulse generator with variable amplitude (100-3000 V) and duration (100-2000 μs) has been designed and developed. The variable duration pulse has been generated by adopting a simple and novel technique of varying the turn off delay time of a high voltage Metal Oxide Semiconductor Field Effect Transistor (MOSFET) based switch by varying external gate resistance. The pulse amplitude is made variable by adjusting biasing supply of the high voltage switch. The high voltage switch has been developed using a MOSFET based stack of 3 kV rating with switching time of 7 ns.
In this paper, a ramp generator with programmable slope is presented. It consists of a high voltage step generator, followed by integrator. The capacitor and inductor in the integrator are designed such that they can be varied by a microcontroller. This circuit generates two bipolar ramps with fastest speed <1 ns and provides continuous speed variation from 6 to 30 ns for a ramp of 500 V. This is being developed as a part of automated streak camera for deflection of electron beam.
A simple power supply and control electronic system to operate microchannel plate (MCP) detectors for imaging transient events such as X-ray emission from laser-produced plasmas is described. The power supply consists of two parts, viz. a high voltage pulse generator of 1 kV amplitude with a variable pulse duration of 100 jxs to 1 ms for the MCP input, and a regulated 5 kV d.c. for biasing the phosphor screen. The control unit synchronizes the high voltage pulse with the event and operates a safety switch to guard the detector against any accidental rise in the background pressure. A signal-to-noise ratio >_ 75 is obtained, limited by the noise contribution of the Charge Coupled Device (CCD)-frame grabber combination attached to the MCP. The system is compact, has provision for both positive and negative pulses, is extendable to higher voltages for operating two-stage MCP, and is immune to electromagnetic interference.Keywords. Microchannel plate; X-ray imaging; pulsed high voltage supply.
An investigation of a monochromatic point X-ray
source of photon energy ∼5 keV was carried out. The
source was set up using a laser produced Al plasma as a
cathode and a point-tip Ti anode. Optimum parameters of
the diode were determined from experimental measurements
of X-ray intensity dependence on laser pulse energy, applied
accelerating voltage, and distance between target (cathode)
and anode, using Nd:glass laser pulses (FWHM 30 ns) of
2 mJ to 4 J energy. Electron temperature characterization
of the target plasma was also performed from the XUV emission
spectrum (5–80 Å). Parameters of X radiation
in Ti K-shells are (1) spectral brightness of
∼1020 photons/cm2-sec-sr-keV,
(2) spatial size ∼300 microns, and (3) X-ray pulse
duration less than 20 ns.
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