Half Day IoP Meeting: Neutrinoless Double Beta Decay, 12.10.2011 University College London, Great...

Half Day IoP Meeting: Neutrinoless Double Beta Decay, 12.10.2011 University College London, Great Britain

The GERDA Experiment at Gran Sasso

Grzegorz ZuzelInstitute of Physics, Jagiellonian University, Cracow, Poland

on behalf of the GERDA Collaboration


Overwiew

• Goals of GERDA• Design of the experiment• Present status - Background for natGe - Background for enrGe - Liquid argon instrumentation: LArGe - GERDA phase II• Conclusions and future plans


The Collaboration

95 physicists from 17 institutions from Germany, Italy, Russia,

Poland,Belgium,Switzerland and China

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Goals of GERDA

• GERDA (GERmanium Detector Array) has been designed to investigate neutrino-less double beta decay of 76Ge

- Ge mono-crystals are very pure - Ge detectors have excellent energy resolution - Detector = source - Enrichment required (7.4 % 86 %)

• Background level: 10-2 – 10-3 cts/(keV kgy)

• Realization in phases: - Phase I: 17.8 kg (8 diodes) of enrGe from HdM & IGEX experiments available (15.3 kg of 76Ge) - Phase II: adding new detectors, 37.5 kg of enriched material in hand, p-type BEGe detectors (~20 kg) will be produced - Phase III: world-wide collaboration, O(500 kg) of 76Ge

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Bare high purity enrGe detectors

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Sensitivities

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.

<mßß> ~ 0.1 eV

KKDC

phase I

phase II


Sensitivities

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.

KK claim


t = 3/6 cm copper

Ø 4.2 m

h 8

.9 m

Active cooling

Design of the experiment

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Design of the experimentclean room

lock

water tank + veto

cryostat

cryo-mu-lab

control room

water plantRn monitor

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Design of the experiment

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Unloading of cryostat

6 Mar 08

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Construction of water tank

Water tank:

Ø 10 m h = 9.5 m V = 650 m3

VH2O = 590 m3

19 May 08

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Construction of clean room

27 Feb 09

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Muon veto in water tank

12 aug 09

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


GERDA in Hall C

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


GERDA milestones

• 2005 – 2010: GERDA funded, designed and constructed in LNGS Hall A

• June 2010: Commissioning started. One string (3 natGe detectors, 7.6 kg) deployed for the first time. Checking the detector’s performance

• June 2010 – June 2011: Detailed investigation of background sources with natGe (42Ar, 228Th, cosmogenics)

• June 2011: Deployment of the first string of enrGe (3 detectors, 6.7 kg)

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Background for natG: 42Ar

2.1 cts/kg/day @ 1525 keV

92 d exposure (July – November 2010)

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.



GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.



I @ 1524 keV < 0.094 (cts/kg*d)

I @ Q <1.7 10-3 (cts/keV kgy)

• 42Ar production: 40Ar(,2p)42Ar reaction in atmosphere and fall-out from atmospheric nuclear explosions

• 42Ar concentration: measured < 50 Bq/l < 0.094 cts/(kgd) in GERDA geometry, for an homogeneous distribution around the detectors.

Background @ Qbb

• From 42K -s when decays happen in the detector borehole or @ Li layer

• Hard bremssthralung of > 2 MeV -s in LAr

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Background for natG: other sources

GERDA Rate @ 2614 keV = 4.83 cts/(kgy) HdM Rate @ 2614 keV = 26 cts/(kgy)

GERDA Rate @ Q = 2.210-2 cts/(keV kgy) HdM Rate @ Q = 1.110-1 cts/(keV kgy)

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


NEW: spectrum for enrG

39 Ar: 1.01 Bq/kg from WARP NIM A 574:83-88,2007

42Ar spectrum normalized to peak assumin homogeneous distribution

76Ge: 1.74 ·1021 y from HdM ref. NIM A 522,371-406, 2004

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


LArGe

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Background suppression by LAr instrumentation

228Th

Q: R ~ 104

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


42Ar spike in LArGe

Added 42Ar activity ~ 5 Bq

spiked

natspikednat R

RAA

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


GERDA phase II: BEGe detectors

0-like

-bgdDEP89

11%

- Low capacitance high energy resolution. E ~ 1.6 keV @ 1.332 MeV- Increased field near electrode improved - S/B rejection capability by ID event topologies - Pulse Shape cuts accepting 90 % of 232Th DEP - (mostly Single Site Events 0-like) - ~10% survival of the g-line 212Bi line (mostly - Multi-Site Events -like)

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.



3 natGe + 4 deplGe BEGe detectors produced and tested in 2009-2010 in vacuum cryostat: all show excellent resolution (1.6 keV @ 1332 keV) and Pulse Shape discrimination performances

deplGeO2:

deplGe (6N)

crystal slice

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


3 natGe + 4 deplGe BEGe detectors produced and tested in 2009-2010 in vacuum cryostat: all show excellent resolution (1.6 keV @ 1332 keV) and Pulse Shape discrimination performances


GERDA phase II: enrGe

97 % of the available 37.5 kg of enrGe is now 6N material. The integrated exposure to cosmic ray is 5.2 days.

All the material was stocked underground.

Contract with the industrial partner to grow enrGe crystals & produce BEGe diodes following the process of deplBEGe: signed.

Current schedule: Phase II detectors produced and tested by Summer 2013.

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


Conclusions and future plans

• GERDA is taking data since June 2010

• Phase I detectors perform well:– LC < 50 pA and stable E @ 2.614 keV 208Tl: (3.6 – 6.0) keV

• Background:– Unexpected 42Ar, but background from 42K aviodable

– Th/U for natGe smaller than in previous 0 experiments

– At Q natGe (1839-2239 keV): 0.06 ± 0.02 cts/(keV kg·y)

– At Q enrGe < 0.06 cts/(keV kg·y) (90 % C.L.)

– For enrGe observed spectrum well reproduced by overlapping of 39Ar, 2 of 76Ge and 42Ar

• Deployment of 8 enrGe detectors by the end of 2011

• Instrumentation of LAr in GERDA

GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.


B = 10-3 cts/(keVkg y)

BOREXINOGERDA

B = 10-6 cts/(keVkg y) !GERDA’s goals

Present status

Deign

Conclusions

Bcg for natGe

Bcg for enrGe

LArGe

GD Phase II.

GERDA vs BOREXINO


Backup slides


M = detector mass (active) t = measurement time b = background

E = energy resolution

• No bg:

• With bg:

Backup slides

0

Half Day IoP Meeting: Neutrinoless Double Beta Decay, 12.10.2011 University College London, Great BritainBologna, 20th September 2010

Shroud

MS

Shroud/Mini Shroud

Outer shroud: diameter 760 mmMini shroud: diameter 115 mm

Many field configurations tested!

Backup slides

Run 10 with Mini Shroud


21/04/23 TAUP 2011- Munich 36

3 natGeno M

Attrack ions to Mrun1

4

10 12

3 natGeWith M

3 enrGeWith M3 natGeWith M

14

M’ 0VS 0V

M 0VS 0 Vh+700

M 0VS 3.0 kVh +700

M 0VS 0 Vh 0

no M

Tested several electrostatic and shields config

Reverted bias

Run 3 w/o M


Backup slides

LArGe


LArGe

Backup slides

Half Day IoP Meeting: Neutrinoless Double Beta Decay, 12.10.2011 University College London, Great...

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