the large hadron collider n.
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  1. THE LARGE HADRON COLLIDER Chuck Hobson BA, BSc(hons) Press right arrow to advance slide

  2. LARGE HADRON COLLIDER CERN Geneva Switzerland Conseil Européen pour la Recherche Nucléaire European Organization for Nuclear Research

  3. WHERE IS THE LARGE HADRON COLLIDER MAP AERIAL VIEW Cement lined tunnel 3.8m diameter 27km circumference 50m to 170m below the surface.

  4. WHAT DOES IT LOOK LIKE LHC control room Inside LHC Tunnel CMS Detector (1 of 4 large detectors) Worker beside magnet

  5. 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.

  6. 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

  7. 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

  8. 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

  9. 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 20µs–150µs 1s rate 50MeV protons (185mA) at 1/3c Quadrupole magnet beam focusing

  10. 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.

  11. 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

  12. SUPERCONDUCTING MAGNETS Magnet and blue cooling unit being assembled (One of 1232 magnets) Assembled length 14.2m Weight > 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

  13. 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

  14. 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

  15. PROTON SYNCHROTRON (PS) 628m circumference Proton Synchrotron built in late 1950’s Input 1.4GeV protons from 4 ring Proton Booster Output 25GeV protons to Super Proton Synchrotron

  16. SUPER PROTON SYNCHROTRON (SPS) 7km circumference ring buried ~20m 744 dipole magnets for steering and 216 quadropole mag

  17. 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 LHCBEAM PARAMETERS

  18. 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

  19. 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)

  20. LHC EXPERIMENTS Protons moving clockwise (red) Protons moving anticlockwise (blue) Proton colision points shown at experiments:ALICE ATLAS CMS LHCb

  21. 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, didn’t he!!!

  22. 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