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arXiv2014

Coherent noise source identification in multi channel analysis

The evaluation of coherent noise can provide useful information in the study of detectors. The identification of coherent noise sources is also relevant for uncertainty calculations in analyse where several channels are combined. The study of the covariance matrix give information about coherent noises. Since covariance matrix of high dimension data could be difficult to analyse, the development of analysis tools is needed. Principal Component Analysis (PCA) is a powerful tool for such analysis. It has been shown that we can use PCA to find coherent noises in ATLAS calorimeter or the CALICE Si-W electromagnetic calorimeter physics prototype. However, if several coherent noise sources are combined, the interpretation of the PCA may become complicated. In this paper, we present another method based on the study of the covariance matrix to identify noise sources. This method has been developed for the study of front end ASICs dedicated to CALICE calorimeters. These calorimeters are designed and studied for experiments at the ILC. We also study the reliability of the method with simulations. Although this method has been developped for a specific application, it can be used for any multi channel analysis.

physics.ins-det↗

arXiv2014

NEWS : a new spherical gas detector for very low mass WIMP detection

The main characteristics of a new concept of spherical gaseous detectors, with some details on its operation are first given. The very low energy threshold of such detector has led to investigations of its potential performance for dark matter particle searches, in particular low mass WIMP's : original methods for energy and fiducial volume calibration and background rejection are described and preliminary results obtained with a low radioactivity prototype operated in Laboratoire Souterrain de Modane ("Frejus" lab) are presented. Typical expected sensitivities in cross section for low mass WIMP's are also shown, and other applications briefly discussed.

astro-ph.IM↗

arXiv2014

Water softening by single-bowl ion exchange filter efficiency estimate and improvement

The article presents results of experimental investigations of the water softener in a laboratory installation of uninterruptible countercurrent ion exchange filter, which has a movable layer of ion exchange material. The installation provides for two simultaneous processes: counter ion sorption and regeneration of the sorbent with the processing capability of the sorbent in the regeneration zone by ultrasonic radiation.

physics.chem-ph↗

arXiv2014

The CMS Particle Flow Algorithm

A particle flow event-reconstruction algorithm has been successfully deployed in the CMS experiment and is nowadays used by most of the analyses. It aims at identifying and reconstructing individually each particle arising from the LHC proton-proton collision, by combining the information from all the subdetectors. The resulting particle-flow event reconstruction leads to an improved performance for the reconstruction of jets and MET, and for the identification of electrons, muons, and taus. The algorithm and its performance will be described. The commissioning phase, during which it was demonstrated that the algorithm was performing as expected from the simulation up to a high level of precision, will be presented. Finally, a selection of recent improvements in the CMS analyses obtained thanks to the particle-flow algorithm will be discussed.

hep-ex↗

arXiv2014

Further investigations on the Neutron Flux Generation in a Plasma Discharge Electrolytic Cell

Our recent paper on the "Search for Neutron Flux Generation in a Plasma Discharge Electrolytic Cell" [1] has as main goal the validation of the experiment in Ref.[2]. As a follow-up, Ref.[3] moves a set of objections on our procedure and presents argumentations on why the experiments should not yield the same results. We collect here additional material and calculations that contribute to understanding the observed discrepancies. Furthermore we prove that the absence of signals from Indium activation detectors reported also for the experiment of Ref.[2] is a clear indication that neutron production does not occur. [1] R.Faccini et al arXiv:1310.4749 [2] D.Cirillo et al, Key Engineering Materials 495, 104 (2012). [3] A.Widom et al. arXiv:1311.2447

nucl-ex↗

arXiv2014

Recent Progress on D$^3$ -- The Directional Dark Matter Detector

Direction-sensitive WIMP dark matter searches may help overcome the challenges faced by direct dark matter detection experiments. In particular, directional detectors should be able to clearly differentiate a dark matter signal from background sources. We are developing a Directional Dark Matter Detector (D$^3$) based on a gas Time Projection Chamber (TPC) using Gas Electron Multipliers (GEMs) for charge amplification and pixel electronics for readout. This approach allows the three-dimensional reconstruction of nuclear recoils in a room-temperature detector with low energy threshold and low noise. We present an overview of our past and ongoing work developing this technology, including the performance measurements of small prototypes, as well as our planned future work constructing a m$^3$-scale detector to clearly determine whether the signals seen by DAMA, CoGeNT, and CRESST-II are due to low-mass WIMPs or background.

physics.ins-det↗

arXiv2014

The cosmic ray electron and positron spectra measured by AMS-02

The AMS-02 detector is operating on the International Space Station since May 2011. More than 30 billion events have been collected by the instrument in the first two years of data taking. A precision measurement of the positron fraction and of the positron flux in primary cosmic rays up to 350 GeV, of the electron flux up to 500 GeV and of the combined electron plus positron flux up to 700 GeV are presented. The separate and combined electron and positron fluxes are preliminary and represent work in progress. Systematic uncertainties must still be investigated further.

physics.ins-det↗

arXiv2014

Development of COTS ADC SEE Test System for the ATLAS LAr Calorimeter Upgrade

Radiation-tolerant, high speed, high density and low power commercial off-the-shelf (COTS) analog-to-digital converters (ADCs) are planned to be used in the upgrade to the Liquid Argon (LAr) calorimeter front end (FE) trigger readout electronics. Total ionization dose (TID) and single event effect (SEE) are two important radiation effects which need to be characterized on COTS ADCs. In our initial TID test, Texas Instruments (TI) ADS5272 was identified to be the top performer after screening a total 17 COTS ADCs from different manufacturers with dynamic range and sampling rate meeting the requirements of the FE electronics. Another interesting feature of ADS5272 is its 6.5 clock cycles latency, which is the shortest among the 17 candidates. Based on the TID performance, we have designed a SEE evaluation system for ADS5272, which allows us to further assess its radiation tolerance. In this paper, we present a detailed design of ADS5272 SEE evaluation system and show the effectiveness of this system while evaluating ADS5272 SEE characteristics in multiple irradiation tests. According to TID and SEE test results, ADS5272 was chosen to be implemented in the full-size LAr Trigger Digitizer Board (LTDB) demonstrator, which will be installed on ATLAS calorimeter during the 2014 Long Shutdown 1 (LS1).

physics.ins-det↗

arXiv2014

Measuring Quasi-Static and Kinetic Coefficient of Restitution Simultaneously using Levitation Mass Method: Experiment and Simulation

Observed peaks in a levitation mass method (LMM), which are usually addressed to signal noise, are discussed in this work. This phenomenon arises due to bounce from plate which is collided by moving part in LMM measurement system. Normally, the moving part and the plate stick very good after their first contact. Simulation using molecular dynamics (MD) method is performed to prove the bounce prognosis.

physics.ins-det↗

arXiv2014

Development of CMOS pixel sensors for tracking and vertexing in high energy physics experiments

CMOS pixel sensors (CPS) represent a novel technological approach to building charged particle detectors. CMOS processes allow to integrate a sensing volume and readout electronics in a single silicon die allowing to build sensors with a small pixel pitch ($\sim 20 μm$) and low material budget ($\sim 0.2-0.3\% X_0$) per layer. These characteristics make CPS an attractive option for vertexing and tracking systems of high energy physics experiments. Moreover, thanks to the mass production industrial CMOS processes used for the manufacturing of CPS the fabrication construction cost can be significantly reduced in comparison to more standard semiconductor technologies. However, the attainable performance level of the CPS in terms of radiation hardness and readout speed is mostly determined by the fabrication parameters of the CMOS processes available on the market rather than by the CPS intrinsic potential. The permanent evolution of commercial CMOS processes towards smaller feature sizes and high resistivity epitaxial layers leads to the better radiation hardness and allows the implementation of accelerated readout circuits. The TowerJazz $0.18 μm$ CMOS process being one of the most relevant examples recently became of interest for several future detector projects. The most imminent of these project is an upgrade of the Inner Tracking System (ITS) of the ALICE detector at LHC. It will be followed by the Micro-Vertex Detector (MVD) of the CBM experiment at FAIR. Other experiments like ILD consider CPS as one of the viable options for flavour tagging and tracking sub-systems.

physics.ins-det↗

arXiv2014

A new concept for safeguarding and labeling of long-term stored waste and its place in the scope of existing tagging techniques

The idea of a novel labeling method is suggested for a new way of long-term security identification, inventory tracking, prevention of falsification and theft of waste casks, copper canisters, spent fuel containers, mercury containers, waste packages and other items. The suggested concept is based on the use of a unique combination of radioisotopes with different predictable half life. As an option for applying the radioisotope tag to spent fuel safeguarding it is suggested to use a mixture of α-emitting isotopes, such as 241Am etc., with materials that easily undergo α-induced reactions with emission of specific γ-lines. Thus, the existing problem of the disposing of smoke detectors or other devices [1] which contain radioisotopes can be addressed, indirectly solving an existing waste problem. The results of the first pilot experiments with two general designs of storage canisters, namely a steel container which corresponds to the one which is commonly used for long-term storing of mercury in Europe and USA and a copper canister, the one which is in applications for nuclear repositories, are presented. As one of the options for a new labeling method it is proposed to use a multidimensional bar code symbology and tungsten plate with ultrasound techniques. It is shown that the new radioisotope label offers several advantages in the scope of existing tagging techniques (overview is given) and can be implemented even with low activity sources.

physics.ins-det↗

arXiv2014

Backgrounds at future linear colliders

A brief review of the background for experiments at future electron-positron linear colliders is done. Two sources of background are discussed: the beam delivery system and the interaction point. The abundance of background muons, neutrons, photons and electron-positron pairs is quoted for different sub-detectors and both background sources. The background caused by the beamstrahlung is described in more detail. Space distributions are sketched and the impact on calorimeters is discussed for the background neutrons.

physics.ins-det↗

arXiv2014

Detector Optimization Studies and Light Higgs Decay into Muons at CLIC

The Compact Linear Collider (CLIC) is a concept for a future $e^{+}e^{-}$ linear collider with a center-of-mass energy of up to 3 TeV. The design of a CLIC experiment is driven by the requirements related to the physics goals, as well as by the experimental conditions. For example, the short time between two bunch crossings of 0.5 ns and the backgrounds due to beamstrahlung have direct impact on the design of a CLIC experiment. The Silicon Detector (SiD) is one of the concepts currently being discussed as a possible detector for the International Linear Collider (ILC). In this thesis we develop a modified version of the SiD simulation model for CLIC, taking into account the specific experimental conditions. In addition, we developed a software tool to investigate the impact of beam-related backgrounds on the detector by overlaying events from different simulated event samples. Moreover, we present full simulation studies, determining the performance of the calorimeter and tracking systems. We show that the track reconstruction in the all-silicon tracker of SiD is robust in the presence of the backgrounds at CLIC. Furthermore, we investigate tungsten as a dense absorber material for the hadronic calorimeter, which allows for the construction of a compact hadronic calorimeter that fulfills the requirements on the energy resolution and shower containment without a significant increase of the coil radius. Finally, the measurement of the decays of light Higgs bosons into two muons is studied in full simulation. We find that with an integrated luminosity of 2 ab$^{-1}$, corresponding to 4 years of data taking at CLIC, the respective Higgs branching ratio can be determined with a statistical uncertainty of approximately 15%.

physics.ins-det↗

arXiv2014

Regeneration tests of a room temperature magnetic refrigerator and heat pump

A magnetic heat pump apparatus consisting of a solid magnetic refrigerant, gadolinium, and a liquid regenerator column of ethanol and water has been tested. Utilizing a 7T field, it produced a maximum temperature span of 80 K, and in separate tests, a lowest temperature of 241 K and a highest temperature of 328 K. Thermocouples, placed at intervals along the regenerator tube, permitted measurement of the temperature distribution in the regenerator fluid. No attempt was made to extract refrigeration from the device, but analysis of the temperature distributions shows that 34 watts of refrigeration was produced.

physics.ins-det↗

arXiv2014

Electron-Phonon Coupling on the NbSi Transition Edge Sensors

We have built an electron-phonon coupling model to describe the behavior of the NbxSi1-x transition edge sensor (TES) bolometers, fabricated by electron-beam coevaporation and photolithography techniques on a 2-inch silicon wafer. The resistance versus temperature curves of several sensors with different thickness are measured with different bias currents, ranging from 200 nA to 10 micro A, and the electron-phonon coupling coefficient and the electron-phonon thermal conductance are calculated herein. Our values are quite comparable with those in metallic TES samples of other groups using different measurement methods, while we are using the transition region of our TES sample to calculate the electron-phonon coupling interaction.

astro-ph.IM↗

arXiv2014

A Detailed Look at the First Results from the Large Underground Xenon (LUX) Dark Matter Experiment

LUX, the world's largest dual-phase xenon time-projection chamber, with a fiducial target mass of 118 kg and 10,091 kg-days of exposure thus far, is currently the most sensitive direct dark matter search experiment. The initial null-result limit on the spin-independent WIMP-nucleon scattering cross-section was released in October 2013, with a primary scintillation threshold of 2 phe, roughly 3 keVnr for LUX. The detector has been deployed at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, and is the first experiment to achieve a limit on the WIMP cross-section lower than $10^{-45}$ cm$^{2}$. Here we present a more in-depth discussion of the novel energy scale employed to better understand the nuclear recoil light and charge yields, and of the calibration sources, including the new internal tritium source. We found the LUX data to be in conflict with low-mass WIMP signal interpretations of other results.

hep-ex↗

arXiv2014

Monte Carlo Simulation of RPC-based PET with GEANT4

The Resistive Plate Chambers (RPC) are low-cost charged-particle detectors with good timing resolution and potentially good spatial resolution. Using RPC as gamma detector provides an opportunity for application in positron emission tomography (PET). In this work, we use GEANT4 simulation package to study various methods improving the detection efficiency of a realistic RPC-based PET model for 511keV photons, by adding more detection units, changing the thickness of each layer, choosing different converters and using multi-gaps RPC (MRPC) technique. Proper balance among these factors are discussed. It's found that although RPC with materials of high atomic number can reach a higher efficiency, they may contribute to a poor spatial resolution and higher background level.

physics.ins-det↗

arXiv2014

Lup-Like Cantilever Beam for Small Deflection

A lup-like cantilever beam are discussed in this work. For small deflection it can be approximated as a spring-mass system with certain spring constant whose effective mass is larger than the usual constant rectangular cross section cantilever beam. A new parameter $β$ is introduced to relates some the properties of lup-like cantilever beam to the usual one. Influence of beam witdh $B_0$ and head width $B_t$ to value of $β$ is also presented.

physics.ins-det↗