High-power regenerative Nd:phosphate glass amplifier.
A compact high-power regenerative Nd:phosphate glass amplifier is described which incorporates spatial filtering and full image relay techniques. Output energies up to 1.2 J at a pulse duration of 140 ± 10 psec (FWHM) and 3 J at 900 ± 70 psec (FWHM) are achieved in a smooth nearly flattop beam intensity profile. Even with present-day technology, this system could be scaled into a terawatt regime.
Short pulse injection seeding of Q-switched Nd:glass laser oscillators-theory and experiment
A 0.5-GW-peak-power solid-state laser source that is based on injection seeding a Q-switched Nd:Glass laser is discussed. In the first experimental demonstration, a Q-switched oscillator producing 101 mJ was seeded by a train of 11-ps pulses from a CW (continuous-wave) mode-locked laser to produce injection-mode-locked pulses under a 91-ns envelope. A theoretical analysis of injection seeding of a high-gain Q-switched oscillator by the output of a mode-locked oscillator is presented. The numerical analysis predicts the minimum signal power required for injection mode locking and the temporal shape of the output pulse. The experimental results agree well with the theoretical predictions. The amplification demonstrated by this technique is 104.4 dB, which is much greater than that demonstrated by a multipass or regenerative amplifier. The experimental advantages of injection mode locking include greater than 100 dB of effective amplification and noncritical cavity length adjustment of the seed resonator. >
rPET detectors design and data processing
Small animal PET systems based on rotating planar detectors posses some interesting advantages for high sensitivity, high resolution imaging. We have designed the rPET detectors based on MLS crystals assembled on a 30times30 matrix optically coupled to a flat-panel PS-PMT. Weighted position readout circuits pre-process the 64 signals from the 8times8 anodes matrix, which are digitized using a charge-integrating converter. The amplification electronics, including the trigger output for coincidence detection, and the high voltage supply are integrated in a three PCBs stack that forms the base attached to the back of the PMT. The whole assembly is enclosed in a light tight, lead (Pb) shielded aluminum box. The detectors are mounted on a rotating gantry with more than 180 degrees rotation span. The digitized events are screened and histogramed, and a modified center of gravity algorithm removes from the position calculation those signals with poor signal to noise ratio. Apparent mean crystal size on the 511 keV field-flood images is 0.6 mm, mean peak-to-valley ratio is better than 8, and intrinsic resolution is 1.5 mm at the central row, with the energy window wide open. Sensitivity (CPS) for a pair of these detectors set in coincidence at 160 mm distance is 1%