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Recirculation Concept - Cyclotron
Radio frequency
alternating voltage
D-shaped RF cavities
time t =0
Hollow metal
drift tubes
time t =½ RF period
• Orbit radius increases with momentum
• Orbital Frequency independent of momentum
• Particle motion and RF in phase
Lawrence:
4” – 80 keV
11” - 1.2 MeV
Constant revolution frequency
Equilibrium Orbit
Magnetic
Force
Centrifugal
=
Force
momentum
f rev 
v
2 

p

eB
v eB
eB

2  mv 2  m
mv p
B 

e
e
radius
magnetic
field
Synchrotron Ring Schematic
Bending magnets
Accelerating
Voltage
• During acceleration,
momentum increases
• Increase magnetic field
during acceleration.
• Constant orbital radius
Vacuum
tube
Focusing magnets
Colliding Beam Synchrotron
Equilibrium Orbit
momentum
Constant revolution frequency
f rev
v
v eB
eB



2  2  mv 2  m
mv p
B 

e
e
radius
p

eB
magnetic
field
CERN Seen from the Air
• Tunnels of CERN accelerator complex
superimposed on a map of Geneva.
• Accelerator is 50 m underground
• 25 km in circumference
Alors, c’est fini!
Et maintenant?
Interaction of Charged Particles with Matter
• All particle detectors ultimately use
interaction of electric charge with matter
– Track Chambers
– Calorimeters
n  0
– Even Neutral particle detectors
•
•
•
•
•
Ionization
Multiple Scattering
Cerenkov
Transition Radiation
Electron’s small mass - radiation
How we did it in the past – Bubble Chamber
Magnet
You could actually see what was going on
1960s
computer
Bubble Chamber – ionization trails in superheated liquid hydrogen
Electron knocked
out of atom
Spirals in magnetic field
•

•
 e e
  e e


     
K 0    
 0    e ee e
Generic Detector

Layers of Detector Systems around Collision Point
R.S. Orr 2009 TRIUMF Summer Institute
Generic Detector

Different Particles detected by different techniques.


Tracks of Ionization – Tracking Detectors
Showers of Secondary particles – Calorimeters
R.S. Orr 2009 TRIUMF Summer Institute
Generic Detector

Different Particles detected by different techniques.


Tracks of Ionization – Tracking Detectors
Showers of Secondary particles – Calorimeters
R.S. Orr 2009 TRIUMF Summer Institute
Computer Display of Event

Layers of Detector Systems around Collision Point
R.S. Orr 2009 TRIUMF Summer Institute
ATLAS Detector

Different Particles detected by different techniques.


Tracks of Ionization – Tracking Detectors
Showers of Secondary particles – Calorimeters
R.S. Orr 2009 TRIUMF Summer Institute
ATLAS Wedge

Different Particles detected by different techniques.


Tracks of Ionization – Tracking Detectors
Showers of Secondary particles – Calorimeters
R.S. Orr 2009 TRIUMF Summer Institute
Wire Chamber
R.S. Orr 2009 TRIUMF Summer Institute
3 stages in signal generation
1) Ionization by track passing through cell
2) Ionization drifts in E field
time
3) In high E field region near wire, primary ionization
electrons gain enough energy to start ionizing the gas
- Avalanche
- More charges
7
- Charge amplification ~ 10
- Noise free amplifier
R.S. Orr 2009 TRIUMF Summer Institute
microvolt signal if
no amplification
Generic Detector
R.S. Orr 2009 TRIUMF Summer Institute
Generic Detector
R.S. Orr 2009 TRIUMF Summer Institute
Simple Drift Chamber
R.S. Orr 2009 TRIUMF Summer Institute
The ATLAS Inner Detector
TRT endcap A+B
TRT barrel
Pixels
TRT endcap C
SCT endcap
SCT barrel
ATLAS Tracker
R.S. Orr 2009 TRIUMF Summer Institute
Inner Detector (ID)
The Inner Detector (ID) comprises
four sub-systems:
•Pixels
(0.8 108 channels)
•Silicon Tracker (SCT)
(6 106 channels)
•Transition Radiation Tracker
(TRT)
(4 105 channels
ATLAS Wedge

Different Particles detected by different techniques.


Tracks of Ionization – Tracking Detectors
Showers of Secondary particles – Calorimeters
R.S. Orr 2009 TRIUMF Summer Institute
PN Junction
R.S. Orr 2009 TRIUMF Summer Institute
SCT barrel
Pixel Layer-2 – half shell
Pixel Layer2, once clamped, outside
“Ready for installation” date is 1st April 2007
Pixel Layer2, once clamped, inside
ATLAS Wedge

Different Particles detected by different techniques.


Tracks of Ionization – Tracking Detectors
Showers of Secondary particles – Calorimeters
R.S. Orr 2009 TRIUMF Summer Institute
Why Is It Called a Calorimeter?
Charged Particle
Liquid Argon/Metal
Kinetic Energy of Particle
Converted to Ionization
Of Liquid Argon
Electrical Signal
Proportional to
Incoming Energy
Readout Electronics
Comparison of Hadronic & Electromagnetic Showers
R.S. Orr 2009 TRIUMF Summer Institute
LAr and Tile Calorimeters
Tile barrel
Tile extended barrel
LAr hadronic
end-cap (HEC)
LAr EM end-cap (EMEC)
LAr EM barrel
LAr forward calorimeter (FCAL)
LAr Forward Calorimeters
• FCAL C assembly into tube – Fall 2003
Oct 2002
Hadronic Endcap
HEC – FCAL Assembly