Digital I/Q Demodulator* SLAC-PUB-95-6857
I/Q demodulation is a common and useful RF signal processing technique used in charged-particle accelerators. When implemented with conventional analog RF components, a number of inherent errors can degrade the I/Q Demodulator performance, including gain balance, quadrature-phase balance, DC offsets, impedance match, and carrier leakage. Recent advances in high-speed analog-to-digital converters allow the I/Q demodulator to be implemented digitally, greatly reducing these systematic errors. This paper describes the design of a digital I/Q demodulator that will be applied to the PEP-II B factory.
rf feedback development for the PEP-II B factory
In PEP-II heavy beam loading along with a relatively long revolution period combine to strongly drive lower coupled-bunch modes through interaction with the fundamental cavity mode. Feedback techniques can be applied to reduce the cavity impedance seen by the beam. Several RF feedback loops are planned to reduce the growth rates down to a level which can be damped by the relatively low power bunch-by-bunch longitudinal feedback system[l]. This paper describes the RF feedback loops as well as hardware tests using a 500 kW klystron, analog and digital feedback loops, and a low power test cavity.
Nuclear spin-lattice relaxation in transition metal compounds with local tetragonal symmetry.
We report on the various contributions to the total spin-lattice relaxation rate in metallic materials with local tetragonal symmetry. The analytical formulae are given in the tight-binding approximation. The calculations show the relation between various partial electron densities of states and corresponding contributions to the relaxation rates. The presented formulae can be used to compare theoretically calculated electron band structure parameters with those obtained from NMR spin-lattice relaxation time measurements.