july 2001 neil spooner ukdm programme update on nai, zeplin and drift neil spooner, university of...

July 2001 Neil Spooner

UKDM ProgrammeUKDM ProgrammeUpdate on NaI, ZEPLIN and DRIFTUpdate on NaI, ZEPLIN and DRIFT

Neil Spooner, University of Sheffield


New Caverns

More lab space than Soudan

50 m

£3.1M Award to University of Sheffield - Joint Infrastructure Fund grant

Collaboration with RAL

Surface facilities

Workshop, offices, etc.

Underground facilities

New much larger clean area

Upgrade of existing areas

New U/G Infrastructure 2000New U/G Infrastructure 2000


50m

Stub 2

Stub 2a,3

‘H’ Area

JIF Area

Boulby U/G FacilitiesBoulby U/G Facilities


~1500m2 new lab space

Experimental Halls

Clean Bay

Control Room

WorkshopDRIFT

Bay

Store

Workshop

Mess

Coms/Elecs.

Changing

Control RoomClean

Clean Bay

Runningboards

6m

20m

47m 14m

8m

8m

20m

Transfer Transfer

3.8mLaboratoriesClean roomsWorkshopMessFibre optic/Enet

New JIF Underground FacilityNew JIF Underground Facility


~ 1500 m2 new space

New Area Under ConstructionNew Area Under Construction


Main experimental hall will have 4-5m FLAT room

DRIFT 1 site

DRIFT Area ConstructionDRIFT Area Construction


New Surface LaboratoryNew Surface Laboratory


Contact me: Neil Spooner - [email protected]

Facility Management Board International Boulby Research Board

Facility manager and staff Projects co-ordinator

Institute for Underground Science

Plenty of new lab space available

Call For ProposalsCall For Proposals


NaIsmall array

20 kg

NAIADhigh rate array

50 kg

UK-Saclay20 kg

NAIAD array

existing

ramp down

ZEPLIN-Isingle phase

PSD4 kg

ZEPLIN-IIion-scint

two phase Xe30 kg

ZEPLIN-IIIIon-scint

two phase Xehigh field

6 kg

ZEPLIN array

under construction

existing ZEPLIN-MAXion-scint

two phase Xe1000 kg

MULTINATIONAL

concept

under construction

DRIFT 1directional

1 m3

DRIFT array

DRIFT 10directional

10 m3

MULTINATIONAL

concept

2000 2002 2003 2004+2001

Boulby Dark Matter ProjectsBoulby Dark Matter Projects


QMW: J. C. Barton University of Surrey: E. Morton, P. Sellin

CERN/Padova: A Pietropaulo ITEP: D Akimov, V Lebedenko, A Danilov

Coimbra: A Policarpo, M Salete Leite, R Ferreira Marques, V Chepel

UCLA: D Cline, M Atac, H Wang, J K Woo, J Park Columbia: C Hailey, J Hong, E Aprile, A Castellina

UCSD: K Griest, G Masek, K BucklandTemple University: C J Martoff, P Ambrozewicz, E Kaczanowicz

University of Sheffield: T. Gamble, V. A. Kudryavtsev, T. B. Lawson, M. Carson, S. Paling, P. K. Lightfoot, J. E. McMillan, B. Morgan, M. Robinson, N. J. C. Spooner, L. Thompson, D. R. Tovey, G. Nicklin

Rutherford Appleton Laboratory: G. J. Alner, E.G. Capocci, S. P. Hart, J. D. Lewin, R. Lüscher, R. M. Preece, J. W. Roberts, N. J. T. Smith, P.F. Smith

Imperial College of Science, Technology and Medicine: B. Ahmed, A. Bewick, D. Davidge, J. V. Dawson, A. S. Howard, I. Ivaniouchenkov, W. G. Jones, M. K. Joshi, V. Lebedenko, I. Liubarsky, T. J. Sumner, J. J. Quenby

Torino: P Picchi, L Periale, G Mannocchi, C Taricco, C Castagnoli, A CurioniSaclay: G. Gerbier

Occidental College: D Snowden-Ifft, T Ohnuki, N Villaume, J Burwell LLNL: B Craig, M J Lehner

UKDMC Boulby Dark Matter Collaboration (BDMC)

People Involved in Dark MatterPeople Involved in Dark Matter


Boulby NAIAD ProgrammeBoulby NAIAD Programmestatus and programme

• Low-A target (Na) for WIMP masses < 200 GeV/c2 to reach 0.1/kg/d

MotivationMotivation

• Pulse shape discrimination and known technology that can be scaled up

--> Complements liquid Xe high-A

--> satisfies requirement for (i) recoil identification and (ii) diagnostic array capability

• Information relevant to DAMA using the same target, NaI


UKDMC NaI - PSAUKDMC NaI - PSA

low activity silica

light guides & PMT shield

double zone refined NaI(Tl) crystalPMT

Example time constant distributions for new crystal DM72

showing log gauss neutron and compton fits and data.

E - 12-15 keV

neutron

Compton1996 limit from DM46 spin-independent

Schematic of early NaI detector e.g. DM46

NaI(Tl) Integrated Pulse-Shape


• Following improvement to DM46 (5 kg) - discovery of fast events in NaI

Data (E 35-40 keV)

calibration

Example histogram for DM46 showing anomalous events

Typical fast event energy distributions in various crystals of different geometry

NaI Anomalous Events (1998)NaI Anomalous Events (1998)

Anomaly


UKDMC NaI + SaclayUKDMC NaI + Saclay• Collaboration with Saclay to run a “DAMA” crystal at Boulby

• very similar spectrum of fast events seen again

RESULT

• this despite very different manufacture and geometry

UKDMC spectrum

anomalous event spectra in NaI

Saclay (“DAMA”) spectrum


DAMA PSDDAMA PSDDAMA PSDDAMA PSD

UKDMC anomalous event spectra

Limit on anomalous events from DAMA old PSD data


• Many underground and laboratory tests performed

lead/copper shieldingwater

shielding

paraffin light guide

silica light guides

• not internal activity• too fast for neutrons

RESULT

• not external betas….

• most likely surface implanted outgoing alphas

(a)

Example distribution for DM26 exposed to external low E alphas

alphas gammas

E 30-40 keV

NaI Anomalous Events (1998)NaI Anomalous Events (1998)

Anomaly seen in many crystals: Different manufacture, Different aspect ratio, Different history


Outgoing Surface Alphas?Outgoing Surface Alphas?

• Outgoing events

– Radon implantation?

– Surface contamination?

• Supported by recent surface treatment results

• 222Rn → 218Po + α; • 218Po → 214Pb + α; • 214Pb → 214Bi + β + ν (+ γ); • 214Bi → 214Po + β + ν (+ γ); • 214Po → 210Pb + α; • 210Pb → 210Bi + β + ν (+ γ); • 210Bi → 210Po + β + ν (+ γ); • 210Po → 206Pb + α;

0.0001

0.001

0.01

0.1

1

1 10 100 1000

E keV

10-4

10-3

10-2

10-1

100

10.0 100.0 1000.0 10000.0

Energy (keV)

~0.005ppb U


Identification of the eventsIdentification of the events

• Confirmed with CsI - easier to use unencapsulated than NaI

anomalous events

CsI Test (DM71)

known internal alphas

after surface polish

prior to surface polishCsI


UKDMC spectrum


DM74 limit onfast event spectrum

UKDMC spectrum


DM74 limit onfast event spectrum

anomalous event spectra in NaI

• anomalous events reduced in NaIRESULT

• BUT at least 3-4 months exposure to Rn would be needed! - difficult to explain

• Confirmed with unencapsulated NaI (DM74)

distribution for pre-polished unencapsulated crystal DM74 after 5 mns operation

no fast eventswithin stat

Identification of the eventsIdentification of the events

Are the fast events in any way related to the DAMA result?


NAIAD DesignNAIAD Design

dry nitrogen or mineral oil

• Unencapsulated units for 5-10 kg NaI crystals built

OFHC boxOFHC boxPTFE PTFE

crystal crystal cagecagecrystal


NAIAD Programme - H-AreaNAIAD Programme - H-Area• 35 kg Unencapsulated surface controlled NaI

• 15 kg Encapsulated high light yield NaI

• 10 kg Saclay crystal

NaI unencapsulatedcraneglove

box

to JIF area

H area map

H 1

H 2

Controlroom


NAIAD InstallationNAIAD Installation


NAIAD Preliminary ResultsNAIAD Preliminary Results


Boulby Xenon ProgrammeBoulby Xenon Programme

Xe*

+Xe

Xe2*

Triplet27ns

Singlet3ns

2Xe2Xe

175nm175nm

Excitation

(recombination)

Xe** + Xe

Xe2+

+e-

Xe+

+XeIonisation

Nuclear/Electron Recoil

three discrimination three discrimination techniquestechniques

(1) scintillation pulse shape

(2) ionisation-scintillation

- low field-

(3) ionisation-scintillation

- high field, low threshold -

single phase Xe two phase Xe

liquid liquid

gas

• ICARUS-UCLA • ITEP• Doke group (Japan) • DAMA

World expertise

• UKDMC• Columbia


Boulby Xenon ProgrammeBoulby Xenon Programme

ZEPLIN-Isingle phase

PSD4 kg

ZEPLIN-IIion-scint

two phase Xe30 kg

ZEPLIN-IIIIon-scint

two phase Xehigh field

6 kg

ZEPLIN ZEPLIN arrayarray

under construction

running

demonstrate basic discrimination with PSD - set first limits

basic ionisation-scintillation and high target mass- improve by x10 - UCLA concept

ionisation-scintillation and high field- ultimate discrimination, low threshold -

ZEPLIN-MAXion-scint

two phase Xe1000 kg

new (5 years)

A multinational programme

: Involved in programmes:

UCLA, CERN/Padova, Torino, ITEP, Coimbra, Columbia,

RAL, ICSTM, Sheffield


UKDMC Xenon - ZEPLIN IUKDMC Xenon - ZEPLIN I

Xe*

+Xe

Xe2*

Triplet27ns

Singlet3ns

2Xe2Xe

175nm175nm

Xe** + Xe

Xe2+

+e-

(recombination)

Xe+

+Xe


ZEPLIN I UndergroundZEPLIN I Underground

Pb shielding

Top of ZEPLIN I veto

Boulby stub 2 laboratory

xenon purification

Stable operation demonstrated

Counts vs. time

Xe temp vs. time

room temp vs. time


ZEPLIN Operations at BoulbyZEPLIN Operations at Boulby


ZEPLIN I Laboratory testsZEPLIN I Laboratory tests

• Compton veto (1 ton PXE) found to have ~50 keV threshold

• PMT background events rejected by turret fiducial cuts as expected

137Cs eventsorigin is where all 3 PMTs

record identical signals

turret events rejected by asymmetry cut


• Light collection exceeds design spec of 1 pe/keV

pe/keV

keV0

1

2

Z I data

theory

• Up to 50% difference in neutron and gamma time constants

tau (ns)

500 1000 1500 20000

0

50

0 20 40 60 80 100

keV



ZEPLIN I DiscriminationZEPLIN I Discrimination

QuickTime™ and aGIF decompressor

are needed to see this picture.

QuickTime™ and aGIF decompressor

are needed to see this picture.

Gammasource

Neutronsource

10-20keV 20-30keV

(ns)

(ns)

n


ZEPLIN I - Results ZEPLIN I - Results

85Kr < 10-17 atoms/atom

Predictions for 1 year


• Light Yield– Increases at low energy

• Spatial Uniformity– 137Cs Source

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 500 1000 1500 2000

E (keV)

dE/dx (Emax)

dE/dx (Eav)

Z-I data

Doke parameters:

h = 0.16, C = 0.51

S2 = .0097/.00032

12

3

45

6789

1011

1

1.5

2

2.5

3

3.5

4

0 1 2 3 4 5 6 7 8 9 10 11 12

Spatial Uniformity of ZEPLIN I

Light Yield (keV/p.e.)

Light Yield (keV/p.e.)

Source Position

Under PMTs Side BeamsIn CentreBetween PMTs

Data

Theory



ZEPLIN I - Predicted LimitsZEPLIN I - Predicted Limits


ZEPLIN IIZEPLIN II (UKDMC collaboration with US and Italy)

• Completion due end 2001

cooling ringsPTFE cone

OFHC copper plate

shielding, integration, readout, daq

UKDMC

~30kg Lxe detector

UCLA, Torino, Padova

ionisation-scintillation discrimination


ZEPLIN III ZEPLIN III ionisation-scintillation - low threshold

• 6 kg liquid Xe

• High field (20 kV) operation for better discrimination

31 two-inch photomultipliers

Xe

• Completion due end 2001

(UKDMC collaboration with US and Russia)

1kg test chamberresult


ZEPLIN-MAX A BDMC multinational programme

• Final design by mid 2002• Recoil Discrimination• Construction 2004+

Options being explored:(I) single unit, (II) 4 units, (III) modular(IV) mass + low threshold units

RESULT: (a) attain 0.0001/kg/d, (b) diagnostic array with complementary techniques

3 modules

80 kg target

4 sub- units

shielding

One possibility

ZEPLIN - 1 ton ConceptZEPLIN - 1 ton Concept


PMT Removal for Scale-Up?PMT Removal for Scale-Up?

Liquid Xe

Xe Gas

HeCooling

GEMs

CsI

PTFEReflector

CsI

FieldShapingRings

nucl.rec.

elec.rec.

CsI photocathodes in LXe: E.Aprile, NIMA 338 (1994), 328; NIMA 343 (1994), 121.

GEM phototubes in noble gases:http://gdd.web.cern.ch/GDD/A.Buzulutskov, NIMA, 443 (2000), 164.

• Sheffield test cell


GEM Prototype TargetGEM Prototype Target

High or low field operation

In-house CsI photocathode production

GEMs of Sheffield design from CERN


GEM RigGEM Rig


ZEPLIN locations at BoulbyZEPLIN locations at Boulby

Stub 2

ZEPLIN-I

ZEPLIN-MAX

ZEPLIN-III

ZEPLIN-II

JIF Facility


NaI 1996 limit

ZEPLIN 2002/3

ZEPLIN I/II 2003

ZEPLIN II/III 2004

10-3

10-4

10-5

10-6

10-7

10-8

10-9

10-10

10 100 1000

WIMP-nucleoncross-section, pb

WIMP mass GeV

CDMS II

CRESST II

ZEPLIN-MAX 2006

ZEPLIN predictionsbased on prototype tests and operation of ZEPLIN I

ZEPLIN-XENON Predictions ZEPLIN-XENON Predictions


DIRECTIONAL ProgrammeDIRECTIONAL Programme

• Q: What else can we do to identify a WIMP signal?

• A: We can be more cleverWe can be more clever: : S(A,ES(A,ERR) is in fact also function ) is in fact also function

of recoil direction due to of recoil direction due to earth’s motion through DM earth’s motion through DM halo. => halo. => Search for diurnal modulation to signal in directional detector.

6

600

~30 kms-1

~220 kms-1Sun

Earth

Jun. 2nd

WIMPWIMP

S(A,ES(A,ERR) => S(A,E) => S(A,ERR,,) ~ exp(-((v) ~ exp(-((vEEcoscos - v - vminmin)/v)/v00))22))

D.N. Spergel, Phys. Rev. D 37 (1988) 1353


WIMP “wind” (at Boulby)WIMP “wind” (at Boulby)


Galactic Halo ModelsGalactic Halo Models

UKDMC simulated directional data for standard halo

UKDMC simulated directional data for elongated halo (vz = 170 kms-1)

• If a signal is seen then we can probe galactic halo parameters

--> CDM streaming, infall, halo sphericity, co-rotation


DRIFT Project DRIFT Project

MWPCOccidental

TempleSS vacuum vessel with internal

Cu shielding, access flanges and silica calibration windows

vesselUKDMC

The DRIFT-1 detectorThe DRIFT-1 detector

1.1 m

Multi-Wire Proportional Counter Readout

field cage

Gas and data

UKDMC

(UKDMC collaboration with US)


DRIFT ConceptDRIFT Concept

• New technique - Directional Recoil Identification From Tracks (DRIFT) uses low pressure (40 Torr) CS2 gas.

• CS2 soaks up charge and carries it to read-out plane as CS2

-.

• High mass of ions limits transverse diffusion to < 1mm over 1m drift distance!

• No need for magnet.

• Discriminate with track-length.

CSCS22 gas gas

EE

CSCS22--

ions driftions drift

SS

MWPC


DRIFT ConceptDRIFT Concept

Negative Ion Drift

An old idea

E.W McDaniels et al., RSI 28 (1957) 864H.R. Crane et al., RSI 32 (1961) 953

E

CS2-

ions drift

Xe

WIMP

anode MWPC readout

cathode

• Longitudinal and transverse diffusion of ions is much less than for electrons

--> typically < 1mm per m

• No need for magnet

• Readout by conventional MWPC

• Use CS2 + Ar, Xe at 10-80 Torr

• Electrons from ionised tracks reversibly attach to CS2 and drift to anode


• DRIFT: low pressure gaseous TPC– Recoil direction correlation– CS2 minimises diffusion

• 1 foot cube detector @6keV– 99.9% gamma rejection– 95% alpha rejection (from wires)

• DRIFT 1m3 Module under construction– 200m wire chamber 2cm pitch– 20m MWPC readout 2mm pitch

• CS2+Xe,Ar at 10-80 Torr

DRIFT DesignDRIFT Design

gammas

recoil discrimination

C recoils

S recoils

gammas

recoil discrimination gammas

alphas

S recoil region (>90%)

alpha discrimination


DRIFT-1 Integration at SheffieldDRIFT-1 Integration at Sheffield

vessel


1 m

DRIFT-1 DetectorDRIFT-1 Detector


DRIFT-1 Integration at SheffieldDRIFT-1 Integration at Sheffield


DRIFT-1 Predicted limitsDRIFT-1 Predicted limits

Full background audit for DRIFT-1 completed (tests and MCs)

a background of ~ 5 counts per year per m3 is feasible

• DRIFT-1 can yield a limit below DAMA

CONCLUSION

• DRIFT-1 could just detect a directional signal at 10-5 pb

3 m3yr

30 WIMP events

80 WIMP events


DRIFT 1 site

Installation Aug 01

Part of 1500 m2 new facility at Boulby - 3000 mwe depth

DRIFT 1 - Installation Aug 01 DRIFT 1 - Installation Aug 01


DRIFT module - low cost materials

15 cm removable, low costPb shielding

CS2 manifold and storage

3 m

DRIFT-10, towards 1 ton a BDMC - multinational programme

--> need 1 ton to get enough counts at minimum SUSY

DRIFT-1

DRIFT-10

1 ton

CS2

Xe

DRIFT-MAX - 1 Ton gasDRIFT-MAX - 1 Ton gas


SummarySummary

• DAMA NaI annual modulation as objective

WIMP or fluctuating low energy noise?

• UKDMC ‘anomalous events’ as surface alphas?

Seen in Saclay (DAMA) crystal

• CDMS recoil limit (almost) excludes DAMA

Subtraction of neutron signal

• Several detectors becoming sensitive at 10-6 pb

• Many more direct searches underway to reach ≈10-8pb

• Indirect searches reaching sensitivities to exclude models

WIMPs (10-9(or -12) pb < scp < 10-6 pb, 50 GeV < m <600 GeV)

july 2001 neil spooner ukdm programme update on nai, zeplin and drift neil spooner, university of...

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