2,555 research outputs found
Bayesian Approach for Linear Optics Correction
With a Bayesian approach, the linear optics correction algorithm for storage
rings is revisited. Starting from the Bayes' theorem, a complete linear optics
model is simplified as "likelihood functions" and "prior probability
distributions". Under some assumptions, the least square algorithm and then the
Jacobian matrix approach can be re-derived. The coherence of the correction
algorithm is ensured through specifying a self-consistent regularization
coefficient to prevent overfitting. Optimal weights for different correction
objectives are obtained based on their measurement noise level. A new technique
has been developed to resolve degenerated quadrupole errors when observed at a
few select BPMs. A necessary condition of being distinguishable is that their
optics response vectors seen at these specific BPMs should be near-orthogonal.Comment: 6 pages, 6 figure
InGaAs/InP heteroepitaxial Schottky barrier diodes for terahertz applications
This paper explores the feasibility of planar, sub-harmonically pumped, anti-parallel InGaAs/InP heteroepitaxial Schottky diodes for terahertz applications. We present calculations of the (I-V) characteristics of such diodes using a numerical model that considers tunneling. We also present noise and conversion loss predictions of diode mixers operated at 500 GHz, and obtained from a multi-port mixer analysis, using the I-V characteristics predicted by our model. Our calculations indicate that InGaAs/InP heteroepitaxial Schottky barrier diodes are expected to have an I-V characteristic with an ideality factor comparable to that of GaAs Schottky diodes. However, the reverse saturation current of InGaAs/InP diodes is expected to be much greater than that of GaAs diodes. These predictions are confirmed by experiment. The mixer analyses predict that sub-harmonically pumped anti-parallel InGaAs/InP diode mixers are expected to offer a 2 dB greater conversion loss and a somewhat higher single sideband noise temperature than their GaAs counterparts. More importantly, the InGaAs/InP devices are predicted to require only one-tenth of the local oscillator power required by similar GaAs diodes
Designing linear lattices for round beam in electron storage rings using the solution by linear matrices analysis
For some synchrotron light source beamline applications, a round beam is
preferable to a flat one. A conventional method of obtaining round beam in an
electron storage ring is to shift its tune close to a linear difference
resonance. The linearly coupled beam dynamics is analyzed with perturbation
theories, which have certain limitations. In this paper, we adopt the Solution
by LInear Matrices (SLIM) analysis to calculate exact beam sizes to design
round beam lattices. The SLIM analysis can deal with a generally linearly
coupled accelerator lattice. The effects of various coupling sources on beam
emittances and sizes can be studied within a self-consistent frame. Both the
on- and off-resonance schemes to obtain round beams are explained with
examples. The SLIM formalism for two widely used magnet models:
combined-function bending magnets, and planar wigglers and undulators, is also
derived.Comment: 11 pages, 15 figure
- …