Full EXO in Cryopit

Cryopit Workshop August 2011David Sinclair

What is EXOEnriched Xenon Observatory

Search for neutrinoless double beta decay in 136Xe

200 kg detector operating at WIPP

Gas R&D underway

Full EXOA detector at up to 10 tonnes of sensitive material

Needed as next step towards the normal hierarchy

EXO SAGENAP GG 4 Apr 16, 2004

Assumptions: 1) 80% enrichment in 1362) Intrinsic low background + Ba tagging eliminate all radioactive background3) Energy res only used to separate the 0ν from 2ν modes: Select 0ν events in a ±2σ interval centered around the 2.481MeV endpoint4) 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 neutrino effective mass sensitivity

Case Mass(ton)

Eff.(%)

Run Time(yr)

σE/E @ 2.5MeV

(%)

2νββBackgroun

d(events)

T1/20ν

(yr, 90%CL)

Majorana mass(meV)

QRPA‡ (NSM)#

Conservative 1 70 5 1.6* 0.5 (use 1) 2*1027 33 (95)

Aggressive 10 70 10 1† 0.7 (use 1) 4.1*1028 7.3 (21)

EXO-200

Why limit to 10 TAnnual 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

Why XenonPurity

Can be made into detectors

Excellent multi-site ID

Good background rejection

Least expensive isotope to produce

Possible Ba tag

Infrastructure NeedsDepthWe 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

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

SpaceThe 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

ServicesNo unusual requirements foreseen beyond what is already provided

SafetyBoth 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 LXeInstalled into SNOLAB CRYOPIT

Clean High BayAssembly area

HFE Storage, UPS Electrical UtilitiesMachine Shop

Control CenterOffices, KitchenRestrooms

Clean room – Class 100/1K

Showers/Gowning areaClean room – Class 1KXe System & bottles

Water PurificationCryogenicsXe Storage

Clean AccessTunnel

CleanBa++ Tagging& ElectronicsRoom

1M Clear forPersonal Access

3.1M Clear forEquipment Access

EXO Full LXe Chamber Size11.25M X 8.5M X 35.5M

EXO Full Building Size7.1M X 6.1M X 14M7.1M X 3.1M X 14MTotal Length 28M

Staging / storagearea

Shielding Water

Clean AccessTunnel

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 TagBa+ 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 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

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