EMMA at Daresbury

batchquonochontaugΠολεοδομικά Έργα

29 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

98 εμφανίσεις

EMMA at Daresbury

An accelerator to solve the
problems of the 21
st

century

Dr. Peter Williams, Accelerator Physicist

STFC Daresbury Laboratory & Cockcroft Institute

Talk given at British Association Mini Science Festival, Daresbury, 3
rd

Oct 2010

Particle Accelerators

What is a particle accelerator?


A charged particle sees a voltage difference

and accelerates away from a like charge


This electron passes through

a difference of 1.5 V. It has

energy of 1.5
electron volts


An electron volt is the

unit of energy we use

Particle Accelerators

What is a particle accelerator?


A cathode ray tube


old TV set


A hot filament boils

off electrons


Needs to be done in

a vacuum or electrons

are stopped by air

molecules

Particle Accelerators

Why were they developed?



Wilhelm Roentgen (1845


1923)

experimented passing electricity

through vacuum tubes

Particle Accelerators

Why were they developed?



Hand
mit

ringen


Wilhelm
Röntgen's

first

X
-
ray, of his wife's hand,

taken on 22 December 1895


She said, “I have seen my death!”

Particle Accelerators

Why were they developed?




We now call this

diagnostic radiology

Particle Accelerators

They were refined

and made more powerful


The high energy particles produced

are akin to super
-
microscopes,

we can bounce them off stuff just

as we bounce light to see things


The difference is we can “see” much

smaller things


Cockcroft & Walton aided

Rutherford in discovering the

nucleus of the atom

Particle Accelerators

They were refined

and made more powerful


The high energy particles

are akin to super
-
microscopes,

we can bounce them off stuff just

as we bounce light to see things


The difference is we can “see” much

smaller things


Cockcroft & Walton aided

Rutherford in discovering the

nucleus of the atom

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Nature of matter

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Evolution of

the universe

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Secrets of life

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Secrets of life

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Fight against disease

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Higher yielding

crops

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Durable concrete

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Tougher steel

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Safer jet engines

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Better fuel efficiency

Particle Accelerators

Particle accelerators enabled the science & technology
of the 20
th

century


Understanding

the past

Particle Accelerators

Particle accelerators can be deployed to solve the big
problems facing society in the 21
st

century


EMMA at Daresbury (funded by the CONFORM project)
will help us address at least two very different problems:




UK’s leading cause of death, cancer




Need for large scale, zero
-
carbon source of
electricity

Robert Winston: Intro

Types of Modern
Accelerator

Most research particle accelerators today
come in two types:




Cyclotrons




Synchrotrons

Types of Modern
Accelerator

Most research particle accelerators today come in
two types:




Cyclotrons




Synchrotrons



They both use the fact that a charged particle moving
in a constant magnetic field is deflected into a circle


we bring the particle back to the voltage difference
and kick it again, and again ...

Cyclotron

The first modern accelerator


Developed by Ernest Lawrence

at Berkeley, California in 1932


This fits on the palm of your hand

and produced 80,000 electron volt

protons

Cyclotron

It is like swinging a stone on a string,

Proton is the stone, magnetic field is the string, alternating
voltage across the gap between the two D
-
shaped magnets
increases the speed of the stone, string tension
constant
, so
string length
increases


The proton

spirals out

to the edge

Cyclotron

The 60,000,000 electron volt proton cyclotron
at
Clatterbridge

Oncology Centre on the Wirral


In operation since

1988 treating eye

tumours


Maximum

penetration depth

of 31mm

Cyclotron

The 590,000,000 electron volt proton cyclotron
at Paul
Scherrer

Institut
, Switzerland


The highest

energy cyclotron

in the world


Predominantly

nuclear physics

research




Cyclotron

Pro: We can inject a large number of particles at the start
continuously, we say it is a
high current
machine



Con: The orbit increases with energy, we must keep the
magnetic field constant, therefore the magnets soon
become prohibitively expensive (we also have trouble
coping with relativity). So practically it is a
low energy

machine (certainly less than 1,000,000,000 electron volts)

Types of Modern
Accelerator

Most research particle accelerators today
come in two types:




Cyclotrons




Synchrotrons

Synchrotrons

The quest for higher energy = better microscope.
Nuclear & particle physics need high energy



Back to swinging a stone on a string,

this time we keep the string length
constant

and let
the tension in the string
increase
as we kick the
stone

Synchrotrons

Focusing magnets

Vacuum

tube

Accelerating


cavity

Bending magnets

Synchrotrons

Swinging a stone on a string,

this time we keep the string length
constant

and let
the tension in the string
increase
as we kick the
stone


To do this we put the particles in a ring, then
increase the strength of the magnets, all the while
keeping the revolution frequency constant with a
voltage difference kick (called an RF cavity)

Synchrotrons

Pro: The energy limit is
given by our ring radius
and magnet strength. It is
a
high energy

machine


CERN Large Hadron
Collider: Energy
7,000,000,000,000
electron volts

Synchrotrons

Pro: The energy limit is given by our ring radius and
magnet strength. It is a
high energy

machine



Con: We put a small amount of particles in, then need to
wait while the magnets increase in strength, then extract
our particles at high energy. Changing the strength of
magnets is a
slow process
. So it is a
low current

machine

Solution: The ns
-
FFAG

A cross between a cyclotron and a synchrotron


A long & complex name: Non
-
Scaling Fixed Field
Alternating Gradient accelerator


We keep the magnetic field fixed and let the
orbit change
position and shape

in standard magnets


not a circle or a
spiral

Solution: The ns
-
FFAG

However, no
-
one has ever built one before


We do not know if the beam can be controlled


We need a prototype .....

EMMA ... the world’s first ns
-
FFAG

Robert Winston:
Accelerators

EMMA Application:
Particle Therapy

Cancer is frequently treated using
radiotherapy


High energy photons (X
-
rays) are directed at a tumour


The aim is to kill cancerous cells, whilst leaving healthy cells


Photons are not the best way to achieve this

EMMA Application:
Particle Therapy

EMMA Application:
Particle Therapy

EMMA Application:
Particle Therapy

Other countries (Switzerland, Germany, USA) are
developing particle therapy centres


Clatterbridge

was one of the first (1988) but its low
energy cyclotron can only treat tumours on the of eye due
to the small penetration depth (31mm)


NHS is now sending patients abroad for treatment of
other cancers, but cannot afford a UK centre


Need for a cheaper accelerator ... EMMA as prototype

Robert Winston:
Particle Therapy

EMMA Application:
ADSR

We need to stop burning fossil fuels




they cause

climate change

EMMA Application:
ADSR

We need to stop burning fossil fuels




they cause

climate change

EMMA Application:
ADSR

We need to stop burning fossil fuels




they are becoming

increasingly difficult

to find & extract

EMMA Application:
ADSR

Renewables

cannot fill the gap


Even country
-
sized developments will not be enough


I would need to give an hour long

talk to fully justify this statement,

not today!



A wind turbine typically delivers

only 1.5 MW peak

EMMA Application:
ADSR

Renewables

cannot fill the gap


Fossil fuels will need to be

replaced by a basket of

alternatives


It is impossible to put such a

basket together without

nuclear power




EMMA Application:
ADSR

Nuclear power has an image problem



Safety: Chernobyl


Waste disposal: NIMBY


Proliferation: Rogue states


& terrorists


EMMA Application:
ADSR

Nuclear power has an image problem



My view: there is no problem.


I would need to give another

Set of one hour talks on

each of the three main

objections to nuclear power

to fully explain.

Again, not today!

EMMA Application:
ADSR

Nuclear power has an image problem


Putting those to one side


Wouldn’t it be nice if we could

have nuclear power without

critical reactors, long
-
lived

waste and weapons grade

by
-
products?


We can.

EMMA Application:
ADSR

A neutron splits (fissions) a uranium nucleus, which produces

More neutrons, which produce more fissions
-

a chain reaction


Each fission absorbs 1 neutron and produces ~2.5


Some neutrons lost, leaving

k neutrons to produce k fissions


A conventional reactor has k = 1 exactly,

we call this
critical


If k < 1 it stops, if k > 1 it explodes

EMMA Application:
ADSR

We can run the reactor
sub critical
(k < 1)


But we need an external source of extra neutrons


Use an accelerator to provide the extra neutrons




Hence: Accelerator Driven Subcritical Reactor (ADSR)


Allows us to abandon U
-
Pu

cycle, and move to Thorium

EMMA Application:
ADSR

Turn off the accelerator and the reaction stops


manifestly safe


What type of accelerator do we need?


High energy, high current, but cheap


A ns
-
FFAG ... EMMA

(and PAMELA as the next stage)



EMMA


a prototype driver for a sub
-
critical reactor

OFF

Robert Winston: ADSR

EMMA: The Adventure
Begins

EMMA now fully constructed


First beam was in June

EMMA: The Adventure
Begins

Multiple turns achieved 26
th

August

First Turn

Second Turn

EMMA: The Adventure
Begins

Now taking real machine data

First Turn

Second Turn

Kicker

Optimisation of injection

T
unes

from fit

EMMA: The Adventure
Begins

Now taking real machine data

First Turn

Second Turn

September
-

beam circulates
more than 1000 turns

Synchrotron oscillations observed

EMMA: See For Yourself

Please take the opportunity
to visit EMMA, the Electron
Model of Many Applications,
at the base of the tower


Open access today


It is co
-
located with ALICE,
our other prototype
accelerator, which I haven’t
even mentioned!