Zhimin Wang Liu Ruoqing, Tang ChenYang, Charling Tao, Changgen Yang, Changjiang Dai, Tsinghua & IHEP , Shanghai

A Simple New Gas Detector Developed by Ioanis Giomataris, Saclay, France Natural focusing: – large volumes can be instrumented with a small readout surface and few (or even one) readout lines 4  coverage: better signal Still some spatial information achievable: – Signal time dispersion Other practical advantages: – Symmetry: lower noise and threshold with large volume – Low capacity – No field cage Simplicity: few materials. They can be optimized for low radioactivity. Low cost 2

A prototype D=1.3 m D=1.3 m V=1 m 3 V=1 m 3 Spherical vessel made of Cu (6 mm thick) Spherical vessel made of Cu (6 mm thick) P up to 5 bar possible (up to 1.5 tested up to now) P up to 5 bar possible (up to 1.5 tested up to now) Vacuum tight: ~10 -6 mbar (outgassing: ~10 -9 mbar/s) Vacuum tight: ~10 -6 mbar (outgassing: ~10 -9 mbar/s)

Typical spectra 5

Run with Ar/CH 4 + 3g mb SPC 130cm LSM Rise time (  s) Amplitude  210 Po 5.3 MeV n capt on 3 He 764 keV 222 Rn 218 Po 214 Po If localised energy deposition, rise time depends of radius (diffusion) If track, rise time depends on orientation of track (different drift times) NB: no start => risetime records place and/or history of energy deposition derivative alpha de/dx 6

Rise time (  s) Amplitude  210 Po 5.3 MeV n capt on 3 He 764 keV  210 Po 5.3 MeV from 210 Cu surface R = 15 cm n capt on 3 He => p + T 222 Rn 218 Po 214 Po Unwanted Radon daughter deposit on surface : fast neutron expected here Taux 400 capt/j Run with Ar/CH 4 + 3g mb SPC 130cm LSM 7

Basic performance Mixtures tested: Mixtures tested: –Ar+10% CO 2 –Ar+2% Isobutane Pressures from 0.25 up to 1.5 bar tested up to now Pressures from 0.25 up to 1.5 bar tested up to now High gains (>10 4 ) achieved with simple spherical electrode High gains (>10 4 ) achieved with simple spherical electrode No need to go to very high V (better for minimizing absorption) No need to go to very high V (better for minimizing absorption)

Applications – Dark Matter – Coherent neutrino scattering – Double beta decay – Axion – SN neutrino monitoring – Neutron spectroscopy – Neutron counter for industrial application – Low level neutron counting – Radon low level counting – Atmospheric neutron and Muon monitoring – Gamma ray spectroscopy in harsh environment – …

Some physics applications 10 arXiv: arXiv: Gerbier et al. DM WIMP Reactor neutrino

LSM neutron flux From Savvidis ilias doi: / /203/1/012030

An international working group “NEWS” from G. Gerbier

Ex. Dark matter 13 From G. Gerbier Journal of Modern Physics, 2012, 3,

Activities at IHEP &Tsinghua Detector performance studies  Plan to measure neutrons in Jinping with 1g He3 14

STPC goals NEWS network: 4m detector. Where?  Jinping?  SNO? Gerbier in Canada with 10 M$ grant Training for low radioactivity gaseous detector for large volume TPC  Solar neutrino (HELLAZ like)  Directional Dark Matter (also an old idea!) 15

Hellaz simulation (1997?) The HELLAZ solar pp neutrino project Tom Ypsilantis, Jacques Séguinot et al…, with a Micromegas

Dark matter detection with hydrogen proportional counters Comments : for some DM types not Mass but Number of nuclei is important G. Gerbier, J. Rich, M. Spiro, C. Tao Nuclear Physics B - Proceedings Supplements Volume 13, February 1990, Pages

Gaseous detectors are beautiful ! Cylindrical Drift chamber in PhD thesis back for Fermilab DIS muon CHIO in Smithsonian (Washington DC) : UA1 Central Detector 1 st W event in UA1 CD Personal interest for > 20 years Technology OK and keeps improving For DM: needs detection from >2 nuclei AND directionality!!! Is our science case compelling enough? CDM vs WDM debate

Directional DM Detectors CYGNUS 2013: 4th Workshop on Directional Detection of Dark Matter Tatsuhiro Naka and Kentaro Miuchi J. Phys.: Conf. Ser CYGNUS 2013: 4th Workshop on Directional Detection of Dark Matter Workshop Series Boulby 2007, MIT 2009, Aussois 2011 Many projects: DMTPC, NEWAGE, DRIFT, MIMAC emulsions

MIMAC MIMAC bi-chamber prototype The MIMAC bi-chamber prototype is composed of two chambers sharing the same cathode being the module of the matrix active volume (V 5:8 l) 70%CF4 + 28%CHF3 + 2%C4H10 at a pressure of 50mbar. The primary electron- ion pairs produced by a nuclear recoil in one chamber of the matrix are detected by driving the electrons to the grid of a bulk micromegas and producing the avalanche in a very thin gap (256 mu). Track reconstruction in MIMAC. The anode is read every 20 ns. The 3D track is reconstructed, from the consecutive number of images

The bi-chamber prototype at the Laboratoire Souterrain de Modane in June The bi-chamber module is identified in red and the bluer volume in blue. The position of peaks of Cd (3.2 keV), Cr (5.4 keV), Fe (6.4 keV), Cu (8.1 keV) and Pb (10.5 and 12.6 keV) tted by a linear calibration in ADC channels as a function of time, highlighting the gain stability during the data taking period. 4. Preliminary analysis of the first months of data taking The first available data set of the bi-chamber prototype was started on July 5th 2012 Bi-chamber prototype at the Laboratoire Souterrain de Modane

Background in LSM

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Electron vs nuclei recoil 24 The length [cm] vs. Energy [ADC channel] of electrons and proton recoils produced by neutrons of 144 keV in pure isobutane (C 4 H 10 ) at 50 mbar. The maximum of the proton energy corresponds to 144 keV. (Right): The NIS (normalized integrated straggling) for recoil events (in black) and for electrons (in blue).

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1.5 keV He4 recoils 26

3D-Track reconstruction 34 keV

Some tracks in MIMAC 28 8 keV hydrogen nucleus in 350 mbar 4He+5%C4H10, a fluorine nucleus leaving 50 keV in ionization in 55 mbar (70% CF4 + 30% CHF3) and a 5.5 MeV alpha particle in 350 mbar 4He+5%C4H10

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MIMAC 1m 3 in preparation

WIMP distribution

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