Development of Resonance
Ionization Spectroscopy for Single
Ion Transport
María Montero Díez
Karl Twelker
Stanford University
APS April Meeting 2011
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Motivation - Full EXO R&D
Full EXO ~ ton scale gas or liquid TPC
• “Tagging” of 0nbb daughter nucleus 136Ba ion
for background rejection – R&D underway
• Ion extraction from a TPC
• Hot Tip
• Cryo Tip
• RIS Tip – presented here
• Ion trapping
• Buffer gas cooled quadrupole linear
ion trap
• Ion identification with
• Laser Induced Fluorescence (LIF)
• Resonant ionization spectroscopy
(RIS)
•Others…
Transporting single
Ba+ ions
 NON TRIVIAL!
“Tagging” 136Ba ion in real time may
allow for rejection of all backgrounds
except 2nbb.
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Resonance Ionization Spectroscopy
• RIS uses lasers tuned to atomic
resonances to first excite and then
ionize specific atoms.
• We use pulsed dye lasers at 553.5 nm
and 389.7 nm.
Ba+ 5d
5d8d 1P1
Ba+ 6s
389.7nm
Autoionization:
•The 5d8d 1P1 state decays to a lower
energy ionized state.
This allows use of the high cross
section of the resonance to achieve
ionization.
6s6p 1P1
553.5nm
6s2 1S0
Ba ground state electron configuration: [Xe]6s2
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Initial DRIS Setup
• Neutral Ba is deposited on the target with a Barium oven.
• An infrared Nd:YAG laser releases ions from the target.
• RIS lasers ionize the neutral Ba. (spectroscopic
identification)
• The ion drifts to a channeltron. (time of flight mass
spectrometry)
3 cm
Si
5 cm
2-3 usec
channeltron
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Presented at APS April Meeting 2010
Low-Flux Setup
Ion Source
Si Target
Ti Support
• Si target (4x4mm,
8x8 mm)
• Ti components
for low
background
• Uses our
radionuclidedriven ion
source.
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Ion Source Schematic
BaF2
148Gd
alpha
Surface Barrier Detector
M. Montero Díez, et al. Rev. Sci. Instrum. 81 113301 (2010)
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Low-Flux Operation
Loading
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DRIS
How We Use the Low Flux Setup
• We deposit overnight in the loading
configuration.
• We run the lasers at 10 or 1 Hz, alternating RIS
on/off.
• Simulations show that the barium time of
flight should be about 7.5 μsec. (after the RIS
lasers)
• The delay between the desorption and RIS
lasers is 1.5 μsec.
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With and Without RIS Lasers
Desorption+RIS lasers (Black)
Desorption only (Red)
Barium window
Desorption
laser fires
RIS lasers fire
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Detuning
• We detuned the 553.5 nm laser by +/- 3nm
On Resonance (Black)
Detuned -3 nm (Red)
Detuned +3 nm (Blue)
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Efficiency?
• The ion source produces about 2 Ba+/sec, we run
it for 14 hours: about 105 ions deposited.
• Over the entire run we get about 250 back from
RIS.
• That’s only half, because in 50% of the shots we
didn’t use RIS lasers.
• Finally, detection is not 100% efficient (optics,
CEM).
Thus, approximately 10-3 efficiency
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Single Ion Setup
12”
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Loading the Target
Green: Ion trajectories
Red: Potentials
Simulated loading efficiency with plate around target: 85%. Without plate: 65%
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DRIS Stage
Green: Ion trajectories
Red: Potentials
Simulated transport efficiency: 99%
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Desorption Optics
• Suggested to achieve an even illumination across the target
• Can be imaged using a CCD to make sure that the image is focused
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New Target Design
A voltage across the Si target will help bring ions to the center of the target
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DRIS R&D Progress
Trap Ba ions in
buffer gas
Trap single Ba
ions
Gas phase RIS
Desorption RIS
(DRIS)
Single ion DRIS
Implement
DRIS in ion trap
Done
In progress
To do
Demonstrate
single ion DRIS
in trap
Integrate DRIS
probe with LXe cell
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D.Auty, M.Hughes, R.MacLellan, A.Piepke, K.Pushkin, M.Volk,
Dept of Physics & Astronomy, U. of Alabama, Tuscaloosa AL
M.Auger, D.Franco, G.Giroux, R.Gornea, M.Weber, J-L.Vuilleumier,
High Energy Physics Lab,Bern,Switzerland
P.Vogel Physics Dept Caltech, Pasadena CA
A.Coppens, M.Dunford, K.Graham, P.Gravelle, C.Hägemann, C.Hargrove,
F.Leonard, K.McFarlane, C.Oullet, E.Rollin, D.Sinclair, V.Strickland,
Carleton University, Ottawa, Canada
C.Benitez-Medina, S.Cook, W.Fairbank Jr., K.Hall, N.Kaufhold, B.Mong,
T.Walton, Colorado State U., Fort Collins CO
L.Kaufman, Indiana University
M.Moe, Physics Dept UC Irvine, Irvine CA
D.Akimov, I.Alexandrov, V.Belov, A.Burenkov, M.Danilov, A.Dolgolenko, A.Karelin, A.Kovalenko, A.Kuchenkov,
V.Stekhanov, O.Zeldovich, ITEP Moscow, Russia
E.Beauchamp, D.Chauhan, B.Cleveland, J.Farine, D.Hallman, J.Johnson, U.Wichoski, M.Wilson, Laurentian U., Canada
C.Davis, A.Dobi, C.Hall, S. Slutsky, Y-R. Yen, U. of Maryland, College Park MD
J. Cook, T.Daniels, K.Kumar, A.Pocar, K.Schmoll, C.Sterpka, D.Wright, UMass, Amherst
D.Leonard, University of Seoul, Republic of Korea
M.Breidenbach, R.Conley, W.Craddock, S.Herrin, J.Hodgson, J.Ku, D.Mackay, A.Odian, C.Prescott,
P.Rowson, K.Skarpaas, M.Swift, J.Wodin, L.Yang, S.Zalog, SLAC, Menlo Park CA
P.Barbeau, L.Bartoszek, J.Davis, R.DeVoe, M.Dolinski, G.Gratta, F.LePort, M.Montero Diez,
A.Müller, R.Neilson, A.Rivas, A. Saburov, K.O’Sullivan, D.Tosi, K.Twelker, Physics Dept Stanford U., Stanford CA
W.Feldmeier, P.Fierlinger, M.Marino, TUM, Garching, Germany
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EXO Majorana mass <mbb> sensitivity
Assumptions
1. 136Xe, 80% enrichment
2. Intrinsic low backgrounds & Ba tagging eliminate all radioactive backgrounds
3. Energy resolution used to separate 0nbb from 2nbb modes (select 0n events in +/- 2s interval
around 2.458 MeV endpoint)
4. 2nbb (T1/2 > 1x1022 yr, Bernabei et al.)
Case
Mass
[ton]
Efficiency
[%]
Run time
[yr]
sE/E @ 2.5
MeV [%]
2nbb background
[events]
T1/20nbb [yr, 90% CL]
Neutrino majorana mass
[meV]
QRPA
NSM
Conservative
1
70
5
1.6(3)
0.5 (~1)
2.0x1027
19 (1)
24 (2)
Aggressive
10
70
10
1.0(4)
0.7 (~1)
4.1x1028
4.3 (1)
5.3 (2)
(1) Simkovic et al. Phys. Rev. C79, 055501(2009) ) (use RQRPA and gA = 1.25)
(2) Menendez et al., Nucl. Phys. A818, 139(2009) (use UCOM results)
(3) sE/E = 1.6% obtained in EXO R&D, Conti et al., Phys. Rev. B 68 (2003) 054201
(4) sE/E = 1.0% considered aggressive but realistic guess with large light collection
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