Professor Jocelyn Monroe

Abstract:

The known direction of motion of dark matter particles relative to the Earth may be a key for their unambiguous identification even in the presence of backgrounds. A direction-sensitive detector prototype using a low-density CF4 gas with a 10 liter fiducial volume is operated for several weeks in a basement laboratory. We present initial results that confirm good detector performance and set preliminary limits on spin-dependent dark matter interactions. © 2010 IOP Publishing Ltd.

Abstract:

We have performed three searches for high-frequency signals in the solar neutrino flux measured by the Sudbury Neutrino Observatory, motivated by the possibility that solar g-mode oscillations could affect the production or propagation of solar 8B neutrinos. The first search looked for any significant peak in the frequency range 1-144day-1, with a sensitivity to sinusoidal signals with amplitudes of 12% or greater. The second search focused on regions in which g-mode signals have been claimed by experiments aboard the Solar and Heliospheric Observatory satellite, and was sensitive to signals with amplitudes of 10% or greater. The third search looked for extra power across the entire frequency band. No statistically significant signal was detected in any of the three searches. © 2010. The American Astronomical Society.

Abstract:

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 TimeProjection 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°. 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. © 2009 American Institute of Physics.

Abstract:

A significant advance in the detection of neutrons and determination of their energy and direction of motion in a simple, compact device has been reported. The new detector can be used to determine the neutron flux, the energy distribution, and the direction of motion neutron for both fast and thermal neutrons. The detector is free of backgrounds from X-rays, gamma rays, beta particles, relativistic singly charged particles, and cosmic ray neutrons. It is capable of determining the location of a source of fission neutrons based on the characteristics of elastic scattering of neutrons by helium nuclei. The light collecting system included an ultraviolet lens and an image intensifier that was followed by a phosphor screen. Image analysis software to automate data analysis has also been developed.