ROSEBUD Collaboration
UNIZAR - IAS
Cryogenic particle
detection at the
Canfranc Underground
Laboratory
First International Workshop for the Design of the
ANDES Underground Laboratory
Centro Atómico Constituyentes
Buenos Aires, Argentina
11-14 April, 2011
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
Canfranc
Underground
Laboratory (LSC)
Universidad de Zaragoza
UNIZAR (Spain)
Institut d’Astrophysique Spatiale
IAS (Orsay, France)
ROSEBUD Collaboration
(Rare Objects SEarch with Bolometers UndergrounD)
N. Coron, C. Cuesta, E. García, C. Ginestra, J. Gironnet, P. de Marcillac, M. Martínez, A. Ortiz
de Solórzano, Y. Ortigoza, C. Pobes, J. Puimedón, T. Redon, T. Rolón,
M.L. Sarsa, L. Torres and J.A. Villar.
Nuclear and Astroparticle Physics Group (GIFNA)
University of Zaragoza (Spain)
Spectrométrie Thermique pour l’Astrophysique et la Physique (STAP)
Institut d’Astrophysique Spatiale – IAS (Orsay, France)
Goals of ROSEBUD
ROSEBUD scientific website: http://www.unizar.es/lfnae/rosebud/
 Testing of particle detector prototypes in a low background environment.
 R&D line: characterization of scintillating materials at low temperature. All
materials tested have shown scintillation at low temperature: CaWO4, BGO, LiF,
Al2O3 and SrF2.
 Multi-target approach: use of scintillating bolometers of different materials in
the same experimental set-up.
 Nuclear recoils discrimination against b/g background through light + heat
technique for WIMP search. *
Sapphire bolometers:
25, 50, 200 and 1000 g
Ge optical bolometer
Ø 25 mm
Ø 40 mm
* light + heat technique has shown to be also a powerful tool for nuclear physics
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
7
The Scintillating Bolometer
Thermal model of a simple bolometer
n
Properties of bolometers
E
T 
C
 T 
C   
 D 
3
Dielectric and
diamagnetic crystal
1. Wide choice of different
absorber materials.
2. High energy resolution
FWHM.
3. Low energy threshold for
particle detection.
4. Particle identification
capability in hybrid
measurements of heat-light
or heat-ionization energies.
The Scintillating Bolometer
8
BGO 92 g
Optical bolometer
(Ge disk)
Cu frame
20 mK
Thermal link
Scintillating
crystal
(absorber)
Thermal link
Ge-NTD thermistor
Ge-NTD
thermistor
Internal reflecting
cavity
(Cu coated with Ag)
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
Detector response
Sapphire Bolometer (50 g)
Calibration 252Cf &
241Am internal source
c / channel
59.5 keV (241Am)
Light pulse amplitude (mV)
Particle Discrimination Capability
alphas
Nuclear recoils
region
Heat pulse amplitude (mV)
59.5 keV (241Am)
b/g spectrum
Nuclear recoils spectrum
10
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
Experimental set-up in the old LSC facilites
12
The underground laboratory
Canfranc Underground Laboratory (LSC)
Tobazo Peak
Spanish Pyreness
10 m2
ROSEBUD
10 m2
1995 - today
118 m2
Muon flux decreased by a factor
~105
2450 m.w.e.
2.5·10-3 m-2s-1
Experimental set-up in the old LSC facilites
The scintillating bolometers
BGO (Bi4Ge3O12)
Mass 46 g
209Bi: ↑A,  sensitive to  and 
SI
SD interactions
207Bi contamination (clean BGOs available)
b/g spectrometer ↑Z
LiF
Mass 33 g
Monitoring of neutrons through 6Li(n,t)
Sapphire (Al2O3)
Mass 50 g
27Al: ↓A  sensitive to  and 
SI
SD interactions
High β/γ background rejection ↓Z & low energy threshold
T = 20 mK
13
Experimental set-up in the old LSC facilites
The dilution refrigerator and shielding
14
Experimental set-up in the old LSC facilites
The Faraday Cage and the cryogenic pumping system
Faraday cage
(2  2  3 m3)
Pumping and control systems
15
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
Sapphire Light REF
(b/g :  : NR)
Light signal amplitude (mV)
136.5 keV
210Po
122 keV
+
57Co
59.5 keV
241Am
 events
Heat signal amplitude (mV)
Light output (γ) = 13.5 keV / MeV
Light output (α) = 1.3 keV / MeV
REF (γ / NR) = 17.5 ± 1.5 (@ 200 keV )
REF (g / α) = 10.3 ± 1.0 (@ 5.3 MeV )
17
BGO Light REF
(b/g :  : NR)
252Cf
REF(b/g:)
18
Sapphire Thermal REF (206Pb nuclear recoils:b/g)
Relevant for the calibration of
the dark matter signal
Thermal REF of NR
206Pb
recoils at 103.08 ± 0.10 keV from
210Po
 source
REF (nuclear recoils : b / g )  1.044  0.008stat
206Pb
Al2O3
recoil
0.056
0.008syst
Spectrum of the events in
the NR band
19
BGO Thermal REF (237Np nuclear recoils:b/g)
BGO irradiation with 241Am  source
237Np
recoiling nuclei at 92.40 ± 0.12 keV from
241Am
REF (nuclear recoils : b / g )  0.937  0.015stat
 source
0.302
0.004syst
136.5 keV (57Co)
57Co
241Am
Al
2O3 +
122.1 keV (57Co)
59.5 keV (241Am)
Light pulse amplitude (mV)
Energy partition in Sapphire and BGO
scintillating bolometers
Heat pulse amplitude (mV)
 + h + 0 = 1
Al2O3
 = 0.112  0.013 h = 0.778  0.103 0 = 0.110  0.104
BGO
 = 0.058  0.006 h = 0.464  0.093 0 = 0.478  0.093
21
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
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 %
8.7
95 %
10.0
99 %
13.0
99.9 %
17.1
99.99 %
21.3
C.L (1 tailed)
E (keV)
99.9%
33.3
Discrimination of NR down to
90%
23.5
≈25 keV
23
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
25
The BGO scintillating bolometer as g-ray spectrometer
The BGO allows to note the
background level increase and
also to identify its origin
222Rn
inside the Pb
shielding
The BGO scintillating bolometer as g-ray spectrometer
Heat channel energy resolution
The LiF scintillating bolometer as neutron spectrometer
6Li(n,t)
neutron
Thermal
detection efficiencies
n 25meV of
LiF bolometers
capture
elastic
scattering
1keV
Resonance
capture
total
27
Scintillating bolometers as neutron spectrometers
Fast neutron flux inside the shielding
Irradiation of a 33 g LiF and a 50 g Al2O3 scintillating bolometers with 252Cf
LiF
&
Al2O3
6Li(n,)
resonance
 events
6Li(n,)
NR
NR
Qth = 4.78
MeV
Previous work presented at TAUP09: J Phys: Conf Series 203 (2010)012139
Hypothesis: fast neutron flux inside the lead shielding

F 0  E  E T  dE
  e
(  1)  T 
T
We estimated the region of three parameters (F0,,T) compatible with experimental data
Scintillating bolometers as neutron spectrometers
Fast neutron flux inside the shielding
Present work: Testing hypothesis about the fast neutron flux inside the shielding

F 0  E  E T  dE
  e
(  1)  T 
T
Al2O3 heat NR spectra
measured
MCNP-PoliMi
 = −0.9
T = 1.48 MeV
Spectra shape in good agreement
Comparison of full experimental data with MC calculation is in progress
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
ROSEBUD in the new LSC facilities
http://www.lsc-canfranc.es/
31
ROSEBUD in the new new LSC facilities
Hall B
3  3  4.5 m³
ROSEBUD in the new new LSC facilities
Hall B
Outline
The ROSEBUD Collaboration
The scintillating bolometer
Particle discrimination capability
Experimental set-up in the old LSC facilities
Main results:
Light & heat response to different particles
WIMP search prototypes
Gamma and neutron spectroscopy
ROSEBUD in the new LSC facilities
EURECA
UNIZAR and IAS integrated in EURECA
EURECA project
Institut d’Astrophysique
Spatiale IAS
http://www.eureca.ox.ac.uk/
 Target mass 1 ton.
 Semiconductor bolometers
built with the
technology of EDELWEISS (LSM).
 Scintillating bolometers
built with the
technology of
CRESST (LNGS) and
ROSEBUD (LSC).
 To be carried out at the Modane Underground
Laboratory (LSM) in France.
See also Gilles Gerbier’s talk!
Universidad
de Zaragoza
35
Conclusions
ROSEBUD is a collaborative effort dedicated to the
development of scintillating bolometers for nuclear and
particle physics experiments, focusing on rare event
search experiments.
Scintillating bolometers characterized by ROSEBUD
(Al2O3, BGO and LiF) have shown excellent
capabilities for particle discrimination and background
rejection.
ROSEBUD is currently moving to the Hall B in the
new LSC facilities planning to restart measurements in
2012. New materials are being characterized in IAS.
UNIZAR and IAS also participate in EURECA.
UNIZAR and IAS participation in EURECA
Radiopurity measurements of materials (crystals,
cryogenic resins, shieldings, detector components,
dilution unit pieces) at LSC using ultra-low
background germanium detectors.
Development of new scintillating bolometers.
Test of scintillating bolometers at the Canfranc
Underground Laboratory (LSC) in order to
characterize and optimize scintillators in a low
background environment , evaluating these for use
as potential dark matter targets in EURECA.