the daya bay antineutrino detectors - yale...

Daya Bay CD-2/3a Review, January 8, 2008 Karsten Heeger, Univ. Wisconsin 1

The Daya Bay Antineutrino Detectors

Karsten HeegerUniversity of WisconsinUS Antineutrino Detector System Manager

BNL CD-2/3a Review January 8, 2008


1. Scope of Task

2. Requirements & Design Overview

3. Main AD Subsystems - Detector Tank (PRC)- Acrylic Vessels (US/Taiwan)- Lifting (PRC)- Liquid Scintillator (PRC, US, Russia)- PMT AD Mechanical Systems (US)- AD Instrumentation (PRC, US)- AD Filling and Target Mass (US)- Assembly&Installation (PRC, US)

4. US cost, schedule, summary

Outline

Daya Bay CD-2/3a Review, January 8, 2008 Karsten Heeger, Univ. Wisconsin

Antineutrino Detector Task - Overview & Scope

3

design & fabrication of all detector elements and instrumentation



4


assembly



5


assembly

scintillator preparation

LS Hall (Hall 5)

filling & target mass measurement


Antineutrino Detector Requirements

4 ANTINEUTRINO DETECTOR 83

4 Antineutrino Detector2922

The measurement of sin2 2!13 to <0.01 is an experimental challenge. A value of 0.01 for sin2 2!132923

yields a tiny oscillation effect. This corresponds to a small difference in the number of antineutrino events2924

observed at the far site from the expectation based on the number of events detected at the near site after2925

correcting for the distance under the assumption of no oscillation. To observe such a small change, the2926

detector must be carefully designed following the guidelines discussed in Chapter 1, and possible systematic2927

uncertainties discussed in Chapter 2. To make this measurement the antineutrino detector must meet the2928

physics performance requirements summarized in Table 4.1.

Item Requirement Justification

Target mass at far site !80 T Achieve sensitivity goal in three years over al-

lowed !m231 range

Precision on target mass "0.3% Meet detector systematic uncertainty baseline

per module

Energy resolution "15%/#

E Assure accurate calibration to achieve re-

quired uncertainty in energy-threshold cuts

(dominated by energy threshold cut)

Detector efficiency error <0.2% Should be small compared to target mass un-

certainty

Positron energy threshold "1 MeV Fully efficient for positrons of all energies

Radioactivity singles rate "100 Hz Limit accidental background to less than

other backgrounds and keep data rate man-

ageable

Table 4.1. Physical requirements of the antineutrino detector.

2929

The technical requirements of the individual subsystems for the antineutrino detector are summarized2930

in similar format at the beginning of each of the following sections.2931

In addition, the following considerations enter the design of the antineutrino detector:2932

1. The detector modules should be homogeneous to minimize edge effects.2933

2. It is important to precisely know the target mass and composition. The number of protons in the target2934

liquid scintillator should be well known, implying that the scintillator mass and the proton to carbon2935

ratio should be precisely determined. The target scintillator should come from the same batch for2936

each pair of near-far detector modules or for all detectors, and the mixing procedure should be well2937

controlled to ensure that the composition of each antineutrino target is the same.2938

3. The detector module should not be too large; otherwise, it would be difficult to move from one detector2939

site to another for cross check to reduce systematic effects. In addition, beyond a certain size, the rate2940

of cosmic-ray muons passing through the detector module is too high to be able to measure the 9Li2941

background.2942

4.1 Detector Geometry and Dimensions2943

Several previous neutrino experiments have designed spherical or ellipsoidal detectors to insure uniform2944

energy response in the entire volume. This type of detector vessel is expensive and requires many PMTs for2945

4" coverage. Two types of alternative detector geometries have been investigated: cubic and cylindrical.2946

Both are attractive from the viewpoint of construction. Monte Carlo simulation shows that a cylindrical2947

Physics Design Criteria3-zone detector with the following general characteristics

6

key feature of experiment: > “identical detectors” at near and far sites

detectors will never be identical but we can control relative target mass & composition to < 0.30% relative antineutrino detection efficiency to < 0.25% between pairs of detectors

≤50 Hz


Antineutrino Detector Requirements


4 Antineutrino Detector2922

The measurement of sin2 2!13 to <0.01 is an experimental challenge. A value of 0.01 for sin2 2!132923

yields a tiny oscillation effect. This corresponds to a small difference in the number of antineutrino events2924

observed at the far site from the expectation based on the number of events detected at the near site after2925

correcting for the distance under the assumption of no oscillation. To observe such a small change, the2926

detector must be carefully designed following the guidelines discussed in Chapter 1, and possible systematic2927

uncertainties discussed in Chapter 2. To make this measurement the antineutrino detector must meet the2928

physics performance requirements summarized in Table 4.1.

Item Requirement Justification

Target mass at far site !80 T Achieve sensitivity goal in three years over al-

lowed !m231 range

Precision on target mass "0.3% Meet detector systematic uncertainty baseline

per module

Energy resolution "15%/#

E Assure accurate calibration to achieve re-

quired uncertainty in energy-threshold cuts

(dominated by energy threshold cut)

Detector efficiency error <0.2% Should be small compared to target mass un-

certainty

Positron energy threshold "1 MeV Fully efficient for positrons of all energies

Radioactivity singles rate "100 Hz Limit accidental background to less than

other backgrounds and keep data rate man-

ageable

Table 4.1. Physical requirements of the antineutrino detector.

2929

The technical requirements of the individual subsystems for the antineutrino detector are summarized2930

in similar format at the beginning of each of the following sections.2931

In addition, the following considerations enter the design of the antineutrino detector:2932

1. The detector modules should be homogeneous to minimize edge effects.2933

2. It is important to precisely know the target mass and composition. The number of protons in the target2934

liquid scintillator should be well known, implying that the scintillator mass and the proton to carbon2935

ratio should be precisely determined. The target scintillator should come from the same batch for2936

each pair of near-far detector modules or for all detectors, and the mixing procedure should be well2937

controlled to ensure that the composition of each antineutrino target is the same.2938

3. The detector module should not be too large; otherwise, it would be difficult to move from one detector2939

site to another for cross check to reduce systematic effects. In addition, beyond a certain size, the rate2940

of cosmic-ray muons passing through the detector module is too high to be able to measure the 9Li2941

background.2942

4.1 Detector Geometry and Dimensions2943

Several previous neutrino experiments have designed spherical or ellipsoidal detectors to insure uniform2944

energy response in the entire volume. This type of detector vessel is expensive and requires many PMTs for2945

4" coverage. Two types of alternative detector geometries have been investigated: cubic and cylindrical.2946

Both are attractive from the viewpoint of construction. Monte Carlo simulation shows that a cylindrical2947

Physics Design Criteria

7

key feature of experiment: > “identical detectors” at near and far sites

detectors will never be identical but we can control relative target mass & composition to < 0.30% relative antineutrino detection efficiency to < 0.25% between pairs of detectors

> vessel size

> reflector

> radiopurity> cleanliness

> identical vessels > minimum use of acrylic and other structures

> filling and target mass system

Requirements -> Design Features


Antineutrino Detector - Simulations


)2(m2R

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Photoelectron

0

50

100

150

200

250

300

350

400

Fig. 4.7. Antineutrino detector response (in number of photoelectrons) as a function of

the square of the radial location of a 1 MeV electron energy deposit. The mineral oil

volume has been removed and the PMTs are positioned directly outside the γ-catchervolume. The vertical blue line is 15 cm from the PMT surface and indicates the need

for at least 15 cm of buffer between the PMT surface and the region of active energy

deposit in order to maintain uniform detector response.

Distance of PMT Front Face to Gamma Catcher

Isotope Concentration 20 cm 25 cm 30 cm 40 cm

(Hz) (Hz) (Hz) (Hz)238U 40 ppb 2.2 1.6 1.1 0.6232Th 40 ppb 1.0 0.7 0.6 0.340K 25 ppb 4.5 3.2 2.2 1.3

Total 7.7 5.5 3.9 2.2

Table 4.2. Radiation from the PMT glass detected in the Gd-scintillator (in Hz) as a

function of the oil-buffer thickness (in cm). An oil buffer of more than 45 cm thickness

will provide 20 cm of shielding against radiation from the PMT glass.

reflective panels can be put close to the top and bottom of the γ-catcher vessel to enlarge the photocathode3043

coverage. As shown in Fig. 4.7, the photoelectron yield increases as the light source approaches the wall of3044

the detector. However, the detector response will be uniform in the direction of the axis of the cylinder if a3045

reflector with∼100% specular reflectivity is used.While specular and diffuse reflection have no difference in3046

the total photoelectron yield, specular reflection is preferred because it will simplify vertex fitting algorithms3047

(Sec. 4.2).3048

Using a reflector can also greatly simplify the mechanical design and assembly of the detector. To3049


Gamma catcher thickness (cm)0 10 20 30 40 50 60 70 80 90

Eff

icie

ncy

(%

)

70

75

80

85

90

95

100

Fig. 4.6. The neutron detection efficiency as a function of the thickness of the !-

catcher. The neutron energy cut is set at 6 MeV. The thickness of the ! catcher of

the Daya Bay experiment will be 42.5 cm.

the vertex selection uncertainty, the resulting efficiency values are consistent with simulation. After a com-3018

prehensive study of detector size, detection efficiency, and experimental uncertainties, we choose 42.5 cm3019

as the thickness of the !-catcher.3020

4.1.5 Oil Buffer3021

The outermost zone of the detector module is composed of mineral oil. The PMTs will be mounted3022

in the mineral oil next to the stainless steel vessel wall, facing radially inward. This mineral oil layer is3023

optically transparent and emits very little scintillation light. There are two primary purposes for this layer:3024

1) to attenuate radiation from the PMT glass, steel tank and other sources outside of the module; and 2)3025

to ensure that PMTs are sufficiently far from the liquid scintillator so that the light yield is quite uniform.3026

Simulations indicate that the location of light emission should be at least 15 cm away from the PMT surface,3027

as indicated in Fig. 4.7.3028

The oil buffer is also used to attenuate radiation from the PMT glass into the fiducial volume. Simulation3029

shows that with 20 cm of oil buffer between the PMT glass and the liquid scintillator, the radiation from the3030

PMT glass detected in the liquid scintillator is 7.7 Hz, as summarized in Table 4.2.3031

The welded stainless steel in KamLAND has an average radioactivity of 3 ppb Th, 2 ppb U, 0.2 ppb3032

K, and 15 mBq/kg Co. Assuming the same radioactivity levels for the vessel of the Daya Bay antineutrino3033

detector module, the corresponding rate from the stainless steel tank can be found in Table 4.3. The total3034

rate is !20 Hz.3035

The natural radioactivity of rock, buffer water, mineral oil, dust, radon and krypton in air play a minor3036

role, as described in Section 2.3.4. The total ! rate is <50 Hz. The oil buffer will be sufficient to suppress3037

the ! rate and the subsequent uncorrelated backgrounds to an acceptable level.3038

The dimensions of the antineutrino detector modules are shown in Table 4.4.3039

4.1.6 Optical Reflective Panels3040

Optical reflective panels will be put at the top and bottom of the cylinder. PMT numbers can be reduced3041

to nearly one half comparing to the 4" PMT installation, while keeping the same photocathode coverage. The3042

Detector Design and Geant4 Simulationsgamma catcher thickness

MO buffer thickness Gd-LS(20 tons)

-> for details see the TDR

< 5m (tunnel limitations)

> 15cm buffer between PMT and OAV

= 42.5cm gamma catcher

8

Dimensions of 3-Zone Detector

LS

MO


Antineutrino Detector - OverviewA Short Guide to the AD

• PMT cable feedthroughs and dry boxes

• calibration boxes• gas and electrical distribution

boxes• overflow tanks• calibration pipes• auxiliary ports for monitoring

and filling• PMTs• PMT ladders and mounts• inner 3-m acrylic vessel• acrylic support ribs • outer 4-m acrylic vessel• stainless steel vessel

9


Antineutrino Detector - Scope&Responsibilities

Taiwan - blue- 3m acrylic vessel with bonded lid US - orange - 4m acrylic vessel with removable lid - acrylic overflow tanks for Gd-LS and LS- calibration pipes + bellows- overflow tank instrumentation- PMT mounts and ladders- PMTs, bases, and testing- PMT cables and feedthroughs- Gd-LS and LS

PRC - grey - stainless steel vessel (SSV)- SSV lid - reflector- mineral oil (MO) overflow tank- overflow tank instrumentation- Gd-LS, LS, and MO

10

A Broad Overview (details in MOU list of deliverables)


Organization, Management, WBS

1.1 Detector Tank (Zhuang, IHEP)

1.2 Acrylic Vessels (Heeger, UW / Hsiung, NTU)

1.3 Liquid Scintillator (Yeh, BNL / Zhang, IHEP)

1.4 PMT AD Mechanical Systems (Virostek, LBNL / Cherwinka, UW)

1.5 System for Measuring Physical Detector Properties (Wise, UW)

1.6 Lifting (Zhuang, IHEP)

1.7 Materials & Compatibility Testing (Yeh, BNL / Chen, IHEP)

1.8 Other AD Systems (Wise, UW)

1.9 AD Integration (Heeger, UW / Cao, IHEP)

1.10 AD Assembly & Installation (Cherwinka, UW / Cao, IHEP)

1.11 Subsystem Management (Heeger, UW / Cao, IHEP)

11

L3 ManagementAntineutrino Detector Co-Managers Jun Cao, IHEP - China

Karsten Heeger, UW - USA

L3s combination of scientists and engineers as appropriate for subsystems


Acrylic Vessel System (WBS 1.1.2)

3m vessel 4m vessel

lids

ribs and support structure

calibration pipe connectionsPair of Nested Vessels

FEA analysis of worst case scenario:uneven filling

independent FEA by UW-PSL and Reynolds Polymer Technology → stress still below

long-term limit12


AV Prototype - 4m Vessel at Reynolds (WBS 1.1.2)

Status- Reynolds built 4m vessel prototype vessel - design of 4m prototype essentially same as fabrication vessel- UW team surveyed vessel, meets specifications.- AV FDR in Dec 07. - will finalize fabrication drawings in Jan 2008, almost ready for procurement -> long lead item

before bonding AV bottom 13


Other Acrylic Vessel Work (WBS 1.1.2)

December 6, 2007 Bryce LittlejohnUniv. Wisconsin - Madison

Simulation Setup

• Use G4dybApp.exe to simulate AD with and without pads

• Viton material not defined; used stainless steel:

• relatively non-reflective

• very short path length in material

• serves as a good worse-case estimate

• Checked detector response to:

• 1 MeV electrons: ~800k events

• 8 MeV electrons: ~100k events

• Q: Why electrons? A: Quicker simulation!

• All Events generated in GDLS

3

3m Vessel Prototype at Nakano, Taiwan

Geant4 Simulations of AV- optical impact of support structure- vessel shifts and variations

Status of AV Simulations- verified all design features in simulations

> vessel thickness> ribs and support structure> variations between vessels and detectors

example:- impact of vessel support pads

example:- impact of vessel shifts

!!

"

!!"#$%&'()*&+(%",()-(.#('/01),.)2&%"*/&'".,)

3"3(+)./)+$33./')+'/$2'$/(+4

!!5"6')",,(/)&2/0%"2)7(++(%)85"%()%(&7",-).$'(/)

&2/0%"2)7(++(%)2(,'(/(9)",)9('(2'./

!):.#3&/()+'&,9&/9);<)#('/"2+)&')9"66(/(,')

%.2&'".,+1

"=66"2"(,20

"=,(/-0)!2&%()>,2(/'&",'0

?;@)!5"6')!('$3

-> see TDR appendix for details 14


Gd Liquid Scintillator Production (WBS 1.1.3)

15

Requirements

high-light yield

3-Phase Process and Production plan1. Procurement of chemical and purification equipment -> long lead item2. Mass production of Gd-solid (~1 ton): organo-gadolinium solid will be synthesized at IHEP,

transported to Daya Bay and dissolved in LS Hall underground3. Dissolution and mixing of 0.1% Gd-LS (~200 tons): 200 tons of LS (LAB + fluors) will be

prepared first, followed by 200 tons of Gd-LS (Gd-LAB + fluors) production

Progress Since CD-1• In-lab R&D for Gd-LS synthesis finished in

04/2007.• Aging test (40 C) has been running since

07/2007.• Baseline plan of final Gd-LS production

selected in 08/2007.• Scope distribution between US and China

finished in 09/2007.

Stability Tests of Gd-LS(UV absorption values at 430 nm)

days

abso

rptio

n va

lue


Gd Liquid Scintillator Production (WBS 1.1.3)

16

Solid Production Process

Status• PDR of Gd-LS synthesis and

handling in Oct 07• FDR of Gd-LS production in

Mar 08

LS Mixing and Preparation Undergroundin LS Filling Hall (Hall 5)

Gd-LS mixing

212t LS

185t Gd-LS

176t MO AD


PMT Mounts and Ladders (WBS 1.1.4)

17

PMT Mounts• A pair of prototype mounts is currently being fabricated• Cost estimate close to that of MiniBoone• Material for interface pads between mounts and PMT’s still must be

identified and tested for MO compatibility

PMT Ladders• Ladder has been integrated with the SSV final design and other

internal AD components• Ladder is installed at a slight angle to clear SSV flange and to allow

adequate clearance from outer AV after installation• Ladder design allows for placement of an optical shield


PMT Cable Feedthroughs and Drybox (WBS 1.1.4)

to electronics

to PMTs

Objective- PMT cables carrying the signals from the PMTs must pass through the walls of tank - convenient to have electrical break in the cable to allow for easier transportation and testing of the ladder as well as movement of the ADs. - dry box houses this electrical junction.

Design Features- design also facilitates testing and provides possibility for corrective action if a leak develops. - allows good leak checking of all seals- cables paths adjusted to same length- electrical cables connected with flange held open

Status - design essentially final- prototype under construction- PDR in Dec 07- FDR in March 2008

18


MO overflow 1

MO overflow 2

Calib. box 10

Calib. box 12

Calib. box 11

gas distribution boxelectrical interface box

Central overflow

MO attenuation length monitoring device MO fill

LED wiring

MO fill monitor

Antineutrino Detector Lid


central calibration tube off-center calibration tubes

GDLS overflow

LS overflow

calibration boxes(see calibration talk)

concentric Teflon bellows

Overflow Tanks & Calibration Tubes (WBS 1.1.5)

gate valves

expected liquid level


AD Target Monitoring and Instrumentation (WBS 1.1.5)

MO level sensors, 2 types(pressure, ultrasound)

LS visual level monitor(CCD)

Gd-LS visual level monitor(CCD)s

LS level sensors, 2 types(pressure, ultrasound)

Gd-LS level sensors, 2 types(pressure, ultrasound)

Karsten Heeger, Univ. Wisconsin December 12, 2007

Ultrasonic Thickness Gauge

- started some R&D on measuring liquid heights with ultrasonic

> need to immerse transducer in liquid. cannot measure through air or acrylic.

> watertight transducers are available or can be obtained through potting electrical

connections

> mm accuracy seems attainable. some systematic issues to be studied

(reflections from wall etc.)

ultrasonic gauge

pressure sensor

CCD camera to monitor fill level

21


Assembly of Antineutrino Detector (WBS 1.1.10) Surface Assembly Building

- assembly line for pairs of detectors (one near + one far)

- pits for vessel+tank assembly in SAB

- modular PMT structure, prefabricated, tested


AD Assembly Sequence in SAB (WBS 1.1.10)

4m AV

bottom reflector

3m AV

top reflector SSV lid

4m AV lid

work platform

lifting fixture

23

PMT installation


AD Assembly Sequence in SAB (WBS 1.1.10)

4m AV

bottom reflector

3m AV

top reflector SSV lid

4m AV lid

work platform

lifting fixture

Nov 10, 2008

Jan 23, 2009

Feb 27, 2009 Apr 25, 2009

dates for AD #1,2 assembly

Dec 17, 2008

- AD fully assembled but not filled

24


Moving the Detector Underground

1. Installation and Deployment - moving down <10% grade when empty (20 t) - moving on 0.5% tunnel grade when full (100 t) - lifting full AD into water pool (100t)2. Detector Swapping (optional)

transporter

lifting

< 10%

< 0.5%

< 0.5%

Note: transporter part of WBS 1.7

LS Hall


Filling the Detector & Measuring the Target Mass (WBS 1.1.5)

Gd-LS

LSMO

I. Target: 0.1% Gd-loaded liquid scintillator (Gd-LS)II. γ-catcher: liquid scintillator (LS)III. Buffer shielding: mineral oil (MO)

Three Detector Liquids:

Filling Requirements- all detector volumes have to be filled simultaneously to minimize stress on AVs- detectors are filled “in pairs” from common storage tanks, i.e. in sequence within a short period of time (~ 1-2 weeks)- filling system must be compatible with Gd-LS, LS, and MO

Target Mass Measurement Requirements- Gd-LS target mass measured to < 0.1%- LS and MO mass measured to < 0.5%

- redundant measurement methods: > load cells, > Coriolis mass flow meters, > electromagnetic flow meters

conceptual drawing of detector filling with equal fill levels


load cell equipped Gd-LS ISO weighing tank with < 20 t capacity

flow meters

diaphragm pump

AD Filling System & Target Mass Measurement (WBS 1.1.5)

calibration boxes removed during AD filling

Sartorius load cell accuracy < 0.015% pulse

damper

Gd-LS

purge/waste container

Gd-LS

MO

LS


load cell equipped Gd-LS ISO weighing tank

flow meters

diaphragm pump




damper

Gd-LS

LS

MO


Gd-LS

MO

LS


load cell equipped Gd-LS ISO weighing tank

flow meters

diaphragm pump




damper

Status- load cells tested, accuracy verified- ISO tank specifications drafted, ready for procurement, -> long lead item- PDR of system in Oct 07- FDR of system in March 08

Gd-LS

LS

MO


Gd-LS

MO

LS


Antineutrino Detector Design Status & Reviews

• Jul/Aug 2007 – AD PDR

• Oct 2007 – Steel Vessel FDR– LS Hall and Gd-LS Synthesis PDR

• Dec 2007 – PMT FDR– AV and SSV Lid FDR – PMT AD Mechanical Systems PDR

• Mar/Apr 2008– Gd-LS production and LS Hall FDR– PMT AD Mechanical Systems FDR

30

PDR = prelim design reviewFDR = final design review

> completed FDRs in green


Antineutrino Detector Design Status & Reviews

• Jul/Aug 2007 – AD PDR

• Oct 2007 – Steel Vessel FDR– LS Hall and Gd-LS Synthesis PDR

• Dec 2007 – PMT FDR– AV and SSV Lid FDR – PMT AD Mechanical Systems PDR

• Mar/Apr 2008– Gd-LS production and LS Hall FDR– PMT AD Mechanical Systems FDR

31

PDR = prelim design reviewFDR = final design review

> completed FDRs in green

→ long-lead item: PMTs→ long-lead item: 4m AVs

→ long-lead item: Gd-LS chemicals→ long-lead item: ISO tank


AD Baseline Cost and Contingency

32

20%

Antineutrino Detector WBS & Cost (US scope)

o 4-m acrylic vessels + lids + overflow tanks o target mass measurement and filling system

PRC scope

PRC scope


Antineutrino Detector Selected Risks & Further R&D

Risk, R&D, and Development Items

• Gd-LS Production (risk)– time for large-scale, batch production– long-term degradation of Gd-LS

• Materials Compatibility (risk, R&D)– Gd-LS, LS, MO degradation due materials

incompatibility– materials compatibility study and archive of all detector

materials

• Fabrication QA (R&D)– finalizing consistent QA plan for all AD subsystems

between countries and continents

• AD Assembly & Installation (R&D)

– develop and build special tooling for AD assembly and installation. conceptual designs exist.

33

→ ongoing R&D

→ full-scale batch test in spring 2008

→ ongoing program

→ ongoing effort, visit to fabrication facilities, sharing of samples

→ ongoing effort with PDR and FDR planned in 2008

→ see risk registry for details


Schedule and Milestones

34

• CD-2 review• start fabrication of acrylic vessels #1,2• complete chemical procurement for Gd-LS and LS• PMT mounts and ladders at Daya Bay • acrylic vessels #1, 2 delivered to Daya Bay• mixing of LS and Gd-LS begins in LS Hall• target mass system installed in LS Hall• LS Hall ready for AD filling • complete assembly of AD #1,2• complete filling of AD #1,2• Daya Bay near site ready for data taking• complete assembly of AD #3,4• complete assembly of AD #5,6• complete assembly of AD #7,8• Ling Ao near site ready for data taking• Daya Bay far site ready for data taking

Jan 08Apr 08Jul 08Dec 08Dec 08Jan 09May 09May 09May 09Jul 09Nov 09Sep 09Dec 09Jun 10Jul 10Dec 10


Summary

• Antineutrino Detector System is in an advanced design stage, PDRs for all subsystems and FDRs for major detector elements.

• Critical and novel detector elements have been prototyped or prototypes are being evaluated (AVs, PMT feedthroughs, precisions load cells, etc.)

• Simulation for all principal detector elements completed. • Cost estimates for major subsystems based on full-size

prototype work (e.g. AVs)• Antineutrino Detector system expected to meet or exceed

(e.g target mass) design requirements. • Construction of subsystem elements can begin in Spring

2008 and will meet international project schedule.

35

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