THE LARGE HADRON COLLIDER

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THE LARGE HADRON COLLIDER
Chuck Hobson BA, BSc(hons)
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LARGE HADRON COLLIDER
CERN Geneva Switzerland
Conseil Européen pour la Recherche Nucléaire
European
Organization for Nuclear Research
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WHERE IS THE LARGE HADRON COLLIDER
MAP
AERIAL VIEW
Cement lined tunnel 3.8m diameter 27km
circumference 50m to 170m below the surface.
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WHAT DOES IT LOOK LIKE
LHC control room
Inside LHC Tunnel
CMS Detector (1 of 4 large
detectors)
Worker beside magnet
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WHAT IS THE LARGE HADRON COLLIDER?
Very briefly
A huge synchrotron in a subterranean concrete
lined tunnel 100m deep The synchrotron has two
evacuated tubes running in opposite
directions Protons are accelerated to near light
speeds in these tubes and collided Four
extremely complicated detectors are located along
the tubes They are placed at four designated
collision points The detectors are named ATLAS,
ALICE, CMS and LHCb Collision by-products are
studied in the quest for new particles Why bother
when expenditures to date (4/20/10) are 10
billion Euros? The following 2.5 minute video
offers some answers
Video 1 Note To return to slide
presentation when video finishes, click on left
arrow located on upper left corner of web page
and continue nto next slide.
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HOW DOES THE LHC WORK?

• CERN is a massive complex of scientific equipment
  consisting of
• The LHC, a 27km circumference synchrotron
• Three smaller synchrotrons
• A linear accelerator
• A proton generator
• Four huge detectors
• The way this all works is described in the
  following video

Video 2
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CERN PARTICLE ACCELERATORS

• Electrons stripped from hydrogen and injected
  into Linear accelerator
• Linear accel. Accelerates protons to 100 million
  m/s (proton energy 50MeV)
• Booster accel. Protons to 275 million m/s (proton
  energy 800MeV)
• Proton synchrotron increases speed to 99.9 c
  giving proton 25GeV energy and increases rest
  mass x 25
• SPS increases proton energy to 450GeV and rest
  mass x 450
• LHC increases proton energy to 7TeV and rest mass
  x 7000 There are 2 beams of protons counter
  rotating for 2 hours before entering the
  collision area

Y- Lead ions pb 54 54 of 82 e stripped
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LINEAR ACCELERATORS
(How they work)
THREE STAGE DC LINEAR ACCELERATOR
(for illustrative purposes only)


Proton enter on the left Protons shown in
accelerating gap Note rf polarities rf
polarities change as protons enter drift
tubes Protons accelerated five times Note disk
spacing Higher energy protons exit on right
FIVE STAGE RF PROTON LINEAR LINEAR ACCELERATOR
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PROTON LINEAR ACCELERATOR
Large Hadron Collider (LHC) Linear
Accelerator LINAC-2 2007 Ran 5044 hrs. 98.7 up
time! INPUT Proton (hydrogen ions
350mA) OUTPUT Pulsed protons 20µs150µs 1s
rate 50MeV protons (185mA) at 1/3c Quadrupole
magnet beam focusing
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PROTONS IN MAGNETIC FIELDS
Protons enter bottom at a constant speed
(drifting up from bottom) Magnetic field causes
protons to bend in a direction that is right
angle to the magnetic lines of force. The proton
speed remains constant becaust the magnet does
not add or subtract energy from the proton
SECTION OF SYNCHROTRON
As the proton gains speed and relativistic mass,
the magnetic strength is increased to keep the
proton beam centered in the pipe.
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MAGNETISM
LHC RELIES ON MAGNETS FOR BEAM FOCUSSING AND
BENDING
The SI unit of magnetic field flux density is the
Tesla T T units very are large. µT and nT
units more practical Another unit in common usage
is the gauss G , (CGS) 1T 10,000G

• THREE TYPES OF MAGNETS
• Permanent (strontium ferrite) 0.1T 0.2T
• Resistive (Iron dominant) upper limit 2T
  saturation
• Super-conducting 10T

Large Hadron Collider ring ( 27km circumference)
Uses 1232 dual 56mm aperture 14.2m long SC
Magnets (8.4T) Called arc magnets. Bends proton
beam around the circle Magnet increases 0.54T to
8.4T as proton energy increases .45TeV 7TeV
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SUPERCONDUCTING MAGNETS
Magnet and blue cooling unit being assembled
(One of 1232 magnets) Assembled length
14.2m Weight gt 20 tonnes Strength 0.54T to
8.4T Bending for 0.51 7.0TeV protons 13,000A
at maximum strength Cooled to 269.1 C 1.9
kelvin Niobium-titanium alloy wire 200 tonnes
of NbTi cable in the LHC and kept at 1.9k
700,000 litres of liquid Helium feeds all cables
and magnets
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BRIAN COX ON WHAT WENT WRONG
Professor Brian Cox returned to Monterey
California (TED) to report on LHC super cooled
magnet failures and subsequent actions.
Video
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PROTON BOOSTER (PSB)
Four rings stacked 36cm sep Each ring has its own
RF accelerator cavity 32 four beam bending
magnets 48 quadrupole beam focussing magnets
(magnets not shown in figure)

• Entering Protons begin speeding around taking
  1.67µs per turn
• The Protons are given synchronized kicks every
  turn by the RF cavity
• After many rotations protons reach 275m/s taking
  0.64µs per turn
• RF freq. increased as protons speedup maintaining
  beam sync.
• Proton ring outputs recombined 4 x 2 bunches of
  protons at 1.4GeV

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PROTON SYNCHROTRON (PS)
628m circumference Proton Synchrotron built in
late 1950s Input 1.4GeV protons from 4 ring
Proton Booster Output 25GeV protons to Super
Proton Synchrotron
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SUPER PROTON SYNCHROTRON (SPS)
7km circumference ring buried 20m 744 dipole
magnets for steering and 216 quadropole
mag http//blog.modernmechanix.com/2008/10/05/coll
iding-beam-accelerators-E28094-will-they-reveal
-the-ultimate-particles/
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LARGE HADRON COLLIDER
In tunnel 50m 170m deep Two 60mm beam tubes to
carry protons in opposite directions Beam tubes
filled twice a day 1232 super conducting beam
bending magnets 386 super conducting beam
focussing magnets Many small correcting magnets
for beam corrections 400MHz RF cavities for
proton beam accelerators All of above bathed in
liquid helium keeping Temp. at -269.30 C
LHC BEAM PARAMETERS
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ATLAS AND CMS DETECTORS
Atlas detector Largest ever made
46m long
x 25m high x 25m wide
(Half as big as the Notre Dame
cathedral) Weight 7000 tonnes (Weighs same
as the Eiffel Tower)
ATLAS
CMS
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PROTON COLLISIONS AT ATLAS
2800 bunches of protons are going around LHC at
7TeV near c Bunches spaced 7m each being 80mm
long and 16µm diameter 100 billion protons per
bunch 20 collisions occur 2800 bunches making
11,000 turns/s 31 million crossings Thus 600
million protons collide each second. One
petabyte of raw data per second is collected. One
petabyte 1000 terabytes (1000 trillion bytes
X 8 gives bits)
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LHC EXPERIMENTS
Protons moving clockwise (red) Protons moving
anticlockwise (blue) Proton colision points shown
at experimentsALICE ATLAS CMS LHCb
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EXPERIMENTAL RESULTS

• FOUR LARGE DETECTORS ATLAS CMS ALICE - LHCb
  
• Located around the 27km ring at particle
  collision points
• Very busy places
• They identifies particles measure their momentum
  and energy
• Atlas collects 1 peta-byte (1000 trillion bytes)
  of data per second
• This is enough data to fill 1.5 million double
  layer DVDs
• Worldwide LHC Computing Grid (WLCG) a vast
  computing network
• Combines computing resources of 100,000
  processors at 170 cites
• Provides near real time access to scientists in
  34 countries.
• Data to US is via fibre optics from CERN
• Data from the (28-03-2010) 7TeV collisions being
  analysed now
• It will take years to do the analyses
• J. J. Thompson really started something, didnt
  he!!!

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Many thanks for taking the time to view my
presentation on the Large Hadron Collider. I hope
you found it informative and enjoyable
Chuck Hobson BA, BSc(hons)
Comments and suggestions CLICK