Transcript HendersonKickoff

Nebraska’s Statewide Outreach and Education Experiment
Washington Area Large Time-coincidence Array
The Cosmic Ray Observatory Project
Needles in a Haystack
Neutrinos Among The Cosmic Rays
The Henderson Mine Project
Tuesday, September 28, 2004
Dan Claes
University of Nebraska-Lincoln
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-field
points
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
Also necessary to be
•far removed from any
radioactive samples
But even when
•shielded with 2 inches of lead
STILL slowly discharges!
seemed to indicate an unknown radiation with greater penetrability
than 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.
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.
0
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
Hess lands following a historic 5,300 meter flight.
August 7, 1912
National Geographic photograph
1937 Marietta Blau and
Herta Wambacher
report “stars” of tracks
resulting from cosmic
ray collisions with
nuclei within the emulsion
50mm
Cosmic ray
strikes a nucleus
within a layer of
photographic
emulsion
Before the explosion:
Mass, M
vo = 0
After the explosion:
v1
v2
m1
m2
With no external forces,
the momentum P must be conserved.
Initially:
P=0
vo = 0
P = m1v1 + m2v2 = 0
Finally:
v1
v2
m1
m2
m1v1 = - m2v2
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)
B)
C)
D)
0
½
1
20
m/s
m/s to the right
m/s to the left
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
232Th
238U
230Th
238Pu
230U
220Rn
222Ac
216Rn
212Po
216Rn
KE(MeV)
4.01
4.19
4.69
5.50
5.89
6.29
7.01
8.05
8.78
8.78
t1/2
1.41010 y
4.5109 y
8.0104 y
88 years
20.8 days
56 seconds
5 seconds
45.0 msec
0.30 msec
0.10 msec
l(sec-1)
1.610-18
4.910-18
2.810-13
2.510-10
3.910-7
1.210-2
0.14
1.5104
2.3106
6.9106
1930 Series of studies of nuclear beta decay, e.g.,
Potassium goes to calcium
Copper goes to zinc
Boron goes to carbon
Tritium goes to helium
 20Ca40
64
64
29Cu  30Zn
12  C12
B
5
6
3  He3
1H
2
19K
40
Potassium nucleus
Before decay:
After decay:
A
B
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.
Ee = (mA2 - mB2 + me2)c2/2mA
but this only seems to match
the maximum value
observed on a spectrum of
beta ray energies!
No. of counts per unit energy range
0
5
10
15
20
Electron kinetic energy in KeV
The beta decay spectrum of tritium ( H  He).
Source: G.M.Lewis, Neutrinos
(London: Wykeham, 1970), p.30)
1932
n  p + e- + neutrino
charge
mass
0
+1
-1
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, 1959
Savannah River (1000-MWatt)
Nuclear Reactor in South Carolina
looked for the inverse of the
process:
n  p + e- + neutrino
Cowan & Reines
p + neutrino  n + e+
with estimate flux of
51013 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 tall
40 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
$500M
major components: photomultiplier tubes,
excavation, water purification system.
The optimal detector depth to perform
the full proposed scientific program of
UNO  4000 meters-water-equivalent
or deeper
SALTA: Snowmass Area Large
Time-Coincidence Array
Empire
• 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
• Clear Creek High School,
Empire, CO
SALTA Workshop, July 2001, Snowmass, CO
Making detectors light-tight
Polishing scintillator
edges outside
Conference Center
mass
phototube
gluing
CROP article in Lincoln Journal Star, 7 August 2003
The Chicago Air Shower Array
CROP recycles retired detectors from the Chicago Air Shower Array
•Located in the Utah Desert
•1089 stations, 15m spacing each houses 4 scintillators w/tubes
1 high and 1 low voltage supply
•covering 0.23 square km
The CROP team at Chicago Air Shower Array (CASA) site
U.S. Army Photo
September 30,
1999
2000 scintillator panels, 2000 PMTs,
500 low and power supplies at UNL
CASA detectors’ new home
at the University of Nebraska
Read out by
10 stage
EMI 9256
photomultiplier tube
2 ft x 2 ft x ½ inch
PMMA (polymethyl methacrylate)
doped with a scintillating fluor
Recycling material inherited from
The Chicago Air Shower Array
1 Leadville
10 miles
Henderson
Mine
Visit
Dec 4, 2003
hosted by
Chip deWolfe
Marc Whitley
Aspen High School
Diana Kruis
Basalt High School
Michelle Ernzen
Lake County School
Nancy Spletzer
Clear Creek High School
Laura French
Roaring Fork Valley
Hans-Gerd Berns
University of Washington
Dan Claes
University of Nebraska
Scouted 3 possible locations
between 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 Workshop
July 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.
Detector Configuration
Two modules each a pair of telescoped of detectors
•requiring a coincidence in each pair helps cut down “noise”
•sandwiched with lead sheet
¼ in lead
•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 Station
An ~identical pair of modules will run in a fixed
location (surface office) to establish a baseline