Synchrotron Radiation Storage Rings Vic Suller: CAMD Louisiana & SRS Daresbury Synchrotron Radiation...

Synchrotron Radiation Storage RingsVic Suller: CAMD Louisiana & SRS Daresbury

Synchrotron Radiation Sources

Past, Present and Future

By Vic Suller


Contents

•The Origins of Synchrotron Radiation

•Synchrotron Radiation Characteristics

•Storage Rings as Sources

•Insertion Devices

•The Future with 4th Generation Sources


Crab Nebula - the first Synchrotron source observed??


CAMD in Baton Rouge, LA

Center for Advanced Microstructures and Devices


Accelerator Synchrotron Radiation


CBA .

Discovery of ElectronJJ ThompsonOctober 1897

Accelerated Charge RadiationLienard

July 1898


Field lines from a stationary charge

Field lines from an accelerated charge

3

22

3

2

c

aq

dt

dU

3

22

3

2

c

aq

dt

dU

3

22

3

2

c

aq

dt

dU

ELECTROMAGNETIC RADIATION


z

y

x

Spatial distribution of radiationfrom a charge accelerated

along the z axis


CoilSteel

Vacuum chamber

Cross section of a Betatron

Principle of Betatron Acceleration

Acceleration by Induction - The Betatron


Prediction of Energy loss by radiationin an accelerator

Iwanenko & Pomeranchuk June 1944


GEC(USA) electron accelerators 1946


First attempt to Detect Synchrotron Radiation

John Blewett 1947 – used a microwave receiver expecting Harmonics of the orbit frequency (100 MHz) - nothing found!

First correct theory of Synchrotron Radiation

Julian Schwinger 1947 – showed the importance of relativistic effects


Light from the GE Synchrotron 1947


Betatron - CERAMIC Synchrotron - GLASS


Relativistic effects in Synchrotron Radiation

1. Contraction of the orbit in the electron frame

Result:- Orbit frequency increases by factor

2. Relativistic Doppler shift from the electron frame to the lab

Result:- Frequency further increases by factor 2

3. Relativistic forward focusing of the emission

Result:- Frequency further increases by factor

2


acceleration

Electron frame

acceleration

Lab frame

velocity

Relativistic focusing of Synchrotron Radiation

tan sin cos Transformation between frames:-

If 900 then


Relativistic effects in Synchrotron Radiation (cont)

The effect of 3 relativistic processes upshifts the orbit frequency by

3

For example 2 GeV electrons in a 100m orbit

orbit frequency 3 MHz

= 3914 6.0 1010 100m 1.7 nm (0.7 keV)

For protons to radiate equivalently in a 100m orbit

Energy = 3.7 TeV and magnetic field = 10 kT


Synchrotron Radiation Features

1. Continuum source from IR to X-rays

2. Source in a clean UHV environment

3. High Intensity and Brightness

4. Highly Polarized

5. Stable & controllable pulsed characteristics

…highly attractive for research applications!!!


The synchrotron radiation spectrum is described with reference to a characteristic (often called 'critical') wavelength , or photon energy

)()(

6.18

)(

)(59.5)(

23 GeVETeslaBGeVE

mRAo

c

)(

39.12)( o

c

cA

keV

where B is the bending magnetic field.

Synchrotron Radiation Features


When the radiation at a given wavelength is integrated over all angles of vertical emission the resultant Spectral Flux Intensity is given by

cc

GGeVEAId

dF

2

013 )()(1046.2 photons/sec/mr/0.1% bandwidth

c

G

is a numerical factor which essentially governs the shape of the spectrum.

Synchrotron Radiation Spectral Flux Intensity


Synchrotron Radiation Spectra

E(GeV) R(m) B(T) c(Å) c(keV)

NSLS-VUV 0.74 1.91 1.3 25.9 0.48 HELIOS 0.7 0.52 4.5 8.5 1.5 LSU-CAMD 1.3 2.93 1.48 7.45 1.66 SPEAR-3 3.0 7.86 1.27 1.63 7.6 APS 7.0 39.0 0.60 0.63 19.6 CERN-LEP 100.0 3096 0.108 0.017 718.3

Examples of spectra produced by electron storage rings:-


Flux Output

100000

1000000

1E+07

1E+08

1E+09

1E+10

1E+11

1E+12

1E+13

1E+14

1.0 10.0 100.0 1000.0 10000.0 100000.0 1000000.0

Photon Energy (eV)

Flu

x (p

hoto

ns/

s/m

rad

/0.1

%)

CAMD

APS

NSLS-VUV

Typical Synchrotron Radiation Spectra


Typical Synchrotron Radiation Spectra 2

Flux Output

0

2E+12

4E+12

6E+12

8E+12

1E+13

1.2E+13

1.4E+13

1.6E+13

1.8E+13

1 10 100 1000 10000 100000 1000000

Photon Energy (eV)

Flu

x (

ph

oto

ns

/s/m

rad

/0.1

%)

APS

CAMD

VUV


1st Generation Synchrotron Radiation Sources

SOURCE COUNTRY TYPE ENERGY (GeV)

TANTALUS USA Storage Ring 0.24

SPEAR-1 USA Storage Ring 3.0

NINA UK Synchrotron 5.0

DESY Germany Synchrotron 6.0

BONN Germany Synchrotron 0.5

ACO France Storage Ring 0.54

VEPP-2m Russia Storage Ring 0.7

Originally built for some other purpose (1965 – 1975)


2nd Generation Synchrotron Radiation Sources

Dedicated, purpose designed (1975 – 1985)

Some examples:-

SOURCE COUNTRY ENERGY (GeV) Emittance nm rads

SOR-ring Japan 0.38 320

SRS UK 2.0 110

NSLS-VUV USA 0.744 88

NSLS-XR USA 2.5 80

BESSY-1 Germany 0.8 20

Photon Factory Japan 2.5 130


dddzdx

F4d = Brightness SpectralNotice that Brightness, as here defined, is often referred

to as Brilliance, with an accompanying incorrect use of the term brightness for the Spectral Flux Density. It is best to avoid confusion by using the well established radiometric definitions as given here.

Synchrotron Radiation Brightness


Note that source Brightness as defined is anisotropic, the value depends on the source density distribution and on the observation angle. It is often more convenient to use, as a figure of merit, an average brightness which for dipole sources is defined

Average Spectral Brightness = /36.236.236.2

zx

ddF

is the vertically integrated flux, 2.36x is the fwhm of the horizontal electron beam size, 2.36z is the fwhm of the vertical electron beam size, and 2.36

/ is the fwhm of the photon emission angle in the vertical plane. The latter is a combination of the electron beam vertical divergence and the photon emission angle thus

ddF

2

2// 141.0

cz


Radiation

Dispersion

Betatron oscillation

Initial momentum

Final momentum

RF restores

Radiation loss

Radiation excitation

Radiation damping

Radiation excitation and damping of oscillations


The equilibrium of the excitation and the damping of the betatron oscillations determines the emittance of the stored beam with the result:

The emittance is determined by the behaviour of the dispersion - and the horizontal betatron function within the bending magnets. The emittance is given by the lattice of the machine.


Q(d) Q(d)

s

Q(f) B Q(f) B Q(f)

Beta(x,s)

Disp(s)

s

32 .154

1.

1..

xqx J

C

Minimum emittance of Chasman-Green lattice

58

3min magLLs

8

3*


Q(d) Q(d)

s

Q(f) B Q(f)

Beta(x,s)

Disp(s)

s

Theoretical Minimum Emittance lattice

32

154

1

3

11 x

qx JC

152min

L

0

2

min 24 L


3rd Generation Synchrotron Radiation Sources

SOURCE COUNTRY ENERGY (GeV) Emittance nm rads

SUPER-ACO France 0.8 37

ALS USA 1.8 4.9

ESRF France 6.0 4.5

APS USA 7.0 8.0

SPRING-8 Japan 8.0 7.0

Dedicated, high brightness, designed to includeInsertion Device Sources (1985 – 2005?)

Some examples:-


APS at Argonne National Laboratory


Source Energy( GeV ) Emittance (nm rad) Circumference(m)

MAX II 1.5 9 90

ALS 1.9 5.6 196.8

BESSY II 1.9 6.4 240

ELETTRA 2 7 258

Swiss LS 2.4 5 288

NSLS 2.5 50 170

SESAME 2.5 24.4 124.8

SE-ALS 2.5 4.7 191

SOLEIL 2.75 3.72 354

Canadian LS 2.9 18.2 170.4

Australian LS 3 6.88 216

DIAMOND 3 2.74 561.6

ESRF 6 4 844

APS 7 8.2 1104

Spring-8 8 6 1436

Trends in 3rd Generation Light Source Performance


0.000

5.000

10.000

15.000

20.000

25.000

0.000 2.000 4.000 6.000 8.000 10.000 12.000 14.000

Beta H

Beta V

10x Dispersion

DOUBLE BEND LATTICE FUNCTIONS

Length (m)

Proposed South East Advanced Light Source (1)

Energy 2.5 GeV

Circumference 170 m

Emittance 7.9 nm rads


TRIPLE BEND LATTICE FUNCTIONS

0.000

5.000

10.000

15.000

20.000

25.000

0.000 2.000 4.000 6.000 8.000 10.000 12.000 14.000 16.000 18.000

Length(m)

Be

ta H

, Be

ta V

, 10

xD

isp

Proposed South East Advanced Light Source (2)

Energy 2.5 GeV

Circumference 190 m

Emittance 4.7 nm rads


Wiggler or Wavelength Shifter

•Placed in a straight section

•Net deflection zero

•High magnetic field 5-10T

•Large horizontal fan ~200 mr


CAMD Wiggler

•Central pole 7 Tesla

•End poles 1.5 Tesla

•Made by Budker Institute


SRS Daresbury 6 Tesla Wiggler


Multi Pole Wiggler

•Multiple alternating poles

•High magnetic field 2-5T

•Small horizontal fan ~20 mr

•Superposition of source points


SRS Daresbury 2.4 Tesla Permanent Magnet MPW


Undulator

•Multiple alternating poles

•Period u = 10s of mm

•Beam deflection < 1/

•Interference makes line spectrum

•Very high brightness


electronc

Undulatormagnetic field

u

Undulator approximate theory

In the laboratory frame the electron travels towards the undulator magnetic field at relativistic velocity.

stationary electron

Undulatorelectromagnetic wave

u

c

In the electron frame the undulator appears as an EM-wave relativistically contracted to u.

There is then a relativistic Doppler shift back to the laboratory frame.

Thus the undulator produces monochromatic radiation of

2u

rad 2

2u

rad 2


Undulator correct theory

It is essential to account for the transverse motion of the electron in the undulator.

41

*2

41

*2

2

k

2

2

2u

rad 1

222

22

2u

2u

rad

1

*

1-k

1-k

Introduce the deflection parameter k


Undulator constructive interference

photon

electronA B

As an electron moves from A to B the photon moves ahead.A photon emitted at point A will constructively interfere with one emitted at point B if it gains by a whole number of wavelengths:-

uu

rad

41

2

n

2

k

2n

2

2u

rad 1

n = 1,3,5,…


Undulator Spectrum (calculated)


ESRF Undulator


SRC

In vacuum Undulators – for small gap / period


SRC Wisconsin 6 EM Undulator


Elettra – SLS Helical Wiggler/Undulator


Undulator Brightness Output

1.00E+16

1.00E+17

1.00E+18

1.00E+19

1.00E+20

0.0 1000.0 2000.0 3000.0 4000.0 5000.0 6000.0 7000.0

Photon Energy (eV)

Bri

gh

tnes

s (p

ho

ton

s/s/

mm

^2/

mra

d^

2/0.

1%)

1st Harmonic

3rd Harmonic

5th Harmonic

SE-ALS Undulator 50 mm


4th Generation Synchrotron Radiation Sources

What could be their characteristics?

•Extremely high brightness

•Ultra short electron bunches

•Coherent radiation

Conclusion:- It must be based on a Free Electron Laser


Oscillator type Free Electron Laser


SASE type Free Electron Laser•SASE = Self Amplification of Spontaneous Emission


Free Electron Laser- present limitations

•Wavelength limited by mirrors- use SASE

•Low rep rate hence low average brightness- use Energy Recovery Linac


Energy Recovery Linac

High brightness cw e-gunSuperconducting RF

SASE Free Electron Laser

Low energy beam dump


ERLs Past and Future

TJNAL (USA) 160 MeVBINP (Rus) 100 MeV4GLS (UK) 600 MeVKEK ERL (J) 2.5GeVPERL NSLS (USA) 2.7 GeVLUX LBL (USA) 3 GeVERLSYN (D) 3.5 GeVCornell-TJNAL (USA) 5 GeVMARS BINP (Rus) 6GeV


Conclusion for Synchrotron Radiation

The Future is EVEN BRIGHTER than this!

Thank You!


The brightness of an undulator is calculated slightly differently.

The flux in the central cone of an undulator Fn at a specified wavelength is averaged over the emission angle of that cone to give the Average On-axis Brightness.

Because of the usually very small source size and divergence in an undulator diffraction effects must be taken into account.

Average On-axis Brightness = //436.2 zzxx

nF

zz are the photon source sizes in both planes and z/z

/ are the photon source divergence in both planes, taking into account diffraction effects.

BRIGHTNESS of Undulators


22,, zxzx Ln

4

1

2/2/,

/, zxzx

Ln

/

L = undulator length

u = undulator period

Radiation in the nth harmonic in an undulator

deflection parameter k = 93.4 u(m)Bo(Tesla)

21

2

2

2

k

nu

n

flux in the central cone Fn=1.43 1014 I0 Qn(k) photons/sec/0.1% bandwidth

n

fkkQ n

n

21)(

2

fn is a numerical factor, related to k.

Synchrotron Radiation Storage Rings Vic Suller: CAMD Louisiana & SRS Daresbury Synchrotron Radiation...

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