Characterizing the influence of neutron fields in causing single-event effects using portable detectors

The malfunction of semiconductor devices caused by cosmic rays is known as Single Event Effects(SEEs). In the atmosphere, secondary neutrons are the dominant particles causing this effect. The neutron flux density in atmosphere is very low. For a good statistical certainty, millions of device hours are required to measure the event rate of a device in the natural environment. Event rates obtained in such testings are accurate. To reduce the cost and time of getting the event rate, a device is normally taken to artificial accelerated neutron beams to measure its sensitivity to neutrons. Comparing the flux density of the beam and the flux density of a location in the atmosphere, the real time event rate can be predicted by the event rate obtained. This testing method was standardized as the neutron accelerated soft error rate (ASER) testing in JEDEC JESD89A standard. However, several life testings indicated that the neutron flux density predictions given by the accelerated testings can have large errors. Up to a factor of 2 discrepancy was reported in the literature. One of the major error sources is the equivalence of the absolute neutron flux density in the atmosphere and in accelerated beam. This thesis proposes an alternative accelerated method of predicting the real-time neutron error rate by using proxy devices. This method can avoid the error introduced by the uncertainty in the neutron flux density. The Imaging Single Event Effect Monitor (ISEEM) is one of the proxy devices. It is the instrument originally developed by Z. Török and his co-workers in the University of Central Lancashire. A CCD was used as the sensitive element to detect neutrons. A large amount of data sets acquired by Török were used in this work. A re-engineered ISEEM has been developed in this work to improve ISEEM performance in life testings. Theoretical models have been developed to analyze the response of ISEEM in a wide range of neutron facilities and natural environment. The agreement of the measured and calculated cross-sections are within the error quoted by facilities. Because of the alpha contamination and primary proton direct ionization effects, performance of ISEEM in life testings appeared to be weak

X-Ray Synchrotron Emitting Fe-Rich Ejecta in SNR RCW 86

Supernova remnants may exhibit both thermal and nonthermal X-ray emission. We present Chandra observations of RCW 86. Striking differences in the morphology of X-rays below 1 keV and above 2 keV point to a different physical origin. Hard X-ray emission is correlated fairly well with the edges of regions of radio emission, suggesting that these are the locations of shock waves at which both short-lived X-ray emitting electrons, and longer-lived radio-emitting electrons, are accelerated. Soft X-rays are spatially well-correlated with optical emission from nonradiative shocks, which are almost certainly portions of the outer blast wave. These soft X-rays are well fit with simple thermal plane-shock models. Harder X-rays show Fe K alpha emission and are well described with a similar soft thermal component, but a much stronger synchrotron continuum dominating above 2 keV, and a strong Fe K alpha line. Quantitative analysis of this line and the surrounding continuum shows that it cannot be produced by thermal emission from a cosmic-abundance plasma; the ionization time is too short, as shown both by the low centroid energy (6.4 keV) and the absence of oxygen lines below 1 keV. Instead, a model of a plane shock into Fe-rich ejecta, with a synchrotron continuum, provides a natural explanation. This requires that reverse shocks into ejecta be accelerating electrons to energies of order 50 TeV. We show that maximum energies of this order can be produced by radiation-limited diffusive shock acceleration at the reverse shocks.Comment: ApJ, accepted; full resolution images in http://spider.ipac.caltech.edu/staff/rho/rcw86chandra.p

Characterizing the influence of neutron fields in causing single-event effects using portable detectors

The malfunction of semiconductor devices caused by cosmic rays is known as Single Event Effects(SEEs). In the atmosphere, secondary neutrons are the dominant particles causing this effect. The neutron flux density in atmosphere is very low. For a good statistical certainty, millions of device hours are required to measure the event rate of a device in the natural environment. Event rates obtained in such testings are accurate. To reduce the cost and time of getting the event rate, a device is normally taken to artificial accelerated neutron beams to measure its sensitivity to neutrons. Comparing the flux density of the beam and the flux density of a location in the atmosphere, the real time event rate can be predicted by the event rate obtained. This testing method was standardized as the neutron accelerated soft error rate (ASER) testing in JEDEC JESD89A standard. However, several life testings indicated that the neutron flux density predictions given by the accelerated testings can have large errors. Up to a factor of 2 discrepancy was reported in the literature. One of the major error sources is the equivalence of the absolute neutron flux density in the atmosphere and in accelerated beam. This thesis proposes an alternative accelerated method of predicting the real-time neutron error rate by using proxy devices. This method can avoid the error introduced by the uncertainty in the neutron flux density. The Imaging Single Event Effect Monitor (ISEEM) is one of the proxy devices. It is the instrument originally developed by Z. Török and his co-workers in the University of Central Lancashire. A CCD was used as the sensitive element to detect neutrons. A large amount of data sets acquired by Török were used in this work. A re-engineered ISEEM has been developed in this work to improve ISEEM performance in life testings. Theoretical models have been developed to analyze the response of ISEEM in a wide range of neutron facilities and natural environment. The agreement of the measured and calculated cross-sections are within the error quoted by facilities. Because of the alpha contamination and primary proton direct ionization effects, performance of ISEEM in life testings appeared to be weak.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Gamma Ray Bursts: recent results and connections to very high energy Cosmic Rays and Neutrinos

Gamma-ray bursts are the most concentrated explosions in the Universe. They have been detected electromagnetically at energies up to tens of GeV, and it is suspected that they could be active at least up to TeV energies. It is also speculated that they could emit cosmic rays and neutrinos at energies reaching up to the $10^{18}-10^{20}$ eV range. Here we review the recent developments in the photon phenomenology in the light of \swift and \fermi satellite observations, as well as recent IceCube upper limits on their neutrino luminosity. We discuss some of the theoretical models developed to explain these observations and their possible contribution to a very high energy cosmic ray and neutrino background.Comment: 12 pages, 7 figures. Text of a plenary lecture at the PASCOS 12 conference, Merida, Yucatan, Mexico, June 2012; to appear in J.Phys. (Conf. Series

The IceCube Neutrino Observatory I: Point Source Searches

Searches for point sources of astrophysical neutrinos and related measurements: Searches for steady and time-variable sources; Follow-up programs; AGNs; GRBs; Moon shadow; Submitted papers to the 32nd International Cosmic Ray Conference, Beijing 2011.Comment: Papers submitted by the IceCube Collaboration to the 32nd International Cosmic Ray Conference, Beijing 2011; part

Solar High-energy Astrophysical Plasmas Explorer (SHAPE). Volume 1: Proposed concept, statement of work and cost plan

The concept of the Solar High-Energy Astrophysical Plasmas Explorer (SHAPE) is studied. The primary goal is to understand the impulsive release of energy, efficient acceleration of particles to high energies, and rapid transport of energy. Solar flare studies are the centerpieces of the investigation because in flares these high energy processes can be studied in unmatched detail at most wavelenth regions of the electromagnetic spectrum as well as in energetic charged particles and neutrons

Implications of Particle Acceleration in Active Galactic Nuclei for Cosmic Rays and High Energy Neutrino Astronomy

We consider the production of high energy neutrinos and cosmic rays in radio-quiet active galactic nuclei (AGN) or in the central regions of radio-loud AGN. We use a model in which acceleration of protons takes place at a shock in an accretion flow onto a supermassive black hole, and follow the cascade that results from interactions of the accelerated protons in the AGN environment. We use our results to estimate the diffuse high energy neutrino intensity and cosmic ray intensity due to AGN. We discuss our results in the context of high energy neutrino telescopes under construction, and measurements of the cosmic ray composition in the region of the ``knee'' in the energy spectrum at $\sim 10^7$ GeV.Comment: 37 pages of compressed and uuencoded postscript; hardcopy available on request; to be published in Astroparticle Physics; ADP-AT-94-

IceCube and HAWC constraints on very-high-energy emission from the Fermi bubbles

The nature of the $\gamma$-ray emission from the \emph{Fermi} bubbles is unknown. Both hadronic and leptonic models have been formulated to explain the peculiar $\gamma$-ray signal observed by the Fermi-LAT between 0.1-500~GeV. If this emission continues above $\sim$30~TeV, hadronic models of the \emph{Fermi} bubbles would provide a significant contribution to the high-energy neutrino flux detected by the IceCube observatory. Even in models where leptonic $\gamma$-rays produce the \emph{Fermi} bubbles flux at GeV energies, a hadronic component may be observable at very high energies. The combination of IceCube and HAWC measurements have the ability to distinguish these scenarios through a comparison of the neutrino and $\gamma$-ray fluxes at a similar energy scale. We examine the most recent four-year dataset produced by the IceCube collaboration and find no evidence for neutrino emission originating from the \emph{Fermi} bubbles. In particular, we find that previously suggested excesses are consistent with the diffuse astrophysical background with a p-value of 0.22 (0.05 in an extreme scenario that all the IceCube events that overlap with the bubbles come from them). Moreover, we show that existing and upcoming HAWC observations provide independent constraints on any neutrino emission from the \emph{Fermi} bubbles, due to the close correlation between the $\gamma$-ray and neutrino fluxes in hadronic interactions. The combination of these results disfavors a significant contribution from the \emph{Fermi} bubbles to the IceCube neutrino flux.Comment: 9 pages, 4 figures, to appear in PR