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EXO-Development Program

EXO-Development Program. DUSEL Workshop Washington, November 2007 David Sinclair Carleton/TRIUMF. We need to develop new strategies to eliminate backgrounds to probe the allowed space. Inverted. Barium tagging may offer a way forward. Normal.

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EXO-Development Program

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  1. EXO-Development Program DUSEL Workshop Washington, November 2007 David Sinclair Carleton/TRIUMF

  2. We need to develop new strategies to eliminate backgrounds to probe the allowed space Inverted Barium tagging may offer a way forward Normal

  3. Xe offers a qualitatively new tool against background: 136Xe 136Ba++ e- e- final state can be identified using optical spectroscopy (M.Moe PRC44 (1991) 931) Ba+ system best studied (Neuhauser, Hohenstatt, Toshek, Dehmelt 1980) Very specific signature “shelving” Single ions can be detected from a photon rate of 107/s 2P1/2 650nm 493nm 4D3/2 • Important additional • constraint • Huge background • reduction metastable 80s 136Ba+ 2S1/2

  4. Ba+ spectroscopy in high pressure noble gases RF quadrupole trap loaded in UHV from a Ba dispenser and e-beam ionizer Xe can be injected while observing the ions

  5. Millikan experiment with ions in vacuum The signal amplitudeis proportionalto integers

  6. Ba tagging for the Liquid Detector Currently, two ion transfer methods are under parallel development, both involving the capture and transport of the ion on the surface of a specially designed tip • 1) Resonance Ionization Spectroscopy • After a real-time ββ trigger, a ~400 μm fiberwith a metallized end and biased at a negative potential is inserted near the event site in LXe. • The Ba+ ion is attracted to the tip and trapped • The ion is released with a laser pulse, resonantly ionized with two other pulses, and injected into the trap where it is detected.

  7. Cryo-tip lHe cryostat Shielded cables To LCR meter Au-coated leads Vespel sleeves sensor Actuator Read-out cables 2mm Ice sensor Cu cold finger W heater wire LXe cell

  8. Results – PID-controlled Thin Layer Freezing from liquid Xe in 700 mbar Xe PID control temp, feedback on capacitance

  9. Liquid or Gas Pros Liquid Compact detector No pressure vessel Small shield -> lower purity reqd. Gas Energy resolution Tracking & multi-site rejection In-situ Ba tagging bb angular correlation Cons Large detector Needs very large shield Pressure vessel is massive Large Cryostat Poorer energy, tracking resolution Ex-situ Ba tagging

  10. Understanding Physics of Double Beta Decay • Recent paper by Ali, Borisov and Zhuridov • Probing New Physics in the Neutrinoless Double Beta Decay using Electron Aangular Correlation arXiv:0706.4165v2

  11. Possible concept for a gas double beta counter Anode Pads Micro-megas WLS Bar Xe Gas + ??? Electrode Laser . . . . . . . . . . . . . . . . Grids PMT For 200 kg, 10 bar, box is 1.5 m on a side

  12. Technical issues for a Gas counter • Need to demonstrate good energy resolution (<1% to completely exclude bb2n ) • Want to have gas gain if possible • Need to demonstrate Ba tagging • Deal with pressure broadening • Ba ion lifetime • Ba++ -> Ba+ conversion • Can we cope with background of scattered light

  13. Progress on energy resolution s = 0.6% Alpha spectrum at 2 b pressure.

  14. Energy Resolution in Gas • Better than 1% (sigma) achieved in pure Xe and several mixtures • In pure Xe, at 2 bar, amplitude is constant to 0.2% for drift up to 17 cm • Pure Xe is slow

  15. Other gas requirements • If we add something to the gas to speed up electrons and quench gain stage then • Does the additive kill the 172 nm light • Do electrons attach to the additive • Will the additive trap Ba ions • Will the additive convert Ba++ to Ba+

  16. Ba tagging in high-pressure Xe • We need to deal with pressure broadening • Requires higher laser power to get fluorescence rate (perhaps factor of 1000) • Higher density gives more scattering • However, in high pressure Xe the D state will quickly de-excite collisionally • Plan to excite with blue laser and look for red emission photons

  17. Xe offers a qualitatively new tool against background: 136Xe 136Ba++ e- e- final state can be identified using optical spectroscopy (M.Moe PRC44 (1991) 931) Ba+ system best studied (Neuhauser, Hohenstatt, Toshek, Dehmelt 1980) Very specific signature “shelving” Single ions can be detected from a photon rate of 107/s 2P1/2 Red light out 650nm 493nm Laser In 4D3/2 • Important additional • constraint • Huge background • reduction De-excite by collisions 2S1/2

  18. Future Program • Demonstrate the liquid detection technique at WIPP, measure (bbnn) in Xe, Measure (bb0n) if at HM value • Develop the Ba tagging for a liquid detector • Demonstrate a gas phase detection • Develop the Ba in-situ tag in gas phase • Build the ultimate, ton scale detector for double beta decay

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