- JRA2 ADVANCED TECHNIQUES FOR RARE EVENT DETECTION Tentative structure

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1 Paris, 26/9/2006 ILIAS-next - JRA2 ADVANCED TECHNIQUES FOR RARE EVENT DETECTION Tentative structure Andrea Giuliani Drafting group: L.Baudis, A. Giuliani, J. Jochum, A. Juillard, H. Kraus, Ch. Marquet, L.Oberauer, A. Rubbia, N. Spooner, S. Schoenert, C. Weinheimer, K. Zuber Participating Institutions: RWTH Aachen University, Aachen, Germany INFN Milano-Bicocca, Milano, Italy Laboratori Nazionali del Gran Sasso, INFN, Assergi (AQ), Italy Università dell Insubria, Como, Italy University of Tuebingen, Tuebingen, Germany Université Paris XI, Orsay, France University of Oxford, Oxford, UK CENBG, Gradignan, France TUM, Munich, Germany ETH, Zurich, Switzerland University of Sheffield, UK MPIK, Heidelberg, Germany University of Muenster, Muenster, Germany CTU, Praha VERY PRELIMINARY!

2 Main objective develop specific aspects of various detector technologies (both classical and innovative) aiming at improving the sensitivity in the search for rare events ameliorate existing experiments set the bases for new projects increase the value of the infrastructures which normally host these searches, i.e. the underground laboratories impact on key aspects of astroparticle physics: neutrino physics dark matter discovery and identification rare event searches in general

3 Four Work Packages WP1 Very low temperature solid state detectors WP2 Noble liquid and gas detectors WP3 Advanced semiconductor detectors with active and passive background control WP4 Scintillation detectors optimized for rare event search

4 WP1 1.1 New scintillating crystals for Double Beta Decay and Dark Matter searches develop novel scintillating bolometers for rare event searches (i) select compounds for scintillating crystals of potential interest for Double Beta Decay and Dark Matter (ii) characterize the light yield at low temperatures of the selected crystals (iii) operate the crystals as bolometers with double read-out configuration (iv) test preliminarily the background in the relevant energy regions 1.2 Single-photon light detectors operated at very low temperatures realize light detectors suitable to be operated in the mk range, to be used in dark matter search with very low threshold scintillation+heat bolometers (i) select the optimal materials for bolometric light detectors (ii) develop phonon sensor technology for bolometric light detectors (iii) study coating methods to widen the sensitive band (iv) exploit the so-called "Luke effect" to approach single optical photon sensitivity 1.3 Fast microcalorimeters for direct measurement of neutrino mass realize detectors at kev energies with time response in the microsecond range in order to measure single beta decay with minimization of pulse pile-up (i) study of magnetic microcalorimeters (ii) development of transition edge sensors (iii) realization of kinetic inductance detectors (iv) develop synergies with CMB and astrophysical X-ray detection techniques

5 WP1 1.4 Macro-bolometers with event localization capability for background identification develop macrobolometers capable to identify alpha and beta particles absorbed at the surface (i) advanced study of pulse formation (heat, ionization and light channels) (ii) optimization of thin film sensors sensitive to athermal phonons (iii) events localization through pulse shape analysis (phonon and ionization), and development of simulation tools (iv) event localization by exploiting the dynamics of heat flow in composite bolometers 1.5 Improvement of charge collection in heat+ionization detectors Objective : Improve the charge collection efficiency for surface events in heat and ionization detectors (i) advanced study of charge collection and charge trapping in semiconductors at very low temperatures in low electric field (ii) optimization of amorphous Ge and Si sublayers under the electrodes and minimization of trapping at the surfaces (iii) development of simulation tools 1.6 High energy resolution microcalorimeters operated in medium high magnetic fields to operate a low-temperature high-energy-resolution calorimeter in a few T magnetic field, in view of an advanced KATRIN s detector system (i) characterize phonon sensors in medium-high magnetic field, in particular of NTD Ge and implanted Si thermistors, in terms of R-T behaviour and of electron-phonon decoupling (ii) realize a single pixel calorimetric detector operating in a few T magnetic field (iii) study and design a dilution refrigerator able to host a low temperature calorimeter in a few T field and suitable to be matched to the KATRIN s main spectrometer

6 WP2 2.1 Advanced methods of charge readout To develop and qualify advanced low background micro-pattern charge readout technology for TPCs to be used in rare event search (i) Technical comparison of state of the art in GEMs, LEMs and Micromegas (ii) Optimization of position resolution and gain at low energies (iii) Optimisation of quench gases and gas mixtures for single and two phase operation (iv) Development of improved electronics, HV and software including imaging (v) Low background material selection 2.2 Advanced methods of light readout To develop low background, UV sensitive, low temperature photon sensors of large area for TPCs to be used in rare event search (i) Technical comparison of state of the art in PMTs, Si-PMTs and APDs (ii) Development of improved light collection - large area photocathodes, CsI coatings, UV wavelength shifters, liquid-pmt coupling including flanges. (iii) Development of fiducialisation and position sensitivity techniques (iv) Optimisation for robustness and long-term, low noise operation in gas and liquid (v) Low background material selection

7 WP2 2.3 Target medium purification and isotopic separation To develop gas and liquid target materials with optimum low background, isotopic, purity and optimum electron or photon transport properties (i) Production of "dead argon" (argon free of 39Ar) (ii) Krypton, tritium and radon removal and control (iii) Recirculation and pumping technology including cartridge purity (iv) isotopic enrichment 2.4 Ionisation and scintillation processes at kev energies To improve understanding of the fundamental processes of particle interactions in gases and liquids at kev energies (i) New measurements of quench factors at low energy using neutron beams including systematic measurements for different elements, purity, temperature and pressure using the same chambers and electronics (ii) Cooperation with condensed matter community on relevant low energy ionisation physics and new measurement techniques in Noble liquids and gases (inc. Hitachi) (iii) Improved understanding of non-statistical ionisation and scintillation fluctuations

8 WP2 2.5 Event reconstruction and imaging To establish improved software and techniques for reconstruction, fiducialisation and imaging of events in TPCs (i) Study of lateral and transverse diffusion, timing and position resolution in TPC gases - influence on detector designs (ii) Development of optimised event positioning concepts (iii) Development of optimised track reconstruction procedures for low energy ionisation events in gases for directional detectors 2.6 Advanced study of pulse shape properties of LAr scintillation light To develop improved pulse shape discrimination techniques for particle discrimination methods in liquid argon applicable in dark matter detection (i) Study of the time distribution of scintillation photons in response to α, β, γ and neutron radiation and its dependence on chemical impurities and on electrical fields. (ii) Development of optimized front-end and digital electronics for pulse shape analysis purpose (iii) Development of novel numerical analysis tools for discrimination of α-, β-, γ- events and recoil events 2.7 Propagation of XUV photons in liquid argon To study the propagation of 128 nm XUV scintillation photons in liquid argon and to develop MC simulation tools for detector modelling. (i) Study of elastic and inelastic scattering of XUV photons in liquid argon and the dependence on chemical trace impurities (ii) Development of Monte Carlo tools for the simulation of XUV light propagation including wavelength shifting processes to model the detector response of large liquid argon detectors.

9 WP3 3.1 Ultra-low background Ge array for material selection Development of an ultra-low background Ge detector array for material assay at the 1 µbq/kg level in underground laboratories (i) Simulation and optimization of geometry of array with passive and/or active shielding system (ii) Design, development and calibration of system 3.2 Electrode segmentation in Ge detectors for event identification To study the discrimination of multi-site from single-site events (i.e. background events from double beta decay signal) using electrode segmentation in low-background Ge detectors. (i) Study of the operation of segmented bare Ge detectors with low-background contacts in liquid argon (ii) Localization and event reconstruction using mirror charges (iii) Comparison of background reduction factors of calibration data with MC simulations 3.3 Novel liquid argon active veto system for Ge detectors To study background suppression of bare Ge detectors submerged in liquid argon by using the scintillation light of liquid argon. Detectors both with segmented and unsegmented electrodes will be investigated (i) Operation of bare Ge detectors in a liquid argon with scintillation light read out at an underground laboratory (ii) Development of full MC description of a LArGe hybrid detector system (iii) Study of orthogonality of background reduction of segmentation and LAr active veto (iv) Study of LArGe system sensitivity for double beta decay and sample counting

10 WP3 3.4 Advanced pulse shape analysis in Ge and LArGe hybrid detectors Exploit time structure of charge signals from Ge detectors and LArGe hybrid detectors for event recognition and background reduction in double beta decay. Task: (i) Study of the time structures for various event classes in Ge (segmented, unsegmented, coaxial, truecoaxial) and LArGe hybrid detectors (ii) Modelling of characteristic time distribution of events in Ge detectors and LArGe hybrid detectors including the scintillation signal for various event classes and comparison with experimental data 3.5 Pixellization in CdZnTe detectors for particle identification Explore pixel pattern in CdZnTe semiconductor detectors to identify different particles as active background reduction in double beta decay. (i) Model various particles (alpha, betas and gamma) as well as double beta decay events in pixellated CdZnTe detectors to explore their characteristic features and optimise pixel size. (ii) Study such a detector underground to prove the expected performance after extensive calibration on the surface. 3.6 Advanced Pulse shape analysis in CPG CdZnTe Explore pulse shape of each of the two electrodes in coplanar grid CdZnTe detectors for vertex determination and extension of events. Task: (i) Develop readout of individual grids by modifying available preamplifier and study pulse rise-times (ii) Use high energy gamma sources for pair production as an approximation to double beta events and low energy sources for point-like charge depositions.

11 WP3 3.7 Performance of CdZnTe semiconductors in liquid scintillator Run CdZnTe semiconductors with a minimum of material within a Liquid Scintillator acting as an active veto for background reduction. Task: (i) Find reasonable scintillators, materials and run a naked CdZnTe detector in it

12 WP4 4.1 Liquid scintillators for low energy neutrino detection To improve the low background, the scintillation yield and attenuation length of liquid scintillators (i) Production of new liquid scintillators formulation highly doped with metallic compounds (ii) Improvement of the radiopurity level by removing noble gas radioactive isotopes (iii) Optimisation of the chemical compatibility with other plastics including optical fibers and plastic scintillators (iv) Simulation of the light propagation 4.2 Solid organic scintillators To improve the production and collection of the light, the transparency and the stability of the plastic scintillators (i) Development of scintillators polymer base (ii) Study of new backlight reflectors for the scintillator wrapping (iii) Simulation of the light propagation 4.3 High-efficiency low-radioactivity photomultipliers To develop high quantum efficiency and very low radioactivity PMT and to be able to survey the gain of the PMT with very high accuracy (i) Development of new low background glasses and ceramics (ii) Selection of radiopure PMT materials (iii) Optimisation of photocathodes and dynodes characteristics for photoelectrons production and collection (iv) Development of PMT gain survey with very high precision

13 Budget considerations Number of subtasks Subtotals Budget for each subtask WP WP WP WP Total 2760