CLYC4DM - Agenda

CLYC4DM CLYC scintillatingg
CLYC4DM:
crystals for Dark Matter searches
PI: C.M. Cattadori INFN
INFN-MiB
MiB
CSNV 29/09/2015
Goal of the Proposal
• The proposal
– Explores
p
the p
potentialityy of the unique
q features of Lielpasolite Cs2LiYCl6 (CLYC) scintillating crystals for
WIMP Dark Matter (DM) direct searches
– Aim
Ai to
t CLYC tailoring
t il i for
f direct
di t Dark
D k Matter
M tt searches.
h
• The project will deliver a miniarray of
6 (8) x (3“x
(3“ 3") CLYC scintillating
i till ti crystals
t l
(New! Recentest price for 3” CLYC is 38 kEu/det  array of 8
detectors possible with same money)
– 3(4)x crystals Li-6 enriched
– 3(4)x crystals Li
Li-7
7 enriched
– custom pulled from powders purified from
radiocontaminants
– mounted in low activity assembly, for total mass of
29/09/2015about 7 (9)~kg .
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Novelty and innovation
• The claimed indications/evidences of WIMP
WIMP-DM,
DM come from
scintillating crystals (NaI(Tl)), Ge or bolometric detectors; all of
them have superior spectrometric performances but poor or non
specific n/γ discrimination.
• CLYC scintillating detectors have better/comparable spectroscopic
performances of NaI(Tl) or CsI(Tl) but unique capability of n and γ
dual detection by pulse shape discrimination (PSD)
• So far
– CLYC have not yet been considered for direct DM searches
– CLYC n/γ PSD, identification of NR & measurement of NR
quenching factor, have *never* been investigated at low (keV)
energies,
– CLYCs intrinsic radiopurity never characterized
– CLYCs radiopurification never explored
This projects aims to address these points and deliver a CLYC
prototype array.
array
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WIMP DM interaction with CLYC
• Cs2LiYCl6 : 2x 133 + 7 + 89 + 35 x6 = 572 g/molCLYC
– Cl: 37%
– Li: 1.2%
– Cs: 46.5%
46 5%
– Y: 15.6%
• Both the spin-independent and spin-dependent
channels accessible
• Nuclear Recoils events: For a WIMP of 100 GeV/c2
Continuum energy spectrum of NR up to ~ 25 keV
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Direct detection of WIMP
• Elastic Scattering of WIMP over target nuclei
• The
Th nucleus
l
recoils
il with
ith an E
Energy
ER =
2
q
2mN
=
μ2v2
mN
q = momentum transfer = 2μ 2 v 2( 1- cosϑ)
μ = reduced mass(mN , m χ : nucleus,WIMPmasses)
μ=
mN ⋅ mχ
mN + mχ
v = mean WIMPvelocity
l it
relativeto the target
v~ 220kms −1 = 0.75 x 10-3 c
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From scattering to interaction rates
(1 − cosϑ )
2
ϑ = scattering angle in the center of mass system
E R = Ei r
4m χ ⋅ m N
4μ 2
r=
=
m χ ⋅ m N (m χ + m N ) 2
m=
mχ ⋅ mN
mχ + mN
kinematical
factor
reduced mass
• Correct v for:
1 Galactic escape velocity
1.
2. Velocity of the Earth vE
• Th
Then include
i l d nuclear
l
f
form
f t and
factor
d
spin-(in)dependent cross section
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Spin-Indepedent
p
p
interaction and differential rates
2
s ∝ M ∝ A2
Mass number
Expected rates for different elements
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Spin Indepedent interaction
Spin-Indepedent
• The scattering amplitude is dominated by the
p
nucleon
unpaired
• In CLYC
– 37% is
i Cl:
Cl
• A .I. 35Cl ~ 75%
• A.I. 37Cl ~ 25%
Spin-independent
S
i i d
d t
interaction accessible
with CLYC
– 47% is Cs
• A.I. 133Cs= 100%
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Very preliminar!
Sensitivity of 3.5 kg x 1 year CLYC, thrs 10 keVr
No interaction
observed on Cl
Very Preliminar:
Excellent Sensitivity!
Computed by Aldo Ianni
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Published Survey of WIMP
searches experimental sensitivity
sensitivity..
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State of the art on CLYCs
• Superior spectroscopic response, better than NaI(Tl)
•They can be grown
• enriched in Li-6 (nth detection σabs=940 barn enhanced)
through the reaction 6Li(n,α)3H energy of 3500 keV γ
equivalent
• enriched in Li-7
Li 7 (for fast n detection)
• Fast n are detected via the 35Cl(n,p)35S and the 35Cl(n,α)32P
• n spectrometer: p and α energy are linearly related to the
energy of the incoming n
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γ/n identification: PSD
γs and
d ns produce
d
very different
diff
t light
li ht pulses
l
!
• Gamma ray signal contains CVL while
• neutron/recoils do not contain CVL
neutrons
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Fast Neutron Identification: TOF and spectrometry
Fast Neutron Identification: TOF and spectrometry
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Test of a C7LYC at LNL-CN (results from a test performed
in March 2015 in the framework of the CLYC project CSNV)
Ep= 5 MeV; CLYC at 0 deg
PSD =n & TOF
35Cl(n,p)35S
35Cl(n,α)32P
All
events
PSD =n & TOF
En= 3.3 MeV
En= 3.8 MeV
Ep= 5.5 MeV; CLYC at 0 deg
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Experimental program of CLYC4DM
 n/γ
/γ PSD ((Available info)) to be verified at low
energies
• Never
N
measured
d so far
f
– Identification of Nuclear Recoils events (NR) at
low energies ( ~ 10 keVnr)
– Measurement of NR q
quenchingg factor at low
energies 2-50 keVnr,
– CLYCs intrinsic radiopurity
– CLYCs radiopurification starting from mineral
powders used in the crystal growing process
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Identification and measurement of NR
events (target 1”C6LYC)
• NR quenching
hi ffactor iin scintillators:
i ill
Light from Nuclear Re coil[ E ]
Qf [ E ] =
Light from Electron Re coil[ E ]
– due to the small fraction of energy
gy transfer to
electrons, NR typically produce less scintillation
light compared with electron recoils with the
same energy deposition. This factor is crucial in
interpretation of DM experimental data to
t
translate
l t th
the observed
b
d electron
l t
equivalent
i l t energy
into nuclear recoil energy for dark matter analysis.
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Reference: review of QF measured for NaI(Tl)
From PRC 92,1(2015)
Calaprice 2015
CLYC Qf could be totally different
because of the 3 different scintillation
light components.
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Measurement of CLYC Instrinsic Radiopurity
So far the only unpublished measurement is the following: performed
by the CLYC group of INFN-MI
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Measurement of CLYC Instrinsic Radiopurity
• Three complementary techniques
– Self measurement of a CLYC detector coupled to a low
activity PMT in a heavely shielded environment : this
requires the crystal are mounted in clean holders (Cu
instead of standard Al)
– γ spectrometry of CLYC nake crystal with HPGe
spectrometer (@LNGS or LSC(lab.
LSC(lab Souteraine de
Canfranc)
– ICPMS measurement (for Th, U, Pb)
• CLYC self measurement thanks to superior PSD
and time response allows the identification of
characteristic n,α,γ chains from U and Th
progenitors
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Radiopurification of mineral powders for the crystal
growth
SABRE vs DAMA
(Claimed) SABRE
State of the art. from
J.Xu talk 2014 and Al.
Ianni talk 2015
Planned activity
y
for CLYC
• Radiopurity measurements: γ-spectrometry (LNGS&LSC) and
ICPMS at LNGS
• Radiopurification of mineral powders will be tested in
collaboration with LNGS Chemical Service & RMD (Radiation
(
Mononitor and Detector Co.)
• Radiopurification Methods defined in LENS and MetaLS project
will be applied an tested
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Acquisition of 6 (8) 3” CLYC detectors and PMTs
and installation of a CLYC prototype array
Only if radiopurification is satisfactory (funds
protected) 6 to 8 C6LYC and C7LYC detectors
purchased and assembled with PMTs
PMTs: Same as SABRE
Low radioactivity PMT
• Hamamatsu R11065-series PMT
~ 30-35%
30 35% Q.E.
QE
~ 1 mBq U and Th (lower chain activity)
~ 1 mBq Co,
Co ~ 10mBq K
• High light collection efficiency w.o. light
guide
• Use LNGS preamplifier to improve S/N
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C C
CLYC
23
Mounting the CLYC crystals & PMT
in radiopure assembly
Same as SABRE
Mounting crystal and PMTs
assembly in Cu holders
electroformed (possibly
(p
y
underground) at LSC.
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Participants: Institutions
INFN-MiB
C. Cattadori
0.7 FTE: Expertize in low
activity astroparticle project
F. Salamida
0.7 Expertize in low activity
astroparticle project
INFN-LNGS
Servizio Tecniche Witten statements from
Speciali
Director and Responsibles of
ICPMS and γ−spectrometry
Lab Souterain de Canfranc
I.Balanc
A. Ianni
0.4 + 2 x (2
(2” x2
x2”)) CLYCS
available starting from 2016
Electroforming Cu facility
available
Institute fur Kristallzuchtung
(IKZ) -Berlin
tbd
Shanghai
Sh
h i IInstitute
tit t off
Ceramics, Chinese Academy of
Sciences (SICCAS) - China
tbd
University of Zurich
(group of L. Baudis)
tbd
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Participants: Companies
• RMD A Dynasil Company (CLYC producers,
production of low activityy NaI(Tl)
( )
involved in p
for SABRE project
• Saint Gobain (NaI and CLYC producer (latter
not yet on the market), has the know how of
l activity DAMA/LIBRA
low
/
NaI))
• CAEN: INFN partner, Producer of Digitizers and
HV systems etc.
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Project Organization
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€ 585.040
585 040 (VAT Included)
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