1. Monte Carlo Studies for the Gerda/Majorana Experiments and 2. - - PowerPoint PPT Presentation

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1. Monte Carlo Studies for the Gerda/Majorana Experiments and 2. - - PowerPoint PPT Presentation

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1. Monte Carlo Studies for the Gerda/Majorana Experiments and 2. Highly Segmented HPGe Detectors for DBD Reyco Henning The Majorana Collaboration 9/19/2005 Recyo Henning -- DNP Maui 1 1. Monte Carlo Studies for Majorana/Gerda 1. The

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SLIDE 1

9/19/2005 Recyo Henning -- DNP Maui 1

  • 1. Monte Carlo Studies for the

Gerda/Majorana Experiments and

  • 2. Highly Segmented HPGe

Detectors for DBD

Reyco Henning The Majorana Collaboration

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SLIDE 2

9/19/2005 Recyo Henning -- DNP Maui 2

  • 1. Monte Carlo Studies

for Majorana/Gerda

  • 1. The Majorana and Gerda

Experiments

  • 2. The Joint Majorana/Gerda

Simulation Package Framework-- MaGe

  • 3. Majorana Results
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9/19/2005 Recyo Henning -- DNP Maui 3

Ge Detection Principle

  • Majorana and Gerda search for DBD

in 76Ge.

  • Ge is semiconductor -- Diode.
  • Ionizing radiation creates electron-

hole pairs.

  • Signal generated by collecting

electrons and holes.

  • Gamma-ray spectroscopy

Mature Technology

electrons holes Ionizing radiation interaction site

Gammasphere RHESSI

Eurisys (Commercial) n p

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9/19/2005 Recyo Henning -- DNP Maui 4

  • Measure extremely rare decay rates :

T1/2 ~ 1026 -1027 years

  • Large, highly efficient source mass.
  • Extremely low (near-zero) backgrounds in the

0νββ peak region-of-interest (ROI) (1 count/t-y)

  • High Q value
  • Best possible energy

resolution

– Minimize 0νββ peak ROI to maximize S/B – Separate 2νββ/0νββ

Experimental Considerations for DBD

  • U. Zargosa
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9/19/2005 Recyo Henning -- DNP Maui 5

  • The facility will be located in HAll A of

LNGS and will serve a dual purpose:

  • It will probe the neutrinoless double

beta decay of 76Ge with a sensitivity of T1/2 > 1024 y at 90% confidence level, corresponding to a range of effective neutrino mass < 0.09 - 0.20 eV within 3 years.

  • It will be a pioneering low-level facility

which will demonstrate the possibility

  • f reducing backgrounds by 2-3
  • rders of magnitude below the current

state-of-the-art.

top µ- veto water tank lead shieldi ng cryo vessel neck Ge array

GERDA

GERDA is a new experiment for the search of 76Ge neutrinoless double-beta decay at LNGS. The principle of GERDA is to operate germanium detectors made out of isotopically enriched material inside a cryogenic fluid shield.

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9/19/2005 Recyo Henning -- DNP Maui 6

57 crystal module

Conventional vacuum cryostat made with electroformed Cu. Three-crystal stack are individually removable.

The Majorana Modular Approach

Cold Plate 1.1 kg Crystal Thermal Shroud Vacuum jacket Cold Finger Bottom Closure 1 of 19 crystal stacks

Cap Cap Tube (0.007” wall) Tube (0.007” wall) Ge (62mm x 70 mm) Ge (62mm x 70 mm)

Tray (Plastic, Si, etc) Tray (Plastic, Si, etc)

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9/19/2005 Recyo Henning -- DNP Maui 7

– Allows modular deployment, early operation – Contains up to eight 57-crystal modules (M180 populates 3 of the 8 modules) – Four independent, sliding units

– Use 180-Kg of material to probe degenerate mass region.

The Majorana Conceptual Design

Top view

57 Detector Module Veto Shield Sliding Monolith LN Dewar Inner Shield

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9/19/2005 Recyo Henning -- DNP Maui 8

History & Goals of Simulation

1. To provide the collaboration with a physics simulation package to aid in the optimal design, operation and analysis of data from the Majorana experiment. 2. The package must persist over the long lifetime of the experiment. 3. The package must be well- maintained, upgradable, documented, and robust. 4. Maintain record of results. 1. Energy deposition of particles from radioactive sources, cosmic rays, and signal sources. Low-energy electromagnetic and neutron interaction packages are critical. 2. Pulse-shape formation in crystals, different segmentation schemes, and crystal geometries. Use expertise from Gretina/GRETA collaborators. 3. Electronics. 4. Shielding (neutron absorption and muon tagging). 5. Radioactive decay chains and emissions. 6. Signals (double-beta decay, dark matter, axions…). 7. Activation in detector material. 8. Optimization of close-packed crystal packing arrangements for self-vetoing 9. …….

  • Much previous work from PNNL,

NCSU, U.W. & others.

  • Jan. 2004. Decided to develop

integrated software package using professional programming techniques.

  • Philosophy: Use Geant4. Improve

where needed. Create Framework first

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SLIDE 9

9/19/2005 Recyo Henning -- DNP Maui 9

Interface: MaGe

Framework

Build common interface using powerful object-oriented capabilities of C++

Geometry “Library”

  • Clover detector
  • 57 Banger
  • MSU Detector
  • …

Generator “Library” PNNL Radioactive Decay Chain Geant 4 RDM TUNL FEL Beam Volume Sampler Surface Sampler Neutron generators… Geant 4 Database Output Formats Materials Optimal Physics Processes DBD, optical, etc…

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SLIDE 10

9/19/2005 Recyo Henning -- DNP Maui 10

Interface: MaGe

The Majorana/Gerda Collaborative Effort

  • Started Oct. 2004, Gran

Sasso

  • Twice as many developers,

test cases, etc…

  • Very Sucessful

Geometry “Library”

  • Clover detector
  • 57 Banger
  • MSU Detector
  • GERDA
  • Test Facility MPI

Generator “Library” PNNL Radioactive Decay Chain Geant 4 RDM TUNL FEL Beam Volume Sampler Surface Sampler Neutron generator Muon Generators Geant 4 Database Output Formats AIDA Materials Optimal Physics Processes DBD, optical, etc…

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SLIDE 11

9/19/2005 Recyo Henning -- DNP Maui 11

Example Documentation

User’s Guide Reference Guide

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9/19/2005 Recyo Henning -- DNP Maui 12

Canberra Clover Detector Simulation

External Combined 57Co

60Co Source measured at

LANL

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9/19/2005 Recyo Henning -- DNP Maui 13

Clover at TUNL-FEL

Segmented NaI Barrel to Tag DEP Events. DEP Events are Single- Site: Useful for PSD Studies DEP

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9/19/2005 Recyo Henning -- DNP Maui 14

Background Models

Different Designs Potential Backgrounds Background Models

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9/19/2005 Recyo Henning -- DNP Maui 15

Example: 57 Banger for Majorana Background Model

  • Cu Cryostat: 5mm, 37-kg.
  • Lead Shield (20, 50) cm
  • Cu Rod, 1-gm/cm
  • Polypropylene Support Rings

Geant 4 Engineering

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9/19/2005 Recyo Henning -- DNP Maui 16

Radioactive Contaminants in 57 Banger Design

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9/19/2005 Recyo Henning -- DNP Maui 17

Counts in ROI

Cryostat Shield Cu Tubes Plastic Rings Active Regions Dead Layers “Small Parts” Attic

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9/19/2005 Recyo Henning -- DNP Maui 18

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9/19/2005 Recyo Henning -- DNP Maui 19

Conclusions

  • Other Majorana: Neutron background,

See K. Hudek, FR 53, CEU Poster Session, 13:00 Wednesday

  • MaGe Framework successful
  • Collaboration with Gerda ongoing and

lucrative.

  • Simulations critical for background model

(See following talk by C. Aalseth).

  • Provides input for waveform simulations.
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9/19/2005 Recyo Henning -- DNP Maui 20

  • 2. Highly Segmented Ge

Detectors for DBD

  • 1. Germanium detector segmentation
  • 2. Underground test facility at Oroville
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9/19/2005 Recyo Henning -- DNP Maui 21

Crystal Segmentation

  • Multiple conductive contacts
  • Additional electronics and small

parts

  • Examples

– MSU experiment (4x8 segments) – LANL Clover detector (2 segments) – LLNL+LBNL detector (8x5 segments) – Gretina Prototype + AGATA

60Co

γ γ 0νββ νββ γ (“Low” Energy) γ (“High” Energy)

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9/19/2005 Recyo Henning -- DNP Maui 22

Detector Fabrication

Detector blank Li diffused n+ contact Segmented p+ contact

Surface Exposure time has to be minimized

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9/19/2005 Recyo Henning -- DNP Maui 23

Pulse Shape Discrimination (PSD)

  • Excellent rejection for

internal 68Ge and 60Co (x4)

  • Moderate rejection of

external 2615 keV (x0.8)

  • Shown to work well with

segmentation

Central contact (radial) PSD

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SLIDE 24

9/19/2005 Recyo Henning -- DNP Maui 24

Segmentation test & simulation comparison

Experiment with MSU/NSCL Segmented Ge Array

  • N-type, 8 cm long, 7 cm diameter
  • 4x8 segmentation scheme: 4 angular 90 degrees each, 8 longitudinal, 1 cm each
  • 60Co source
  • Segmentation successfully rejects backgrounds.
  • Data are in good agreement with the simulations

Experiment GEANT Crystal

1x8 4x8

Counts / keV / 106 decays

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9/19/2005 Recyo Henning -- DNP Maui 25

LLNL Detector at Oroville

~200 mwe

Kai Vetter, David Campbell (LLNL) Kevin Lesko, Yuen-Dat Chan, Reyco Henning, Donna Hurley,Michelle Perry, Alan Poon, Al Smith (LBNL)

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9/19/2005 Recyo Henning -- DNP Maui 26

Goals

  • First Highly Segmented Detector with

Pulse Digitization in Low Background Environment.

  • Determine Background rejection for

natural radioactivity for a detector in the field.

  • Additional Data to Verify MC against.
  • Access to Low Background Counting

Facility.

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9/19/2005 Recyo Henning -- DNP Maui 27

The Detector System

40-fold segmented, closed-ended coaxial HPGe detector (built by ORTEC in summer 2002)

  • N-type HPGe crystal: 8cm length and 5cm diameter
  • 5 Transversal segments with Dz=1cm
  • 8 Longitudinal segments with Df=45deg.
  • Custom-made, compact preamplifiers mounted on circular

motherboard close to feedthroughs equipped with warm FETs.

  • Energy resolution: 0.9keV at 60keV and 1.9keV at

1332keV

  • Data acquisition: Six 8-channel waveform digitizer

modules built by Struck Innovative Systems (optical VME- PCI readout)

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9/19/2005 Recyo Henning -- DNP Maui 28

Installation

  • Installed 6/14-15
  • All Segments

Survived 3 hr. drive!

  • Replenish Disk

Drives Every Two

  • Weeks. ~20 GB/day
  • 2” Pb Shield +

400lb Table.

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9/19/2005 Recyo Henning -- DNP Maui 29

Installation

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9/19/2005 Recyo Henning -- DNP Maui 30

20 40 60 80 100 120 140 160 180 1 501 1001 1501 2001 2501 Series1

40K 208Tl 208Tl 214Bi

First Day’s Spectra

Energy (keV) Counts

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9/19/2005 Recyo Henning -- DNP Maui 31

Initial Pulse shapes

φ segments z segments See poster by

  • M. Perry, FR 47, CEU Poster Session
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9/19/2005 Recyo Henning -- DNP Maui 32

Conclusions

  • First highly segmented detector operating at low

background facility.

  • Quantitative measurement of background reduction

efficiency from segmentation, PSD and gamma- tracking.

  • Neutron response measurements.
  • Have first publishable results in 6 months.
  • Session JG, Thursday, 9:00, Techniques for Neutrino

Science

  • Session KD, Thursday 14:00, Mini-symposium on

New Technology in Gamma Ray detection