Plastic scintillating fibers for track detection

A particle track detector consisting of plastic scintillating fibers and a gatable image intensifier system has been developed and tested with pion, proton and deuteron beams of 1 GeV/c. We have observed clear tracks of beams and scattered particles at a beam rate of up to 10⁵ particles per second. Tracks have been recorded by using a CCD video camera at a trigger rate of around 30 Hz. The energy and spatial resolutions have been investigated.     

Data acquisition system for dark matter detectors

Progress in Ge detector technology has resulted in ultralow backgrounds of less than 0.3 counts keV^–1 kg^–1 d^–1 at energies between 5 and 12 keV, and less than 1.0 counts kev^–1 kg^–1 d^–1 for energies between 3 and 5 keV. Coupled with good energy resolution, 0.4 keV FWHM at 10 keV, this allows searches for DM particles with m 8 GeV/c².Electromagnetic interference and acoustical pick-up are the main sources of background in the best Ge detectors. These problems are even more important in cryogenic WIMP detectors under development. A PC-based on line pulse shape analysis system is presented which permits rejection of about 95% percent of the EMI/ acoustical background. The hardware uses a low cost, commercially available digital storage oscilloscope. The software consists of about 20,000 lines of code in Pascal and assembly language. We tested this system using a low radioactive background Ge-system on the Earth's surface. For low energy events (27 keV photons) this system permits improvement in the background from 0.1 cpm to 2 cpd.     

Study of a BGO calorimeter using electron and hadron beams from 1 to 50 GeV

A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained ( ) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement.     

The performance of an L3 hadron calorimeter prototype module with BGO

A prototype of a gas sampling uranium module of the L3 hadron calorimeter was built and subsequently tested with pion beams of energies between 4 and 20 GeV. The construction of the proportional chambers, the assembling of the module, the readout electronics, and the beam test are briefly described. The energy resolution of the calorimeter module alone was measured to be 30.5 ± 3% at 6 GeV, 21 ± 2% at 10 GeV and 18 ± 2% at 20 GeV. For the module together with a BGO crystal matrix in resolution was 29 ± 3% at 4 GeV, 21 ± 2% at 10 GeV, and 17 ± 2% at 20 GeV.     

Theoretical calculations of the primary defects induced by pions and protons in SiC

In the present work, the bulk degradation of SiC in hadron (pion and proton) fields, in the energy range between 100 MeV and 10 GeV, is characterised theoretically by means of the concentration of primary defects per unit fluence. The results are compared to the similar ones corresponding to diamond, silicon and GaAs.     

Results and Prospects for the Cryogenic Dark Matter Search (CDMS) Experiment

The Cryogenic Dark Matter Search (CDMS) experiment, located at the Soudan underground mine, operated 30 low-temperature Ge and Si detectors for several years to search for Weakly Interacting Massive dark matter Particles (WIMPs). Due to their excellent background discrimination power and low energy threshold, our detectors have provided world-leading sensitivity for WIMP-nucleon interactions for most of the past decade over a large WIMP mass range. The final exposure of our CDMS?II detectors yielded two candidate events, with an expected background of 0.9 ± 0.2 events, and this result was published in March 2010 in Science. A reanalysis of 8 Ge detectors with a lowered, 2 keV recoil energy threshold, provided increased sensitivity to interactions from WIMPs with masses below ?10 GeV/c² and excluded possible low-mass WIMP signals from the DAMA/LIBRA and CoGeNT experiments. The CDMS collaboration is moving forward with the SuperCDMS experiments at Soudan and SNOLAB with the goal of probing the zeptobarn scale and beyond over the next decade. To achieve this goal, a new generation of larger mass detectors with interleaved geometry for the phonon and ionization readout has been developed.     

Possibility of increasing proton rejection by detecting primary cosmic radiation electrons using an ionization-neutron calorimeter

Measurements were made of the neutron yields from a lead absorber 60 cm thick in electromagnetic cascades initiated by 200–600 MeV electrons. A comparison between the neutron yields obtained for electrons and the results of similar measurements for protons and pions suggests that the rejection factor of the proton background is increased ∼10² times when an ionization-neutron calorimeter is used to measure primary cosmic radiation electrons at energies above 100 GeV. Pis’ma Zh. Tekh. Fiz. 24, 66–73 (September 26, 1998)     

The CDF plug upgrade electromagnetic calorimeter: test beam results

The CDF Plug Upgrade calorimeter, which fully exploits the tile–fiber technique, was tested at the Fermilab meson beamline. The calorimeter was exposed to positron, positively charged pion and positive muon beams with energies in the range of 5–230 GeV. The energy resolution of the electromagnetic calorimeter to the positron beam is consistent with the design value of , where E is the energy in units of GeV and represents sum in quadrature. The non-linearity for positrons is studied in an energy range of 11–181 GeV. It is important to incorporate the response of the preshower detector, the first layer of the electromagnetic calorimeter which is readout separately, into that of the calorimeter to reduce the non-linearity to 1% or less. The energy scale is about 1.46 pC/GeV with HAMAMATSU R4125 operated typically at a gain of 2.5×10⁴. The response non-uniformity over the surface of a tower of the electromagnetic calorimeter is found to be about 2% with 57 GeV positrons. Studies of several detailed detector characteristics are also presented.     

MARS-2: A “current sensitive” liquid argon calorimeter

The performances of a liquid argon calorimeter with wide gaps (2.8 cm) operating in current sensitive mode have been studied with 6.6–36 GeV electron and 40 GeV pion beams at the IHEP accelerator.The good uniformity in charge collection efficiency obtained with this unusual mode has led to a reduction of sampling fluctuations to values of $\text{σ}{}_{\mathrm{<mtext>S</mtext>}}\text{E}\text{=}\text{0.04}\text{√E}$.Spatial and angular resolutions have been measured as well. The equivalent noise energy was 82 MeV rms for the whole detector.     

Conceptual Design for SuperCDMS SNOLAB

Beyond the present dark matter direct detection experiment at the Soudan underground laboratory, the SuperCDMS Collaboration is engaged in R&D activities for a 100-kg scale germanium dark matter experiment nominally sited at SNOLAB (2070 m overburden of rock). The expected sensitivity after 3 years of running is 3×10^?46?cm² for the spin-independent cross section, an order of magnitude improvement over present exclusion limits for WIMP masses ～80?GeV/c². At this depth, and appropriate design of shielding and cryostat, neutron backgrounds will be negligible. The baseline design is an expanded version of CDMS II with Ge substrates (100×33?mm discs) instrumented with the iZIP phonon sensor layout to achieve the electron surface-event rejection power required.     

A new method to detect gamma ray extensive air showers which directly measures angles and identifies muons

We describe an extensive air shower array (GRAND™) ⁷ which is currently under construction. It is dedicated to recording ultrahigh energy (UHE) gamma rays from stellar point sources by measuring the angle of charged secondaries with proportional wire chamber tracking detectors. This new method is designed to give 0.25° angular resolution for the primary gamma direction with 100 detected secondary electrons. These same tracking detectors make possible a new, inexpensive detector for muons thereby enabling the rejection of muon-rich hadronic shower background.     

Tests of a magnetic emulsion spectrometer by high energy heavy ions

A good momentum resolution (approximately 12% for a 2 GeV/e pion beam) has been successfully obtained at KEK using a magnetic emulsion spectrometer (MES) developed by the authors. An investigation on the usefulness of the MES in the study of intermediate heavy ion reactions (0.8 GeV/c per nucleon nitrogen ions on a tungsten nucleus) has been conducted at Saclay, and the results are reported in this paper.     

Electron-pion discrimination in an iron/streamer tube calorimeter up to 100 GeV

An electron/hadron calorimeter consisting of 2 cm/4 cm iron sampling planes and streamer tube readout modules was exposed to particle beams of electrons and pions in the energy range from 1 to 100 GeV. At the highest energies the observed pion misidentification amounted to 0.95% ± 0.21% at an electron detection efficiency of 95%.     

Low-Mass WIMP Sensitivity and Statistical Discrimination of Electron and Nuclear Recoils by Varying Luke-Neganov Phonon Gain in Semiconductor Detectors

Amplifying the phonon signal in a semiconductor dark matter detector can be accomplished by operating at high voltage bias and converting the electrostatic potential energy into Luke-Neganov phonons. This amplification method has been validated at up to |E|=40 V/cm without producing leakage in CDMS?II Ge detectors, allowing sensitivity to a benchmark WIMP with mass M _χ =8 GeV/c² and σ=1.8×10^?42 cm² (with significant sensitivity for M _χ >2 GeV/c²) assuming flat electronic recoil backgrounds near threshold. Furthermore, for the first time we show that differences in Luke-Neganov gain for nuclear and electronic recoils can be used to discriminate statistically between low-energy background and a hypothetical WIMP signal by operating at two distinct voltage biases. Specifically, 99% of events have p-value <10^?8 for a simulated 20?kg-day experiment with a benchmark WIMP signal with M _χ =8 GeV/c² and σ=3.3×10^?41 cm².     

Measurement of the resolution of a combined hodoscope calorimeter at 18 GeV and 38 GeV

The energy and spatial resolution of a combined detector consisting of the Cherenkov photon calorimeter GAMS-2000 and the modular hadron calorimeter MHC-100 has been studied at 18.5 and 38 GeV incident pion energies at the IHEP accelerator. The energy resolution of the combined setup is substantially improved by applying a correction based on the analysis of the lateral development of hadron showers in GAMS and MHC. It is shown that the parameters of the correction depend only weakly on the hadron energy. The influence of the gap between both photon and hadron calorimeters on the combined detector characteristics is of less importance with increasing energy.     

Hadron-Lepton cascade calculations (1–20 GeV) for a PbAl-lucite calorimeter

The results of Monte Carlo calculations for π^?(1–20 GeV) and e^?(1–10 GeV), normally incident on the center of a cylindrical calorimeter are presented. The calorimeter design has 60 unit cells of alternating PbAlLucite plates and is a simplified model of one to be used at the Stanford Linear Accelerator Center. General characteristics of the total and spatial energy deposition are given. Pulse height spectra, as well as spectra of the transverse fractional energy distributions and of their first and second moments, are given to aid in hadron-lepton discrimination. Sampling fluctuations are also examined for this purpose. Some results for the effects of a uniform probability of incidence over the central transverse strip and also some longitudinal discriminants are presented.     

A background rejection efficiency calculation for a proposed gaseous xenon TPC in a double beta decay experiment

A detailed calculation of the double beta (ββ) decay distribution and probability are presented, together with the results of a Monte Carlo simulation. The expected background rejection efficiency and achievable neutrinoless ββ decay half-life for a proposed high pressure (5–10 atm) gaseous xenon time projection chamber are calculated. The half-life is comparable to or longer than the present limit (∼ 10²³yr). It is found that ∼ 4π sr active shielding with NaI scintillator is effective in rejecting e^-e⁺ events when the energy resolution is 2% or better at 2.5 MeV. Monte Carlo calculations of electron tracks from neutrinoless ββ decay events show that a magnetic field can be used to distinguish ββ decay events from e^-e⁺ events when the energy resolution is ≥ 2%.     

2D Layered Materials for Fast-Charging Lithium-Ion Battery Anodes

The development of electric vehicles has received worldwide attention in the background of reducing carbon emissions, wherein lithium-ion batteries (LIBs) become the primary energy supply systems. However, commercial graphite-based anodes in LIBs currently confront significant difficulty in enduring ultrahigh power input due to the slow Li⁺ transport rate and the low intercalation potential. This will, in turn, cause dramatic capacity decay and lithium plating. The 2D layered materials (2DLMs) recently emerge as new fast-charging anodes and hold huge promise for resolving the problems owing to the synergistic effect of a lower Li⁺ diffusion barrier, a proper Li⁺ intercalation potential, and a higher theoretical specific capacity with using them. In this review, the background and fundamentals of fast-charging for LIBs are first introduced. Then the research progress recently made for 2DLMs used for fast-charging anodes are elaborated and discussed. Some emerging research directions in this field with a short outlook on future studies are further discussed.     

Surface Event Rejection of the EDELWEISS Cryogenic Germanium Detectors Based on NbSi Thin Film Sensors

Near-surface-events are a major limitation to the performance of cryogenic massive germanium heat and ionisation detectors for dark matter search, due to their incomplete charge collection. We present here a powerful method of surface event identification based on the transient heat signal of a Ge bolometer, equipped with two NbSi high impedance thin film sensors. Calibration runs using electrons and low energy gamma particles from a ¹⁰⁹Cd source show highly effective surface event rejection down to the heat threshold energy. Neutron and gamma source calibrations were realised to get information on the fiducial volume of the Ge absorber. First results from low background data taking are discussed.     

Performance of the radphi detector and trigger in a high rate tagged photon beam

We describe the design and operation of a detector system for measuring all-photon decays of mesons photoproduced in a tagged photon beam with energies between 4.3 and 5.4 GeV and a flux of 5×10⁷ tagged photons per second. Photons from meson decays were detected with a lead-glass calorimeter with an energy resolution of 11% at 1 GeV. Various veto and trigger components were also present. Final states with as many as six photons were successfully detected and reconstructed.