Full EXO in Cryopit Cryopit Workshop August 2011 David Sinclair

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

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

Apr 16, 2004EXO SAGENAP GG4 Assumptions: 1)80% enrichment in 136 2)Intrinsic low background + Ba tagging eliminate all radioactive background 3)Energy res only used to separate the 0ν from 2ν modes: Select 0ν events in a ±2σ interval centered around the 2.481MeV endpoint Select 0ν events in a ±2σ interval centered around the 2.481MeV endpoint 4)Use for 2νββ T 1/2 >1·10 22 yr (Bernabei et al. measurement) *  (E)/E = 1.6% obtained in EXO R&D, Conti et al Phys Rev B 68 (2003) †  (E)/E = 1.0% considered as an aggressive but realistic guess with large light collection area 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 neutrino effective mass sensitivity CaseMass (ton) Eff. (%) Run Time (yr) σ E 2.5MeV (%) 2νββ Background (events) T 1/2 0ν (yr, 90%CL) Majorana mass (meV) QRPA ‡ (NSM) # Conserva tive * 0.5 (use 1)2* (95) Aggressi ve †1† 0.7 (use 1)4.1* (21)

EXO-200

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

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

Infrastructure Needs Depth 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. 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

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

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

Services No unusual requirements foreseen beyond what is already provided

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

EXO Full LXe Installed into SNOLAB CRYOPIT

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

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

Staging / storage area Shielding Water Clean Access Tunnel

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

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

Ba Tag?

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

A Tagged Ba++ Source? To measure the overall efficiency of a barium tag a tagged source would be valuable Current concept is to use 252 Cf 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

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