Multistage Yb-doped fiber amplifier generating megawatt peak-power, subnanosecond pulses

A Q-switched microchip laser generating 1064 nm wavelength, subnanosecond pulses at a 13.4 kHz repetition rate was used to seed a dual-stage amplifier featuring a 40 microm core Yb-doped photonic-crystal fiber (PCF) as the power amplifier. From this source, we obtained diffraction-limited (M2 = 1.05), approximately 450 ps pulses of energy > 0.7 mJ, peak power in excess of 1.5 MW, and an average power of approximately 9.5 W. By further amplifying the PCF output in a multimode 140 microm core Yb-doped fiber, we generated a peak power in excess of 4.5 MW, the highest obtained in a fiber source to our knowledge.     

The spectrum of protons produced in pp collisions at 31 GeV total energy

Data are reported on the distributions in longitudinal and transverse momentum of protons produced in the range 0.5 < x < 1.0 (x = Feynman variable) and 0.2 < p_T² < 1.8 (GeV/c)² in proton-proton collisions at 31 GeV c.m. energy at the CERN ISR. The invariant inelastic cross section shows a peak at high longitudinal momenta. The shape of this peak suggests substantial production of states with masses up to at least 7 GeV.     

The theta correspondence for similitudes

In this paper we investigate the theta correspondence for similitudes over a nonarchimedean local field. We show that the two main approaches to a theta correspondence for similitudes from the literature are essentially the same, and we prove that a version of strong Howe duality holds for both constructions. During the period of this work the author was a Research Associate with the NSF 1992–1994 special projectTheta Functions, Dual Pairs, and Automorphic Forms at the University of Maryland, College Park