Title: Atom Smashers Particle Accelerators and Detectors Mats Selen, UIUC
1Atom SmashersParticle Accelerators and
DetectorsMats Selen, UIUC
- Whats the motivation ?
- How to build a particle accelerator.
- How to build a particle detector.
A great web site with lots of links
is http//pdg.lbl.gov/particleadventure/english/i
ndex.html
2Whats the Motivation ?
- Try to make sense of the way the Universe works
- Look for simple explanations to complicated
looking observations !
Complication
Simplification
There is lots of different stuff on earth
3How to build a Particle Accelerator
First get some particles
4Now Accelerate Them
Wed like to give them lots of kinetic energy
(lets say 10 GeV)
Do VdG bubble demo
This cant provide enough energy(only a few
million volts) !
Need bigger voltage (and a vacuum system) !!
5Linear Accelerator
6Linear Accelerator
7Linear Accelerator
8Linear Accelerator
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9Linear Accelerator
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10Linear Accelerator
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11Linear Accelerator
12Some Examples
LINAC at Bates Lab (MIT)(0.5 GeV)
LINAC at Fermilab(0.4 GeV)
13A Bigger Example
SLAC (Stanford)(50 GeV)
14But some people like to recycle...
- Have the particles go through the same
accelerator cavitymany times
Circular track(high-vacuum beam-pipe)
This is called aSynchrotron
Key ingredients
Need to make particles go in a circle
Need to keep everything synchronized
15Forces on Charged Particles
- Both electric and magnetic fields influence the
motion of charges.
E/m demoTV demoGeiger demo
F qv x B
16Synchrotrons
17Fermilab
Booster (8 GeV)
Main Ring (150 GeV)
Tevatron (1000 GeV)
18A slick trick Two for the price of one
19CERN
20LEP Tunnel
21How to build a Particle Detector
Ideally, we want to measure everything (E, Px,
Py, Px) about every particleproduced in the
collision.
Charged Particles
Neutral Particles
22Most Common Approach(for colliding beam
experiments)
Detector package looks like a beer can
23The Parts
24How it works
- All of the parts work more or less the same way
- Charged particles ionize the material they pass
through, and we can detect signs of this
ionization.
1)
Geiger counter
25How it works
- All of the parts work more or less the same way
- Charged particles ionize the material they pass
through, and we can detect signs of this
ionization.
2)
detect photon
Scintillator counter
26Lets Try It
- We dont have an accelerator handy so lets look
at cosmic rays
Cloud chamber
27Scintillation Detector
- Photons are produced in the plastic by
scintillating molecules when a cosmic ray muon
whizzes through it. - These photons are detected by a photo-multiplier
tube, and result in pulses on the oscilloscope.
Singlescoincidencebeta
28Concluding Remarks
- The pursuit of High Energy Physics is motivated
by a quest for fundamental understanding. - Current accelerator and detector technology is
very cool.
29The Periodic Table
30The Periodic Table Explained ?
proton
neutron
electron
31The nucleus is much smaller than the atom
Even so, the nucleus contains gt 99.9 of the
mass of the atom !
32Energy vs Mass
He (m4.0026 u)
O (M15.9995 u)
So energy is the same as mass somehow ??
Units
33Mass from Energy
34Mass from Energy
Ebefore Eafter
35Units
E mc2
Preferred unit of Energy/Mass GeV
This is a small amount of energy (more
appropriate for chemistry)
1GeV 109 eV (a billion eV)
(about the mass of a protonappropriate scale for
us)
36It gets more complicated again...
fj
D2
Lc
f2
f3
B
h
Sc
w
D
f4
f2
W
p2
a4
p
f0
K
K3
S
r
a1
h1
a0
Bc
h0
f1
K2
D1
w3
D2
Bs
Ds
K
L
K2
w
D
K1
a2
f
h
K4
B
K3
r3
37quarks leptons
38quarks anti-quarks
(baryons)
Now we can easily build any ofof the particles
we have discovered(and predict some we haven't)
(mesons)
39Example CLEO
40Example L3
41Vertex Detector (CLEO)
42Drift Chamber
43Calorimeter
44Solenoid