The ZEPLIN III Detector Results from surface calibrations

The ZEPLIN III Detector Results from surface calibrations (Coimbra, Edinburgh, ICL, ITEP, RAL, Rochester, Texas, UCLA) Cryodet - March 2006 8

Simultaneous Measurement of Scintillation and Ionisation Cryodet - March 2006

ZEPLIN III Features l 8 kg fiducial mass l 31 PMTs in liquid l 3. 5 cm drift depth l 0. 5 cm electroluminescent gap l reverse field region l position sensitivity l open plan – no surfaces - reduced feedback Cryodet - March 2006

Simulations l Light collection –liquid phase –gas phase l Position sensitivity –gas electroluminescence l Internal gamma/neutron backgrounds l Fully implemented GEANT 4 model l Test data set production Cryodet - March 2006

Cryodet - March 2006

Araujo et al. , 2006 year 2 year 3

ZEPLIN III is built CAPAC - May 2001 Cryodet – March 2006

Cryodet - March 2006

Cryodet - March 2006

Three cool-downs so far 1. Check-out of thermal control system, xenon transfer and PMT response using internal radioactive sources. l Thermal design verified – 1 litre/hour LN boil off! l All PMTs operational l Xenon transferred several times during 6 week run l Am 241 spectra obtained with up to 17 pe/ke. V! l Dual-range 62 channel DAQ readout l High precision waveforms collected (including neutron source) Cryodet - March 2006

Three cool-downs so far First two-phase run (after removal of radioactive sources) ☺ Level setting with capacitive sensors ☺ HV established J Two-phase signal recovery from full depth L HV breakdown seen L Xenon leak into vacuum jacket (☺mass spec. ) ☺ Xenon recovery from vacuum jacket – no loss! Open system, located fractured HV feedthrough, replaced, closed up again 2. Cryodet - March 2006

Three cool-downs so far 3. Second two-phase run ☺ HV established (~4 k. V/cm (at the moment) – liquid – sustained for several days without trip) J Two-phase signal recovery J Event classification started J 57 Co spectrum from external source – as expected – working on light yield ☺ Purification cycles started – to recover from recent opening of detector Cryodet - March 2006

First cool-down 11 -14% FWHM • Single phase (no liquid/gas interface) 7 -11 pe/ke. V • Dual phase (with liquid/gas interface) ~17 pe/ke. V • MC simulations imply Xe yield probably > 60 photons/ke. V • Linear to better than 10% - 8 to 60 ke. V

Second cool-down

Third cool-down Primary scintillation

Third cool-down

Summary • ZEPLIN II is operating in Boulby mine. • Full depth operation • Final in-situ calibrations ongoing • ZEPLIN III is up and running. • Performance so far is as expected. • Some indication of higher photon yield than expected in xenon. • Further surface evaluation and optimisation in progress – another 3 months • FP 7 Design Study proposal for ton scale – ELIXIR – Lo. I submitted to ILIAS/Ap. PEC • FP 7 Single Project proposal for ZEPLIN III deployment - Lo. I submitted to ILIAS/Ap. PEC Cryodet - March 2006