1

Steve Dye, John Learned, Shigenobu Matsuno, Marc Rosen,

Michinari Sakai, Stefanie Smith, Gary Varner, and students

Univ. of Hawaii:

Plus some other colleagues elsewhere

The mini-Time-CubeA Portable Directional Anti-Neutrino Detector

Presentation at ANT11, Philadelphia, 10 October 2011

10 October 2011 John Learned at ANT11 in Philadelphia 2

mTC Idea Do imaging with (100 ps) fast timing, not optics (time reversal imaging).

Small portable 2.2 liter scintillating cube, Boron doped plastic.

4 x 6 MCP (x64 pixels each) fast pixel detectors on surrounding faces

Get neutrino directionality.

Reject noise on the fly.

~10/day anti-neutrino interactions (inverse beta decay signature) from power reactor (San Onofre).

13 cm

2.2 liter

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mTC Virtues

• Small size avoids positron annihilation gammas which smear resolution (Xo ~42 cm).... gammas mostly escape, permitting precise positron creation point location.

• Fast pixel timing (<100ps) and fast pipeline processing of waveforms rejects background in real time.

• Having many pixels plus use of first-in light permits mm precision in vertex locations.

• Neutrino directionality via precision positron production and neutron absorption locations.

• No need for shielding (unlike other detectors).

• Feasible even in high noise environment, near reactor vessel, at surface (eg. in a truck).

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Snapshot of the Fermat Surface for a Single Muon-likeTrackSnapshot of the Fermat Surface for a Single Muon-likeTrack

Track

HuygenHuygens s

waveletwaveletss

Incoherent sum coincident with

Cherenkov surface:Not polarized!

J. Learned arXiv:0902.4009v1

Time Reversal Image Reconstruction

10 October 2011 John Learned at ANT11 in Philadelphia 5Figure by Mich Sakai

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Hiroko Watanabe (Workshop Towards Neutrino Technologies 2009)

Directional Measurement

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2.40 cm γ radiation length.

2.α & triton stop ~immediately (mm).

Hiroko Watanabe (Workshop Towards Neutrino Technologies 2009)

Reactions in the Liquid Scintillator

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Hiroko Watanabe (Workshop Towards Neutrino Technologies 2009)

Neutrino Capture Nucleus Choices

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Hiroko Watanabe (Workshop Towards Neutrino Technologies 2009)

KamLAND resolution

KamLAND Calculations

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Study using KamLAND LS and Resolution

Hiroko Watanabe (Workshop Towards Neutrino Technologies 2009)

We can, in principle, do much better with mTC.

Much further gain possible if can sense first neutron elastic scattering location.

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Gammas Usually Leave mTC

Gamma from neutron inelastic capture

Gamma from positron annihilation

2m

Neutrino interaction point

Conclusion: Gammas from positron annihilation leave mTC detector without interaction, thus not confusing vertex resolution.

Mini-TimeCube

Inverse Beta Kinematics

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Trickier than you may realize...

The positron gets the kinetic energy and the neutron gets the momentum.

Neutron only gets15.75 keV mean, most to positron.

Average over reactor spectum

Plots by Stefanie Smith

We can select an event sample with good pointing

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Early neutrino captures point better

Early n captures: strong correlationbetween neutron and positron scattering angles.

Most early captures out ~ cm distance

Lower energies a little better

Some tentative conclusions on neutrino direction determination in mTC

Get interaction vertex to ~1 mm and positron directions using fast timing and first hit reconstruction.

Proton scatters by neutron would be most useful, but probably not enough light to reconstruct.

Neutron capture location determined best with 6 Lithium by detecting alpha and triton.

Can select golden events for best pointing. How good still TBD.

Maximally utilize full information, employing full MaxL, yet to be done.

We are exploring use of a neural network.

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Fitting the Positron Streak

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First mTC version using B loaded plastic scintillator

First casting with bubble from Eljen

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Mini-TimeCube + PMTs and Readout Electronics (Portable)

~43cm (<1’6”)

Volume ~ (2 ft)3

Weight < 30 kg

Plus separate processing electronics box.

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Examples of PMT Read-outs Developed by IDL, Hawaii (Gary Varner)

Fast waveform digitizer for the Photonis MCP is currently under development evolving from existing technology used in BELLE, BESS, ANITA. Length beyond photo-sensor will be ~125mm. One module per MCP.

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Dat

a pr

oces

sing

car

d (x

3)

cPCI crate

cPCI CPU

Data Acquisition System (DAQ) Based on cPCI Format

3Gbs fiber link x 8

x3 (= 24 PMTs)

x1

MCP PMT and Digitizer Internet

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Mini Time Cube: 13cm3 Boron Loaded Plastic Scintillator

MTC with read-out electronics on one faceMTC fully populated with read-out electronics

38 cm

MTC within 2ft3 anodized Al enclosureStackable transport cases

Computer and DAQ

fits upper case

Detector and power supplies in lower case

The mTC Being Assembled

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Gas and RF tight box

UV laser illumination

Rosen design

Picosecond Calibration Laser System

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Matsuno/Rosen

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Estimate Real World Unshielded Noise Rate from Italian CORMORAD Experiment

Refer to CORMORAD talk given by Marco Battaglieri (Genoa) at Trieste 2009.

Prototype segmented detector of square logs of NE110 plastic scintillator, 3 inch PMTs on ends, 40x30x30 cm^3 total volume.

No shielding => big background, outside containment building.

CORMORAD noise rate near Romanian reactor: => R = ~120 Hz (single) => 2 x R^2 x τ = ~10 Hz

(for two hits in time window τ = 330μs)

mTC noise rate implications:≤ 1/30 vol. x 1/10 time resol. x CORM. rate

= few Hz in mTC

Similar numbers from 2 expts at San Onofre (info: LLNL/Sandia group and Juan Collar)

» good enough for real-time background analysis & rejection, with no shielding

Software rejection needed ~10^5 (< KamLAND)

”A proposal for a high segmented power reactor antineutrino detector”, Marco Battaglieri, July 13~17, 2009, Workshop Towards Neutrino Technologies”

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Mini-TimeCube Sensitivity(13cm^3 cube with 24 MCP's)

•Photo sensitive Area 75% coverage of 1,014 cm^2

•Pixel count 1536 (= 64/pmt * 4 pmt/side * 6 sides)

•Typical reactor anti-neutrino several PE/pixel

•100ps MCP time resolution 2 mm spatial resolution/hit

•2 ns scint decay constant 120 PE/MeV in first 200ps.

•Vertex recon. with 1st hits ~1 mm level.

•Rate ~10 anti-neutrino events/day (25m from 3.3GW reactor)

•Rough cost ~$300K (includes electronics, mostly MCP tubes)

much less with future LAPPDs

Summary of what we can measure

• Neutrino energy, via positron energy

• Positron vertex and direction.

• Neutron capture point & direction from vertex to capture point.

• Enough information to get neutrino direction along a cone and maybe better using full constraints.

• Possibly more: total neutron kinetic energy.

• Probably too difficult: location of first n scatter.

• Conclusion: We can do better than anyone has in the past. How much better remains to be demonstrated.

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mTC Study and Plans

Backgrounds stopping muon, decay processes, random internal/external gamma (from reactor), thermal neutron...

Solid scintillators boron loaded plastic from Eljen for initial build, not ideal

Liquid scintillators short n capture time, best n absorb vertex: 6Li loading... soon

Pulse shape discrimination for neutron capture?

Can we do anything with neutron elastic scattering? First scatter important but tough.

GEANT Simulation of mini-Time Cube in progress…. Understanding tricks of simplekinematics and determining if golden sample identifiable.

Careful evaluation of angular resolution with full analysis of waveforms.

Time to activation waiting on electronics construction.

mTC operating in Lab early 2012, and take to reactor ASAP thereafter.

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On the Road to Short and Long Range Nuclear Reactor Monitoring and Other Physics

• Start with demonstrations of detection of reactors, first close up, then further away.

• Importance of directionality understood.

• Focus upon resolving positron production and neutron absorption locations.

• Start with very small demonstration…. mTC.

• Build ~1 m^3 detector, range to ~200m

• Possible detailed search for short range oscillations

• Place a number of modules in shipping container and monitor out to few km

2 litersmTC

1 m^3

Truck size

TC

200 m

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Photonis 8 x 8 Multi-channel plate PMT

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408nm laser, 100 Photo-Electrons

Conclusion: Gain: 40mV/100PE ~ 0.4mV/PE (25m) at 2100 V

5mV/100PE ~ 50 V/PE (10m) at 2500V 10m longer trailing edge Seems that rise time does NOT depend upon the amplitude

=> We choose 25=> We choose 25μμm pore sizem pore size

Evaluation MCP Signal

Under development

Jean-Francois Genat, ANT Workshop, August 13, 2009

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The Photo-Sensor: Photonis XP85012 (64 channel MCP)

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Impulse Dark Noise vs HV

Conclusion: At optimum efficiency (25m 2000V, 10m 2400V),dark counts rates are: 25Hz (25m) ,20 (10Hz )m per pixel

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Neutron Capture Cross Section

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Neutrino Vertex Resolution

KamLAND example: center of ionization for e+ and n capture >10 cm… not useful for present concerns.

120 PE/MeV on Fermat surface => ~20mm/sqrt(120*E/MeV) = 1.3 mm (2 MeV anti-neutrino).

Neutrino Vertex Resolution => Several mm -> directionality

Problem: exponential decay of scintillator.

Solution: employ first hits

In actuality do full liklihood analysis. Initial promising results from NGA collaborators employing medical imaging like algorithms.