Measurement of arrival time of particles in extensive air showers using TDC32     

S. K. Gupta  J. Christiansen  Y. Hayashi  A. Jain  P. K. Mohanty  K. C. Ravindran  B. Satyanarayana 《Experimental Astronomy》2013,35(3):507-526

Arrival time of particles in an extensive air shower (EAS) is a key physical parameter to determine its direction. EAS direction is useful for studies of anisotropy and composition of cosmic rays, and search for multi-TeV γ-rays sources. Accurate timing may be used to search exotic phenomena such as production of new particles at extremely high energies available during early stages of development of EAS and also for detecting sub-relativistic hadrons in EAS. Time to digital converters (TDCs) are used to perform this task. Traditional TDCs operate in the START-STOP mode with limited dynamic range and single-hit capability. With the advent of high luminosity collider LHC, need for TDCs with large dynamic range, multi-hit capability and TRIGGERED mode of operation became necessary. A 32 channel TDC was designed for the GRAPES-3 experiment on a CAMAC platform around TDC32, an ASIC developed by micro-electronics group at CERN, Geneva. Four modules were operated in the GRAPES-3 experiment. Here, we present details of the circuit design and their performance over several years. The multi-hit feature of this device was used to study the time structure of particles in the EAS on time scale of ~1 μs. The distribution of time intervals in the multi-hit data shows an exponential profile with a time constant of ~370 ns. These delayed particles are likely to be neutrons produced in the EAS core that were recorded in the scintillator detectors following the relativistic EAS front.  相似文献   

A New Method for Polar Field Interpolation   总被引：1，自引：0，他引：1  

X. Sun  Y. Liu  J. T. Hoeksema  K. Hayashi  X. Zhao 《Solar physics》2011,270(1):9-22

The photospheric magnetic field in the Sun’s polar region is not well observed compared to the low-latitude regions. Data are periodically missing due to the Sun’s tilt angle, and the noise level is high due to the projection effect on the line-of-sight (LOS) measurement. However, the large-scale characteristics of the polar magnetic field data are known to be important for global modeling. This report describes a new method for interpolating the photospheric field in polar regions that has been tested on MDI synoptic maps (1996 – 2009). This technique, based on a two-dimensional spatial/temporal interpolation and a simple version of the flux transport model, uses a multi-year series of well-observed, smoothed north (south) pole observations from each September (March) to interpolate for missing pixels at any time of interest. It is refined by using a spatial smoothing scheme to seamlessly incorporate this filled-in data into the original observation starting from lower latitudes. For recent observations, an extrapolated polar field correction is required. Scaling the average flux density from the prior observations of slightly lower latitudes is found to be a good proxy of the future polar field. This new method has several advantages over some existing methods. It is demonstrated to improve the results of global models such as the Wang–Sheeley–Arge (WSA) model and MHD simulation, especially during the sunspot minimum phase.  相似文献