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.     

Charge collection in partially depleted silicon detectors

The behaviour of partially depleted silicon detectors deserves some attention in the design of large systems such as electromagnetic or hadronic calorimeters in which these detectors are used and conservative operating conditions must be imposed [1–3].We have experimentally investigated charge collection from the undepleted region in silicon detectors manufactured for high energy calorimetry by Ansaldo Semiconductors S.p.A.The observed results are compared with a simple model.     

Experimental results from a sandwich calorimeter using U absorbers and 0.25 m of Si active area

The electromagnetic section of a hadronic calorimeter, consisting of uranium absorbers and of silicon sampling units with an active area of 0.25 m², was investigated. The overall performance of the silicon detectors and especially developed associated electronics, seems to be stable and reliable. During a four-week run at the t₉, CERN-PS (Proton Synchrotron) electron beam (energies of 2 to 6 GeV), no variation of energy calibration of the calorimeter was observed. The energy resolution for electromagnetic showers was found to be about , where E is the energy of the incoming electron and τ is the number of radiation lengths of passive material interspaced between two active samplers, for a calorimeter depth of 15.6 X₀ (radiation lengths), with Si samplers depleted to 200 μm. The fiberglass supports of the silicon mosaics cause a reduction of energy response to electromagnetic showers. It can be exploited to equalize the response of a Si/U hadronic calorimeter to incoming electrons and hadrons.     

Radial and longitudinal behaviour of hadronic cascade showers induced by 300 GeV protons in lead and iron absorbers

The profile of three-dimensional hadronic cascade showers initiated by 300 GeV protons in lead and iron is investigated using photo-sensitive films. The lateral and longitudinal distribution of shower particles are determined with a minimum of distortion that is inevitably introduced by an insertion of detectors between the metal plates.     

Experimental Characterization of Space Charge in IZIP Detectors

Interleaved ionization electrode geometries offer the possibility of efficient rejection of near-surface events. The CDMS collaboration has implemented this interleaved approach for the charge and phonon readout for our germanium detectors. During a recent engineering run with negligible ambient radiation, the detectors were found to lose ionization stability more quickly than expected. This paper summarizes studies done in order to determine the underlying cause of the instability, as well as possible running modes that maintain stability without unacceptable loss of livetime. Additionally, first results are shown for the new version IZIP mask which attempts to improve the overall stability of the detectors.     

Performance of different phoswich configurations in a balloon flight experiment

Four different phoswich units were included in a modular hard X-ray balloon experiment launched on August 10, 1982 in order to check the dependence of background level and rejection efficiency of NaI(Tl)/CsI(Na) phoswich detectors on scintillator thicknesses. The results concern the dependence of the background intensity on both the thickness of the active shield, for a fixed primary detector thickness, and on the thickness of the primary detector, given the active shield thickness. A direct comparison of phoswich detectors with passively shielded NaI(Tl) crystals is also given. As a consequence practical hints for designing new phoswich detectors are derived and the limiting sensitivity of these detectors for hard X-ray observations of celestial sources is inferred.     

Measurement of the time development of particle showers in a uranium scintillator calorimeter

We report on the time evolution of particle showers, as measured in modules of the uranium-scintillator barrel calorimeter of the ZEUS detector. The time development of hadronic showers differs significantly from that of electromagnetic showers, with about 40% of the response to hadronic showers arising from energy depositions which occur late in the shower development. The degree of compensation and the hadronic energy resolution were measured as a function of integration time, giving a value of for a gate width of 100 ns. The possibilities for electron-hadron separation based on the time structure of the shower were studied, with pion rejection factors in excess of 100 being achieved for electron efficiencies greater than 60%. The custom electronics used to perform these measurements samples the calorimeter signal at close to 60 MHz, stores all samples for a period of over 4 μs using analog switched capacitor pipelines, and digitizes the samples for triggered events with 12-bit ADCs.     

TANGO Array.: 2. Simulations

The angular and energy resolutions of the TANGO Array were obtained using extensive Monte Carlo simulations performed with a double purpose: (1) to determine the appropriate parameters for the array fitting to the desired range of sensitivity (the knee energy region), and (2) to construct a reliable shower database required for reference in the analysis of experimental data. The AIRES code, with the SIBYLL hadronic collision package, was used to simulate Extended Air Showers produced by primary cosmic rays (assuming protons and iron nuclei), with energies ranging from 10¹⁴ to 10¹⁸ eV. These data were fed into a realistic code which simulates the response of the detectors (water Cherenkov detectors), including the electronics, pickup noise, and the signal attenuation in the connecting cables. The trigger stage was considered in the simulations in order to estimate the trigger efficiency of the array and to verify the accuracy of the reconstruction codes. This paper delineates the simulations performed to obtain the expected behavior of the array, and describes the simulated data. The results of these simulations suggest that we can expect an error in the energy of the primary cosmic-ray of ∼60% of the estimated value and that the error in the measurement of the direction of arrival can be estimated as ∼4°. The present simulations also indicate that unambiguous assignments of the primary energy cannot be obtained because of the uncertainty in the nature of the primary cosmic ray.     

The EDELWEISS-III Project and the Rejection Performance of Its Cryogenic Germanium Detectors

The EDELWEISS-III experiment searches for Dark matter using cryogenic germanium detectors in the low radioactivity environment of the Laboratoire Souterrain de Modane. The experiment and the FID detector design, whereby all surfaces are covered with interleaved electrodes, are described. The performance for gamma-ray and surface event rejection of these detectors is discussed. In particular, recent calibrations with a \(^{210}\) Pb source reveals that the excellent surface event rejection already demonstrated with planar interleaved electrodes also extends to the entire surface of the large FID detectors, even on their cylindrical outer surfaces, where the electric field has a more complicated geometry. Expected results with the full exposure of the EDELWEISS-III experiment are discussed.     

Characteristics of the ATLAS and CMS detectors

The goal for the detection of new physics processes in particle collisions at Large Hadron Collider energies, combined with the broad spectrum of possibilities for how the physics might be manifest, leads to detectors of unprecedented scope and size for particle physics experiments at colliders. The resulting two detectors, ATLAS (A Toroidal LHC ApparatuS) and CMS (compact muon spectrometer), must search for the new physics processes within very complex events arising from the very high-energy collisions. The two experiments share many basic design features-in particular, the need for very selective triggering to weed out the bulk of the uninteresting events; the order in which detector types are arrayed in order to provide maximum information about each event; and the very large angular coverage required to constrain the energy carried by any non-interacting particles. However, within these basic constraints, the detectors are quite different given the different emphases placed on issues such as resolution and background rejection. Both common features and the distinct differences will be presented.     

Concept of Metallic Magnetic Calorimeters for Rare Event Search in the LUMINEU Project

The project LUMINEU is mainly aiming at the search for neutrinoless double-beta decay of the candidate nuclide \(^{100}\) Mo using cryogenic ZnMoO \(_4\) detectors with simultaneous heat and scintillation light detection for radioactive background rejection. It also includes some development for dark matter search using cryogenic Ge detectors with simultaneous heat and ionization detection for background rejection. For both cases, metallic magnetic calorimeters (MMCs) are studied among several thermometer types. In double-beta decay search, the intrinsically fast response of MMCs reading out the light detector may allow for a very fast signal rise time and help to reduce the potential background due to pile-up of two-neutrino double beta decay events. In dark matter search, MMCs reading out the heat channel may improve the energy resolution with respect to the standard NTD Ge thermistor readout and hence the sensitivity of the detectors for low-mass WIMPs.     

Silicon detectors in electromagnetic and hadronic calorimetry

A review of investigations performed by SICAPO collaboration at CERN and Si/W and Si/U sandwich calorimeters employing silicon detectors as active medium is presented. Experimental results, such as the response of sensed energy versus incoming electron energy and depleted layer width, of the longitudinal and lateral development of electromagnetic showers and of the energy resolution, are described. Mosaic modules of silicon detectors, which enable the construction of silicon sampling hadronic calorimeters, are also given. A comparison of results from SICAPO, Hamburg (Si/Pb) and from Tokyo (Si/Pb and Si/W) calorimeters is shown.     

ZnMgO基紫外探测器的研究进展及分析

ZnO基三元合金半导体材料因其重要的带隙调制作用,已成为紫外探测器发展的一个重要方向,特别是Zn_(1-x)Mg_xO基紫外探测器,可以探测日盲区紫外光,更是受到了各国极大的关注.当前,Zn_(1-x)Mg_xO基紫外探测器大多采用MSM叉指结构,响应峰位于300nm附近,响应时间最高可达ns量级,紫外可见光抑制比亦可大于4个数量级.扼要介绍了国内外相关小组的研究进展,并着重分析了薄膜组分、结构以及探测器性能参数等.     

Neganov–Luke Phonon Amplification in P-type Point Contact Detectors

The Cryogenic Dark Matter Search (CDMS) detectors measure ionization and athermal phonons in high purity germanium crystals to discriminate between nuclear recoils from dark matter candidates and radioactive backgrounds. In order to reach lower energy detection thresholds, the CDMSlite experiment operates the CDMS detectors with a larger voltage bias to increase the signal-to-noise ratio using the Neganov–Luke effect. Breakdown in those detectors was observed at fields of order 30 V/cm, but the reason for the breakdown is unknown. It is unclear if the breakdowns are due to surface leakage current, impact ionization in the bulk of the crystals, or some other effect due to the very low operating temperatures of the detectors. Germanium detectors used in gamma spectroscopy at 77 K are regularly operated with fields in excess of 1,000 V/cm. In order to understand the origin of breakdown in the CDMS detectors, a P-type Point Contact detector was equipped with transition edge phonon thermistors and operated at a base temperature of \(\sim \) 30 mK. The linearity of the Neganov–Luke phonon amplification was studied and no sign of breakdown for biases up to 400 V was observed. This excludes impact ionization on neutral impurity states as the primary cause of the breakdown observed in the CDMSLite detectors. This demonstrates that the Neganov–Luke phonon amplification is a viable method for lowering the energy threshold in germanium detectors of masses of order 1 kg.     

Status and Prospects of the EDELWEISS Direct WIMP Search Experiment

We report the final results of EDELWEISS-II, obtained with ten 400?g heat-and-ionization cryogenic detectors equipped with InterDigit electrodes for the rejection of near-surface events. Results from fourteen months of continuous operation and a total exposure of 384?kg?day are presented. We also present the status of EDELWEISS-III, which will accumulate more than 3000?kg?day of data with 40 new 800?g detectors in the coming years.     

Kapton Polymeric Films to Shield X-Ray Detectors in Orbit

We are investigating possible technical solutions to minimize the instrumental non X-ray background (NXB) of the X-ray Micro-calorimeter Spectrometer (XMS) for the ATHENA space mission. In the proposed design, XMS will be provided with an anti-coincidence system in order to reject most of the X-ray-like events produced by primary solar and cosmic particles that are expected to populate the L-2 space environment. However, the rejection efficiency of events produced by secondary particles cannot be as good as that of events produced directly by primary particles. Among secondary emitted particles, knock-on electrons have in general a major impact in determining the NXB level of X-ray detectors. For this reason, it may be helpful to adopt some techniques of passive shielding together with the use of the active anti-coincidence. We present preliminary results of a study on polyimide sheets, which could be employed to reduce the fluence of knock-on electrons onto XMS and, more in general, to optimize the design and configuration of X-ray detectors in orbit.     

The structure of lateral electromagnetic shower development in Si/W and Si/U calorimeters

In order to find the optimal granularity of the electromagnetic section of a hadronic calorimeter, with tungsten or uranium absorbers, lateral shower extension is to be defined. A test was performed in t₉ beam at the CERN-PS (proton synchrotron) with incoming electron energies of 2, 4 and 6 GeV. It was found that in the investigated radial region, the structure of the lateral shower development has two components.     

Neutron detection gamma ray sensitivity criteria

The shortage of ³He has triggered the search for effective alternative neutron detection technologies for national security and safeguards applications. Any new detection technology must satisfy two basic criteria: (1) it must meet a neutron detection efficiency requirement, and (2) it must be insensitive to gamma-ray interference at a prescribed level, while still meeting the neutron detection requirement. It is the purpose of this paper to define measureable gamma ray sensitivity criteria for neutron detectors. Quantitative requirements are specified for: intrinsic gamma ray detection efficiency and gamma ray absolute rejection. The gamma absolute rejection ratio for neutrons (GARRn) is defined, and it is proposed that the requirement for neutron detection be 0.9<GARRn<1.1 at a 10 mR/h exposure rate. An example of the results from a ³He based neutron detector is provided showing that this technology can meet the stated requirements. Results from tests of some alternative technologies are also reported.     

Xenon10 and Noble Liquid Dark Matter Detectors

In the field of direct searches for WIMP dark matter, noble liquid detectors have recently proven an increasingly competitive technology. Although less demanding in terms of cryogenics, they are relatively easily scalable to large target masses and can offer good position reconstruction and background rejection power. Here we illustrate the more recent progress of this technology, through the particular example of the Xenon10 experiment. S. Fiorucci for the Xenon Collaboration.     

Applying Statistical Mechanics to pixel detectors

Pixel detectors, being made of a large number of active cells of the same kind, can be considered as significant sets to which Statistical Mechanics variables and methods can be applied. By properly redefining well known statistical parameters in order to let them match the ones that actually characterize pixel detectors, an analysis of the way they work can be performed in a totally new perspective. A deeper understanding of pixel detectors is attained, helping in the evaluation and comparison of their intrinsic characteristics and performance.