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Search Results: 1 - 10 of 138753 matches for " K. Mavrokoridis "
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Optical readout tracking detector concept using secondary scintillation from liquid argon generated by a thick gas electron multiplier
P. K. Lightfoot,G. J. Barker,K. Mavrokoridis,Y. A. Ramachers,N. J. C. Spooner
Physics , 2008, DOI: 10.1088/1748-0221/4/04/P04002
Abstract: For the first time secondary scintillation, generated within the holes of a thick gas electron multiplier (TGEM) immersed in liquid argon, has been observed and measured using a silicon photomultiplier device (SiPM). 250 electron-ion pairs, generated in liquid argon via the interaction of a 5.9KeV Fe-55 gamma source, were drifted under the influence of a 2.5KV/cm field towards a 1.5mm thickness TGEM, the local field sufficiently high to generate secondary scintillation light within the liquid as the charge traversed the central region of the TGEM hole. The resulting VUV light was incident on an immersed SiPM device coated in the waveshifter tetraphenyl butadiene (TPB), the emission spectrum peaked at 460nm in the high quantum efficiency region of the device. For a SiPM over-voltage of 1V, a TGEM voltage of 9.91KV, and a drift field of 2.5KV/cm, a total of 62 photoelectrons were produced at the SiPM device per Fe-55 event, corresponding to an estimated gain of 150 photoelectrons per drifted electron.
Characterisation of a silicon photomultiplier device for applications in liquid argon based neutrino physics and dark matter searches
P. K. Lightfoot,G. J. Barker,K. Mavrokoridis,Y. A. Ramachers,N. J. C. Spooner
Physics , 2008, DOI: 10.1088/1748-0221/3/10/P10001
Abstract: The performance of a silicon photomultiplier has been assessed at low temperature in order to evaluate its suitability as a scintillation readout device in liquid argon particle physics detectors. The gain, measured as 2.1E6 for a constant over-voltage of 4V was measured between 25degC and -196degC and found to be invariant with temperature, the corresponding single photoelectron dark count rate reducing from 1MHz to 40Hz respectively. Following multiple thermal cycles no deterioration in the device performance was observed. The photon detection efficiency (PDE) was assessed as a function of photon wavelength and temperature. For an over-voltage of 4V, the PDE, found again to be invariant with temperature, was measured as 25% for 460nm photons and 11% for 680nm photons. Device saturation due to high photon flux rate, observed both at room temperature and -196degC, was again found to be independent of temperature. Although the output signal remained proportional to the input signal so long as the saturation limit was not exceeded, the photoelectron pulse resolution and decay time increased slightly at -196degC.
First Demonstration of Imaging Cosmic Muons in a Two-Phase Liquid Argon TPC using an EMCCD Camera and a THGEM
K. Mavrokoridis,J. Carroll,K. J. McCormick,P. Paudyal,A. Roberts,N. A. Smith,C. Touramanis
Physics , 2015, DOI: 10.1088/1748-0221/10/10/P10004
Abstract: Colossal two-phase Liquid Argon Time Projection Chambers (LAr TPCs) are a proposed option for future long-baseline neutrino experiments. This study illustrates the feasibility of using an EMCCD camera to capture light induced by single cosmic events in a two-phase LAr TPC employing a THGEM. An Andor iXon Ultra 897 EMCCD camera was externally mounted via a borosilicate glass viewport on the Liverpool two-phase LAr TPC. The camera successfully captured the secondary scintillation light produced at the THGEM holes that had been induced by cosmic events. The light collection capability of the camera for various EMCCD gains was assessed. For a THGEM gain of 64 and an EMCCD gain of 1000, clear images were captured with an average signal-to-noise ratio of 6. Preliminary 3D reconstruction of straight cosmic muon tracks has been performed by combining the camera images, PMT signals and THGEM charge data. Reconstructed cosmic muon tracks were used to determine THGEM gain and to calibrate the intensity levels of the EMCCD image.
Argon Purification Studies and a Novel Liquid Argon Re-circulation System
K. Mavrokoridis,R. G. Calland,J. Coleman,P. K. Lightfoot,N. McCauley,K. J. McCormick,C. Touramanis
Physics , 2011, DOI: 10.1088/1748-0221/6/08/P08003
Abstract: Future giant liquid argon (LAr) time projection chambers (TPCs) require a purity of better than 0.1 parts per billion (ppb) to allow the ionised electrons to drift without significant capture by any electronegative impurities. We present a comprehensive study of the effects of electronegative impurity on gaseous and liquid argon scintillation light, an analysis of the efficacy of various purification chemicals, as well as the Liverpool LAr setup, which utilises a novel re-circulation purification system. Of the impurities tested - Air, O_2, H_2O, N_2 and CO_2 in the range of between 0.01 ppm to 1000 ppm - H_2O was found to have the most profound effect on gaseous argon scintillation light, and N_2 was found to have the least. Additionally, a correlation between the slow component decay time and the total energy deposited with 0.01 ppm - 100 ppm O_2 contamination levels in liquid argon has been established. The superiority of molecular sieves over anhydrous complexes at absorbing Ar gas, N_2 gas and H_2O vapour has been quantified using BET isotherm analysis. The efficiency of Cu and P_2O5 at removing O_2 and H_2O impurities from 1 bar N6 argon gas at both room temperature and -130 ^oC was investigated and found to be high. A novel, highly scalable LAr re-circulation system has been developed. The complete system, consisting of a motorised bellows pump operating in liquid and a purification cartridge, were designed and built in-house. The system was operated successfully over many days and achieved a re-circulation rate of 27 litres/hour and high purity.
Optical Readout of a Two Phase Liquid Argon TPC using CCD Camera and THGEMs
K. Mavrokoridis,F. Ball,J. Carroll,M. Lazos,K. J. McCormick,N. A. Smith,C. Touramanis,J. Walker
Physics , 2014, DOI: 10.1088/1748-0221/9/02/P02006
Abstract: This paper presents a preliminary study into the use of CCDs to image secondary scintillation light generated by THick Gas Electron Multipliers (THGEMs) in a two phase LAr TPC. A Sony ICX285AL CCD chip was mounted above a double THGEM in the gas phase of a 40 litre two-phase LAr TPC with the majority of the camera electronics positioned externally via a feedthrough. An Am-241 source was mounted on a rotatable motion feedthrough allowing the positioning of the alpha source either inside or outside of the field cage. Developed for and incorporated into the TPC design was a novel high voltage feedthrough featuring LAr insulation. Furthermore, a range of webcams were tested for operation in cryogenics as an internal detector monitoring tool. Of the range of webcams tested the Microsoft HD-3000 (model no:1456) webcam was found to be superior in terms of noise and lowest operating temperature. In ambient temperature and atmospheric pressure 1 ppm pure argon gas, the THGEM gain was approximately 1000 and using a 1 msec exposure the CCD captured single alpha tracks. Successful operation of the CCD camera in two-phase cryogenic mode was also achieved. Using a 10 sec exposure a photograph of secondary scintillation light induced by the Am-241 source in LAr has been captured for the first time.
Towards a liquid Argon TPC without evacuation: filling of a 6 m^3 vessel with argon gas from air to ppm impurities concentration through flushing
A. Curioni,L. Epprecht,A. Gendotti,L. Knecht,D. Lussi,A. Marchionni,G. Natterer,F. Resnati,A. Rubbia,J. Coleman,M. Lewis,K. Mavrokoridis,K. McCormick,C. Touramanis
Physics , 2010, DOI: 10.1088/1742-6596/308/1/012024
Abstract: In this paper we present a successful experimental test of filling a volume of 6 m$^3$ with argon gas, starting from normal ambient air and reducing the impurities content down to few parts per million (ppm) oxygen equivalent. This level of contamination was directly monitored measuring the slow component of the scintillation light of the Ar gas, which is sensitive to {\it all} sources of impurities affecting directly the argon scintillation.
First demonstration of a sub-keV electron recoil energy threshold in a liquid argon ionization chamber
S. Sangiorgio,T. H. Joshi,A. Bernstein,J. Coleman,M. Foxe,C. Hagmann,I. Jovanovic,K. Kazkaz,K. Mavrokoridis,V. Mozin,S. Pereverzev,P. Sorensen
Physics , 2013, DOI: 10.1016/j.nima.2013.06.061
Abstract: We describe the first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time projection chamber. This is an important step in an effort to develop a detector capable of identifying the ionization signal resulting from nuclear recoils with energies of order a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82 keV and 0.27 keV, following the K- and L-shell electron capture decay of Ar-37, respectively. The Ar-37 source preparation is described in detail, since it enables calibration that may also prove useful in dark matter direct detection experiments. An internally placed Fe-55 x-ray source simultaneously provided another calibration point at 5.9 keV. We discuss the ionization yield and electron recombination in liquid argon at those three calibration energies.
Measurements of neutrons produced by high-energy muons at the Boulby Underground Laboratory
H. M. Araujo,J. Blockley,C. Bungau,M. J. Carson,H. Chagani,E. Daw,B. Edwards,C. Ghag,E. V. Korolkova,V. A. Kudryavtsev,P. K. Lightfoot,A. Lindote,I. Liubarsky,R. Luscher,P. Majewski,K. Mavrokoridis,J. E. McMillan,A. St. J. Murphy,S. M. Paling,J. Pinto da Cunha,R. M. Preece,M. Robinson,N. J. T. Smith,P. F. Smith,N. J. C. Spooner,T. J. Sumner,R. J. Walker,H. Wang,J. White
Statistics , 2008, DOI: 10.1016/j.astropartphys.2008.05.004
Abstract: We present the first measurements of the muon-induced neutron flux at the Boulby Underground Laboratory. The experiment was carried out with an 0.73 tonne liquid scintillator that also served as an anticoincidence system for the ZEPLIN-II direct dark matter search. The experimental method exploited the delayed coincidences between high-energy muon signals and gamma-rays from radiative neutron capture on hydrogen or other elements. The muon-induced neutron rate, defined as the average number of detected neutrons per detected muon, was measured as $0.079 \pm 0.003$ (stat.) neutrons/muon using neutron-capture signals above 0.55 MeV in a time window of 40-190 $\mu$s after the muon trigger. Accurate Monte Carlo simulations of the neutron production, transport and detection in a precisely modeled laboratory and experimental setup using the GEANT4 toolkit gave a result 1.8 times higher than the measured value. The difference greatly exceeds all statistical and systematic uncertainties. As the vast majority of neutrons detected in the current setup were produced in lead we evaluated from our measurements the neutron yield in lead as $(1.31 \pm 0.06) \times 10^{-3}$ neutrons/muon/(g/cm$^2$) for a mean muon energy of about 260 GeV.
Development of wavelength shifter coated reflectors for the ArDM argon dark matter detector
The ArDM Collaboration,V. Boccone,P. K. Lightfoot,K. Mavrokoridis,C. Regenfus,C. Amsler,A. Badertscher,A. Bueno,H. Cabrera,M. C. Carmona-Benitez,M. Daniel,E. J. Daw,U. Degunda,A. Dell'Antone,A. Gendotti,L. Epprecht,S. Horikawa,L. Kaufmann,L. Knecht,M. Laffranchi,C. Lazzaro,D. Lussi,J. Lozano,A. Marchionni,A. Melgarejo,P. Mijakowski,G. Natterer,S. Navas-Concha,P. Otyugova,M. de Prado,P. Przewlocki,F. Resnati,M. Robinson,J. Rochet,L. Romero,E. Rondio,A. Rubbia,N. J. C. Spooner,T. Strauss,J. Ulbricht,T. Viant
Physics , 2009, DOI: 10.1088/1748-0221/4/06/P06001
Abstract: To optimise the design of the light readout in the ArDM 1-ton liquid argon dark matter detector, a range of reflector and WLS coating combinations were investigated in several small setups, where argon scintillation light was generated by radioactive sources in gas at normal temperature and pressure and shifted into the blue region by tetraphenyl butadiene (TPB). Various thicknesses of TPB were deposited by spraying and vacuum evaporation onto specular 3M{\small\texttrademark}-foil and diffuse Tetratex{\small\textregistered} (TTX) substrates. Light yields of each reflector and TPB coating combination were compared. Reflection coefficients of TPB coated reflectors were independently measured using a spectroradiometer in a wavelength range between 200 and 650 nm. WLS coating on the PMT window was also studied. These measurements were used to define the parameters of the light reflectors of the ArDM experiment. Fifteen large $120\times 25$ cm$^2$ TTX sheets were coated and assembled in the detector. Measurements in argon gas are reported providing good evidence of fulfilling the light collection requirements of the experiment.
LAr1-ND: Testing Neutrino Anomalies with Multiple LArTPC Detectors at Fermilab
C. Adams,C. Andreopoulos,J. Asaadi,B. Baller,M. Bishai,L. Camilleri,F. Cavanna,H. Chen,E. Church,D. Cianci,G. Collin,J. Conrad,A. Ereditato,B. Fleming,W. M. Foreman,G. Garvey,R. Guenette,C. Ignarra,B. Jones,G. Karagiorgi,W. Ketchum,I. Kreslo,D. Lissauer,W. C. Louis,K. Mavrokoridis,N. McCauley,G. B. Mills,O. Palamara,Z. Pavlovic,X. Qian,L. Qiuguang,R. Rameika,D. W. Schmitz,M. Shaevitz,M. Soderberg,J. Spitz,A. M. Szelc,C. E. Taylor,K. Terao,M. Thomson,C. Thorn,M. Toups,C. Touramanis,T. Strauss,R. G. Van De Water,C. R. von Rohr,M. Weber,B. Yu,G. Zeller,J. Zennamo
Physics , 2013,
Abstract: This white paper describes LAr1-ND and the compelling physics it brings first in Phase 1 and next towards the full LAr1 program. In addition, LAr1-ND serves as a key step in the development toward large-scale LArTPC detectors. Its development goals will encompass testing existing and possibly innovative designs for LBNE while at the same time providing a training ground for teams working towards LBNE combining timely neutrino physics with experience in detector development.
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