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NeutrinoDetectors

Prepared by:

Carmela Ariane D. Aliazas

BS Chemistry 321

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Neutrino detectors are typically large tanks filled with afluid that reacts to the passage of neutrinos.

To take advantage of the high flux of neutrinos passingthrough the Earth (billions per second), neutrinodetectors are made as large as possible. Neutrinos areweakly interactive with other particles of matter.

The larger the detector, the more neutrinos can bemeasured in a reasonable amount of time.

Neutrino detectors are often built underground to isolatethe detector from cosmic rays and other backgroundradiation.

The field of neutrino astronomy is still very much in itsinfancy the only confirmed extraterrestrial sources sofar are the Sun and supernova SN1987A.

About

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First Neutrino Observation

The first experimental observation of theneutrino interacting with matter was made

by Frederick Reines, Clyde Cowan, Jr,

and collaborators in 1956 at the Savannah

River Plant in South Carolina. Their

neutrino source was a nuclear reactor.

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Early neutrino detectors were filled withperchloroethane (a type of cleaning fluidcontaining chlorine).

A portion of the chlorine is isotope 37 (17protons and 20 neutrons), which can react withneutrinos to produce Argon-37 (18 protons and19 neutrons). The amount of Argon-37 createdis then used to measure the neutrino flux.

Another fluid used for neutrino detection iswater. Neutrino interactions in water produce theCherenkov effect.

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GALLEX detector

a radiochemical neutrino detection experimentthat ran between 1991 and 1997 at the

Laboratori Nazionali del Gran Sasso (LNGS).

uses Gallium in 30 tons of Gallium trichloride todetect neutrinos. It is buried far below a

mountain in Italy.

It was designed to detect solar neutrinos andprove theories related to the Sun's energy

creation mechanism.

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Sudbury Neutrino Observatory

uses 1000 tons of ``heavywater'' buried far below groundoutside of Sudbury, Ontario(Canada) to detect solarneutrinos.

Heavy water uses the deuteriumisotope of hydrogen instead ofthe ordinary isotope of hydrogenin the water molecule (H2O).Deuterium has 1 proton+1neutron in its nucleus instead of

just the 1 proton of ordinary

hydrogen. The extra neutron makesdeuterium twice as massive asordinary hydrogen, so the``heavy water'' molecule is about10% heavier than ordinarywater.

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To detect charged particles, the KAMIOKANDEdetector utilizes Cherenkov radiation in the

water. Cherenkov radiation is generated when a

charged particle pass through the matter with

velocity greater than that of light in the matter.

Cherenkov photon is detected by the 20"PMTwhich is attached inside of the water tank. Awing

to a total of 2140 t of water, KAMIOKANDE can

detect rare events such as a nucleon decay and

a neutrino event.

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Super-Kamiokande experiment

Super-Kamiokande isa large, underground,

water Cherenkov

detector located in anactive zinc mine in the

Japanese Alps. The

experiment began

data taking in April1996.

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Large volume water detectors were invented todiscover proton decay, but so far have only set

limits. As Super-K is 6-10 times larger than the

previous generation of detectors, it can reach a

proton lifetime of 10**34 years, probing

predictions of modern Grand Unified Theories.

Among the possible decay modes are veryinteresting signatures, such as p -> neutrino K+,

which would provide evidence for mediation bythe supersymmetric particles.

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Another hint for massive neutrinos is found inthe apparent deficit of solar neutrinos, asrecorded by several experiments of diversetechnique.

Super-K records about 4000 solar neutrinoevents per year, approximately 50% of thenumber expected by the Standard Solar Model.

The rate of these low energy neutrinos isconstantly monitored, to be on the lookout for asudden burst of events from a distant, but dyingsun.

The Super-K detector would record 4,000supernova neutrino interactions from asupernova in the center of our galaxy.

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Water Cerenkov Detector

Highly purified water is used as the detectingelement. High energy charged particles passing throughthe water produce Cerenkov light which is detected byPhoto Multiplier Tubes (PMTs) surrounding the water.Based on the patter of Cerenkov light emission, these

detectors can identify both electrons/positrons andmuons/antimuons. Energy reconstruction of very highenergy (E 5 GeV) is difficult because of a largenumber of particles in the hadron shower produced inthe deep inelastic scattering, many of which will be

below their Cerenkov threshold. There is no magneticfield with these detectors and hence the charge of aparticle can not be identified

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Liquid Argon Detector

Liquid Argon is used as the detectingmedium. The tracks produced by chargedparticles are identified in the liquid and

based on the pattern of tracks the particleis identified. The detector has goodcalorimetry along with excellent particleidentification capability. There is no

magnetic field hence it is not possible todistinguish between particles andcorresponding anti-particles.

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Iron Calorimeter

Iron Calorimeters consist of iron (steel)modules interspersed with sensitiveelements in which charged particles

deposit energy. These detectors can notbe used to detect electron-type neutrinosand hence are capable of observing only and . A magnetic field, however, canbe added, in which case distinctionbetween the produced and + ispossible.

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Emulsion Detector

In this detector emulsion films (50 mthick) are employed to observe thetrajectories of and its decay products.

These films are interleavened with 1 mmthick lead plates to provide a large (1.8ktons) target mass. In addition to theemulsion films, the detector also contains

a magnetic spectrometer which measuresthe charge and the momentum of muonsgoing through it.