A Measurement of Photon Production in Electron Avalanches in CF4

This paper presents a measurement of the ratio of photon to electron production and the scintillation spectrum in a popular gas for time pro jection chambers, carbon tetrafluoride (CF4), over the range of 200 to 800 nm; the ratio is measured to be 0.34+/-0.04. This result is of particular importance for a new generation of dark matter time projection chambers with directional sensitivity which use CF4 as a fill gas.Comment: 19 pages, including appendix. 8 figure

DMTPC: A dark matter detector with directional sensitivity

By correlating nuclear recoil directions with the Earth's direction of motion through the Galaxy, a directional dark matter detector can unambiguously detect Weakly Interacting Massive Particles (WIMPs), even in the presence of backgrounds. Here, we describe the Dark Matter Time-Projection Chamber (DMTPC) detector, a TPC filled with CF4 gas at low pressure (0.1 atm). Using this detector, we have measured the vector direction (head-tail) of nuclear recoils down to energies of 100 keV with an angular resolution of <15 degrees. To study our detector backgrounds, we have operated in a basement laboratory on the MIT campus for several months. We are currently building a new, high-radiopurity detector for deployment underground at the Waste Isolation Pilot Plant facility in New Mexico.Comment: 4 pages, 2 figures, proceedings for the CIPANP 2009 conference, May 26-31, 200

Charge amplification concepts for direction-sensitive dark matter detectors

Direction measurement of weakly interacting massive particles in time-projection chambers can provide definite evidence of their existence and help to determine their properties. This article demonstrates several concepts for charge amplification in time-projection chambers that can be used in direction-sensitive dark matter search experiments. We demonstrate reconstruction of the 'head-tail' effect for nuclear recoils above 100keV, and discuss the detector performance in the context of dark matter detection and scaling to large detector volumes.Comment: 15 pages, 9 figure

First Dark Matter Search Results from a Surface Run of the 10-L DMTPC Directional Dark Matter Detector

The Dark Matter Time Projection Chamber (DMTPC) is a low pressure (75 Torr CF4) 10 liter detector capable of measuring the vector direction of nuclear recoils with the goal of directional dark matter detection. In this paper we present the first dark matter limit from DMTPC. In an analysis window of 80-200 keV recoil energy, based on a 35.7 g-day exposure, we set a 90% C.L. upper limit on the spin-dependent WIMP-proton cross section of 2.0 x 10^{-33} cm^{2} for 115 GeV/c^2 dark matter particle mass.Comment: accepted for publication in Physics Letters

The Optical Alignment System of the ATLAS Muon Spectrometer Endcaps

The muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC) at CERN consists of over a thousand muon precision chambers, arranged in three concentrical cylinders in the barrel region, and in four wheels in each of the two endcaps. The endcap wheels are located between 7m and 22m from the interaction point, and have diameters between 13m and 24m. Muon chambers are equipped with a complex on-line optical alignment system to monitor their positions and deformations during ATLAS data-taking. We describe the layout of the endcap part of the alignment system and the design and calibration of the optical sensors, as well as the various software components. About 1% of the system has been subjected to performance tests in the H8 beam line at CERN, and results of these tests are discussed. The installation and commissioning of the full system in the ATLAS cavern is well underway, and results from approximately half of the system indicate that we will reach the ambitious goal of a 40mu alignment accuracy, required for reconstructing final-state muons at the highest expected energies