The ZEPLIN programHanguo Wang,

UCLA, Physics and Astronomy

Stony Brook, May. 5, 2006

1. Status of ZEPLIN II2. A possible ZEPLIN-IV design 3. Long term plan

Detector response to WIMPs and Background

Radioactivebackground

electronrecoil

Target Nuclei

nuclear recoilWIMP orNeutron

(I,S,Th)

(I, S, Th)

Background Discrimination

Ionization

Scintillation

Phonon

e-

Secondary (S2)Electroluminescence

Primary (S1)Scintillation

PMT

LXe

Gasliquid

γn-r

e-

PMT PMT

ZEPLIN II Design Principle

PTFE

Rec

oil E

vent

S1 S2

Drift and Luminescence

Field Modeling

Mesh Structure

Main Drift Volume

PMT

ZEPLIN II Detector

ColdHead

HV & signal

Feedthrough

Gas Xenon

PMT

Field Rings

Liquid Xe

Vacuum

Zep II Charge Extraction & Luminescence Field Grid

88% transparency

Wiremesh

HV feedthrough

& internal cable

PTFE

Baffle

ZEPLIN II Operation Underground at Boulby Mine, UK Detector fully operational Physics data taking in progress Data analysis in progress

Lead Shield

Purifier

Safety

Dump

Neutron shield &

Compton Veto

ZEPLIN II Electron Lifetime and

Light Collection in Liquid Xenon

57Co

103pe/122keV

1000

5 day

Liquid purification well understood

Greater than 1-ms electron lifetime typical

1.5 photoelectron/keV at zero field

e-li

feti

me

(µs)

P1 – Primary of Neutron

S1 – Secondary of Neutron

P2 – Primary of Gamma

S2 – Secondary of Gamma

P2

S2

S1P1

3-D Event Display

XY

Z

Data from: z2_060226

57Co

waveforms from ZEPLIN II

89% signal4-sigma cut

3.2x10-5

Log10(S2/S1) vs S1 Plot Background Discrimination

Gamma S2

S1

AmBe Run &

Dark Matter run

Possible neutron double

scatter overlap S2 Very clean waveform

Excellent recoil discrimination

from S2/S1

Summary of ZEPLIN II System Integration Status

Cooling System Stable Slow Control System operational HV System, Feedthroughs complete Luminescence grid capable for 100% charge extraction good

S2 gain DAQ system and Software Tested Liquid level monitoring with S2 pulse width and drift time Instrument tilt/grid shape monitor across whole surface with S2 Recirculation system to purify xenon continuously

Routine two-phase operation established underground 9 hours to fill and 6 hours to empty Electron lifetime reach well above 1-ms Calibration and preliminary data runs started

Performance Ionization yield from xenon nuclear recoil observed! Primary light yield as expected (~1.6pe/keVee @zero field) Excellent background discrimination

ZEPLIN II

ZEPLIN IV/MAX 0.250 ton

ZEPLIN III

30kg

8kg

ZEPLIN long term strategy I

+ =

Direct Scale-up Based on the ZEPLIN II/III

250kg

250kg fiducial mass Two phase xenon 50 5-inch-PMT

19 on bottom31 on top

30-cm total drift length Light yield ~ 4pe/keV 45kV @ E=1.5kV/cm Xenon Purification

Forced Circulation

in liquid Active liquid recovery ~R x H = 0.5 (m) x 1.0 (m)

1-ton 5-ton

ZEPLIN long term strategy II

Towards ton-scale PMT-less detector

CsI

Nano-Tip Readout

Reverse operation of a cold-emission

Type device to achieve charge gain in liquid near the tip

Local high electric field for high gain100 % primary charge collectionLow absolute field with nano-structure

VI

Xe Target

VII

Xenon Purification and Safety System for ZEPLIN IV

VI, VII, are vacuum pumpsActive Xenon collection system will take less space (1.4 x linear size)Xenon purification in liquid phase (less cooling power)

Manual Valve

Cooling

Pum

pG

ette

r.

SafetyDump

Cooling

Vacuum Insulated LineC.B.

C.B. Control Box

ZEPLIN IV/MAX layout

1, Target Detector: (250kg ton scale) 8m x 8m x 6m (WxLxH)Central detector, Active neutron and Compton vetoLead shield, Neutron Shield.

2, Electronic & Control: 5m x 4m x 3mDAQ system, Slow control,

3, Auxiliary systems: 8m x 8m x 4m

Active xenon recovery system and related pipe-works and controls

4, Total Peak Power 25kW

5, Office

Current ZEPLIN II Collaboration GroupsDB Cline, W.C. Ooi, F Sergiampietri(a), H Wang, P Smith(b), X Yang Physics and Astronomy, UCLA , (a) Pisa, (b) RAL&UCLA

JT White, J Gao, J. Maxin, G. Salinas, R. Bissit, J. Miller, J. Seifert Department of Physics, Texas A&M University

T Ferbel, U Schroeder (Chemistry), F Wolfs, W Skulski, J TokeDepartment of physics and Astronomy, Rochester University

Y GaoSouthern Methodist University, Texas

GJ Alner, C Bungau, B Camanzi, TJ Durkin,, R LuscherJD Lewin, RM Preece, NJT Smith, PF SmithParticle Physics Department, Rutherford Appleton Laboratory, Chilton, Oxon

H Araujo, A Bewick, D Davidge, JV Dawson, AS Howard, WG Jones, MK Joshi, V Lebedenko, I Liubarsky, T J Sumner, J J Quenby, R WalkerBlackett Laboratory, Imperial College of Science, Technology and Medicine, London

MJ Carson, E Daw, J Davis, T Gamble, VA Kudryavtsev, TB Lawson, PK Lightfoot, JE McMillan, B Morgan, SM Paling, M Robinson, NJC Spooner, DR ToveyDepartment of Physics and Astronomy, University of Sheffield

A. S. Murphy, C GhagUniversity of Edinburgh, Department of Nuclear Physics

M. Danilov, D Akimov, A. Kovalenko, V. StekhanovITEP, Moscow,

A. Policarpo, I. Lopes, V. ChepelLIP-Coimbra