Nebraska’s Statewide Outreach and Education Experiment

The Cosmic Ray Observatory Project

Dan ClaesUniversity of Nebraska-Lincoln

Washington Area Large Time-coincidence Array

Needles in a HaystackNeutrinos Among The Cosmic Rays

The Henderson Mine ProjectTuesday, September 28, 2004

Henri Becquerel (1852-1908) received the 1903 Nobel Prize in Physics for the discovery of natural radioactivity.

Wrapped photographic plate showed clear silhouettes, when developed, of the uranium salt samples stored atop it.

1896 While studying the photographic images of various fluorescent & phosphorescent materials, Becquerel finds potassium-uranyl sulfate spontaneously emits radiation capable of penetrating thick opaque black paper

aluminum plates copper plates

Exhibited by all known compounds of uranium (phosphorescent or not) and metallic uranium itself.

•In ordinary photographic applications light produces spots of submicroscopic silver grains•a fast charged particle can leave a trail of individual Ag grains

•1/1000 mm (1/25000 in) diameter grains

•plates coated with thick emulsions (gelatins carrying silver bromide crystals) clearly trace the tracks of charged particles

1898 Marie Curie discovers thorium (90Th) Together Pierre and Marie Curie discover polonium (84Po) and radium (88Ra)

1899 Ernest Rutherford identifies 2 distinct kinds of rays emitted by uranium - highly ionizing, but completely

absorbed by 0.006 cm aluminum foil or a few cm of air

- less ionizing, but penetrate many meters of air or up to a cm of

aluminum.

1900 P. Villard finds in addition to rays, radium emits - the least ionizing, but capable of penetrating many cm of lead, several feet of concrete

B-fieldpoints

into page

1900-01 Studying the deflection of these rays in magnetic fields, Becquerel and the Curies establish rays to be charged particles

1900-01 Using the procedure developed by J.J. Thomson in 1887 Becquerel determined the ratio of charge q to mass m for

: q/m = 1.76×1011 coulombs/kilogram identical to the electron!

: q/m = 4.8×107 coulombs/kilogram 4000 times smaller!

1900 Charles T. R. Wilson’s ionization chamber Electroscopes eventually discharge even when all known causes are removed, i.e., even when electroscopes are

•sealed airtight•flushed with dry,

dust-free filtered air

seemed to indicate an unknown radiation with greater penetrabilitythan x-rays or radioactive rays

Speculating they might be extraterrestrial, Wilson ran underground tests at night in the Scottish railway, but

observed no change in the discharging rate.

•far removed from any radioactive samples

Also necessary to be

•shielded with 2 inches of leadBut even when

STILL slowly discharges!

0

1909Jesuit priest, Father Thomas Wulf , developed an ionization chamber with a design planned specifically for high altitude balloon flights.

A taut wire pair replaced the gold leaf.

This basic design became the pocket dosimeter carried to record one’s total exposure to ionizing radiation.

Hess lands following a historic 5,300 meter flight.August 7, 1912 National Geographic photograph

1911-12 Austrian physicist Victor Hess, of the Vienna University, and 2 assistants, carried Wulf ionization chambers up in a series of hydrogen balloon flights.

• taking ~hour long readings at several altitudes

• both ascending and descending• radiation more intense above 150 meters than at sea level• intensity doubled between 1000 m to 4000 m• increased continuously through 5000 meters

Dubbed this “high” level radiation Höhenstrahlung

50m

Cosmic ray strikes a nucleuswithin a layer of

photographicemulsion

1937 Marietta Blau andHerta Wambacher

report “stars” of tracks resulting from cosmic

ray collisions with nuclei within the emulsion

Before the explosion:

vo = 0

m1 m2

v1 v2

After the explosion:

Mass, M

With no external forces, the momentum PP must be conserved.

Initially: PP = 0

Finally: PP = m1vv1 + m2vv2 = 0

m1vv1 = m2vv2

m1 m2

vv1 vv2

vo = 0

p = 0 pgas procket

pi = 0 = pf pgas = – procket= pgas + procket

pi = 0 = pf = prifle + pbullet prifle = – pbullet

A cannon rests on a railroad flatcar with a total mass of 1000 kg. When a 10 kg cannon ball is fired at a speed of 50 m/sec, as shown, what is the speed of the flatcar?

A) 0 m/sB) ½ m/s to the rightC) 1 m/s to the leftD) 20 m/s to the right

A bomb at rest explodes into four fragments. The momentum vectors for three of the fragments are shown. Which arrow below best represents the momentum vector of the fourth fragment?

?

-decay

-decay

Some Alpha Decay Energies and Half-lives

Isotope KE(MeV) 1/2 (sec-1)

232Th 4.01 1.41010 y 1.61018

238U 4.19 4.5109 y 4.91018

230Th 4.69 8.0104 y 2.81013

238Pu 5.50 88 years 2.51010

230U 5.89 20.8 days 3.9107

220Rn 6.29 56 seconds 1.2102

222Ac 7.01 5 seconds 0.14216Rn 8.05 45.0 sec 1.510

212Po 8.78 0.30 sec 2.310

216Rn 8.78 0.10 sec 6.910

B

Before decay:

After decay:

Potassium nucleus

A

1930 Series of studies of nuclear beta decay, e.g.,

Potassium goes to calcium 19K40 20Ca40

Copper goes to zinc 29Cu64 30Zn64 Boron goes to carbon 5B12 6C12 Tritium goes to helium 1H3 2He3

1932 Once the neutron was discovered, included the more fundamental n p + e

For simple 2-body decay, conservation of energy and momentum demand both the recoil of the nucleus and energy of the emitted electron be fixed (by the energy

released through the loss of mass) to a single precise value.

but this only seems to match the maximum value

observed on a spectrum of beta ray energies!

Ee = (mA2 - mB

2 + me2)c2/2mA

No.

of c

ount

s per

uni

t ene

rgy

rang

e

Electron kinetic energy in KeV5 10 15 200

The beta decay spectrum of tritium ( H He). Source: G.M.Lewis, Neutrinos (London: Wykeham, 1970), p.30)

1932 n p + e + neutrino

charge 0 +1 1 ?mass 939.56563 938.27231 0.51099906 ? MeV MeV MeV

neutrino mass < 5.1 eV < me /100000 0

1936 Millikan’s group shows at earth’s surface cosmic ray showers are dominated by electrons, gammas, and

X-particles capable of penetrating deep underground (to lake bottom and deep tunnel experiments) and yielding isolated single cloud chamber tracks

1953, 1956, 1959Savannah River (1000-MWatt) Nuclear Reactor in South Carolinalooked for the inverse of theprocess:

n p + e- + neutrino

p + neutrino n + e+

Cowan & Reines

with estimate flux of 51013 neutrinos/cm2-sec

observed 2-3 p + neutrino events/hour

Underground Neutrino Observatory

The proposed next-generation underground water Čerenkov detector

to probe physics beyond the sensitivity of the highly successful Super-Kamiokande detector in Japan

The SuperK detector is a

water Čerenkov detector

40 m tall40 m diameter

stainless steel cylinder

containing 50,000 metric tons of ultra pure water

The detector is located 1 kilometer below Mt. Ikenoyama inside the Kamioka zinc mine.

The main sensitive region is 36 m high, 34 m in dia viewed by 11,146 inward facing Hamamatsu photomultiplier tubes surrounding 32.5 ktons of water

Underground Neutrino Observatory

• 650 kilotons

• active volume: 440 kilotons

20 times larger than Super-Kamiokande

major components: photomultiplier tubes, excavation, water purification system.

$500M The optimal detector depth to perform the full proposed scientific program ofUNO 4000 meters-water-equivalent

or deeper

• Aspen High School, Aspen, CO

• Basalt High School, Basalt, CO

• Roaring Fork Valley High School, Carbondale, CO

• Lake County High School, Leadville, CO The highest-elevation school in U.S. -- 10,152 feet above sea level

SALTA: Snowmass Area Large Time-Coincidence Array

Empire

• Clear Creek High School, Empire, CO

Polishing scintillatoredges outside

Conference Center

Making detectors light-tight

SALTA Workshop, July 2001, Snowmass, CO

massphototube

gluing

CROP article in Lincoln Journal Star, 7 August 2003

The Chicago Air Shower Array

•Located in the Utah Desert•1089 stations, 15m spacing•covering 0.23 square km

each houses 4 scintillators w/tubes1 high and 1 low voltage supply

CROP recycles retired detectors from the Chicago Air Shower Array

U.S. Army Photo

September 30, 1999

The CROP team at Chicago Air Shower Array (CASA) site

CASA detectors’ new home at the University of Nebraska

2000 scintillator panels, 2000 PMTs, 500 low and power supplies at UNL

PMMA (polymethyl methacrylate)doped with a scintillating fluor

Read out by 10 stage

EMI 9256 photomultiplier tube

Recycling material inherited from The Chicago Air Shower Array

2 ft x 2 ft x ½ inch

Leadville1

10 miles

Henderson Mine Visit

Dec 4, 2003hosted by

Chip deWolfe

Marc Whitley Diana Kruis Nancy Spletzer Aspen High School Basalt High School Clear Creek High School

Michelle Ernzen Laura FrenchLake County School Roaring Fork Valley

Hans-Gerd BernsUniversity of Washington

Dan ClaesUniversity of Nebraska

Scouted 3 possible locationsbetween 2800-3900 ft depths

110 power available

January 13-15 – SALTA students checked out condition of their detectors

Aspen Center for Physics July, 2004: Back for MORE!

Aspen Center for Physics Education & Outreach WorkshopJuly 6-8 SALTA schools take over the library, setting up cosmic ray telescopes, for training in the new DAQcard

that will facilitate all their data-taking.

¼ in lead

Detector Configuration

•requiring a coincidence in each pair helps cut down “noise”•sandwiched with lead sheet

Two modules each a pair of telescoped of detectors

•At mining level (3000 mwe) any one (2 ft 2 ft) panel can be expected to count only a handful of events / day•May need week(s) long runs

We will move detectors at 2-3 week intervals

Desktop Base StationAn ~identical pair of modules will run in a fixedlocation (surface office) to establish a baseline