117514206
MWPC with highly segmented cathode pad readout
Experiments being conducted with high energy heavy ion beams at Brookhaven National Laboratory and at CERN have shown the importance of developing position sensitive detectors capable of handling events with high multiplicity in environments of high track density as will also be the case in future high luminosity colliders like SSC and RHIC. In addition, these detectors are required to have a dynamic range wide enough to detect minimum ionizing particles and heavy ions like oxygen or silicon. We present here a description of work being done on a prototype of such a detector at BNL. Results from a similar counter are also presented in this Conference. The ''pad chamber'' is a detector with a cathode area subdivided into a very large number of pixel-like elements such that a charged particle traversing the detector at normal incidence leaves an induced charge on a few localized pads. The pads are interconnected by a resistive strip, and readout amplifiers are connected to the resistive strip at appropriate, carefully determined spacings. The pattern of tracks in a multi-hit event is easily recognized, and a centroid-finding readout system allows position determination to a small fraction of the basic cell size. 5 refs., 9 figs.
13968109
A study of MWPC with chevron cathode pad readout
Abstract An investigation of MWPCs with interpolating chevron shaped cathode pad readout has been carried out as part of the R&D for the particle tracking system of the PHENIX detector at RHIC. Two prototype chambers were designed and constructed. Their response to minimum ionizing particles was tested with secondary beams from the AGS accelerator system at the Brookhaven National Laboratory. Results on resolution, differential non-linearity and overall performance for different chevron patterns and cell geometries are presented.
39772274
Interpolating cathode pad readout in gas proportional detectors for high multiplicity particle tracks
Abstract Experiments which are planned for the Superconducting Super Collider and the Relativistic Heavy Ion Collider will involve interactions in which detectors will identify and localize hundreds or even thousands of particle tracks simultaneously. Most types of conventional position sensitive, proportional detectors with projective geometry are not able to unravel the individual tracks in these environments. We have been investigating several forms of subdivided cathode readout to address this problem. We report here on geometric charge division using chevron shaped cathode pads which lie in rows underneath each anode wire. Investigations have quantified the nonlinear effects due to avalanche angular localization, and how these become negligible with proper design of the cathode pad. Differential nonlinearity of ±5%, and position resolution in the region of 50 μm rms, have been achieved.
195862381
Study of GEM characteristics for application in a MicroTPC
The Gas Electron Multiplier (GEM) may provide a convenient method for obtaining significant electron multiplication over large detector areas. An important potential application of the GEM is for readout of microTPCs. We are conducting a study of a multi-GEM structure with particular emphasis on the following characteristics: gain uniformity/stability, ion feedback and position readout. In particular, we present the first experimental results of interpolating anode pad readout. Initial results provide encouragement that the GEM application in microTPCs may be realized.
109473699
Gas proportional detectors with interpolating cathode pad readout for high track multiplicities
New techniques for position encoding in very high rate particle and photon detectors will be required in experiments planned for future particle accelerators such as the Superconducting Super Collider and new, high intensity, synchrotron sources. Studies of two interpolating cathode ``pad`` readout systems are described in this thesis. They are well suited for high multiplicity, two dimensional unambiguous position sensitive detection of minimum ionizing particles and heavy ions as well as detection of x-rays at high counting rates. One of the readout systems uses subdivided rows of pads interconnected by resistive strips as the cathode of a multiwire proportional chamber (MWPC). A position resolution of less than 100 {mu}m rms, for 5.4 keV x-rays, and differential non-linearity of 12% have been achieved. Low mass ({approximately}0.6% of a radiation length) detector construction techniques have been developed. The second readout system uses rows of chevron shaped cathode pads to perform geometrical charge division. Position resolution (FWHM) of about 1% of the readout spacing and differential non-linearity of 10% for 5.4 keV x-rays have been achieved. A review of other interpolating methods is included. Low mass cathode construction techniques are described. In conclusion, applications and future developments are discussed. 54 refs.
195841173
Investigation Of Chevron Cathode Pads For Position Encoding In Very High Rate, Gas Proportional Chambers
121115414
Impact of the local void on the cosmological parameters
In this paper, I discuss the effects of a local void on the cosmological parameters. It is found that, if the supernova distance is absolutely calibrated, then the bias of all the cosmological parameters is always important, while if the supernova distance is relatively calibrated, the largest effects will appear in the dark energy equation of state. For a local void of size similar to 100Mpc, the bias effects mainly manifest in the low redshift range. Therefore, the piecewise dark energy equation of state, especially the one in the range of lowest redshift, will be more strongly affected than the constant equation of state. In order to reduce this bias in constraining the cosmological parameters, one could require the distance of all the adopted supernovas be greater than 1.2 similar to 1.5 times of the radius of the local void. In this case, the residual bias can be safely ignored.
117246893
Standardization, Distance, Host Galaxy Extinction of Type Ia Supernova and Hubble Diagram from the Flux Ratio Method
In this paper we generalize the flux ratio method Bailey et al. (2009) to the case of two luminosity indicators and search the optimal luminosity-flux ratio relations on a set of spectra whose phases are around not only the date of bright light but also other time. With these relations, a new method is proposed to constrain the host galaxy extinction of SN Ia and its distance. It is first applied to the low redshift supernovas and then to the high redshift ones. The results of the low redshift supernovas indicate that the flux ratio method can indeed give well constraint on the host galaxy extinction parameter E(B-V), but weaker constraints on R_{V}. The high redshift supernova spectra are processed by the same method as the low redshift ones besides some differences due to their high redshift. Among 16 high redshift supernovas, 15 are fitted very well except 03D1gt. Based on these distances, Hubble diagram is drew and the contents of the Universe are analyzed. It supports an acceleration behavior in the late Universe. Therefore, the flux ratio method can give constraints on the host galaxy extinction and supernova distance independently. We believe, through further studies, it may provide a precise tool to probe the acceleration of the Universe than before.
119107919
GAMMA-RAY BURST LUMINOSITY RELATIONS: TWO-DIMENSIONAL VERSUS THREE-DIMENSIONAL CORRELATIONS
The large scatters of luminosity relations of gamma-ray bursts (GRBs) have been one of the most important reasons that prevent the extensive applications of GRBs in cosmology. In this paper, we extend the two-dimensional (2D) luminosity relations with tau(lag), V, E(peak), and tau(RT) as the luminosity indicators to three dimensions (3D) using the same set of luminosity indicators to explore the possibility of decreasing the intrinsic scatters. We find that, for the 3D luminosity relations between the luminosity and an energy scale (E(peak)) and a timescale (tau(lag) or tau(RT)), their intrinsic scatters are considerably smaller than those of corresponding 2D luminosity relations. Enlightened by the result and the definition of the luminosity (energy released in units of time), we discussed possible reasons behind this result, which may give us helpful suggestions on seeking more precise luminosity relations for GRBs in the future.
119271545
New constraints on anisotropic rotation of CMB polarization
The coupling of a scalar field to electromagnetic field via the Chern-Simons term will rotate the polarization directions of the cosmic microwave background radiation. The rotation angle which relies on the distribution of the scalar field on the CMB sky is direction dependent. Such anisotropies will give rise to new distortions to the power spectra of CMB polarization and it can be used to probe the detailed physics of the scalar field. In this paper we use the updated observational data to constrain the anisotropic rotation angle in a model independent way. We find that the dominant effect of the anisotropic rotation on CMB comes from its variance and it is constrained tightly by the current data.
118633745
Type II Radio Emission and Solar Particle Observations
The 28 October 2003 flare gave us the unique opportunity to compare the acceleration time of high-energy protons with the escaping time of those particles which have been measured onboard spacecraft and by neutron monitors network as GLE event. High-energy emission time scale and shock wave height and velocity time dependencies were also studied.