JUNO Veto OverallJUNO Veto Overall

Changgen YangNov. 4, 2013

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Top Tracker Support structure of top tracker Ultrapure water system Tyvek film PMT support frame Pool lining and sealing Pool thermal isolation Coil for magnetic field shielding

Tasks and Preliminary design of VetoTasks and Preliminary design of Veto

StatusStatus Civil construction IHEP （ under optimization ） Top Tracker

RPC(glass/bakelite) Tsinghua/PKU/NCEPU/USTC/XJTU LS+fibre J. Xu PS+fibre （ OPERA ）

Support Structure of top tracker Civil designer + P. Zhang

Ultrapure water system J.C. Liu Water attenuation length C. Shan Tyvek film √ PMT support frameNot yet start Pool lining and sealing Civil designer + P. Zhang Pool thermal isolation F.P. Ning Earth magnetic shielding G.Q. Zhang + JINR + H.Q. Lu MC S.G. Wang+H.Q. Lu

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Civil Overall

实验站工程主要包括地下实验大厅及其附属洞室、进入实验厅的一条斜井和一条竖井，及相关地面建筑物。

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Civil entrance

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实验厅设计

拱顶方案平面图7

斜井底部装卸方案

Two 16t cranes for unloading

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地下安装间装卸方案

20t crane

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Top TrackerTop Tracker

Top tracker can not cover the full solid angle of central detector, so the efficiency of top tracker is not critical

The dead time of central detector might be 30%~50% if cylindrical cut were made with respect to the cosmic muons. Therefore the main function of top tracker is used for background studies, not directly veto of cosmic muon

The muon detection efficiency is depend on the water Cerenkov detector.

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Assumptions Overburden is 700m

E ~ 211 GeV, R~ 3.8 Hz

Single rates from LS and PMT are 5Hz, respectively

Good muon tracking Similar muon efficiency as DYB

Daya Bay Daya Bay II Mass (ton) 20 20,000 E (GeV) ~57 ~211

R (Hz) ~21(0.04) ~3.8(0.004)

Rsingles (Hz) ~50 ~40

JUNO has higher 9Li/8He background than Daya Bay experiment， therefore we need more precise 9Li/8He background studies

How many muon we need to measure? What should be the position precision measurement? ~0.1m in

central detector?

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B/S @ DYB EH1

B/S @JUNO

Techniques used for JUNO detector

Accidentals ~1.4% ~10% Low PMT radioactivity; LS purification; prompt-delayed distance cut

Fast neutron ~0.1% ~0.4% High muon detection efficiency (similar as DYB)

9Li/8He ~0.4% ~0.8% Muon tracking;If good track, distance to muon track cut (<5m) and veto 2s; If shower muon, full volume veto 2s

Top TrackerTop Tracker

Top TrackerTop Tracker PS+fibre （ OPERA ）

Size of each layer 6.7*6.7m^2 ， each with XY readout ， two sub-layer. Total 62 layers.

Each sub-layer with 256 strips, the size of each strip is 6.86m (length)*10.6mm (thickness)*26.3mm (width)

Each module composed of 64 strips, readout with H7546 PMT.

Total 31744 strips. Each strips read with WLS from two ends. Total electronics channels 63488.

This will save huge mount of time and cost. RPC/LS+Fibre R&D

The R&D of RPC/LS + fibre will continue, the 1:1 prototype detector will be tested underground with ambient gamma in Daya Bay

Total area of top tracker can be smaller than the design before 12

Installtion flow chart Installtion flow chart

钢索支撑密封布

导轨（依附在钢结构平台上）支撑密封布 13

Design of top tracker support frameDesign of top tracker support frame Civil designer: Support structure

as crane frame Same designer, cost effective ,

simple Inst. of transportation

The design of frame probably different, cost more probably, more intersections

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Ultrapure waterUltrapure water Depend on the design of central detector: water

volume 20~60kt, 20 days/one circulation ， 60~200t/hr

Design of water purification room underway; Water system parts before RO, include RO, will be

put on the surface. Parts after RO will be put underground, this will reduce the draining of water from underground to the surface.

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Pool liningPool lining 3~5mm 314 stainless steel as the

moldboard for concrete pouring.

The design of water sealing is underway, not very heavy, rusting protect, easy for open and cover

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Water sealingWater sealing

Pool thermal isolationPool thermal isolation The temperature control in Daya Bay

experiment Calculation by F. P. Ning Calculation by Inst. of Kunming Survey and

design All shows the water thermal isolation is not a

problem, there may have some simple design for pool thermal isolation.

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Earth magnetic shielding for PMTEarth magnetic shielding for PMT A layer of mu-metal lining inside the pool

cylinder is most likely not help for PMT magnetic shielding;

Calculation of coil for magnetic field shielding by JINR and IHEP

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Design of PMTDesign of PMT support framesupport frame

PMT install on the inner surface of water pool ？

PMT install on the outer surface of sphere ？

PMT install on both the surface of water pool and central sphere?

Where should Tyvek film to be installed ？

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To reduce the water volume, the bottom of water pool is constructed as hemisphere? Problem of construction? Problem of water circulation?

A step in the lower part of water pool to reduce the length of central sphere support structure?

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SummarySummary

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JUNO Veto detector design and R&D is in good progress. Some of the design could bough from Daya Bay experiment such as the design of the ultrapure water system, the production of Tyvek film;

Some of R&D has get some preliminary result, like the calculation of water pool thermal isolation. We have made a conceptual design on the top tracker support frame which has many intersection with other systems;

Most of the other parts are going on, manpower to work on is fixed.

The design of PMT support frame is not yet start, but we do not expect there will be major difficulties there .