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ZEPLIN II Status & ZEPLIN IV
Muzaffer Atac
David Cline
Youngho Seo
Franco Sergiampietri
Hanguo Wang
ULCA
ZonEd Proportional scintillation in LIquid Noble gases
ZEPLIN Collaboration -- UKDM-UCLA-Italy
Acknowledgement:Roy PreeceNigel SmithPeter SmithRAL, UK Pio Picchi
Frascati
July 7, 2001 H. WANG, ZEPLIN II, UCLA 2
ZEPLIN Construction Status
Engineering design completed (Central detector),
Materials for key parts already arrived, And machining already start at UCLA, All other material orders are placed, Copper cast will be ordered after thermal,
mechanical, vacuum and pressure evaluation,
First assembly at UCLA this fall, The overall design is very cost effective.
July 7, 2001 H. WANG, ZEPLIN II, UCLA 3
Xenon discriminating detector
•Available in Large Quantities•High Atomic Number (ZXe=54, WIMP-Nucleon A2) •High Density (~ 3g/cm3 liquid)•High Light (175nm) & Ionization Yield•Can be Highly Purified long light attenuation length (~m) long free electron life time (~5ms)•Gamma & Recoil signal Discrimination•Easy to Scale up to Large Volume•No Long Lived Radioactive Isotopes
July 7, 2001 H. WANG, ZEPLIN II, UCLA 4
Liquid Xenon Scintillation Mechanism
•Very good for pulse shape discrimination due to decay profile difference between nuclear recoil & electron recoil•Very good background rejection due to (Ei/Es)M.I.P.>> (Ei/Es)H.I.P.
July 7, 2001 H. WANG, ZEPLIN II, UCLA 5
Principle Tests Setup
1. Ceramic2. Quartz Window3. Stainless steel Cathode4. Source5. Grounded Grid 6. Anode wire frame
NIM A327 (1993) 203
July 7, 2001 H. WANG, ZEPLIN II, UCLA 6
Primary & Secondary Scintillation vs field
Alpha
Gamma
July 7, 2001 H. WANG, ZEPLIN II, UCLA 7
Xenon Two-Phase Prototype Detector
Primary-Scintillation
Electro-luminescence
recoil
July 7, 2001 H. WANG, ZEPLIN II, UCLA 8
Proportional scintillation vs field
Single phase 99.8% rejection
P S
P
S
July 7, 2001 H. WANG, ZEPLIN II, UCLA 9
Background and recoil separation
200keV1000Heavy Ionization(recoil signal)
Minimum Ionization(backgrounds)
Primary Scintillation
Seco
nd
ar y
Sci
nti
l lati
on
Gamma
recoil
July 7, 2001 H. WANG, ZEPLIN II, UCLA 10
Electron drift velocity in LXe
July 7, 2001 H. WANG, ZEPLIN II, UCLA 11
Details of ZEPLIN II
1. Fiducially volume: 40kg.2. Two wire-frames provide both:
• electron extraction field• Electro-luminescence
field3. Pure copper rings shapes the
electron drift-field in liquid.4. -HV applies to bottom plate to
have high field for ionization electron extraction in liquid.
5. Extreme care taken to avoid HV discharge in gas.
6. Seven custom made PMTs for use in liquid xenon temperature
7. Custom made surface-mount resister-dividers for PMTs for use in gas xenon.
8. Dead region less than 0.1%
July 7, 2001 H. WANG, ZEPLIN II, UCLA 12
Construction in Progress
Field shaping rings will be made out of pure Oxygen free copper
The largest PTFE piece is being machined at the UCLA Physics department machine shop
July 7, 2001 H. WANG, ZEPLIN II, UCLA 13
ZEPLIN II system Setup
Lead Shielding
The central detector
Active Veto
Liquid xenon target
Copper cast vacuum and target vessel
July 7, 2001 H. WANG, ZEPLIN II, UCLA 14
One Ton Scale-up based on the ZEPLIN II Design
•Total mass: one ton,
•5 inch PMTs: 80
•Copper cast vessels,
•Signal amplification using CsI internal photo-cathode,
Signal cable, HV cable,Cooling system,Vacuum, andXenon port
July 7, 2001 H. WANG, ZEPLIN II, UCLA 15
ANSYS finite element analysis for field configurations
July 7, 2001 H. WANG, ZEPLIN II, UCLA 16
CsI test results
H-2sV-20mV
(E. Aprile et al., NIM A343 1994, 129-134)
July 7, 2001 H. WANG, ZEPLIN II, UCLA 17
Expected limit for ZEPLIN II
and ZEPLIN IV
July 7, 2001 H. WANG, ZEPLIN II, UCLA 18
Conclusion•High A number makes it match better the high mass WIMPs and yields high event rates. ( 2)
•High scintillation and ionization yield makes it easy to achieve the following:
•Low energy threshold: less than 10keV (true recoil energy).
•Gamma and nuclear recoil discrimination by a factor of at least 1000.
•High liquid temperature and high density allows compact design and easy engineering solutions.
•Future development on CsI internal photo-cathode may reduce the background further (not discussed here).
• the 40kg ZEPLIN II detector running for a year may cover completely the DAMA region.
•The ZEPLIN IV future one ton detector will cover most of the SUSY region