DARK MATTER SEARCHES AT CANFRANC: ANAIS AND ROSEBUD: an update INTRODUCTION AND EXPERIMENTAL GOALS SUMMARY OF RECENT ACHIEVEMENTS AND EFFORTS

Transcription

1 DARK MATTER SEARCHES AT CANFRANC: ANAIS AND ROSEBUD: an update María Luisa Sarsa (Universidad de Zaragoza) On behalf of ANAIS & ROSEBUD Collaborations OUTLINE ANAIS INTRODUCTION AND EXPERIMENTAL GOALS NEXT STEPS ROSEBUD INTRODUCTION AND EXPERIMENTAL GOALS NEXT STEPS 1

2 Annual Modulation with NaI Scintillators, ANAIS INTRODUCTION AND EXPERIMENTAL GOALS ANAIS is a project aiming to set up, at the new facilities of the Canfranc Underground Laboratory, a large scale NaI(Tl) experiment to explore the DAMA/LIBRA annual modulation positive result. 40 cm neutron shielding Active vetos 20 cm lead PVC box 2 mm Cd 10 cm Roman lead Vibration isolator 2

3 INTRODUCTION AND EXPERIMENTAL GOALS ANAIS is a project aiming to set up, at the new facilities of the Canfranc Underground Laboratory, a large scale NaI(Tl) experiment to explore the DAMA/LIBRA annual modulation positive result. FURTHER MOTIVATION -Recent Results from CDMS, CoGeNT & CRESST INTRODUCTION AND EXPERIMENTAL GOALS Energy threshold at 2 kevee has been shown with prototypes. Better if lower Background at low energy should be kept as low as possible (below 2 evt/kg/kev/day). Very stable operation conditions should be guaranteed. 3

4 TESTS OF HIGH QUANTUM EFFICIENCY AND ULTRA-LOW BACKGROUND PHOTOMULTIPLIERS (PMTs) 40 K (mbq/pmt) 232 Th (mbq/pmt) 238 U (mbq/pmt) 60 Co (mbq/pmt) ET Ham HE (1066DA) ( ) 10 3 ( ) 10 3 ( ) Ham LB (ZE5331) Ham LB (ZE5336) Ham ULB (ZK5171) Radiopurity levels of the different PMTs tested at the low background HP Ge test bench in Canfranc Ham ULB are under test in Zaragoza and Canfranc 238 U Ra PROGRESS IN THE NAI POWDER PURIFICATION PROCEDURE 4

5 PROGRESS IN THE NAI POWDER PURIFICATION PROCEDURE Manipulation of all the NaI samples in glove box (dry atmosphere) Weighting and tightly closing in special containers for posterior analysis Testing of the samples by AAS and HPGe measurement (cross-checking the Electrochemical Systems Inc. analysis) Purified samples at 0,1 ppm K level are going to be tested along next weeks in Zaragoza STATUS OF THE RADIOPURE NaI(Tl) CRYSTALS GROWING AND ENCAPSULATION PROCEDURE SEVERAL POSSIBILITIES to grow the crystals for ANAIS with the Potassium purified NaI powder are being explored. 5

6 ANAIS-0 module: 9.6 kg NaI(Tl) with light guides and Ham LB PMTs measuring at LSC in the best background conditions at the old LSC. PMT LG NaI(Tl) LG PMT NEXT STEPS ANAIS-0 MODULE ANAIS-0 module: 9.6 kg NaI(Tl) with and without light guides and Ham ULB PMTs are going to be mounted soon and will measure at LSC in the best background conditions. 6

7 Set up of the ANAIS-0 module measuring at Canfranc with three active plastic scintillator vetoes (0.5 m 2 each). Goal: to monitor the muon rate in the laboratory, reject the corresponding contribution to the background and evaluate any possible seasonal variation. Set up of the ANAIS-0 module measuring at Canfranc with three active plastic scintillator vetoes (0.5 m 2 each). A rate of about 30 muons/day is deduced from the data. Up to 40 MeV Canfranc, October 7 th

8 BACKGROUND SIMULATION Schematic view of the geometry (not scaled) prepared to simulate the ANAIS-0 module in the shielding at LSC using GEANT Simulation of the 40 K bulk contamination measured by the coincidence method, in red, and the background of ANAIS-0 module in black. 8

9 Simulation of the 40 K bulk contamination measured by the coincidence method, in red, and the background of ANAIS-0 module in black. In blue is shown the contribution of 40 K bulk contamination in the crystal at the 20ppb level which is the goal for ANAIS Clearly ANAIS-0 module background is presently dominated by the 40 K medium & high energy counts/kev/kg/day Background measured Simulation of internal 40 K (12.7 mbq/kg) Simulation of internal 40 K (20 ppb) Energy(keV) Simulation of the 40 K bulk contamination measured by the coincidence method, in red, and the background of ANAIS-0 module in black. In blue is shown the contribution of 40 K bulk contamination in the crystal at the 20ppb level which is the goal for ANAIS Background measured Simulation of internal 40 K (12.7 mbq/kg) Simulation of internal 40 K (20 ppb) Clearly ANAIS-0 module background is presently dominated by the 40 K low energy counts/kev/kg/day Energy(keV) 9

10 NOISE REJECTION: is one of the main issues Study of the asymmetry between the two PMT signals. Strongly asymmetric events should be rejected. Timing parameters are required to improve the noise rejection 57 Co calibration run Background run We are starting a systematic mutiparametric study of different timing parameters: carefully estimate of cut efficiencies 10

11 LIGHT COLLECTION EFFICIENCY: Low energy pulse show a discrete structure, allowing for counting photoelectrons 3.2 kev (Ar-Xrays) This number of photoelectrons shows a correct behavior with respect to other energy estimators as pulse area or adc value 57 Co calibration 40 K events 11

12 Assuming that the number of peaks in the pulse is a good estimator of the photoelectron number in the pulse: -7.5 photoelectrons/kevee for ANAIS-0 module without light guides for an energy deposited of 3.2 kev. Events ,2keV n = 24-31% reduction of the number of photoelectrons/kevee seen at energy below 6 kev when using light guides in the ANAIS-0 module. 150 no LG n = 34 Events Events n LG n = n n VME ELECTRONICS AND ACQUISITION SYSTEM Benchmark to test new electronic modules and software at the University of Zaragoza labs. 12

13 INSTALLATION OF ANAIS AT THE NEW LSC FACILITIES Last summer consolidation works of the new LSC facilities conclude. Small repairs and conditioning works are still ongoing, but experiments started to move last February INSTALLATION OF ANAIS AT THE NEW LSC Hall B Control room Experimental room (Rn-free and T/H stabilised). 13

14 INSTALLATION OF ANAIS AT THE NEW LSC FACILITIES Presently taking data with the same experimental set-up NEXT STEPS 1. Building and conditioning of the ANAIS housing at LSC Hall B. a) Building ANAIS metallic structure b) Electric installation of ANAIS hut / IMPROVING NOISE 2. Move of the ANAIS-0 shielding and electronics to the new LSC facilities: a) Mounting the present shielding configuration and completing it with neutron shielding. b) Monitoring stability of environmental parameters at the new site, in particular Rn content. 3. Test of new ultra-low-background HAMAMATSU photomultipliers in Zaragoza and in ANAIS-0 module with and without light guides. 4. Development and tests of the acquisition hardware and software. a) Tests and fine tuning. b) Installation of the new acquisition system (VME electronics) with ANAIS-0 module at LSC Hall B. 14

15 Rare Objects SEarch with Bolometers UnDerground, ROSEBUD Integrated in INTRODUCTION AND EXPERIMENTAL GOALS Testing of particle detector prototypes in low background environment. R&D line: characterization of scintillating materials at low temperature. CaWO 4,BGO,LiF,Al 2 O 3,CaF 2,... Search for Dark Matter: Nuclear recoils discrimination against background through light + heat technique. Multi-target approach: different targets in the same experimental set-up distinctive WIMP signal Neutron monitoring Sapphire bolometers: 25, 50, 200 and 1000 g Ge optical bolometers Ø 40 mm Ø 25 mm 15

16 BGO (Bi 4 Ge 3 O 12 ) Mass 46 g 209 Bi: A, sensitive to SI and SD interactions 207 Bi contamination (3 Bq/kg) (clean BGOs available) / spectrometer Z LiF Mass 33 g Monitoring of neutrons through 6 Li(n, ) 3 H T = 20 mk Sapphire (Al 2 O 3 ) Mass 50 g 27 Al: A sensitive to SI and SD interactions High β/γ background rejection Z & low threshold 16

17 Relative Efficiency Factor for LIGHT signal Sapphire 241 Am + 57 Co 59.5 kev 122 kev kev Light signal amplitude (mv)) events 210 Po 241 Am + 57 Co Heat signal amplitude (mv) Light output (γ) = 13.5 kev / MeV REF (γ / NR) = 17.5 ± 1.5 (@ 200 kev ) Light output (α) = 1.3 kev / MeV REF ( / α) = 10.3 ± 1.0 (@ 5.3 MeV ) Particle type Sapphire BGO / n 1 1 Relative Efficiency Factor in the Heat Signal Sapphire 206 Pb recoils at ± 0.10 kev from 210 Po source REF( nuclear recoils : / ) Al 2 O Pb recoil stat syst Spectrum of the events in the NR band BGO 237 Np recoiling nuclei at ± 0.12 kev from 241 Am source REF( nuclear recoils : / ) stat 0.004syst 34 17

18 WIMP searches - Particle discrimination power Sapphire Kyropoulos grown BGO Czochralski grown BGO Discrimination of NR down to C.L (1 tailed) 10 kev E (kev) 90 % % % % % 21.3 C.L (1 tailed) E (kev) Discrimination of NR down to 90% kev 99.9% Neutron Spectroscopy: LiF scintillating bolometer 33 g LiF measuring at LSC capture elastic scattering Resonance capture total 6 Li(n, ) resonances 18

19 Neutron Spectroscopy: LiF +Al 2 O 3 Estimate of the neutron flux inside the lead shielding when irradiated with neutrons from 252 Cf outside the shielding 33 g LiF and 50 g Al 2 O 3 6 Li(n, ) resonances NR Hypothesis: fast neutron flux inside the lead shielding isotropic ( 0 / ( +1))(E/T) exp(-e/t)de/t We estimated the region of three parameters ( 0,,T) compatible with experimental data Neutron Spectroscopy Testing the hypothesis about the fast neutron flux inside the shielding isotropic ( 0 / ( +1))(E/T) exp(-e/t)de/t MC simulation (MCNP-poliMI) of the neutron flux Al 2 O 3 heat NR spectra measured MCNP-PoliMi = 0.9 T = 1.48 MeV Spectra shape in good agreement Full-parameter space comparison is in progress 19

20 ROSEBUD in the new LSC facilities Hall B NEXT STEPS Installation, conditioning and acoustical isolation of the Faraday cage Installation and conditioning of the vacuum and pumping systems and the workshop Completion of the experimental set-up shielding (lead, polyethylene, m-metal and PVC box), radon removal system, electronics inside the Faraday cage, electronics and computers in the control room, optical fiber connection, dilution unit and test of the cryogenic facility. Radiopurity assessing for ROSEBUD and EURECA Development and test of new scintillating bolometers CaF 2, 6 LiF, 6 Li 6 Gd ( 10 BO 3 ) 3 20

21 UNIZAR and IAS integrated in EURECA Target mass 1 ton. Semiconductor bolometers built with the technology developed by EDELWEISS. Scintillating bolometers built with the technology developed by CRESST and ROSEBUD. It will be carried out at the Modane Underground Laboratory (LSM) in France. It plans the first stage of the data adquisition since