An analysis method for time ordered data processing of Dark Matter experiments

The analysis of the time ordered data of Dark Matter experiments is becoming more and more challenging with the increase of sensitivity in the ongoing and forthcoming projects. Combined with the well-known level of background events, this leads to a rather high level of pile-up in the data. Ionization, scintillation as well as bolometric signals present common features in their acquisition timeline: low frequency baselines, random gaussian noise, parasitic noise and signal characterized by well-defined peaks. In particular, in the case of long-lasting signals such as bolometric ones, the pile-up of events may lead to an inaccurate reconstruction of the physical signal (misidentification as well as fake events). We present a general method to detect and extract signals in noisy data with a high pile-up rate and qe show that events from few keV to hundreds of keV can be reconstructed in time ordered data presenting a high pile-up rate. This method is based on an iterative detection and fitting procedure combined with prior wavelet-based denoising of the data and baseline subtraction. {We have tested this method on simulated data of the MACHe3 prototype experiment and shown that the iterative fitting procedure allows us to recover the lowest energy events, of the order of a few keV, in the presence of background signals from a few to hundreds of keV. Finally we applied this method to the recent MACHe3 data to successfully measure the spectrum of conversion electrons from Co57 source and also the spectrum of the background cosmic muons

Development of a front end ASIC for Dark Matter directional detection with MIMAC

A front end ASIC (BiCMOS-SiGe 0.35 \mum) has been developed within the framework of the MIMAC detector project, which aims at directional detection of non-baryonic Dark Matter. This search strategy requires 3D reconstruction of low energy (a few keV) tracks with a gaseous \muTPC. The development of this front end ASIC is a key point of the project, allowing the 3D track reconstruction. Each ASIC monitors 16 strips of pixels with charge preamplifiers and their time over threshold is provided in real time by current discriminators via two serializing LVDS links working at 320 MHz. The charge is summed over the 16 strips and provided via a shaper. These specifications have been chosen in order to build an auto triggered electronics. An acquisition board and the related software were developed in order to validate this methodology on a prototype chamber. The prototype detector presents an anode where 2 x 96 strips of pixels are monitored.Comment: 12 pages, 10 figure

Low energy conversion electron detection in superfluid He3 at ultra-low temperature

We report on the first results of the MACHe3 (MAtrix of Cells of Helium 3) prototype experiment concerning the measurement of low energy conversion electrons at ultra-low temperature. For the first time, the feasibility of the detection of low energy electrons is demonstrated in superfluid He3-B cooled down to 100 microK. Low energy electrons at 7.3 keV coming from the K shell conversion of the 14.4 keV nuclear transition of a low activity Co57 source are detected, opening the possibility to use a He3-based detector for the detection of Weakly Interacting Massive Particles (WIMPs) which are expected to release an amount of energy higher-bounded by 5.6 keV.Comment: 8 pages, 3 figures, to appear in NIM

Electron - nuclear recoil discrimination by pulse shape analysis

In the framework of the ``ULTIMA'' project, we use ultra cold superfluid 3He bolometers for the direct detection of single particle events, aimed for a future use as a dark matter detector. One parameter of the pulse shape observed after such an event is the thermalization time constant. Until now it was believed that this parameter only depends on geometrical factors and superfluid 3He properties, and that it is independent of the nature of the incident particles. In this report we show new results which demonstrate that a difference for muon- and neutron events, as well as events simulated by heater pulses exist. The possibility to use this difference for event discrimination in a future dark matter detector will be discussed.Comment: Proseedings of QFS 2007, Kazan, Russia; 8 pages, 4 figures. Submited to J. Low Temp. Phy

Low energy measurements with Helium Micromegas micro-TPC

The measurement of the ionization produced by particles in a medium presents a great interest in several fields from metrology to particule physics and cosmology. The ionization quenching factor is defined as the fraction of energy released by ionisation by a recoil in a medium compared with its kinetic energy. At low energy, in the range of a few keV, the ionization falls rapidly and systematic measurement are needed. We have developped an experimental setup devoted to the measurement of low energy (keV) ionization quenching factor for the MIMAC project. The ionization produced in the gas has been measured with a Micromegas detector filled with Helium gas mixture.Comment: Proceedings of the fourth international symposium on large TPCs for low energy rare event detection, Paris, France, Dec. 2008 To appear in Journal of Physic

Dark matter directional detection with MIMAC

MiMac is a project of micro-TPC matrix of gaseous (He3, CF4) chambers for direct detection of non-baryonic dark matter. Measurement of both track and ionization energy will allow the electron-recoil discrimination, while access to the directionnality of the tracks will open a unique way to distinguish a geniune WIMP signal from any background. First reconstructed tracks of 5.9 keV electrons are presented as a proof of concept.Comment: 4 pages, proc. of the 44th Rencontres De Moriond: Electroweak Interactions And Unified Theories, 7-14 Mar 2009, La Thuile, Ital

Influence of a CVT on the fuel consumption of a parallel medium-duty electric hybrid truck

Hybrid electric vehicles are being developed to reduce the pollutant emissions and the fossil-fuel consumption of transportation. Innovative technologies are inserted to improve the performance of hybrid vehicles, including trucks and buses. Thereby, trends towards gear shifting automation motivate the research on replacing a discrete conventional Automated Manual Transmission (AMT) with a Continuously Variable Transmission (CVT). Theoretically, such a transmission enables better operation points of the thermal engine, and therefore a reduction of its fuel consumption and emissions. However, the conventional (hydraulic actuated) CVT efficiency during quasi-stationary operation is typically lower than the efficiency of a classical discrete gearbox, which leads to higher fuel consumption. This paper is focused on the study of the interests of a CVT for a medium-duty Hybrid Electric Truck (HET). The complete model and control of CVT-based and AMT-based HET are described in a unified way using Energetic Macroscopic Representation (EMR). These models are transformed to backward-models to be computed by the Dynamic Programming Method (DPM). Such a method leads to define the (off-line) optimal energy management strategies for a fair comparison of both hybrid trucks. For the studied driving cycle, the hybridization allows a fuel saving of 10% with an AMT and 3% with a CVT. The fuel consumption is higher for the CVT-based HET in comparison with the AMT-based HET due to the lowest efficiency of the CVT (85%) compared to the AMT (around 92%). However, future (on-demand) CVTs with an increased efficiency could be a solution of interest to reduce the fuel consumption of such applications. The developed method can be used to test these new CVTs, other vehicles or other driving cycles

Micromegas micro-TPC for direct Dark Matter search with MIMAC

The MIMAC project is a multi-chamber detector for Dark Matter search, aiming at measuring both track and ionization with a matrix of micromegas micro-TPC filled with He3 and CF4. Recent experimental results on the first measurements of the Helium quenching factor at low energy (1 keV recoil) are presented, together with the first simulation of the track reconstruction. Recontruction of track of alpha from Radon impurities is shown as a first proof of concept.Comment: 5 pages, Proc. of the fourth international symposium on large TPCs for low energy rare event detection, Paris, France, Dec. 2008. To appear in Journal of Physic