Development of Resonance Ionization …Development of Resonance Ionization Spectroscopy for Single...
Transcript of Development of Resonance Ionization …Development of Resonance Ionization Spectroscopy for Single...
Development of Resonance Ionization Spectroscopy for Single
Ion Transport
María Montero DíezKarl Twelker
Stanford University
APS April Meeting 2011 1
Motivation - Full EXO R&D
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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…
“Tagging” 136Ba ion in real time may allow for rejection of all backgrounds except 2nbb.
Transporting single Ba+ ions NON TRIVIAL!
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.
6s2 1S0
553.5nm
389.7nm
Ba+ 6s
Ba+ 5d
6s6p 1P1
5d8d 1P1
Ba ground state electron configuration: [Xe]6s2
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Autoionization:
•The 5d8d 1P1 state decays to a lower energy ionized state.
This allows use of the high crosssection of the resonance to achieveionization.
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)
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Si
channeltron
3 cm
5 cm
2-3 usec
Presented at APS April Meeting 2010
Low-Flux Setup
• Si target (4x4mm, 8x8 mm)
• Ti components for low background
• Uses our radionuclide-driven ion source.
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Si Target
Ti Support
Ion Source
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Ion Source Schematic
BaF2
148Gd
Surface Barrier Detector alpha
M. Montero Díez, et al. Rev. Sci. Instrum. 81 113301 (2010)
Low-Flux Operation
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Loading 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
RIS lasers fireDesorption laser fires 9
Detuning
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• We detuned the 553.5 nm laser by +/- 3nm
On Resonance (Black)Detuned -3 nm (Red)Detuned +3 nm (Blue)
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 efficiency11
Single Ion Setup
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12”
Loading the Target
Simulated loading efficiency with plate around target: 85%. Without plate: 65%13
Green: Ion trajectories Red: Potentials
DRIS Stage
Simulated transport efficiency: 99%14
Green: Ion trajectories Red: Potentials
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)
Implement
DRIS in ion trap
Demonstrate
single ion DRIS
in trap
Integrate DRIS
probe with LXe cell
Single ion DRIS
Done
In progress
To do
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, Germany18
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EXO Majorana mass <mbb> sensitivity
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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