CANADA’S NATIONAL LABORATORY FOR PARTICLE AND NUCLEAR PHYSICS
Owned and operated as a joint venture by a consortium of Canadian universities via a
contribution through the National Research Council Canada
In-trap spectroscopy for 2nbb decay
experiments
T. Brunner, S. Ettenauer, C. Andreoiu, D. Frekers, A. Lapierre, R. Krücken, I. Tanihata and J. Dilling
for the TITAN collaboration
Outline:
• Motivation: Neutrinoless double beta decay
• EC-BR setup at TITAN
• Status and first experimental results
LABORATOIRE NATIONAL CANADIEN POUR LA RECHERCHE EN PHYSIQUE NUCLÉAIRE ET EN PHYSIQUE DES PARTICULES
Propriété d’un consortium d’universités canadiennes, géré en co-entreprise à partir d’une
contribution administrée par le Conseil national de recherches Canada
Neutrino experiments
Neutrino oscillation
Tritium decay
KATRIN, picture taken from http://students.washington.edu
SNO, picture taken from http://www.oit.on.ca
Relative mass scale
• Indicate a neutrino mass [1]
• Determination of mixing angle qij
• Indicate mass hierarchy
• Determination of dm²
[1] T. Kajita and Y. Totsuka, Rev. Mod. Phys. 73(2001)85
Absolute mass scale
• Endpoint energy of 3H decay
• Effective mass for degenerated neutrinos:
2
mn   j U e j m2j
2
Double b decay and mn
Some bb decay experiments
Hot topic
GERDA, CUORE, CUORICINO,
COBRA, MOON, EXO
Standard model
New physics
2n double b - decay
0n double b - decay
n  n  2 p  2 b   2n e
n  n  2 p  2 b   0n e
b
b
ne
ne
ne
b
2n 10 17 years2n(76Ge)
Half life>
b b 
Dirac - Neutrino

M
b
Lepton
number violation
If observed:


2
25 years
76
Half life> 1.9x10
0n
0n 1 2[1] ( Ge)!!!
mn e  M
T1 2
eV
Majorana - Neutrino
[1] C.E. Aalseth et al., Phys. Rev. D65(2002)092007
0n and 2n described in same theoretical framework,
but different matrix elements 3
[2] S.R. Elliott and P. Vogel, Annu. Rev. Nucl. Part. Sci. 52(2002)115
0nbb matrix element
Theoretical models to calculate M0n
•
•
•
Interacting Boson Model [3]
Nuclear Shell Model [4]
pn Quasiparticle Random Phase Approximation [5]
But…
•
•
M0n needed with an uncertainty of less than 20% [6]
Calculated M0n vary by a factor 2-5
M0n 76Ge
Measure M2nbb to benchmark theory
[3] J. Barea and F. Iachello, Phys. Rev. C 79(2009)044301
[4] E. Caurrier et al., Nucl. Phys. A 654(1999)973c
[5] V. Rodin et al., Phys. Rev. C 68(2003)044302
[6] V.M. Gehman and S.R. Elliott, J. Phys. G 34(2007)667
Thomas Brunner
TCP2010 conference
[6] and ref. therein
4
Theoretical benchmark
M 2n  
m
0 gf .s. Oˆ 1m 1m Oˆ 0ig .s.
Em  Ei  Qbb 2
Single-State Dominance hypothesis
Transition via lowest 1+ state in intermediate
nucleus accounts for entire M2n
D. Fang et al., Rhys. Rev. C 81(2010)037303
S.K.L. Sjue et al., Phys. Rev. C 78(2008)064317
Knowledge of EC and b- BR can be used to
benchmark the theoretical framework of bb
decays
But:
•Difficult measurement due to a small EC branch and difficult X-ray signatures
•High background due to dominating beta decay and possible bremsstrahlung
•Isobaric contamination
EC-BR measurements
Traditional method: tape station & observe X-rays after EC
Drawbacks:
• Contaminations
• Intense β background
• X-ray absorption in the backing material
Recent development:
S. K. L. Sjue et al., Phys. Rev. C 78, 064317 (2008)
•
•
Contamination free due to ion trap
Implantation into hole in scintillator (veto 90% of β events)
Novel approach proposed:
EC-BR measurement of ions stored in a Penning trap at TITAN
J. Dilling et al., Can. J. Phys. 85, 57 (2007)
remedy to all drawbacks in TITAN setup at TRIUMF
Thomas Brunner
TCP2010 conference
6
ISAC
TITAN
protons
•
•
•
DC protons with 100 mA @ 500 MeV from cyclotron
Protons hit thick target, unstable nuclei produced, diffuse, get
ionized, extracted – ISOL type target
Contamination removed using mass separator (resolution:
m/Δm = 3000)
Yields: 11Li 5x104/s, 74Rb 2x104/s, 62Ga 2x103/s
What is TITAN ?
TRIUMF’s Ion Trap for Atomic & Nuclear Science
Talk by M.
Brodeur
Talk by V. Simon
Aq+
Under construction:
Installation planned
for Dec. 2010
~2 kV • q
A+
~2 ke V
Decelerates beams
– TITAN composed of 3 ion traps (presently)
– Electron Beam Ion Trap (EBIT): Produces Highly Charged
Ions and is used for in-trap decay spectroscopy
~20 - ~60 keV
A+
Radioactive isotopes from an ISOL facility (TRIUMF ISAC).
TITAN-EC technique
•
•
•
Use TITAN facility at ISAC
make use of the open access
Penning trap EBIT (no e-beam)
Spatially separate X-ray and b
detection
Electron Beam Ion Trap
(EBIT) in Penning trap
mode for EC-BR
measurement
 e-gun retracted and
replaced by b detector
Penning trap
Aq+
Helmholtz
A+ coils
Short-lived isotopes from an Isotope
Separator and Accelerator (ISAC)
A+
b detector
X-ray
detector
TITAN-EC technique
Silicon detector
for b-decay
measurements
X-ray detector
X-ray detector
Novel method:
• Backing free
• Isobaric sample
• Spatial separation
of b+
A
and X-ray detection
Bmax ~ 3T 6 T magnetBeta detector
Ion injection
5 kV
Ø5 mm
4.7 kV
5 kV
Trap electrodes
Penning trap
A+
(PIPS)
105 ions injected
High efficient trapping
Storage and
detection
Penning trap
107In
107In
EC signature
107In
has a strong EC branch and comparable
half live of 32.4 min
t1/2= 32.4 min
EC ~ 63.9%
107Cd
t1/2= 6.5 h
Signature 107Cd decay
EC ~ 99.8%
Signature 107In decay
107Ag
Goals of the beam time
Signature 107In decay
Shoot through EBIT
√
Identify 107In after EBIT
√
Store radioactive ions in trap
√
Observe X-rays following an EC
√
Identify X-rays from EC
√
Observe electrons from b decays
X
First observation of an EC in a
Penning trap
BR(EC) = 55 (20) %
S. Ettenauer et al., AIP Conf. Proc. 1182(2009)100
Only one detector
0.02% solid angle!
# ions/shot & half life of 126Cs
Monitoring PIPS
(Passivated Implanted
Planar Silicon)
Half life data obtained
with a MCS
6 hrs beam off before
first 10 pulses 126Cs
t½ = 97.4 ± 2.1 s (fit) (lit: 98.4 ± 1.2s)
for first 10 shots (1st spike)
Beam intensity ≈ 3 * 105 ions/RFQ
extraction pulse @ 10 Hz
EBIT
BUT:
Half life increases for the following t½
measurements
RFQ
Thomas Brunner
TCP2010 conference
 Contamination built up on PIPS
detector (~30% 126Ba contamination)
12
Systematic studies with 124, 126Cs
124Cs
126Cs
t½ = (30.8 ± 0.5) s
t½ = (98.4 ± 1.2) s
Injection of Cs (~1ms)
Monitoring PIPS
V
z
Storage of Cs (25ms)
Observation of decays
LeGe detector
X-ray detection
Ejection of Cs (1ms)
The trap is kept open to
empty completely
PIPS
b detection
RFQ
Thomas Brunner
Empty trap (25ms)
Background
measurement
Ge detector
X/g-ray detection
TCP2010 conference
13
Observation of 124Cs EC X-rays
126Ba
(11.0 min)
EC
126mCs
126Cs
(6.3 s)
(30.8 s)
EC
126Xe
Xe X-ray 354 keV
124Cs signature
K lines
Cu Ka line
89.5 keV &
Cs X-ray lines
96.6keV
124Cs isomer
LeGe detector
X-ray detection
~ 0.1% egeo
~ 2.5 T B field at detector position
Xe X-ray lines: due to 124Cs EC
Cs X-ray lines: probably dominant due to
124Ba contamination and decay of 124mCs
RFQ
Thomas Brunner
Ge detector
X/g-ray detection
PIPS
Passivated Implanted
Planar Silicon
b detection
TCP2010 conference
14
g – b+ time correlation
Ge detector
~ 0.15% egeo
Outside vacuum vessel
Monitoring
PIPS detector
Si detector (500mm)
on magentic field axis
at exit of Penning trap
PIPS
LeGe detector
X-ray detection
g spectrum in
coincidence
with b+ event
PIPS
b detection
RFQ
Thomas Brunner
491 keV
126Cs
388 keV
126Cs
511 keV
PIPS spectrum
in coincidence
First time:
with g event
b+ spectrum from
126Cs ions stored
inside the trap
Ge detector
X/g-ray detection
TCP2010 conference
15
Summary
•
bb nuclear matrix elements needed for theoretical framework
•
EC-BR measurement as benchmark experiment for theoretical description
•
TITAN EBIT offers a novel approach for EC-BR measurements
• Backing free method
• Low background at X-ray detector – spatial separation of b and X-ray detection
• Isobaric sample
•
Successful storage of radioactive ions (long storage times: P < 10-11 mbar)
•
First observation of an Electron Capture decay in a Penning trap
Thomas Brunner
TCP2010 conference
16
For the future
•
•
•
Analyze Cs beam time data
Install MR-TOF-MS (Giessen) for sample purification
Get ready for beam time with 100Tc end of 2010
100Tc
measurement cycle with
• 25 ms background / 2 ms transfer
• 50 ms decay spectroscopy
• 2.1% EC detection efficiency
 1.28 detected EC in 1 h
 100 EC after 78 h
 94 h of beam time with 20% overhead
CANDIDATES FOR BRANCHING RATIO MEASUREMENTS
100Mo
:
100Tc
(EC)
[1+ 0+, T1/2 = 15.8 s]
Ka = 17.5 keV
110Pd
:
110Ag
(EC)
[1+ 0+, T1/2 = 24.6 s]
Ka = 21.2 keV
114Cd
:
114In
(EC)
[1+ 0+, T1/2 = 71.9 s]
Ka = 25.3 keV
116Cd
:
116In
(EC)
[1+ 0+, T1/2 = 14.1 s]
Ka = 25.3 keV
82Se
:
[2- 0+, T1/2 = 6.1 min]
Ka = 11.2 keV
128Te
:
128I
(EC)
[1+ 0+, T1/2 = 25.0 min]
Ka = 27.5 keV
76Ge
:
76As
(EC)
[2- 0+, T1/2 = 26.2 h]
Ka = 9.9 keV
82mBr (EC)
Seven Si(Li) have been ordered January 2010
Thomas Brunner
TCP2010 conference
17
People/Collaborations
M. Brodeur, T. Brunner, J. Dilling, P.
Delheij, S. Ettenauer, A. Gallant, M. Good,
E. Mane, M. Pearson, V. Simon…
… and the TITAN collaboration
as well as A. Lapierre, D. Lunney, R. Ringle,
V. Ryjkov, M. Smith and TRIUMF staff.
U. of Manitoba
U. of Calgary
McGill U.
U. of Windsor
Muenster U.
SFU
MPI-K
UBC
GANIL
TU München
Colorado School of Mines
Yale
Backup slides
Thomas Brunner
TCP2010 conference
19
Isotope Production
500-MeV proton beam
Targets:
Si, Ta, W, …
Residual
proton beam
Exotic isotopes
A>170 under development
Proton
target ass’y
Some heavy masses may be
produced presently from test
actinide targets (e.g., UOx).
A<170
Thomas Brunner
Beam extraction
at 20 kV – 60 kV
TCP2010 conference
20
100Tc
production rate
1.E+11
1.E+10
LaC2
LaC2 target with 50mA p
beam
Ta
1.E+09
In-target Production (/s)
1.E+08
Ta target with 70mA p beam
1.E+07
1.E+06
1.E+05
1.E+04
1.E+03
1.E+02
1.E+01
1.E+00
85
90
95
100
Tc Mass
Hirschegg
18. Jan 2008
105
110
115
Thanks to
Marik Dombsky
21
ECBR Measurements
CANDIDATES FOR BRANCHING RATIO
MEASUREMENTS
100Mo
:
100Tc
(EC)
[1+ 0+, T1/2 = 15.8 s]
Ka = 17.5 keV
110Pd
:
110Ag
(EC)
[1+ 0+, T1/2 = 24.6 s]
Ka = 21.2 keV
114Cd
:
114In
(EC)
[1+ 0+, T1/2 = 71.9 s]
Ka = 25.3 keV
116Cd
:
116In
(EC)
[1+ 0+, T1/2 = 14.1 s]
Ka = 25.3 keV
82Se
:
[2- 0+, T1/2 = 6.1 min]
Ka = 11.2 keV
128Te
:
128I
(EC)
[1+ 0+, T1/2 = 25.0 min]
Ka = 27.5 keV
76Ge
:
76As
(EC)
[2- 0+, T1/2 = 26.2 h]
Ka = 9.9 keV
1+
100Mo
82mBr (EC)
100Tc
QEC = 0.168
e 
0.0018%
b-b-
15.8 s
Qb = 3.202
100Ru
105 ions in trap with one half-life measurement
cycle:
5.7 x 10-3 EC
• solid angle: 2.1%
counts/cycle
• detection efficiency: 30%
100 EC counts  17636 EBIT fills 
74h
9. Jan 2008
88h proposed for
100Tc
Simulations
Ø5
mm
5 kV
4.7 kV
3 MeV electrons
5 kV
Loss through magnetic
bottle for q > 79deg:
 v|| 
  
 v crit
Bmax = 6T
Bmax
1
Bmin
25 mm
284 mm to center
3 MeV electrons hitting a 500mm Si
waver
Loss through wall collisions
 Rotating wall cooling or
side-band cooling
Storage time
39K
< 10 % ion losses after
25 ms storage
39K
Thomas Brunner
@ 4T
@ 4T
TCP2010 conference
24