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Full EXO in Cryopit

The EXO Cryopit is a workshop held in August 2011, featuring David Sinclair discussing the EXO project. EXO is an enriched xenon observatory that aims to search for neutrinoless double beta decay in 136Xe. The workshop covers various aspects of the project, including the need for a larger detector and the use of barium tagging to eliminate radioactive backgrounds. The workshop also discusses the infrastructure needs, such as depth and cleanliness, required for the successful operation of the detector.

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Full EXO in Cryopit

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  1. Full EXO in Cryopit Cryopit Workshop August 2011 David Sinclair

  2. What is EXO • Enriched Xenon Observatory • Search for neutrinoless double beta decay in 136Xe • 200 kg detector operating at WIPP • Gas R&D underway

  3. Full EXO • A detector at up to 10 tonnes of sensitive material • Needed as next step towards the normal hierarchy

  4. EXO neutrino effective mass sensitivity • Assumptions: • 80% enrichment in 136 • Intrinsic low background + Ba tagging eliminate all radioactive background • Energy res only used to separate the 0ν from 2ν modes: • Select 0ν events in a ±2σ interval centered around the 2.481MeV endpoint • 4) Use for 2νββ T1/2>1·1022yr (Bernabei et al. measurement) *s(E)/E = 1.6% obtained in EXO R&D, Conti et al Phys Rev B 68 (2003) 054201 †s(E)/E = 1.0% considered as an aggressive but realistic guess with large light collection area ‡ QRPA: A.Staudt et al. Europhys. Lett.13 (1990) 31; Phys. Lett. B268 (1991) 312 # NSM: E.Caurier et al. Phys Rev Lett 77 (1996) 1954 EXO SAGENAP GG

  5. EXO-200

  6. Why limit to 10 T • Annual production of Xe ~ 40 T/a • ~10% is 136Xe • Enrichment capacity ~ 1.8 T/a • Current world inventory is about 0.7 T • Probably cannot make too big a step in detector size

  7. Why Xenon • Purity • Can be made into detectors • Excellent multi-site ID • Good background rejection • Least expensive isotope to produce • Possible Ba tag

  8. Infrastructure NeedsDepth • We are attempting to measure one of the rarest decay modes ever. Background control is critical. • Strongest case at DUSEL for deep site was for double beta decay. • Pushing mass sensitivity -> pushing down backgrounds • Even with barium tag, cosmogenics can hurt • We need to be deep

  9. Infrastructure Needs Cleanliness • Local radioactive backgrounds are critical • Just as in SNO we face a serious 208Tl background • The signal is in the ‘background wall’ • Cleanliness is critical

  10. Space • The space required for either a liquid or gas detector at the tonne scale is the space available in the Cryopit • The Cryopit was designed with experients such as these in mind

  11. Services • No unusual requirements foreseen beyond what is already provided

  12. Safety • Both liquid and gas detectors have significant inert material loads • A cryogenic liquid can vaporize rapidly giving hazardous conditions • A gas detector is at high pressure and can give hazardous conditions with failure • The Cryopit was designed to mitigate these risks

  13. EXO Full LXe Installed into SNOLAB CRYOPIT

  14. Control Center Offices, Kitchen Restrooms HFE Storage, UPS Electrical Utilities Machine Shop Clean High Bay Assembly area Clean Access Tunnel Clean Ba++ Tagging & Electronics Room Water Purification Cryogenics Xe Storage Showers/Gowning area Clean room – Class 1K XeSystem & bottles • Clean room – Class 100/1K

  15. EXO Full LXe Chamber Size 11.25M X 8.5M X 35.5M 3.1M Clear for Equipment Access 1M Clear for Personal Access EXO Full Building Size 7.1M X 6.1M X 14M 7.1M X 3.1M X 14M Total Length 28M

  16. Clean Access Tunnel Staging / storage area Shielding Water

  17. Gas Detector in Cryopit • Can operate at any pressure up to max pressure so can start with partial fill • Upward load of ~300 T transfer to back • Could use lighter tank if pressure transfer to cavity • Only location in the world where this is possible

  18. Ba Tag • Ba+ single ion tag demonstrated in traps • Issues are how to get ion to a trap and how to convert Ba++ to Ba+ • Current concept is to drift ion to an orifice where it is extracted to low pressure, use ion guides to separate ions from gas, and then transport to trap • System is similar to that used by molecular biologists

  19. Ba Tag?

  20. Short term tagging plan • Need to measure transport of Ba ions in Xe • EG what is the mobility? • Does Ba++ convert to Ba+? • Make new ion source to study these

  21. A Tagged Ba++ Source? • To measure the overall efficiency of a barium tag a tagged source would be valuable • Current concept is to use 252Cf source • Ba is at high mass fragment peak • Fraction of Ba is well known • Deposit on Si counter to tag based on light mass signal • Expect fragments stopping in Xe to end at ++ state

  22. Possible short term use • Move XEL into Cryopit • Include a Ba tag • Demonstrate proof of principle for a detector with Ba tag looking at 2n decay • Current location (above ground) has substantial pile-up issues

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