A S Joshi
Articles written in Sadhana
Volume 31 Issue 5 October 2006 pp 613-620
A single-frame X-ray framing camera has been set up for fast imaging of X-ray emissions from pulsed plasma sources. It consists of two parts, viz. an X-ray pin-hole camera using an open-ended microchannel plate (MCP) detector coupled to a CCD camera, and a high voltage short duration gate pulse for the MCP. The camera uses a 10-Μm pin-hole aperture for imaging on the MCP detector with a magnification of 6 X. The high voltage pulser circuit generates a pulse of variable duration from 5 to 30 ns (at 70% of peak amplitude) with variable amplitude from 800 V to 1.25 kV, and is triggered through a laser pulse synchronized with the event to be recorded. The performance of the system has been checked by recording X-ray emission from a laser-produced copper plasma. A reduction factor of ∼ 6.5 is seen in the dark current contribution as the MCP gate pulse is decreased from 250Μs to 5 ns duration.
Volume 33 Issue 4 August 2008 pp 443-453
A large aperture disc ampliﬁer has been designed, set-up and characterized for its performance on small signal gain, spatial variation of gain, and thermal recovery time. This ampliﬁer, consisting of three elliptical Nd: phosphate glass discs of size 214 × 114 × 20 mm mounted at Brewster angle and pumped by ten xenon ﬁlled ﬂash lamps of 600 mm arc length, provided a small signal gain of 6 at electrical pump energy of 36 kJ (in a pulse of 450 𝜇s) using an in-house developed dual-polarity capacitor bank based power supply. It was coupled to a high power Nd: phosphate glass laser chain and a maximum output pulse energy exceeding 100 J in a 1·5 ns (FWHM) pulse has been measured. A dry nitrogen gas based cooling system was developed for cooling the glass discs with a thermal recovery time of ∼ 20 minutes.