Bulletin of the American Physical Society
2005 Joint New England Sections of APS and AAPT Spring Meeting
Friday–Saturday, April 1–2, 2005; Cambridge, MA
Session PF: Particles and Fields |
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Chair: Ulrich Becker, MIT Room: Room 4-237 |
Saturday, April 2, 2005 8:00AM - 8:15AM |
PF.00001: New Gas Electron Multipliers at MIT: Fabrication, Processing, and Testing Scott Hertel Gas Electron Multipliers (GEMs) concentrate powerful electric fields through holes in metal foils to turn single drifting electrons into cascades large enough to be easily detected. Gains of 10 - 10$^{3}$ are achieved. Until recently fabricated solely at CERN, new GEMs have been developed by Tech-Etch, a private company located in Plymouth, Massachusetts. We describe the testing of these GEMs for detector use. We also investigate coarser-grained GEMs, which have robustness advantages including ease of manufacture. First results will be given. [Preview Abstract] |
Saturday, April 2, 2005 8:15AM - 8:30AM |
PF.00002: Aging and Rejuvenation of Drift Tubes Under High Irradiation Yue Shi The ATLAS spectrometer of the LHC (CERN) consists of $6\times10^5 $ Monitored Drift Tubes(MDT) in its muon chambers. The performance of detector tubes under high radiation is critical. We measured MDT gain performance such as 1)gain deterioration (aging) with the accumulation of charge and Si deposits on anode wire, and 2)gain dependence on gas tube pressure and high voltage. The pressure and anode voltage behavior is fitted to the Diethorn model, from which the effective field of the start of avalanche is found to be 29500 ($\pm800$)V/cm. The effective potential for one ionization in Ar is found to be 30.0($\pm0.9$) V. Using an UV arc lamp source, a tube was aged to $\sim$73\% signal height after accumulating 21C/cm of wire charge. The wire surface was scanned with an Scanning Electron Microscope to differentiate aged and non- aged section with respect to substrate content e.g. Si. An aged tube was then reanimated with 1\% O2 in gas and reverse wire potential (sputtering). [Preview Abstract] |
Saturday, April 2, 2005 8:30AM - 8:45AM |
PF.00003: Use of a Nitrogen Laser for Calibration and Testing of Gas-Type Particle Detectors Grant Elliott We present a technique for calibrating gas-type particle detectors with an ultraviolet laser. A nitrogen laser is focused and shone through quartz windows installed on a time projection chamber (TPC) containing argon with methane quencher. Argon ionization is achieved over the length of the chamber and the trajectory is reconstructed using techniques identical to those used with alpha particles and cosmic muons. As such, the calibration is immediately applicable to the full range of uses of the chamber. Additionally, we outline a methodology for developing such a system, including optics and a test bed containing a tube-style detector outfitted with UV transparent glass. This test bed is used to determine the ionization profile of the focused laser prior to installation on the TPC. The tracks produced with laser calibration occur at known positions and times, are long, and remain straight in the presence of magnetic field. These advantages, combined with the wide applicability and relative ease of use of this system, make it ideal for small particle physics laboratories. [Preview Abstract] |
Saturday, April 2, 2005 8:45AM - 9:00AM |
PF.00004: Relation of Electron Scattering Cross-Sections to Drift Measurements in Noble Gases Blake Stacey I investigate the classic ``inverse problem'' of extracting collision and scattering cross sections from measurements of electron swarm behavior. A Monte Carlo technique for simulating electron motion through a gas of isotropic scatterers is presented, providing a simplified version of Biagi's MAGBOLTZ algorithm. Using this Monte Carlo software, I examine the thermalization of electron swarms, focusing on their drift velocity and Shannon entropy, providing justification for a set of analytic expressions for drift measurements which are valid in the hydrodynamic regime. These expressions are then used to estimate the \heliumfour\ scattering cross section, first by a simple grid interpolation and then through a genetic algorithm (GA). This technique demonstrates that the He-4 momentum-transfer cross section in the 0-7~eV range is approximately 6.5~\AA$^2$, with a peak near 2~eV, in agreement with literature values. [Preview Abstract] |
Saturday, April 2, 2005 9:00AM - 9:15AM |
PF.00005: Large-Area Lithography: Where Special Relativity and Nanotechnology Meet Ralf K. Heilmann, Juan C. Montoya, Mark L. Schattenburg Optical lithography is the dominant technology for the patterning of macroscopic objects (such as 300 mm silicon wafers) with nanometer scale features (such as transistors and integrated circuits). In the semiconductor industry wafer overlay control between different patterning steps is supposed to shrink below 10 nm, which demands nanometer-level position control for the fast-moving wafer stages in industrial steppers and scanners. Most of these stages are controlled via displacement measuring interferometry, which is based on the (classical) Doppler shift that a laser beam undergoes upon reflection from a mirror attached to the moving stage. However, neglected relativistic effects due to stage motion can already require corrections on the nanometer scale for today's lithography tools [1]. We will describe a technique to demonstrate these relativistic effects with our nanometer-precision large-area grating patterning and metrology tool, the so-called nanoruler [2]. [1] R. K. Heilmann, P. T. Konkola, C. G. Chen, and M. L. Schattenburg, ``Relativistic corrections in displacement measuring interferometry,'' J. Vac. Sci. Technol. B \textbf{18}, 3277 (2000). [2] R. K. Heilmann, C. G. Chen, P. T. Konkola, and M. L. Schattenburg, , ``Dimensional metrology for nanometer-scale science and engineering: Towards sub-nanometer accurate encoders,'' Nanotechnology \textbf{15}, S504 (2004). [Preview Abstract] |
Saturday, April 2, 2005 9:15AM - 9:30AM |
PF.00006: Complex dynamics and the high-energy regime of quantum field theory Ervin Goldfain The Standard Model embodies our current knowledge of elementary particle physics and represents a well-tested framework for the study of non-gravitational phenomena at low energies. It is built on the foundations of relativistic quantum field theory (QFT), which provides the correct description of electroweak and strong interactions involving leptons and quarks. It is generally believed that, extending the validity of QFT to energies on or beyond the TeV range must include the unavoidable signature of vacuum fluctuations and strong-field gravity. The key premise of our work is that mathematical tools of fractional calculus and complexity theory are necessary to properly describe the high-energy regime of QFT. The random space-time topology associated with persistent vacuum fluctuations is represented using the fractional wave equation and the Levy flow model. The range of space-time correlations is encoded in the pair of Levy and memory indices, respectively$(\alpha ,\beta )$. We report the following findings: i) relativistic gravitation emerges as a natural part of the picture if $\beta \ne 1$ and through the use of time fractional differential and integral operators. ii) up to a first order analysis, the Levy index $\alpha $ may be used to control convergence of Feynman diagrams and enable the dynamics to become fully renormalizable in all orders of perturbation theory. iii) gauge bosons and fermions emerge as condensates of space-time geometry resulting from fixing$(\alpha ,\beta )$ in the process of cooling from the high-energy scale of TeV physics. [Preview Abstract] |
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