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

3

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