lecture 1 motivations - uspas
TRANSCRIPT
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US Particle Accelerator School
Introduction to Accelerators
Lecture 1
Motivations
William A. Barletta
Director, United States Particle Accelerator School
Dept. of Physics, MIT
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US Particle Accelerator School
Energy & Momentum units
When we talk about the energy or momentum of individualparticles, the Joule is inconvenient
Instead we use the eV, the energy that a unit charge
gains when it falls through a potential, = 1 volt.
For momentum we use the unit, eV/c, where c is the speedof light
e =1.6 10 19 Coulomb
1 eV =1.6 10 19 Joule
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Mass units
We can use Einstein’s relation,
Eo = mc2
to convert rest mass to energy units (m is the rest mass)
For electrons,
Eo,e = 9.1x10-31 kg x (3x108 m/sec)2 =81.9x10-15 J
= 0.512 MeV
For protons,
Eo,p = 938 MeV
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US Particle Accelerator School
Why do we build accelerators?
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Research accounts for a small numebr
From L. Rivkin, CHIPP Lectures, 2008
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What are these machines used for?
From L. Rivkin, CHIPP Lectures, 2008
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Why do we need beams?
Collide beams
Figures of Merit (FOM):
Collision rate,
Energy stability,
Accelerating field
Examples: LHC, ILC, RHIC
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What we know by direct observationWhat we know by direct observation
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How can we understand the underlying
structure of things?
Wilhelm Röntgen Discovered X-rays in 1895
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How it all began
Rutherford explains scattering of alpha particles on gold
& urges … on to higher energy probes!
214Po
source
ilm
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Why do we need high energy beams
Resolution of "Matter" Microscopes
Wavelength of Particles ( , e, p, ...) (de Broglie, 1923)
Higher momentum => shorter wavelength => better the resolution
Energy to Matter
Higher energy produces
heavier particles
Penetrate more deeply into matter
E = mc 2 = m o c
2
1v 2
c 2
= m o c 2
= h / p = 1.2 fm/ p [ GeV/c]
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Examples: Where we are today -
Heavy ion collisions
D - Au at RHIC
Next ALICE @ LHC
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CERN Accelerator Complex
(not to scale)
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Inside the LHC tunnel
This goes on for 28 km!
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Figure of Merit 1: Beam Energy ==>Energy frontier of discovery
SLED
SC cable
Stochastic
cooling
Wakefields, impedances
Strong
focusing
Colliding beams
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Example from High Energy Physics:Discovery space for future accelerators
Log
lum
inos
ity (
cm-2
s-1
)
LinearCollider
SuperLHC
Very Large Hadron Collider
Luminosity =
Energy Current
Focal depth Beam quality
$, , M
W
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High Energy PhysicsFigure of Merit 2: Number of events
Events = Cross - section Collision Rate Time
Beam energy: sets scale of physics accessible
Luminosity = N1 N2 frequency
Overlap Area=
N1 N2 f
4 x y Correction factors
We want large charge/bunch, high collision frequency & small spot size
1
2
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How far can we go with this approach?
1 PeV ?
Str
ength
of
Forc
e
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Limits
of
accelerator-based HEP
E. Fermi
15 min
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How big is a PeV collider?
We will return to this question
near the end of this course
1 PeV ?Romania
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FoM 3: Resolution (Energy/ Energy)
Intertwined with detector & experiment design
In hadron colliders: production change, parton energy distribution
In lepton colliders: energy spread of beams (synchrotron radiation)
SLC
LEP
ILC
ILC-U
μ col
Tevatron LHCLHC-2 VLHC
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The future of HEP runs through CERN
“Après moi, le déluge”
LHC
LHC upgrades rely on advances in magnet technology
Reliability upgrade (2013) - replace IR Quads & collimators
Luminosity upgrade - very high gradient, Nb3Sn quads
Super LHC (energy upgrade) - very high field dipoles
9 min
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Why do we need beams?
Secondary beams
FOM: Secondaries/primary
Examples: spallation neutrons for condensed matter physics,
neutrino beams for high energy physics, rare isotopes
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Example: The Spallation Neutron Source
1 MW liquid Hg target1 MW liquid Hg target
>10>101717 n/secn/sec
SNS
1 GeV, 35 mA of protons,
6% duty factor
Hgn
n
p
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Figures of Merit:Spectrum & time structure
O The measured (circles) neutron flux v. neutron energy
Ref: Paul E. Koehler, Nucl. Instrum. Meth. A292, 541 (1990)
Flu
x (
neu
tro
n/(
cm2 s
eV
))
En(eV)
O - LANCE Flight Path 4
LBNL D-D tube
Neutron flux from D-D tube
(1.2 x 1011 n/s)
80 kV, 1 A, 100 % DF
Liquid MH4 Moderator
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FOM: Flux, Joules per secondary particle
1MW SNS (1 GeV, 60 Hz)
Protons per pulse 1014
Neutrons per pulse 20 x 1014 = 2 x 1015
Rate = 60 Hz ==> yield 1017 n/s.
E/neutron = 1 MW/1017 n/s 10-11 J/n
Overall efficiency for accelerator system ~ 2%
==> ~ 5x10-10 J/n
D-T neutron tube (120kV, 1 A 1014 n/s)
E/neutron 120 kW/1014 n/s 10-9 J/n
DC power supply efficiency > 85%
==> 10-9 J/n
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Nuclear Astrophysics:Radioactive Beam Facilities
Explore nuclear structure & reactions involving nuclei far from the
valley of stability
These nuclei participate in explosive nucleo-synthesis in novae, x-ray
bursts, and supernovae via rapid proton and neutron capture
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Matter to energy:Synchrotron radiation science
Synchrotron light source
FOM: Brilliance v.
B = ph/s/mm2/mrad2/0.1%BW
Science with X-rays• Microscopy
• Spectroscopy
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Progress in X-ray source brightness
4th Generation
FELs
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Figure 4. Full-field mode.
Figure 3. Scanning mode
PR-ZP
OSA
SAM PO-ZP
DET
Source
Figure . Optical scheme of TwinMic.
Coherent Imaging: TwinMic on BACH-ELETTRA
Source
Detector
Sample
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Does the tracheal system limit the sizeof insects?
Research* at the Argonne AdvancedPhoton Source (APS) explains whatlimits size in beetles: the constriction oftracheal tubes leading to legs.
* Alexander Kaiser, C. Jaco Klok, John J. Socha, Wah-Keat Lee, Michael C. Quinlan, and Jon F. Harrison, “Increase in tracheal investment with beetle size supportshypothesis of oxygen limitation on insect gigantism,”Proc. Nat. Acad. Sci. USA 104(32), 13198 (August 7,2007).
What Keeps Bugs from Being Bigger?
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FOM 1 from condensed matter studies:Light source brilliance v. photon energy
Duty factor
correctionfor
pulsed linacsERLsERLs
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Pump-probe experiment concept for
ultra-fast science and/or imaging
ion or e-
detector
excitation pulse
probe pulse
tX-ray
detector
sample
• Pulses can be x-rays, VUV, electrons or ions
• Requires control/measurement of t with a resolution << x-ray
pulse duration (possibly as small as 100 attoseconds)
Near IR pulse
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Matter to energy: Energy RecoveryLinacs (Hard X-rays ==> ~ 5 GeV electrons)
Synchrotron light source
(pulsed incoherent X-ray emission)
Pulse rates – kHz => MHz
X-ray pulse duration ~ 1 ps
High average e-beam brilliance
& e-beam duration ~ 1 ps
One pass through ring
Recover beam energy
High efficiency
SC RF Pulse duration limited by CSR
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Even higher peak brightness requirescoherent emission ==> FEL
to experiment
Dump
long wiggler
Electron Beam
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FIRST FLASH DIFFRACTION IMAGE OF
A LIVE PICOPLANKTON
0 30606030Resolution length on the detector (nm)
March 2007
FLASH soft X-ray laser
Hamburg, Germany
FLASH pulse length: 10 fsWavelength: 13.5 nm
RECONSTRUCTED
CELL STRUCTURE
J. Hajdu, I. Andersson, F. Maia, M. Bogan, H. Chapman, and the imaging collaboration
Filipe Maia, Uppsala
Thanks
J.Hajdu and H. Chapman
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FOM 2 from condensed matter studies:
Ultra-fast light sources
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Uses of beams: looking through matter
Radiography
FOM: Signal/noise ==> Dose at 1 m & resolution (x,t)
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Example: Flash radiography
Debris cloud produced
by an Al sphere impacting
a thin AL shield at hypervelocity.
Source:. http://www.udri.udayton.edu/NR/exeres/9E82E5F2-AC29-4467-8F15-0E5A7FEA48F3.htm
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Industrial uses of beams
Alter matter
FOM: process time
process efficiency
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Ions prepare Si wafers for further processing finallyyielding integrated circuit chips
> 1 B$/year business in semi-conductor “machine tools”
Emerging areasFlat-panel video displays
Ultra-high density electronics
Ion implantation is essential in
semi-conductor production
X-YStage
Wafer
Electrode lensesIon source
Beam
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Example of ion beam lithography
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Therapeutic uses of beams
Therapy
FOM: treatment time
tumor control probability
precision beam control
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Example: Conformal therapy
Multi-axis exposure of tumor
Challenge: Kill the tumor cells
w/o killing healthy tissue
Gamma rays from electron linac
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FOM - Tumor control probability
0
0.2
0.4
0.6
0.8
1
0 10 20 30 40
Tum
or
Contr
ol P
robabili
ty
Tumor RBE-Dose (Gy Eq)
Dots indicate tumor doses near midline of brain for BMRR and LBNL Beams (for specific head, treated to maximal normal tissue dose) BMRR Beam
LBNL Beam
Calculated Tumor Control Probability(Laramore's parameters)
Control of gliobastoma multiformae with neutron capture therapy
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What’s the difference between the beams?
Reactor-based(BNL) 3 MW
Accelerator-basedproduction (LBNL)
Kill healthy cells in frontof tumor
Ideal energyband
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Tumor control with hadron beams
Proton beamBragg peak
Hadron therapy allows for the best
treatment of deep tumors with
minimized dose to healthy tissue
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Ion beams to produce fusion energy
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Matter in extreme conditions can be
driven by intense heavy ion beams
27 min
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The inertial fusion power plant
2. Targets (and a factory
to produce about 5 per second)
1. Driver - accelerator
to heat & compress
the target to ignition
Many beams 3. Focusing
system
4. Fusion chamber to recover
the fusion energy pulses from
the target
5. Steam plant to convert
fusion heat into electricity
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Beams to heat fusion plasmas
Example: neutral beams for TFTR at Princeton
ITER will require 60 MW of neutral beam heaters
Neutral beam injectors
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How much do these things cost?
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Just what are these beams?
That’s the next lecture