Advanced Gamma Tracking Array AGATA

Dino BazzaccoINFN Padova

On behalf of the AGATA Collaboration

180 hexagonal crystals 3 shapes 60 triple-clusters all equalInner radius (Ge) 23.5 cmAmount of germanium 362 kgSolid angle coverage 82 %36-fold segmentation 6480 segmentsSingles rate ~50 kHz

Efficiency: 43% (Mg=1) 28% (Mg=30)Peak/Total: 58% (Mg=1) 49% (Mg=30)

AGATA

6660 high-resolution digital electronics channels Detectors operated in position-sensitive mode Digital EDAQ + Pulse Shape Analysis + g-ray TrackingCoupling to ancillary detectors for added selectivity

AGATAConventional array

Segmented detectors

g-ray tracking

Energy (keV)

Using the detectors in position-sensitive modewill provide very high efficiency and excellent energy resolution , making AGATA ideal for spectroscopic studies of weak channels

Effective energy resolution maintained at “extreme” v/c

v/c = 50%

Mg = 30

MC simulation of a high-multiplicity event Efficiency depends on position resolution

Reconstruction of 0.1÷10 MeV gammas

Position resolution (FWHM, mm)

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

791 keV deposited in segment B4

measured

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm

(10,10,46)

measuredcalculated

791 keV deposited in segment B4

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm

(10,15,46)

measuredcalculated

791 keV deposited in segment B4

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm

(10,20,46)

measuredcalculated

791 keV deposited in segment B4

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm

(10,25,46)

measuredcalculated

791 keV deposited in segment B4

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm

(10,30,46)

measuredcalculated

791 keV deposited in segment B4

Result of Grid SearchAlgorithm

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm

(10,25,46)

measuredcalculated

791 keV deposited in segment B4

Examples of signal decomposition

A B C D E F CC

Eg = 1172 keV net-charge in A1

Eg = 1332 keV net-charge in C3, E1, E3

Status after more than 10 years of R&D

Germanium detectors Pulse Shape Analysis Gamma-ray Tracking AGATA Demonstrator Electronics and DAQ Problems encountered Performance Experiments Evolution

AGATA Crystals

Volume ~370 cc Weight ~2 kg(the 3 shapes are volume-equalized to 1%)

80 mm

90 mm

6x6 segmented cathode

Manufactured byCanberra France

Asymmetric AGATA Triple CryostatChallenges: - mechanical precision - heat development, LN2 consumption - microphony, noise, high frequencies

- integration of 111 high resolution spectroscopy channels- cold FET technology for all signals

A. Wiens et al. NIM A 618 (2010) 223–233D. Lersch et al. NIM A 640(2011) 133-138

Energy resolution at 1332 keVCore: 2.4 keV Segments: 2.1 keV

Manufactured by CTT

The AGATA Demonstrator Objective of the R&D phase 2003-2009

Used for Physics at LNL in 2010-20115 asymmetric triple-clusters

15 36-fold segmented crystals

540 segments555 high-resolution digital-

channelsEff. 3 – 8 % @ Mg = 1Eff. 2 – 4 % @ Mg = 30

Real time operation Pulse Shape Analysis g-ray TrackingHosting sitesLNL

2009-2011GSI

2012-2013GANIL 2014

S. Akkoyun et al. NIM A 668 (2012) 26–58A. Gadea et al. NIM A 654 (2011) 88-96

AGATA Demonstrator + PRISMAinfrastructure at completed mid 2009, all clusters in place May 2011

AGATA: Structure of Electronics and DAQ

TRACKINGControl,

Storage…EVENT

BUILDER

GL TriggerClock

100 MHzT-Stamp

Other detectors

Fast 1st Level Trigger

DetectorLevel

Other Detectors

GTS

DIGITIZERPREAMPL.

Global LevelDAQ-NARVALRUN- & SLOW-Control

High throughput pre-processingFor one crystal:2 ATCA carriers 1 GTS + 7 processing mezzanines

Other detectors:interface to GTS, merge time-stamped data into event builder, prompt local trigger from digitisers

Digital preamplifier concept

100MB/s/detector

200MB/s/seg.

GTS

Processing

Processing

Processing

PSA farm

Core +36 segments

LAN

GTS : the system coordinatorAll detectors operated on the same 100 MHz clock

Downwards 100 MHz clock + 48 bit Timestamp (updated every 16 clock cycles)Upwards trigger requests, consisting of address (8 bit) and timestamp (16 bit)

max request rate 10 MHz total, 1 MHz/detectorDownwards validations/rejections, consisting of request + event number (24 bit)

Some important issues

• Cross talk among the channels of one crystal• Need to run at very high counting rates• Neutron damage and degradation of energy

resolution of the segments• Annealing of crystals to restore the original

energy resolution is a delicate procedure

Sum of segment Energies vs fold

• Crosstalk is present in any segmented detector• Creates strong energy shifts proportional to

fold• Tracking needs segment energies !

Crosstalk

Segment sum energies projected on fold2-folds : centroid of Core and Segment-sum

…all 1260 possible 2-fold combinations

Ener

gy [k

eV]

Cross talk correction: Results

High counting rate• The detection efficiency of AGATA is, so far, provided by a

small number of crystals. Experiments want to collect big statistics and push for running at high singles counting rates.

• Thanks to digital signal processing, we can work in conditions impossible with conventional electronics.

• Under these «extreme» conditions, the performance of the detectors is still acceptable.

• A limit exists, due to pileup of the signals which exhaust the dynamical range of the FADC. Counteract this by reducing the gain of the preamplifiers but then energy resolution worse also at low counting rate.

Singles rates and shaping time6 different rates x 4 trapezoid risetimes x 6 BLR lengths

Two independent sources of dead-time: pile-up rejector and GTS

60Co - fixed

137Cs – 6 positions Francesco Recchia, Padova

Neutron damage: shape of the 1332 keV line

Blue: April 2010 FWHM(core) ~2.3 keV FWHM(segments) ~2.0 keVRed: July 2010 FWHM(core) ~2.4 keV FWHM(segments) ~3 keVDamage after 3 high counting-rate experiments (3 weeks of beam at 30-80 kHz singles)Worsening seen in most of the detectors; more severe on the forward crystals;segments are the most affected, cores almost unchanged (as expected for n-type HPGe)

Crystal C002

The 1332 keV peak as a function of crystall depth (z) for interactions at r = 15mm

The charge loss due to neutron damage is proportional to the path length to the electrodes. The position is provided by the PSA (which is barely affected by the amplitude loss).

corrected

Knowing the path, the charge trapping can be modeled and corrected away (Bart Bruyneel, IKP Köln)

CCr=15mm

SGr=15mm

April 2010

CCr=15mm

SGr=15mm

July 2010

Energy resolution at the end of the LNL campaignBefore and After charge-trapping correction

CoreSum of 15 spectra

SegmentsSum of 15*36=540 spectraFWHM 5.5 keV 2.9 keVFWTM 15.5 keV 6.8 keV

FWHM 3.2 keV 2.8 keVFWTM 7.2 keV 5.6 keV

Undamaged detectors: FWHM ~2.5 keV, FWTM ~4.8 keVEg (keV)

Performance of the AGATA Demonstrator

Just a few examples

Doppler correction usingcenter of crystalsFWHM ~20 keV

Detector FWHM = 2.2 keV

Doppler correction using center of hit segmentsFWHM = 7 keV

Doppler Correction Capability, “small” v/c220 MeV 56Fe 197Au (ATC1 + DANTE, July 2009)

Doppler correction using PSA (AGS) and trackingFWHM = 3.5 keV(3.2 keV using only single hits)

Eg (keV)

v/c 8%E(2+) = 846.8 keV

56Fe 2+ 0+

846.8 keV56Fe 4+ 2+

1238.3 keV4.8 keV FWHM

Au recoils also seen by Dante

OriginalCorrected

Doppler Correction Capability, “large” v/cinelastic scattering 17O @ 20 MeV/u on 208Pb

FO

N

C

B

Be

a

Li

No Doppler Corr.Crystal CentersSegment CentersPSA+Tracking

16O

TKE (MeV)

dE (M

eV)

Fabio Crespi, Milano

v/c 20%

Charged particles detected in TRACE

gg capabilities 135 MeV 32S 110Pd (6 AGATA crystals only)

138Sm6 gates on:347keV,545keV,686keV,775keV,552keV,357keV

871 keV 22+ - 20+

The performance of AGATA using g-ray tracking is comparable to conventional arrays with a much larger number of crystals

Imaging of Eg=1332 keV gamma rays AGATA used as a big Compton Camera

Francesco Recchia

Far Field Backprojection

Near Field Backprojection

All 9 detectors One detector

All 9 detectors One detector20

111cos cmEE

gg

Source at 51 cm Dx ~Dy ~2 mm Dz ~2 cm

neutrons

pro

tons

Neutron drip-line

Lifetime of the 6.792MeV state in 15O

n-rich nuclei

Lifetimes in n-rich Ni, Cu and Zn isotopes

Lifetimes of the

n-rich Cr isotopesLifetimes near

the island of inversion

The Experimental Campaign at LNL

Pygmy and GQR states

Neutron-rich nuclei populated by fission

N=51 nuclei

Lifetimeof 136Te

Neutron-rich nuclei in the vicinity of 208Pb

Proton drip-line

Molecular structure of 21Ne

Coulexof 42Ca

Isospin Mixingin 80Zr

Octupole-deformedRa and Th nuclei

Shape transition in 196Os

N=84 isotone 140Ba

n-rich Th and U

g.s. rotationin Dy, Er, Yb

High-lying statesin 124Sn and 140Ce

20 exp.148 days

Order-to-chaos

transition in 174W

LNL: 2010-20115 TCTotal Eff. ~6%

GSI: 2012-2013≥ 5 TC + 5 DC Total Eff.~10%

GANIL: 2014-201515 TCTotal Eff. ~15%

AGATA+VAMOS

From the Demonstrator to AGATA 1πPlans for the next few years

AGATA D.+PRISMA AGATA + FRS

Status of AGATA at GSI

Mechanics & detector support infrastructure

7 crystals (2 DC, 1 TC) used in the 3rd commissioning test (May 23-28). more detectors added in the next few months.

Electronics and DAQ ready for 15 crystals Second batch of electronics modules under

test to instrument the up 25 crystals. Coupling to FRS, LYCCA, HECTOR done.

First experiments Q4 2012

The AGATA Collaboration

Bulgaria: SofiaFinland: JyväskyläFrance: GANIL, Grenoble, Lyon, Orsay, Saclay, StrasbourgGermany: Darmstadt, GSI, Köln, MünchenItaly: Firenze, LNL, Milano, PadovaPoland: Krakow, WarsawRomania: BucharestSpain: Valencia, Madrid, SalamancaSweden: Göteborg, Lund, Stockholm, UppsalaTurkey: Ankara, IstanbulUK: Brighton, Daresbury, Edinburgh, Liverpool,

Manchester, Paisley, Surrey, York

First implementations of the g-ray tracking array concept

AGATA Demonstrator GRETINA

15 crystals in 5 Triple ClustersCommissioned in 2009 at LNL (with 3 TC)Experiments at LNL in 2010-2011Being reinstalled and expanded at GSI

28 crystals in 7 Quadruple ClustersEngineering runs started early 2011 at LBNLExperiments at LBNL in 2011Being reinstalled at NSCL