Well good evening, everyone.
It's great to see you here.
I am very, very excited
about tonight because I have,
surrounding me here,
an illustrious panel
of some of the world's best--
and some of the world's
most important, I should say--
particle accelerator physicists
who are working on
the next generation
after the Large Hadron Collider.
So just to get a little bit
of a status of where we're at,
can I see a show of
hands for how many of you
have heard of the Large
Hadron Collider before?
[LAUGHTER]
Good, the media
has done its job.
Excellent.
OK, so my name is Susie Sheehy.
Thank you, Martin,
for the introduction.
I'm an accelerator physicist
at the University of Oxford.
And I tend to design
smaller machines
for different
applications, which
is what a lot of our
project, called Accelerators
for Humanity, has been about.
But we couldn't be talking
about particle accelerators
unless we really
brought out the big guns
and talked about accelerators
for particle physics.
So I think you're aware
already that the Large Hadron
Collider is the highest
energy hadron-- that
is, proton collider--
ever built--
27 kilometers in circumference,
underneath the border
between France and
Switzerland, near Geneva.
And it is doing a fantastic
job at colliding protons
together and uncovering the
secrets of the universe.
But I'm often asked, when I talk
about particle accelerators,
well, what's going to come next?
What is the next big
thing after the LHC?
And that is, effectively,
what we're here to talk about.
So the four people I
have surrounding me,
I'll just give you a quick
introduction to each of them.
And then I'm going to
ask them to introduce
their kind of pet project,
or their ideas on what
might be coming after the
Large Hadron Collider.
So first, on your
left, my right,
is professor Phil Burrows.
Phil is a professor in physics
at the University of Oxford
and he's also the associate
director of the John Adams
Institute for accelerated
science, which
is one of two accelerated
institutes in the UK.
And it's also the
one that I work in.
(LAUGHING) So Phils's
actually in my department.
So Phil actually did his degree
and PhD in particle physics,
first at Oxford Uni.
And then he actually move to the
USA for about a decade working
at MIT, and on SLAC,
the linear collider,
which was the first
electron-positron collider
in the world.
He then returned to Oxford,
then became a Professor
at Queen Mary
University, and then
came back to Oxford again--
you've spent a lot of time
at Oxford, Phil-- as a professor
and in his current position
as director of the John Adams.
So Phil has been PI-- that
is, Principal Investigator--
of the UK'S team on linear
electron-positron collider
development and working on the
international linear collider
and the compact
linear collider, which
he'll explain a little bit
more about what those two
projects are.
He's been Principal Investigator
of the CLIC UK collaboration
since 2011, and since 2014
has been the spokesperson
of the CLIC-- that is,
Compact Linear Accelerator
Collaboration-- which
involves about 300 people,
60 institutes, and 31
countries around the world.
All right, so that's Phil.
Could you welcome Phil?
Give him a round of applause.
Thank you.
[APPLAUSE]
OK.
So the next person on the
line is Dr. Frank Zimmermann.
Now I'm particularly
excited to have Frank
here because Frank's actually
come all the way over
from CERN.
Frank is a senior scientist at
CERN in the Accelerator Beams
department, which is obviously
the home of the Large Hadron
Collider.
Frank has worked, it seems,
on just about every project--
major project
going, did his Ph.D
at the University of Hamburg
on a machine called HERA, which
is a proton ring, and has worked
at major labs around the world,
including DESY in
Germany, SLAK in the US,
and has worked at CERN
from 1999, I believe.
So frank has published textbooks
in accelerated physics,
wrote the handbook, he's the
editor of the main journal
in the accelerated field-- The
Physical Review Accelerator,
and Beams-- I know you're
going to rush out and read it
right now.
It's good.
It's a good read, Frank.
It's good.
He's also a coordinator
of a work package of one
of the major
European coordination
in accelerator research and
development, called EuCARD.
The work package is
called Extreme Beams,
which is kind of cool-- I
like it-- and since 2014,
has also been deputy coordinator
of the CERN-hosted Future
Circular Collider Study,
which is mostly, I think,
what you'll be addressing
tonight, hopefully.
So please, welcome Frank.
[APPLAUSE]
OK, so first on my
left, you're right,
this is Professor
Ken Long who is
a professor of particle physics
at Imperial College in London.
And he's done a
lot of work at CERN
on muon-proton scattering as a
graduate student, apparently,
and then returned to the
UK to join an experiment
at DESY in Hamburg.
In fact, these two discovered
they were almost colleagues
at DESY by-- one year,
I think we discovered?--
and has contributed to the
design and construction of that
experiment-- so that's
particle physics experiment.
Now Ken got fascinated
by the discovery
of neutrino oscillations
at one point in career.
And your career seems
to have turned direction
and really focus on neutrinos
and muons since that time.
So Ken chairs the
international design study
for a machine called the
Neutrino Factory, which
hopefully we'll hear more
about, and is spokesman
for an experiment called
the Muon Ionization Cooling
Experiment, which is being
carried out at the Rutherford
Appleton lab in
Oxfordshire-- and is also
chair of the International
Committee for Future
Accelerators, Neutrino Panel.
So Ken focuses mostly on
neutrino and muon accelerators
at the moment.
So please, welcome Ken.
And finally, but by no means
least, Stuart Mangles-- Dr.
Stuart Mangles, on
my far left here,
is a senior lecturer in physics
at Imperial College London
where he also did his PhD.
And he is a faculty member
of the John Adams Institute
as well, I should say.
Now Stuart's focus is a little
different from the other four
of us here, in fact.
In that, he's actually, by
definition, a plasma physicist,
I suppose.
So he researches
plasma-based accelerators.
And he's been doing that
for the past 15 years
using a technique called
Laser Wakefield Acceleration.
So Stuart has a growing
interest in that field,
in both developing laser
Wakefield accelerators--
both for particle physics
and for other applications--
and improving the quality
of the beams from them.
He's also involved in
a project at DESY lab--
DESY keeps cropping up, doesn't
it?-- called Flash Forward,
which will use intense beams
of electrons to drive a plasma
wave.
So that's not going to make a
huge amount of sense right now,
but it will when Stuart gives us
a bit of an introduction later.
So please, welcome Stuart.
[APPLAUSE]
Thank you.
OK, so that is my
illustrious panel,
which is why I'm so excited to
dig into some of the science
behind what they do.
So what I asked each of my
panel to do is actually,
basically, provide a five minute
kind of introduction-pitch
to the types of projects
that they work on
that they think might
happen in the future.
So the first contribution
to that is Phil Burrows.
So hopefully we have
some slides to go along.
Over to you, Phil.
OK.
Thank you very much, Susie.
Is the microphone working?
Can everybody hear me?
OK, super.
Well, ladies and gentlemen thank
you very much for giving up
a rather lovely Friday evening
in September to come and join
is in this conversation
about possible future large
accelerator projects.
Now you've already
identified yourselves
as a very erudite audience
because everybody's heard
of the Large Hadron Collider.
And everybody knows that large
modern, high-energy particle
accelerators are
circular, such as the LHC
that you see on the
photograph here.
Well they're circular, that
is, except when they're not.
And so this is a photograph
of the two-mile long linear
collider at Stanford
in California.
And in fact, frank and
I had the privilege
to work together on this
project in the 1990s.
And you can see,
manifestly, that it is
linear-- it is two miles long.
So what do we do?
What do we want to do with
linear electron-positron
colliders?
Well we want to take
subatomic particles--
electrons-- we want
to collide them
with their
anti-matter partners--
positrons, which have the
opposite electric charge.
When electrons meet positrons,
matter and anti-matter
annihilate, energy is
released, and condenses
out of that energy
are exciting types
of new elementary particles,
for example, the Higgs bosons,
which I'm sure most of
you will have heard.
It was discovered only a
couple of years ago at CERN.
For example, top quarks,
which are very heavy types
of subatomic building
blocks of matter.
And of course, who knows,
maybe dark matter particle,
supersymmetric
particles, something
that has yet to be discovered
about which we would be very
excited and very keen to know.
So linear
electron-positron colliders
are the way forward to serve
as factories for mass-producing
Higgs bosons, top
quarks, and hopefully,
dark matter and other
types of new particles.
We're talking about hundreds
of thousands of Higgs bosons,
hundreds of thousands of
top corks-- samples that
will allow us to really
measure the properties
of these particles with
exquisite precision
and understand what they are.
Now there are two major projects
which are being proposed
for implementation for
high-energy future E+, E-
electron-positron
linear colliders.
This one is the international
linear collider.
To cut a long story short,
you stick electrons in at one
end you, stick positrons
in at the other end,
you accelerate them
together, and you
do matter-anti-matter
annihilations in the middle.
The rest of the detail, you
don't need to worry about.
The footprint of this machine
is about 30 kilometers.
Our friends in Japan
have-- the particle
physics community
in Japan very much
wants to host this machine in
the northern part of Japan just
north of the city of Sendai.
You can see on the map there,
the footprint of the machine.
If you look closely, you
can see a cross-section
through the geology of the
mountains in the Kitakami
region.
So this project,
we hope very much,
will be realized in Japan.
Now another project, which
is perhaps a little bit
further away, is the
compact linear collider.
And I, as Susie said,
I'm privileged to be
the spokesman-- or if
you like, Principal
Investigator-- of this project.
Again, don't worry
about the details.
It's a slightly bigger version
of the international linear
collider.
It's designed to get to
somewhat higher energies
of these collisions.
And never let it be said that
accelerator physicists don't
have a sense of humor
because compact means
50 kilometers long.
But that's a jolly
sight more compact
than it would be
if it weren't made
with this wonderful technology.
As Susie mentioned, I think it's
important to note that these
are global scale projects.
So in the case of the
Compact Linear Collider,
300 people, 50
institutes, 31 countries.
So my joke, at this
point, is the sun never
sets on my empire.
Now if that project
were realized,
it would be realized in
the Geneva region at CERN.
So here you see a little map.
The little white
circle in the middle
is the Large Hadron Collider.
And then you can
see magenta, green,
and blue linear arrays of dots.
And those represent
the different stages
of this project,
leading eventually
to an energy of 3,000
giga-electron volts--
or accelerating
particles-- to energies
of 1.5 trillion volts
for the electrons,
and 1.5 trillion volts
for the positrons.
So these are very
high energy machines.
So what I would hope
to argue this evening
is that the way ahead is linear.
Linear colliders
allow collisions
of point-like particles
under controlled conditions.
They allow
factory-level production
of things such as Higgs
bosons, which we really
need to understand
having just discovered
them a few years ago.
Why linear?
Well, the problem--
and Frank, of course,
will talk about this
in his presentation--
when you try to accelerate
electrons or positrons
in a circle, they emit x-rays.
This is call
synchrotron radiation.
And at some point,
as fast as you
are trying to accelerate them,
they're radiating energy away.
And so it's generally
agreed that,
to get to the very
highest energies,
one should avoid this
synchrotron radiation.
And therefore, the
future is linear machines
with no synchrotron radiation.
They're elegantly expandable
because you can always
make them that bit longer.
and therefore get
to higher energies.
And they are
intrinsically upgradable
because, once you have your
nice 30-kilometer-long tunnel,
when Stuart comes along in 50
years when his technology is
working, you can always stick
it into this beautiful tunnel
and you can get
to higher energies
by upgrading the facility that
you have as technology comes
along and as you're able to get
to higher and higher energies--
so elegantly expandable and
intrinsically upgradable.
And the technologies
that we're developing
with many applications--
this is my last couple
of slides, Susie,
as you know-- this
is the European x-ray-free
electron laser at the DESY
laboratorY-- again, in Hamburg.
And the technology that we've
developed-- superconducting
niobium radio-frequency
accelerating cavity
is the shiny thing,
bottom left, there.
This technology developed for
these big high-energy machines,
such as the International
linear collider,
has now been deployed in
the two-kilometer machine
in Hamburg.
It's a 10% scale model
of the real machine.
And this will serve tens
of thousands of scientists
by producing x-rays to look
at the structure of matter,
materials through
structural biology,
do biomedicine,
chemistry, and so on.
So this is an example
of the spinoff
of the technology for the
great benefit of wider science.
And I love this slide.
This is another example
of the application
of linear accelerating
technology.
The gentlemen, in
the bottom left,
are carrying a
roughly 1-meter-long
accelerating structure
made of copper.
They've developed
structures like that
for the purpose of getting
to the high energies--
the big, two-mile long machine
at Stanford that you see
upstairs-- and
today, there is one
of those structures in more
than 10,000 x-ray therapy
machines that have been
deployed in hospitals
all over the world.
There are more than 10,000
of these machines worldwide.
And in the UK alone,
10,000 people, per day,
are treated with cancer
therapy from machines
like this which are
employing technology
developed with a view to very
high-energy linear colliders.
So I think at that
point, I'd better stop.
And I'll give my
colleagues a chance
to get their 10 cents worth.
Wow.
Right.
What a sales pitch. (LAUGHING)
[APPLAUSE]
OK.
So having heard the sales
pitch for linear colliders,
as I said in my introduction,
at the moment there's
a large study at CERN happening
for a circular collider
instead.
So Frank, over to you.
OK.
Thank you.
Of course, I disagree
with the statement of Phil
that the future is linear.
Maybe, can I stand up here?
I have some problem
with the eyesight.
It's difficult for me
to see on the screen.
OK, here is the history of
colliders-- electron-positron
colliders in blue and center
of mass and Hadron Colliders--
proton colliders in red.
And this is a logarithmic scale
of the center of mass energy.
Over the last 50 or 60 years,
you can see dramatic progress
in the collision energy.
So we got
[? effect our source ?]
in the energy of
electron-positron collisions
and the factor of a hundred
in the energy of Hadron
Colliders-- slightly above 100.
And there were not so
many-- as you can see,
there were not so
many Hadron Colliders
and there used to be more
electron-positron colliders.
And these colliders seem
successful because they allowed
us to construct a so-called
standard model of particle
physics.
In the standard model,
we have meta-particles,
which consists of
quarks and leptons
and we have force carriers
which are these bosons here.
And then there is a different
particles, the six boson, which
is neither matter nore force.
It is completely
different from the others.
So many of these-- all
the heavier particles here
they discovered as
colliders. [INAUDIBLE]
discovered the quark,
and to Tau lepton,
Petra discovered the gruong.
That was in Europe-- at DESY.
That was the only
such discovery which
didn't give a Nobel
Prize for some reason.
Then the SPP at CERN
discovered the NW Boson.
Tevatron discovered
the top quark.
And then the LHC,
as you may know,
a few years ago, discovered this
new particle, the Higgs boson.
So the colliders
were essentially
in unraveling this
part-- the heavier
part of the standard model.
And they have proven a powerful
instrument for discovery
and for precision measurement.
OK-- we have the standard
model, but many questions
are not explained by
the standard model.
Here's an incomplete list.
So the standard model only
describes the known matter--
the visible matter, which
is about 5% of the universe.
There's a large
part, which is called
dark matter, which is visible
in the rotational speed
of the galaxies.
If you believe in
Newton and Einstein,
then you need additional
matter to explain
the observed rotational
velocity seen in the universe.
And then in addition, there is
something called dark energy.
I think that maybe later we
can explain the dark energy.
That comprises even larger--
this comprises even larger part
of the unknown.
So maybe 3/4 of the energy of
the universe is dark energy
and we don't know what it is.
And then we have more matter.
We have only matter.
We have no
anti-matter-- planets,
anti-matter-- why do we have
matter and not anti-matter?
And why do the masses of
these fundamental particles
differ by certain
orders of magnitude.
Anyway, gravity is not really
included in the standard model.
And it's very difficult to
combine it with quantum physics
and with the forces.
And then there's a search
for word equation, which
has so not been accomplished.
Although I think
that some people
tried to develop it
100 years ago already.
OK so we are back on the future
of the circular collider.
In response to the upgrade of
the so-called European strategy
for particle physics,
in 2013, they
requested a study of a
post-LHC collider complex
after the Large Hadron
Collider, based at CERN.
And this would be a
larger circular ring.
Here you see, the LHC
looks small, as unfiltered,
but here we don't talk
about a long line.
But we have another
circle, which
is now 100 kilometers
in circumference, which
would go around
the city of Geneva
and the nearby mountain,
which is called the Saleve.
And it would pass under
the lake of Geneva.
We are quite fortunate.
On this side-- on
the Geneva side,
the lake is rather shallow,
only 15 meters deep.
But on the other side, it
becomes very, very deep
on the opposite side
at [? Montre ?].
So there's no problem.
The LHC is 100 meters
under the surface
and this FCC will be 200
meters under the surface.
So there's no issue
going under the lake.
But we are limited.
We cannot build something much
bigger than 100 kilometers
because on the one side,
there are the Arabs here
and on the other,
the Jura Mountain.
And we don't 1000-meter-deep
access shafts.
So we are somewhat limited
to this 100 kilometers.
Now we would like to go up, in
energy, an order of magnitude
beyond the LHC.
There are reasons to believe
that going up in a factor
10 or so in energy will
help us understand the Higgs
mechanism-- more
properties of the Higgs
particle, the
potential of the Higgs,
and also perhaps help us
understand dark matter,
and with luck dark energy.
So to go to 100 TeV
in this larger ring,
we need 16 Tesla
magnets-- dipole magnets.
And the LHC has eight
tesla and that was already
extremely difficult. And if
you want to go from eight tesla
to 16 tesla, you need
a new technology.
So we need a new type
of superconductor
to make these magnets.
Those are simple equations.
Actually, energy of a Hadron
Collider is very easy.
It's just proportional
to the magnetic field
and the circumference.
So we are increasing both.
So we're increasing
circumference
by a factor 4 almost, and we're
increasing the magnetic field
by factor 2, which is
already quite challenging.
And together, we get almost
a factor 8 in energy.
If we builds this new
tunnel, we can also
think about putting other
colliders in the standard.
For example, we can put a
compositron circular collider.
And that would have a
very excellent performance
at energies where we can
produce a Higgs particle.
So this would also be
a very beautiful Higgs
factory and also a nice
factory of top quark.
So we can actually produce
all the known particles,
and in very large
quantities, and measure
with extreme precision
to see any deviation
from the standard model,
which would give us
a hint at which the next energy
scale in [? new ?] physics
should appear.
Of course, we can also collide
electrons with protons,
as we did at HERA in
Hamburg, where I started.
So people who want to make
a super-HERA with it's
10-times higher energy and 10
to 100-times the luminosity.
So this could also be possible.
And in addition, we have
a less ambitious study.
We developed the
16 tesla magnets,
we could install
these magnets also
in the existing LHC tunnel.
And that would allow
us to double the energy
of the Large Hadron Collder.
This is a time scale of the
large circular colliders
at CERN.
There was LEP that was an
electron positron collider--
study's design started
in the mid-1970s.
And you see, it took
more than 10 years
to design and
construct it and then
it operated twelve
years for physics.
And there's the LHC.
And this will be followed by a
high-luminosity upgrades, which
is an extension of the
LHC to give 10-times
the performance, which is
called the high-luminosity LHC.
And so the LHC and
[INAUDIBLE] together
will run for about 25, 27
years, from 2010 to about 2037.
So we have about
20 years time now
to develop a concept
for a future colliders.
So we have started this
future circular collider
design, which is four different
colliders in one study.
And we aim prototyping phase.
If it is supported by the next
update of the [INAUDIBLE] study
in 2019, we could go
into a prototyping
phase at construction.
And ideally, we would
like to start the physics
at this new machine when the
LHC physics terminates, so
in the second half of the 2030s.
So we must advance
fast now because we
have less time available than
had been available for the LHC.
And this machine is
much bigger and it's
even more advanced technology.
So we don't have so much time.
And our intermediate goal is to
have a solid conceptual design
by the end of 2018.
So we are about halfway
in this process.
And we are looking at
all the items, including
the construction schedule, the
cost, the key technologies,
and parameter space
for operation.
And the one goal is
that we absolutely
must ensure that the promised
performance can be achieved.
It has been the case
for LEP and LHC--
both machines reached
the designed performance
in a rather short time.
And so in principle, we know
that for this type of machine,
we should be able to reach
the promised performance.
But the design study will ensure
that there is enough margin
to accomplish this.
OK here is just a picture
on the magnet technologies.
For a long time, the
US-- United States--
was leading the high-field
magnet development
in Berkeley, already,
in the early 2000s.
They reached a 16 Tesla
field with this magnet, here.
And last year, at CERN, we
built a similar magnet, which
also reached a 16 tesla field.
So in principle, we have
a demonstration that
was using the [INAUDIBLE]
superconductor,
we can achieve a 16 tesla
field, which is twice
the field of the
LHC magnets, which
are based on [? the ?]
titanium superconductor.
But we need some margin.
So we're not quite--
these test magnets
have no aperture for the beam.
So we need to have a beam
pipe inside the magnet
to bend our particles and to
bring them through this magnet.
So we still need
some development
to have accelerator-quality
magnets at the 16 tesla field.
And also, we'd like to
make these magnets as
cheap as possible so as
[? to add to the ?] effort
to reduce the cost
of the superconductor
and of the magnets.
You're at about minus a minute.
Minus a minute-- my last
slide-- this shows you there,
Hadron Colliders unraveling
the secrets of the universe.
So there used to be the
Tevatron in the Chicago,
at the so-called fermilab.
It was from 1983 to 2011 at
2 TeV center of mass energy.
Then now we have the LHC,
factor 7 high energy.
Both were important discoveries.
And then we are planning
to make the next step.
And also I would love
the future to be linear
if you wanted to use
this linear collider
technology to build
a 100 TeV collider,
we would need 3,000 kilometer.
And with this technology, we are
staying below 100 kilometers.
So there is still
a [? juggle. ?]
We think that circular
colliders are still
the way for if you want to
see 100 TV in this century.
OK.
Thank you.
Thank you, Frank.
Thank you.
Alright.
So we can start to see a
little bit of a conversation
may be developing
between linear colliders
and circular colliders.
So a few key points there,
that we'll come back
to in a bit was,
first of all, the time
scale of some of these projects,
which I'll come back to.
Second of all, the
electron-positron machines
in Phil's linear
collider version--
sort of three kilometers
long, maybe-- no sorry,
30 kilometers long,
50 kilometers long.
But to actually do the same
thing for Hadron's would
be, say, 3,000 kilometers long?
That's your estimate,
approximately?
OK so it was saying that there's
some different physics involved
there and how difficult
it is to accelerate
those particles and
the energies you need
to reach the physics
that you're looking for,
which we'll come
back to in a bit.
So the two other speakers
here have slightly different
viewpoints, I think.
And one of the topics
that Phil covered
was synchrotron radiation.
And that's a really important
topic in building accelerators
because if you bend a
particle around a corner,
it loses energy.
So at some point,
you're just fighting
to put that energy back in.
And Ken, I think
some of the machines
you talk about have a different
approach to tackling that.
So--
That's right.
Here you are.
Hand it off to Ken.
Yeah.
So I think actually,
what's exciting is actually
the breadth of science
that can be addressed
by these different techniques.
So what I'm supposed
to talk about
is a different kind
of particle that you
could use to do the science.
And so the jargon title is a
neutrino factory muon collider.
The key thing is they
accelerate muons.
And I hope it will
become obvious why.
So here is the particle
content of the standard model.
You've seen that already.
You've got quarks that make
up what we call the Hadrons.
If you have up and down,
you can make protons.
You have electrons.
That now means you
can make atoms.
And that's basically all
you need for real life.
There are two more families.
And they're there as you go
to the left on that plot.
And you've got a whole
line of particles,
which are called the neutrinos.
So when I did the
particle physics course
at Imperial College in
'98, they were massless.
And then there was the discovery
of neutrino oscillations, which
means they are not massless.
They have some mass.
That means they do not
go the speed of light.
They have no conserved
quantum numbers.
That's important.
That means that a
neutrino can change
from being the partner
of the electron to being
the partner of the muon as it
travels through space and time.
So it's really like a
traveling Schrodinger's Cat.
One minute, it's alive and
the next minute it's dead.
And the good thing is
that the weak interaction
has got the opening
the box thing,
because the weak interaction
picks out the flavor.
And you can tell.
So that's how we know
they've got mass.
OK so I'm going to talk a
little bit about the neutrinos.
What we do, technically,
is we take the neutrinos.
We invent three mass
eigenstates for them,
so there are three
types of neutrino
that are distinguished
by their mass.
We mix them up.
And that's how we
get the flavors.
And we want to measure the
way in which that happens.
So-- can you see that
on the bigger screen?
I can't see this.
So here's the cosmic abundance
of different particle types.
And you will notice that
neutrinos are second only
to the number of protons.
I think it's missing some--
No, it's on the right-hand
side of the screen,
I hope, in that figure.
The other thing you want to know
is that the mass of neutrinos
is way different from
everybody else-- several orders
of magnitude different.
So we found Higgs fantastic.
All the charged
particles, we think,
get their mass from the Higgs.
Neutrinos are several
orders of magnitude
lower-- same mechanism?
Different mechanism?
We need to find out.
OK.
Here's the history of the
universe starting from the Big
Bang.
In one slide?
In one slide, yeah.
So the important thing
is that neutrinos really
have some impact here.
So the impact of neutrinos-- so
if we start at the recent past,
we know that the
universe is expanding
and we know there is dark
matter in the universe,
as was already explained.
We know there is dark energy.
So the neutrinos
are rather special.
They don't have conserved
quantum numbers,
they've got mass, we don't
know how they got the mass.
And those theories,
in principle,
offer explanations for those.
We need to understand
the neutrinos.
Neutrinos are almost massless.
They're not massless.
So they go almost at
the speed of light.
They only interact weakly.
So they can communicate
over vast distances
of space and time.
So they can contribute to
making the universe look
uniform on large scales.
The large-scale structure
and also galaxy formation
might be to do
with neutrino mass.
Inflation-- So inflation
is really important.
And the Bank of England
tries to try to deal with it.
But particle theorists look at
phase transitions of particles
in the early universe.
And there are
theories, which have
really, really heavy
neutrinos, which are partners
to the ones we observe.
And the phase transition where
they go out of interaction
is perhaps driving
the inflation.
So we need to
understand neutrinos.
And finally, if you
meet anti-matter,
you will annihilate.
There is no anti-matter.
We can calculate,
from the bodies
in this room, a
very strong limit
on the amount of
anti-matter in the universe.
And nobody can explain that.
And there are theories.
So they're the same
as the ones that
are generating
this inflation that
take all the anti-matter away.
You really need to
understand neutrinos.
OK so here's the
evolution of the universe
on a different scale.
And what you're seeing is where
the different accelerators
contribute.
The LHC, if you
can pick it out--
I can point to the
screen, but it's useless--
so you can see where
the LHC contributes.
Accelerators, today, go
up to the white line,
which is on the left hand
side-- the vertical white line.
So you want to go beyond.
And there have been
two or three ways
of getting there that have
already been described.
That's really exciting.
There's another way, which
I want to explain here.
Right.
So there is an electron, that's
what you need to make matter.
There's another
particle which has
exactly the same properties.
It's called the muon.
The only way it differs from the
electron is that it's 200 times
as heavy.
And it decays into an electron,
and actually into neutrinos.
The fact that it's
200 times as heavy
makes it technically good
to do the kind of things
that you can't do with
electrons and positrons.
So you can accelerate
them-- they're heavy.
You can do that efficiently.
And actually, you can show that
it's more cost effective if you
can produce enough of them.
They decay.
In particular, they decay
democratically into muon
and electron neutrinos.
And that's critical for what
you need to do the science.
You need new E's because you
need to look at transitions
that are not disappearing.
So you need to see a neutrino
turn into something else.
So Nu is the symbol you give
for the neutrino, right?
Yeah.
Thank you, Susie.
OK, so for both the
energy frontier--
so how do you get the very,
very high energy and how do you
study the properties
of neutrinos?--
muons are ideal because
they're heavy and they decay
to the right particles.
There is a problem.
And that is that they decay.
So the advantage is
also the disadvantage.
They decay in 2.2 microseconds
if they are not moving.
And you produce them
from the decay of pions.
So once you've got your
muons, they typically
occupy a large volume.
So I want you to
think of a watermelon
in a three-dimensional space.
But they're highly divergent.
The cost of your
acceleration is roughly
going as the size, squared.
And then you've got
the stored energy.
So there's a real premium
in making it smaller.
To study neutrinos you
gotta turn the watermelon
into a cucumber because
the length is OK,
but the width you've
got to shrink down.
And so that means that
what we have to do
is demonstrate a technique
to reduce the face space.
That's ionization cooling.
What we-- ah, I can't point.
What we do is we shoot the
muon beam through an absorber,
it loses energy, that
means the momentum
transverse to the beam and
the longitudinal momentum
go down equally.
You accelerate in one direction.
That means the
ratio has gone down
and you've squeezed
the beam down.
Experiment we're doing
at Rutherford lab
now is going to
demonstrate that.
So you look at the top,
which is the concept.
You can see how we
want to realize it.
And that's what it
looks like in the hole.
So I'm only saying
that we're going
to demonstrate
the key technology
and then we can make the
accelerators that can do
what I just tried to explain.
And to finish on the size of
this thing-- on the left hand
side, with the red
squiggle, you can
see the border of the Fermi
National Accelerator Laboratory
in the US.
And you can see the muon
collider fitting on that site.
For comparison, you
can see the LHC, that's
the blue circle, the ILC, which
is the green line, or CLIC,
and on the right hand side is
what used be called the VLHC.
So it's, roughly
speaking, the FCC
that Frank was just describing.
So it's not that-- so these
are different techniques,
they do slightly
different science,
and I think there's
a great strength
in the breadth of
science that you can
do with these different things.
Thank you very much.
OK.
Thank you, Chris.
So one of the key things I
should point out at this stage
is that one of the
useful things about muons
is, because they're
slightly heavier,
they emit less
synchrotron radiation.
So this issue of the
being losing energy
as it goes around the
ring is not such an issue
in the muon collider, right?
Could I--
Yeah.
So I think that
the point to make
is that, if you're
radiating energy,
but you want to keep
colliding at the same energy,
you got to put the energy back.
And that has to come out
of the power station.
So if you radiate less energy,
you have to put less power in.
And that's why there
is an energy, about one
and a half TeV, where
the muon colliders are
more cost effective to
operate, maybe not to build.
OK.
Right, so now onto something
completely different.
Yeah, I don't think
I need to introduce
any further than that,
just completely different.
Go ahead, Stuart.
Hang on-- oh.
Starting on the wrong one.
So, so far, you've heard about
all these different particle
accelerators and
future projects.
And I think they have
one thing in common--
they're all massive machines.
And so the question
I'm looking at
is, why are they so big,
and more importantly,
can we make them a lot smaller?
So Phil was right, I'm not sure
if I agree about the 50 years.
But what we are talking
about a technology
that could be used a bit
further in the future.
I'm very happy with that.
Yeah
And so, again, compulsory
picture-- overhead picture
of a big accelerator.
I went for SI units
rather than miles.
It's about three
kilometers long.
This is slack in America.
And the thing is, that all of
these particle accelerators
are basically using
the same technology
to accelerate particles.
Whether or not they're
accelerating electrons,
protons, or muons they're
using an electric field
to accelerate a particle
inside a vacuum tube.
So it's a low-pressure vessel
with nothing inside it.
And then you put a
radio frequency wave
traveling through it, which
accelerates the particles up
as it goes along.
You can work out the energy
that your charged particle can
get up to by just taking the
strength of the electric field,
which is measured in volts per
meter-- or megavolts per meter,
if you like-- million volts
per meter-- by the distance.
Because they're all using
basically the same technology,
they're all working at
around about 10 to 10--
right at the top end--
100 megavolts per meter.
So just some very simple
math, that tells you,
if you want to get a
particle to just 1 GeV,
you still need 10 to 100
meters of accelerator.
If you want to get
to 100 GeV, you
need, depending
on the technology,
between 10 and 100 kilometers.
I didn't put 100 TeV on there.
But that was with those numbers.
And so effectively, the only
way we can make things shorter
is-- well, there are two ways.
One is we can use the same
accelerating structure over
and over again, which is
a circular accelerator.
But then we hit the problem of
magnet strength and synchotron
radiation.
Or we can turn up the
electric field strength.
They're basically the
only two things we can do.
In fact, the technology to get
up to 100 megavolts per meter,
that's already really hard.
That's a really
cutting edge technology
in vacuum accelerators.
So why can't they go any higher?
Well the problem is-- I
don't know if you've ever
tried this-- but if
you have two electrodes
and you put a lot of
voltage between them in air,
you get a spark
forming between them.
If you turn down the pressure--
so if you put that capacitor
in vacuum-- you can put a
larger voltage before the vacuum
before you get breakdown.
But it doesn't matter how
low in pressure you go,
you will always get to the
point where there's just
one electron-- one or two
electrons between those two
plates and that will
cause an avalanche that
will mean that you
get sparks forming
inside your accelerator.
And that's the sort of
fundamental limit of why,
if you're using this
conventional technology
to accelerate things,
you can't go any higher
than about 100
megavolts per meter.
And that's because
you turn up the field,
and it's just going to
start forming sparks,
which degrade the
whole structure,
they may even destroy it.
And so if you like, what
I'm trying to look at--
and I have been over the
last decade or so-- is,
could we do something else?
Could we actually solve
this breakdown problem
and start with something that
either-- well, one thing,
it would be nice if you
could find something
that just didn't break down.
Not sure that exists.
But instead, actually
do the exhilaration
in something that's
already broken down.
So if you take a volume of
gas, and you fully ionize it,
it can't ionize anymore.
And actually, that's
called a plasma.
And plasmas can support
huge electric fields.
I think we have already
demonstrated, sort of,
fairly useful fields,
depending on your definition,
at 10,000 megavolts per meter.
So just to give you
an idea, I would
say, compared to conventional
accelerators in its very
early days-- we've been
doing things for a while,
in my lifetime, and
in terms of how long
I've been doing it and
significantly before me as
well-- but there are-- did
my microphone just go off?
Yeah, it's come back on.
But there are definitely
things going on.
So this picture
here is an overview
of the Rutherford Appleton
Lab, one of the national labs
in the UK here.
And there are three GeV-- so
small-- particle accelerators
in this picture.
The first one is
at the top here.
That's the diamond light source.
It's a machine not for
doing particle physics
but for making x-rays for
all sorts of scientists.
And at the heart of it
is a 3 GeV electron beam.
In the bottom here is ISIS,
which is a neutron source.
And those neutrons are made by
accelerating protons and using
a process called spallation
to make neutrons.
And at the heart of that is 1
GeV proton accelerator-- .8,
I think.
So they're all
pretty big machines.
Somewhere in that
building, in there, there
is a pretty big laser called
Astro Gemini, which we're
now fairly routinely
producing-- very messy compared
to the beams that come
out of these machines--
but 2 GeV beams
inside that lab there.
The actual accelerator
is this long.
So the actual plasmal
part is that long.
And so the technology
we're working on
is-- I really liked what
Phil said, which was,
if you could imagine replacing
conventional accelerators
with a plasma system,
you could suddenly
make a massive upgrade.
So that's the sort of thing--
the time scale we think--
I think seems realistic.
But just to give you an idea of
how much progress we're making,
here, I've got a plot from
one of my PhD student's
thesis, Jason Cole.
So he took conventional electron
accelerators and there, energy
as a function of
time-- so you can see
they started back in the 1940s.
And they made rapid progress
for the first 30 years,
doubling energy about every
two years, I think it was.
And then it kind of tailed off.
And then you get plasma
accelerators which basically
started in the mid 90s.
And we've been making similar
progress over the last 10
years-- 10, 20 years as well.
So our record is now,
the group at Berkeley
have now produced 4
GeV electron beams
in a plasma that's 9
centimeters long, so that big.
And that corresponds to
an accelerating field that
is 10,000 megavolts per meter.
So I haven't done the
numbers, but if you
wanted to do this
100 TeV machine,
if you could use that it
would get a lot shorter.
So that's what I'm working on.
Thank you very much
OK.
Thanks.
