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Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati
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Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Dec 28, 2015

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Page 1: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Physics of Particle Accelerators

Kalanand MishraDepartment of Physics

University of Cincinnati

Page 2: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

How a Particle Accelerator Works

Speed up particle with E/M field Smash particles into target or other

particles Record collisions with detectors Able to identify product particles

Page 3: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Physics of a Particle Accelerator

Beam production Bunching Electron guns Beam focusing Colliding and Detecting

Page 4: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Beam production

Electron Beam

Thermoionic Emission

Page 5: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Ionizing Hydrogen

•Glow Discharge Column

•From H- Ion

Proton Beam

Page 6: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Other Beams

Secondary Beams:

• Proton

• Antiproton

• Other Particle Beams

Page 7: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Bunching

Bring the Particles in phase.

As spread out beam gives fewer collisions than a narrowly focused one, e- & e+ bunches are sent into

damping rings (e- to north, e+ to south).

Page 8: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Colliding

•Fixed target

E = (2mEp)

•Colliding beam

E = 2Ep

Page 9: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Beam Focusing

As spread out beam gives fewer collisions than a narrowly focused one, e- & e+ beams have to be focused.

This is done by bent magnets.

Page 10: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Two Types

L inear C ircu lar

Acce lera tor

•Linear Path

•Travel once

•Circular Path

•Travel several times

Page 11: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Linear Accelerator

Page 12: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

LINAC Operation

Page 13: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Methods of Acceleration in Linear Accelerator

SLC Polarized Electron Gun

Page 14: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Methods of Acceleration in Linear Accelerator

•Basic idea

•Synchronization

•Length of the tube

•Shielding

Page 15: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

LINAC cont’d

Klystron: Microwave generator

1. Electron gun produces a flow of electrons. 2. Bunching cavities regulate speed of electrons so that bunches arrive at the output cavity. 3. Bunches of electrons excite microwaves in output cavity of the klystron.4. Microwaves flow into the waveguide , which transports them to the accelerator. 5. Electrons are absorbed in beam stop.

Page 16: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Overall Operation of LINAC

Electrons are Accelerated in a Copper Structure

Bunches of electrons are accelerated in the copper structure of the linac in much the same way as a surfer is pushed along by a wave.

Changing Electric and Magnetic Fields:

Page 17: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

E/M waves that push the electrons in the linac are created by higher energy versions of the microwaves used in the microwave ovens in our

kitchens.

The microwaves from the klystrons in the Klystron Gallery are fed into the accelerator via waveguides.

This creates a pattern of E&B fields, which form an E/M wave traveling down the accelerator.

Klystron Operation

Page 18: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

The 2-mile SLAC linear accelerator (linac) is made from over 80,000 copper discs and cylinders brazed together.

LINAC Structure

Microwaves set up currents that cause E pointing along accelerator

and B in a circle around interior of accelerator.

Want e- and e+ to arrive in each cavity at right time to get max. push from E.

e+ needs to arrive when field polarity is opposite.

Page 19: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Circular Accelerator

Page 20: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Methods of Acceleration in Circular Accelerator

Cyclotron

•The Ds

•Electric field across the gap

•Circular orbit

•Increasing radius

Page 21: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Cyclotron

The maximum speed a proton could have

in a dee of radius R and strength B is given

by (ignoring relativistic effects.)

vm = BeR / mp

Page 22: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Synchrotron (synchro-cyclotron)

Methods of Acceleration in Circular Accelerator

• Electromagnetic resonant cavity

• Magnetic field for circular

orbit

• Field synchronization with increasing particle energy

• Synchrotron radiation

• Storage ring

Page 23: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Synchrotron

The radius of curvature of the path of particles of momentum p and charge q in a synchrotron is given by the formula

R = p / q B where B is the field strength.

If a synchrotron of radius R has 4 straight sections of length L each and period of the radio frequency oscillator corresponds to the time of one revolution then

(a) The speed of the particles is v = ( 2pR + 4L ) f

Page 24: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Synchrotron

(b) By considering the relativistic momentum of particles of mass M, the magnetic field strength of the synchrotron is given by

where f is the frequency.

Page 25: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Storage Rings

Similar to a synchrotron, but designed to keep particles circulating at const. energy not increase energy further

SPEAR : 3 GeV

PEP I : 9 GeV

PEP II : e- 9 GeV e+ 3.1 GeV

Page 26: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.

Detection

•Tracking bubble, radiation

•Tracking curvature (charged particle)

Page 27: Physics of Particle Accelerators Kalanand Mishra Department of Physics University of Cincinnati.