H. Tomita

First dark matter search results from a surface run of the 10-L DMTPC directional dark matter detector

Abstract 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 Letter we present the first dark matter limit from DMTPC from a surface run at MIT. 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 × 10 − 33 cm 2 for 115 GeV/c2 dark matter particle mass.

A background-free direction-sensitive neutron detector

The detection and measurements of properties of neutrons are of great importance in many fields of research, including neutron scattering and radiography, measurements of solar and cosmic ray neutron flux, measurements of neutron interaction cross sections, monitoring of neutrons at nuclear facilities, oil exploration, and searches for fissile weapons of mass destruction. Many neutron detectors are plagued by large backgrounds from x-rays and gamma rays, and most current neutron detectors lack single-event energy sensitivity or any information on neutron directionality. Even the best detectors are limited by cosmic ray neutron backgrounds. All applications would benefit from improved neutron detection sensitivity and improved measurements of neutron properties. Here we show data from a new type of detector that can be used to determine neutron flux, energy distribution, and direction of neutron motion. The detector is free of backgrounds from x-rays, gamma rays, beta particles, and relativistic singly charged particles. It is relatively insensitive to cosmic ray neutrons because of their distinctive angular and energy distributions. It is sensitive to thermal neutrons, fission spectrum neutrons, and high energy neutrons, with detection features distinctive for each energy range. It is capable of determining the location of a source of fission neutrons based on characteristics of elastic scattering of neutrons by helium nuclei. A portable detector could identify one gram of reactor grade plutonium, one meter away, with less than one minute of observation time.

Readout technologies for directional WIMP Dark Matter detection

The measurement of the direction of WIMP-induced nuclear recoils is a compelling but technologically challenging strategy to provide an unambiguous signature of the detection of Galactic dark matter. Most directional detectors aim to reconstruct the dark-matter-induced nuclear recoil tracks, either in gas or solid targets. The main challenge with directional detection is the need for high spatial resolution over large volumes, which puts strong requirements on the readout technologies. In this paper we review the various detector readout technologies used by directional detectors. In particular, we summarize the challenges, advantages and drawbacks of each approach, and discuss future prospects for these technologies.

Results from DMTPC 10-liter detector

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.

Glass-panel 6 Li neutron detector

We report on the development of a neutron detector utilizing solid enriched lithium, which has substantial neutron detection efficiency. The detector employs large, thin sheets of lithium in a gas-filled multi-wire proportional chamber (MWPC). Using low-cost design methods, readout electronics, and a small fraction of the already available enriched lithium available from Y-12/Oak Ridge National Laboratory, the amount of 3He equivalent detection capability for nuclear non-proliferation activities can be greatly increased.

The DMTPC detector

Directional Dark Matter detectors have the potential of yielding an unambiguous observation of WIMPs even in presence of insidious background. In addition, by measuring the direction of the Dark Matter particles such detectors can discriminate between the various models that describe Dark Matter in our galaxy. The DMTPC detector is a novel directional DM detector consisting of a low-pressure CF4 time projection chamber with optical readout. Recent measurements proved that this technology is able to reconstruct the energy, direction, and sense of the lowenergy nuclear recoils produced by neutrons from a 252Cf source, as well as efficiently reject electromagnetic backgrounds. A 10-liter DMTPC detector is ready for underground operation. A 1 m3 detector, now in the design phase, will soon allow us to improve the existing limits of SD-interactions of WIMPs on protons by over one order of magnitude.

Dark Matter Time Projection Chamber: Recent R&D Results

The Dark Matter Time Projection Chamber collaboration recently reported a dark matter limit obtained with a 10 liter time projection chamber lled with CF 4 gas. The 10 liter detector was capable of 2D tracking (perpendicular to the drift direction) and 2D ducialization, and only used information from two CCD cameras when identifying tracks and rejecting backgrounds. Since that time, the col- laboration has explored the potential benets of photomultiplier tube and electronic charge readout to achieve 3D tracking, and particle iden- tication for background rejection. The latest results of this eort is described here.