The Majorana Experiment

The MAJORANA Experiment

Ryan Martin for the LBNL MAJORANA Group

NSD Monday Morning Meeting26 April 2010

Outline

• Neutrinoless double-beta decay• The use of 1 tonne of Germanium• The MAJORANA DEMONSTRATOR• Technology Developments at LBNL

2Ryan Martin, LBNL, MMM, 4/26/2010

Neutrinoless Double-Beta Decay2 0

104 0

•Neutrinoless double beta decay is a very rare process that can occur in isotopes where beta-decay is energetically forbidden•Observing this requires excellent energy resolution

Isotope Q %

G. Gratta


Experimental Searches for 0disfavored by 0

Klapdor-Kleingrothaus et al. claimed signalDisfavored by cosm

ology

Tonne Scale T½

0ν = ( G0ν |M0ν|2 〈 mββ 〉 2 )-

1

〈 mββ 〉 ≡ Ue12m1+ Ue2

2m2ei2

+ Ue32m3ei3

Majorana PhasesPMNS Matrix

Phase Space Nuclear Matrix Element

•The half life for 2 is of order 1020 years, so is very rare if it exists• A tonne scale experiment is required to probe m of order the atmospheric mass-squared difference

Klapdor-Kleingrothaus’ 6.4 claim (Mod. Phys. Lett. A 21, 1547 (2006)


Impact of detecting

• Only practical way to see if neutrinos are Majorana particles

• Sets the scale for neutrino masses• Allows for leptogenesis as a way to solve the

matter/anti-matter asymmetry in the Universe


Arguments for using Germanium

• There are several reasons for using Germanium diode detectors (HPGe):– Source is detector– Can be enriched in 76Ge to 86%– Low level of radio-impurities– Technology is well understood– Energy resolution is excellent (~0.2% at 2039keV)– Easy to operate (LN temperature, volume is small)


Towards a 1Tonne Experiment

• In order to build a 1 tonne Ge experiment, one must demonstrate that the required background levels can be achieved with a technology that can scale

• The MAJORANA and GERDA collaborations are both working to demonstrate different technologies to reduce and remove radioactive backgrounds in Ge detector arrays

• There is a cooperative agreement between the two collaborations to share information and come together to build an international 1 tonne Ge experiment that uses the best features from the two technologies


Challenges in detecting

• The main challenges in detecting are backgrounds, backgrounds and backgrounds

• One aims to have backgrounds of the level of 1 count per tonne per year within a 4keV Region Of Interest (ROI) around 2039keV to be sensitive to the atmospheric mass scale

• Need to enrich Ge to have significant quantities of 76Ge


Main backgrounds• Natural radioactivity in detector components

(U, Th)• Surface contaminants ()• Low-energy backgrounds (Ge isotopes, 65Zn,

73As,3H; low-E compton from K, U, Th; 210Pb brem; …)

• Cosmogenic radioactivity (68Ge, 60Co)• Muons, fast neutrons• 2 decay• Neutrino scattering (reactor, solar, atm., geo,

SN…)

Use clean materials

Go deep underground

Not much you can do!


The MAJORANA DEMONSTRATOR

2m

Pb/Cu ShieldLN Dewar

Cu Cryostat

Lift•The MAJORANA experiment is a US-led effort that will be deployed at the Sanford lab in South Dakota•The design focuses on the use of high purity material and will use a Pb/Cu shield•The experiment will be run in phases and will culminate with the use of 60 kg of Ge (30kg of which will be enriched)


Technologies used in MAJORANA

• Electroformed copper• Low-noise electronics and DAQ• Stringent materials assays• Point contact Ge detectors tests• Low background detector mounts• Monte Carlo simulations• Various analysis techniques

LBNL strongly involved!


Electroformed copper

•The use of electroformed copper removes impurities and significantly reduces backgrounds; goal is 0.3 µBq 232Th and 238U/kg Cu (~0.08 x 10-12 g/gCu) •The copper is electroformed on steel mandrels that have the same diameter as the cryostats•A total of 16 baths will be deployed underground. The material from the electroformed cylinders will be machined into various components


Low Noise Electronics

FET

Fused-silica board

Au/Cr pads

Amorphous Ge resistor

•Paul Luke has developed a “low mass front end” (LMFE) board that allows one to have an amplification stage close to the Ge diode and thus reduce the noise in the signal from capacitance•The resistive feedback configuration for this pre-amplier is achieved by using amorphous Germanium and the intrinsic capacitance between the pads. The large resistor also reduces noise in the signal, allowing for a low threshold•Our group is testing and characterizing various implementations for this design

Parylene cable

FET Copper “mount” for the board


Electronics Development•LBNL is playing a leading role in the development of the electronics for the MAJORANA DEMONSTRATOR:

•LMFE board•Cable Characterization•Preamplifier design•Digitizer Card Characterization (Gretina and Struck cards)•Low noise power source


Materials Assays• In order to determine which materials are suitable to go into

the experiment, one needs to be able to assay the radio purity of materials - Several techniques and facilities are being used by the collaboration:– Gamma counting

• Accurate but slow and needs large samples ~ 50-100ppt U,Th at Oroville• Can determine activity from all parts of a decay chain and unexpected contaminants

– Neutron Activation Analysis• Accurate and can use small samples• Can determine activity from all parts of a decay chain and unexpected contaminants

– ICP-MS (Inductively coupled plasma mass spectroscopy)• accurate and can (must!) do small samples ~ <1ppt U, Th at PNNL• Can only determine contributions from top parts of decay chain

•LBNL is responsible for the assay and characterization of the components for the low mass front end board


Point contact Ge detector

coax Ge PC GePoint contact Ge detector allow multi-site events to be identified-invented by Paul Luke (LBNL)


Pulse Shape Analysis

9/30/09 Radford, RedTeam Review

Red: all eventsBlue: PSA-selected events

232Th source data

•The use of point contact detectors allows one to use pulse shape analysis to distinguish Multi-Site Events (MSE, background-like) from Single Site Events (SSE, signal-like)

208Tl DEP


Segmented PPC Prototype – SPPC

LDRD (Amman, Luke, Chan, Lesko)

Segment waveform

Point-contact waveform

•Combination of point contact and segment detector•Idea is to read out both electrodes to determine the position of the events


Mini-PPC Detector

Pin contact

Contactpressure

adjust

To sensor/heater

TempRef plate

To cold finger

IR shield base-plate

Crystalmount

•The main purpose of the mini PPC was to study surface passivation in a conventional setup (shown here)•The detector was also to used to study the low mass front end board (different configuration, not shown) as well as help to characterize the digitizing boards


Low Background Detector Mounts

•The Majorana experiment will employ detector mounts fabricated from electroformed copper in order to reduce backgrounds•These are being tested at LBNL

Cryostat

Cold plate

Detector “blank”

my watchFront end board

“Mercedes” mount

PTFE blocks to support crystal


Detector Simulation• The MAJORANA and GERDA

collaborations have worked on the MaGe Monte Carlo simulation package (using Geant4 and ROOT)

• O(5) publications• Pulse shape calculations also

implemented• Simulation and Analysis task

lead is at LBNL

Example: 60Co in cryostat

granularityPPC PSA


Pulse Shape Simulation

Ryan Martin, LBNL, MMM, 4/26/2010 22

•LBNL group has done work on modelling the electric field to determine pulse shapes•BEGe detector from Canberra shown here

simulated pulsesElectric field and potential

Geometry of BEGe

Point contact

Digital Energy Filter Development

Pulse

Filter

•New energy digital filter was developed to correct for possible changes in the response of the front end electronics (varying pole zero correction) and improve the energy resolution•Individual pulses are fit to determine the pole zero correction and the energy 23Ryan Martin, LBNL, MMM, 4/26/2010

Discreet Wavelet Analysis

•The Discreet Wavelet Transform (DWT) is a reversible transformation (like the Fourier Transform) that can be done on a discreetly sampled signal•Unlike the Fourier Transform, the DWT contains information about the frequencies contained in a signal and when they occur


Can be used to tag SSE and MSE

Can be used for de-noising

Majorana Sensitivity

The Majorana experiment will be able to test the Klapdor claim25Ryan Martin, LBNL, MMM, 4/26/2010

Low noise electronics and DM search

• Low capacitance results in very good resolution and low noise– Can look for low

energy events (Dark Matter searches)

The CoGeNT collaboration, has recently published a paper showing the energy spectrum in a low-threshold point contact Ge detector (http://arxiv.org/abs/1002.4)

2 CDMS EventsDAMA/LIBRA


Summary

• discovery would be a very compelling result• 1 tonne of Ge would allow one to explore mass

scales beyond the inverted mass hierarchy• The MAJORANA Demonstrator will soon start to

evaluate the feasibility of a tonne scale 76Ge experiment as well as test the Klapdor claim

• LBNL is leading the detector development and analysis tasks for the Majorana Demonstrator and will continue to play a leadership role in the experiment


Backup Slides


The GERDA Exeperiment

Ryan Martin, LBNL, MMM, 4/26/2010 29

http://ilias.in2p3.fr/ilias_site/meetings/documents/ILIAS_3rd_Annual_Meeting/Parallel_DBD_Exp_Zuzel.pdf

•The GERDA experiment is a European experiment that is in the final phases of construction at LNGS•The Ge diodes are immersed in LAr inside a stainless steel tank, surrounded by an instrumented tank of water•The first phase of the experiment uses ~18kg of enriched Ge from the IGEX and Heidelberg Moscow experiments - in the second phase, they will have a total of 35-40kg of enriched Ge

Towards a 1 tonne Ge experimentSensitivity depends on energy resolution, background rate and exposure:

Half life

(years)

~Signal

(cnts/ton-year)

~Neutrino mass scale

(meV)

1025 530 400

5x1026 10 100

5x1027 1 40

>1029 <0.05 <10

background rateenergy resolution

active mass live-time

A 1 tonne experiment is well suited for exploring mass scales down to the atmospheric neutrino oscillation mass-squared difference.


Neutrino Mass•We know from neutrino oscillation experiments that neutrinos have mass, but:

•We do not know the hierarchy•We do not know the absolute mass scale•We do not know if the neutrinos have a Majorana mass term (the only particle that could)

Normal hierarchy ? Inverted hierarchy ?

mass

12

312

3

mass (solar, reactor)

(atmospheric, LBL)

? ?

?


Other Experiments


Nuclear Matrix Elements


The MAJORANA and Advanced Detector Development at LBNL

•Staff Scientists: Alan Poon, Yuen-Dat Chan, Brian Fujikawa, Kai Vetter•Engineers: Paul Luke, Harold Yaver, Sergio Zimmerman•Postdocs: Jason Detwiler, James Loach, Jing Qian, Ryan Martin•Undergraduate Student: Justin Tang•Summer Students through mentoring program


The Majorana Experiment

Documents

Transcript of The Majorana Experiment