Corn Silage for Sows

Experiments with more than 2,000 pigs farrowed at Iowa State College show that corn silage- properly supplemented- makes an excellent and low-cost base ration for sows during pre-gestation and gestation

Extraction of electric field in heavily irradiated silicon pixel sensors

A new method for the extraction of the electric field in the bulk of heavily irradiated silicon pixel sensors is presented. It is based on the measurement of the Lorentz deflection and mobility of electrons as a function of depth. The measurements were made at the CERN H2 beam line, with the beam at a shallow angle with respect to the pixel sensor surface. The extracted electric field is used to simulate the charge collection and the Lorentz deflection in the pixel sensor. The simulated charge collection and the Lorentz deflection is in good agreement with the measurements both for non-irradiated and irradiated up to 1E15 neq/cm2 sensors.Comment: 6 pages, 11 figures, presented at the 13th International Workshop on Vertex Detectors for High Energy Physics, September 13-18, 2004, Menaggio-Como, Italy. Submitted to Nucl. Instr. Meth.

Simulation of Heavily Irradiated Silicon Pixel Detectors

We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5x10^{14} Neq/cm^2 to 5.9x10^{14} Neq/cm^2. The model correctly predicts the variation in the profiles as the temperature is changed from -10C to -25C. The measured charge collection profiles are inconsistent with the linearly-varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon. The model is now being used to calibrate pixel hit reconstruction algorithms for CMS.Comment: Invited talk at International Symposium on the Development of Detectors for Particle, AstroParticle and Synchrtron Radiation Experiments, Stanford Ca (SNIC06) 8 pages, LaTeX, 11 eps figure

Exact solutions for a mean-field Abelian sandpile

We introduce a model for a sandpile, with N sites, critical height N and each site connected to every other site. It is thus a mean-field model in the spin-glass sense. We find an exact solution for the steady state probability distribution of avalanche sizes, and discuss its asymptotics for large N.Comment: 10 pages, LaTe

Observation, modeling, and temperature dependence of doubly peaked electric fields in irradiated silicon pixel sensors

We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5x10^{14} Neq/cm^2 to 5.9x10^{14} Neq/cm^2. The model correctly predicts the variation in the profiles as the temperature is changed from -10C to -25C. The measured charge collection profiles are inconsistent with the linearly-varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon.Comment: 8 pages, LaTeX document, 10 figures. Presented at Pixel 2005 Workshop, Bonn, Sept 2005. Small cosmetic revisions in response to referee comments and to fix broken reference link

Position Dependence of Charge Collection in Prototype Sensors for the CMS Pixel Detector

This paper reports on the sensor R&D activity for the CMS pixel detector. Devices featuring several design and technology options have been irradiated up to a proton fluencec of 1E15 n_eq/cm**2 at the CERN PS. Afterward they were bump bonded to unirradiated readout chips and tested using high energy pions in the H2 beam line of the CERN SPS. The readout chip allows a non zero suppressed full analogue readout and therefore a good characterization of the sensors in terms of noise and charge collection properties. The position dependence of signal is presented and the differences between the two sensor options are discussed.Comment: Contribution to the IEEE-NSS Oct. 2003, Portland, OR, USA, submitted to IEEE-TNS 7 pages, 8 figures, 1 table. Revised, title change

Fluence Dependence of Charge Collection of irradiated Pixel Sensors

The barrel region of the CMS pixel detector will be equipped with ``n-in-n'' type silicon sensors. They are processed on DOFZ material, use the moderated p-spray technique and feature a bias grid. The latter leads to a small fraction of the pixel area to be less sensitive to particles. In order to quantify this inefficiency prototype pixel sensors irradiated to particle fluences between $4.7\times 10^{13}$ and 2.6\times 10^{15} \Neq have been bump bonded to un-irradiated readout chips and tested using high energy pions at the H2 beam line of the CERN SPS. The readout chip allows a non zero suppressed analogue readout and is therefore well suited to measure the charge collection properties of the sensors. In this paper we discuss the fluence dependence of the collected signal and the particle detection efficiency. Further the position dependence of the efficiency is investigated.Comment: 11 Pages, Presented at the 5th Int. Conf. on Radiation Effects on Semiconductor Materials Detectors and Devices, October 10-13, 2004 in Florence, Italy, v3: more typos corrected, minor changes required by the refere

The grand canonical ABC model: a reflection asymmetric mean field Potts model

We investigate the phase diagram of a three-component system of particles on a one-dimensional filled lattice, or equivalently of a one-dimensional three-state Potts model, with reflection asymmetric mean field interactions. The three types of particles are designated as $A$, $B$, and $C$. The system is described by a grand canonical ensemble with temperature $T$ and chemical potentials $T\lambda_A$, $T\lambda_B$, and $T\lambda_C$. We find that for $\lambda_A=\lambda_B=\lambda_C$ the system undergoes a phase transition from a uniform density to a continuum of phases at a critical temperature $\hat T_c=(2\pi/\sqrt3)^{-1}$. For other values of the chemical potentials the system has a unique equilibrium state. As is the case for the canonical ensemble for this $ABC$ model, the grand canonical ensemble is the stationary measure satisfying detailed balance for a natural dynamics. We note that $\hat T_c=3T_c$, where $T_c$ is the critical temperature for a similar transition in the canonical ensemble at fixed equal densities $r_A=r_B=r_C=1/3$.Comment: 24 pages, 3 figure

Analysis of conductor impedances accounting for skin effect and nonlinear permeability

It is often necessary to protect sensitive electrical equipment from pulsed electric and magnetic fields. To accomplish this electromagnetic shielding structures similar to Faraday Cages are often implemented. If the equipment is inside a facility that has been reinforced with rebar, the rebar can be used as part of a lighting protection system. Unfortunately, such shields are not perfect and allow electromagnetic fields to be created inside due to discontinuities in the structure, penetrations, and finite conductivity of the shield. In order to perform an analysis of such a structure it is important to first determine the effect of the finite impedance of the conductors used in the shield. In this paper we will discuss the impedances of different cylindrical conductors in the time domain. For a time varying pulse the currents created in the conductor will have different spectral components, which will affect the current density due to skin effects. Many construction materials use iron and different types of steels that have a nonlinear permeability. The nonlinear material can have an effect on the impedance of the conductor depending on the B-H curve. Although closed form solutions exist for the impedances of cylindrical conductors made of linear materials, computational techniques are needed for nonlinear materials. Simulations of such impedances are often technically challenging due to the need for a computational mesh to be able to resolve the skin depths for the different spectral components in the pulse. The results of such simulations in the time domain will be shown and used to determine the impedances of cylindrical conductors for lightning current pulses that have low frequency content