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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.

G0MDK4WHAT DOES IT LOOK LIKE

Worker beside magnet

Inside LHC Tunnel

CMS Detector (1 of 4 large detectors)

LHC control room

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WHAT IS THE LARGE HADRON COLLIDER?

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.

Very briefly:

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HOW DOES THE LHC WORK?

CERN is a massive complex of scientific equipment consisting of:

1. The LHC, a 27km circumference synchrotron

2. Three smaller synchrotrons

3. A linear accelerator

4. A proton generator

5. Four huge detectors

The way this all works is described in the following video

Video 2

G0MDK7CERN PARTICLE ACCELERATORS

1. Electrons stripped from hydrogen and injected into Linear accelerator

2. Linear accel. Accelerates protons to 100 million m/s (proton energy 50MeV)

3. Booster accel. Protons to 275 million m/s (proton energy 800MeV)

4. Proton synchrotron increases speed to 99.9% c giving proton 25GeV energy and increases rest mass x 25

5. SPS increases proton energy to 450GeV and rest mass x 450

6. 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)

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

THREE STAGE DC LINEAR ACCELERATOR (for illustrative purposes only)

FIVE STAGE RF PROTON LINEAR LINEAR ACCELERATOR

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G0MDK9PROTON 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

G0MDK10PROTONS 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

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 MAGNETS1. Permanent (strontium ferrite) ~ 0.1T – 0.2T 2. Resistive (Iron dominant) upper limit ~ 2T saturation3. 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

LHC RELIES ON MAGNETS FOR BEAM FOCUSSING AND BENDING

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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

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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

G0MDK14PROTON BOOSTER (PSB)

• 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

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)

G0MDK15PROTON 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

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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/colliding-beam-accelerators-%E2%80%94-will-they-reveal-the-ultimate-particles/

G0MDK17LARGE 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

TeV 0.45 - 7

Circumference 26.7km

Time between collisions

2.5ns

Crossing angle 300 µradians

n/bunch 11 x 1010

n bunches 2808

Beam radius 16µm

Filling time 7.5 min.

Accelerations 1200

Proton mass X 7,500 @ 7TeV

Beam revolutions 11000/s (90µs)

G0MDK18ATLAS 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

G0MDK19PROTON 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)

G0MDK20LHC EXPERIMENTS

Protons moving clockwise (red)

Protons moving anticlockwise (blue)

Proton colision points shown at experiments:ALICE ATLAS CMS LHCb

G0MDK21EXPERIMENTAL 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!!!

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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)

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