# Presentation: 111333

## Light Sources.

**Light Sources.**
**Brightness and Insertion Devices**

**Fernando Sannibale**

## However other researchers soon realized that synchrotron radiation was the brightest source of infrared, ultraviolet, and x-rays, and that could be very useful for studying matter on the scale of atoms and molecules.

**However other researchers soon realized that ****synchrotron radiation was the brightest source of infrared, ultraviolet, and x-rays****, and that could be very useful for studying matter on the scale of**** atoms and molecules****.**

**Electron accelerators were initially developed to probe ****elementary (subnuclear) particles ****for the study of the fundamental nature of matter, space, time, and energy.**

**In the earlier times, synchrotron radiation was just considered as a ****waste product ****limiting the performance achievable with lepton machines.**

## Slide 3

## We already showed that synchrotron radiation is electromagnetic radiation emitted when charged particles are radially accelerated (move on a curved path).

**We already showed that synchrotron radiation is electromagnetic radiation emitted when charged particles are radially ****accelerated**** (move on a curved path).**

**Electrons ****accelerating**** by running up and down in a radio antenna emit radio waves (long wavelength electromagnetic waves)**

**Both cases are manifestation of the same physical phenomenon:**
***Charged particles radiate when accelerated*****.**

##  We already saw that according to quantum field theory, a particle moving in the free space can be considered as “surrounded” by a cloud of virtual photons that appear and disappear and that indissolubly travel with it.

** ****We already saw that according to quantum field theory, a particle moving in the free space can be considered as “surrounded” by a cloud of ****virtual photons**** that appear and disappear and that indissolubly travel with it.**

** ****The ****acceleration**** process acts as a “kick” that can separate the particle from the photons that become real and independently observable.**

**In the field of the magnets in a synchrotron, charged particles moves on a curved trajectory. The transverse acceleration allows for the separation and *****synchrotron radiation***** is generated.**

**Lighter particles are “easier” to accelerate and radiate photons more efficiently than heavier particles.**

##  Historically, the whole theory was developed well before quantum mechanics was even conceived:

** ****Historically, the whole theory was developed well before quantum mechanics was even conceived:**

** ****The description of synchrotron radiation presented in the previous viewgraph made use of quantum field theory.**

**- in ****1897 Joseph Larmor**** derived the expression for the instantaneous total power radiated by an accelerated charged particle.**

** ****and in ****1898 Alfred Lienard**** **
**(before the relativity theory!) extended Larmor’s result to the case of a relativistic particle undergoing centripetal acceleration in a circular trajectory**

##  Radiated power for transverse acceleration increases dramatically with energy. This sets a practical limit for the maximum energy obtainable with a storage ring, but makes the construction of synchrotron light sources extremely appealing!

** ****Radiated power for transverse acceleration ****increases dramatically with energy****. This sets a practical limit for the maximum energy obtainable with a storage ring, but makes the construction of synchrotron light sources extremely appealing!**

##  In one of the previous lectures, we already dealt with the concept of brightness and showed how this quantity is the one of the main parameters for the characterization of a particle source.

** ****In one of the previous lectures, we already dealt with the concept of ****brightness**** and showed how this quantity is the one of the main parameters for the characterization of a particle source.**

** ****We remind that *****brightness was defined***** *****as the density of particle in the 6-D phase space*****.**

** ****The same definition applies to the photon case****, just taking into account that photons are bosons and that the Pauli exclusion principle does not apply.**

** ****This is an important advantage because, at least from the point of view of quantum mechanics, no limitation to achievable photon brightness exists.**

** ****From the above definitions, one can see that for a given flux, sources with a smaller emittance will have a larger brightness.**

## Remark: the sources are compared

**Remark: the sources are compared**
**at different wavelengths!**

## Radiation becomes more focused at higher energies. 

**Radiation becomes more focused at higher energies. **

## (Doppler effect)

**(Doppler effect)**

**Strong wavelength shortening for relativistic beams!**

## Example for an electron ring with 1.9 GeV and with a bending radius of 5 m:  

**Example for an electron ring with 1.9 GeV and with a bending radius of 5 m:  **

**Very broad band!**

## Slide 13

## This characteristic of synchrotron radiation is heavily exploited in those experiments where the polarization of the light is important.

**This characteristic of synchrotron radiation is heavily exploited in those experiments where the polarization of the light is important.**

## SR offers many characteristics of visible lasers but into the x-ray regime!

** ****High brightness and flux**

**SR offers many characteristics of visible lasers but into the x-ray regime!**

** ****Wide energy spectrum**

** ****Highly polarized and short pulses**

**Recapitulating the main properties of synchrotron radiation:**

** ****Partial coherence**

** ****High Stability**

## Modern synchrotron light sources are accelerators optimized for the production of synchrotron radiation.

**Modern synchrotron light sources are accelerators optimized for the production of synchrotron radiation.**

## Medicine
Biology
Chemistry
Material Science
Environmental Science
and much more

**Medicine**
**Biology**
**Chemistry**
**Material Science**
**Environmental Science**
**and much more**

## Using SR to learn how high temperature superconductors work

**Using SR to learn how high temperature superconductors work**

**Using SR to make miniature mechanical and electromechanical devices**

**Visualizing magnetic bits on a computer hard drive**

**Understanding how debris causes damage to aircraft turbines**

## EUV Lithography

**EUV Lithography**

## Studying Anthrax Toxin components to develop treatment in the advanced stages of infection.

**Studying Anthrax Toxin components to develop treatment in the advanced stages of infection.**

**Measuring very low  levels of mercury in fish and determining its chemical form.**

## Leukemia

**Leukemia**

**Drug Design**
**GLEEVEC**

**Understanding how protein’s are made**

**Ribosomes make the stuff of life. They are the protein factories in every living creature, and they churn out all proteins ranging from bacterial toxins to human digestive enzymes **

## This is an image taken with the x-ray microscope of a malaria-infected blood cell. Researchers at Berkeley Lab use pictures like this to analyze what makes the malaria-infected blood cells stick to the blood vessels. 

**This is an image taken with the x-ray microscope of a malaria-infected blood cell. Researchers at Berkeley Lab use pictures like this to analyze what makes the malaria-infected blood cells stick to the blood vessels. **

## These studies make use of the penetrating power of X-rays, rather than their short wavelength

**Image of a human coronary artery taken with synchrotron radiation at SSRL**

**These studies make use of the penetrating power of X-rays, rather than their short wavelength**

## Sulfuric acid causing the decay of the Vasa, the Swedish warship which sank in Stockholm harbor in 1628

**Sulfuric acid causing the decay of the *****Vasa*****, the Swedish warship which sank in Stockholm harbor in 1628**

***Virgin, Child, and Saint John*****    A renaissance panel painting by Jacopo Sellaio or Filippino Lippi being restored at the Cantor Art Center**

## 18 Nobel Prizes 
Based on X-ray
Work

Chemistry
1936: Peter Debye
1962: Max Purutz and Sir John Kendrew
1976 William Lipscomb
1985 Herbert Hauptman and Jerome Karle
1988 Johann Deisenhofer, Robert Huber and Hartmut Michel
1997 Paul D. Boyer and John E. Walker
2003 Peter Agre and Roderick Mackinnon

**18 Nobel Prizes **
**Based on X-ray**
**Work**
**Chemistry**
- 1936: Peter Debye
- 1962: Max Purutz and Sir John Kendrew
- 1976 William Lipscomb
- 1985 Herbert Hauptman and Jerome Karle
- 1988 Johann Deisenhofer, Robert Huber and Hartmut Michel
- 1997 Paul D. Boyer and John E. Walker
- 2003 Peter Agre and Roderick Mackinnon

**Physics**
- 1901 Wilhem Rontgen
- 1914 Max von Laue
- 1915 Sir William Bragg and son
- 1917 Charles  Barkla
- 1924 Karl Siegbahm
- 1927 Arthur Compton
- 1981 Kai Siegbahn
**Medicine**
- 1946 Hermann Muller
- 1962 Frances Crick, James Watson and Maurice Wilkins
- 1979 Alan Cormack and Godrey Hounsfield

##  54 in operation in 19 countries used by more than 20,000 scientists

** ****54 in operation in 19 countries used by more than 20,000 scientists**
** ****8 in construction **
** ****11 in design/planning **
- For a list of SR facilities around the world see
- http://ssrl.slac.stanford.edu/SR_SOURCES.HTML
- www.sesame.org.jo

## Slide 27

## Slide 28

##  The ultimate performance parameter of a synchrotron light source is the brightness. 

** ****The ultimate performance parameter of a synchrotron light source is the brightness. **

** ****The battle for the brightness maximization is fought in two fronts:**

_** **__**In the accelerator:**_** In storage rings, by increasing the current and designing new lattices capable of smaller emittances. Or designing linac based sources potentially capable of overcoming the storage ring limitations (free electron lasers, energy recovery linacs, ...).**

** ****In the accelerator elements where the synchrotron radiation is actually generated: **_**dipole magnets and insertion devices**_**. And this is where spectacular improvements have been achieved!**

** ****Light sources are usually classified for increasing brightness as:**

** *****1******st****** generation*****: “parasitic”synchrotron radiation sources from dipoles ****	****               in colliders.**

*** ******2******nd****** generation*****: dedicated storage rings with** **sources from dipoles.**

*** ******3******rd****** generation*****: dedicated storage rings with insertion devices**

** *****4******th****** generation*****: free electron lasers, ...**

## Continuous spectrum characterized by c = critical energy

**Continuous spectrum characterized by ********c**** = critical energy**
******c****(keV) = 0.665 B(T)E****2****(GeV)**
***For example*****: **
**for B = 1.35 T  E = 2 GeV  ********c**** = 3.6keV**

**+ harmonics at higher energy**

## “C” shaped for allowing to the radiation to leave the magnet

**“****C” shaped for allowing to the radiation to leave the magnet**

**Normal-Conductive**
**~ 1.5 T Max**

## Spectrum:

**Universal function**

**Spectrum:**

**Critical frequency**

## At the Advanced Light Source three of the existing thirty six 1.3 T dipoles were replaced by three 5 T superconducting dipoles (“superbends”) for extending the spectrum to higher frequencies (>10 keK photons).

**At the Advanced Light Source three of the existing thirty six 1.3 T dipoles were replaced by three**** 5 T superconducting dipoles ****(“superbends”) for extending the spectrum to higher frequencies (>10 keK photons).**

## Remark: The distribution for longer wavelengths does not depend on energy.

**Remark: The distribution for longer wavelengths does not depend on energy.**

## Invented by

**Invented by**
**Klaus Halbach**

## Photons emitted by different poles interfere transforming the continuous dipole-like spectrum into a discrete spectrum

**Photons emitted by different poles interfere transforming the continuous dipole-like spectrum into a discrete spectrum**

**The condition for **_**constructive interference**_** requires that, while traveling along one period of the undulator, the electrons slip by one radiation wavelength with respect to the (faster) photon.**

## The spectrum of the undulator radiation:

**The spectrum of the undulator radiation:**

**depends strongly on the ****strength parameter *****K*****:**

**Remembering that:**

**One can see that *****K***** is proportional to the field *****B*****:**

**In a permanent magnet undulator, *****B***** and consequently *****K***** can be modified by changing the gap height. The larger the gap the lower the field.**

**When *****B *****is increased, both *****K***** and the “wiggling” inside the undulator ****increase as well****. With the larger wiggling, the overlap between the radiated field (****1/********** cone) decreases and the interference is reduced. **
**For *****K***** >> 1**** no interference is present and the undulator presents the continuum spectrum typical of the ****wiggler****.**

## ALS EPU50 (1998)

**ALS EPU50 (1998)**
**Pure permanent magnet technology, Elliptically polarizing capability.**

**Such a device allows for the complete control of the polarization from linear in to elliptical.**

**The arrays of permanent magnets can be mechanically shifted modifying the plane of the "wiggling" and thus the polarization of the radiated light.**

## ... (?)

**Much higher brightness and flux**
**- Free Electron Lasers (from IR to X-ray) **

**  ****- Storage rings (Terahertz)**

**... ****(?)**

**Sources exploiting**** ****coherent emission****:**

**Shorter Pulse Lengths**
**Femto (10****-15****) and Attosecond (10****-18****)**

##  In free electron lasers (FEL), a relativistic electron beam and a laser overlap and travel simultaneously inside an undulator.

** ****In free electron lasers (FEL), a relativistic electron beam and a laser overlap and travel simultaneously inside an undulator.**

** ****Oscillating through the undulator, the electron bunch interacts with the laser and in a minor way with its own electromagnetic field created via spontaneous emission. Depending on the relative phase between radiation and electron oscillation, electrons experience either an increase or a decrease in energy. **

** ****The laser is tuned at the frequency of one of the undulator harmonics. The whole undulator is included inside an optical cavity composed by two reflecting mirrors located at the two undulator extremes. **

** ****In such a schemes the laser beam bounces many times back and forward inside the cavity and has multiple interactions with the electron beam.**

**  ****The dispersion in the undulator, acting on the energy modulated electrons, induces a longitudinal fine structure, the so-called ****micro-bunching****. Particles inside these microstructures radiates coherently (as a single macro-particle) with a high power emission at the laser frequency.**

##  In the self-amplified spontaneous emission (SASE) FEL, there is no laser and the electron beam interacts only with its own spontaneous emission. 

** ****In the self-amplified spontaneous emission (SASE) FEL, there is no laser and the electron beam interacts only with its own spontaneous emission. **

** ****In order to obtain a large gain in the SASE scheme, a long (and expensive) undulator is required. In a “conventional” FEL the undulator is much shorter because the laser beam is re-circulated many times inside the cavity. **

** ****For such a scheme to work, one has to guarantee a good electron beam quality and a sufficient overlap between radiation pulse and electron bunch along the undulator. To achieve that, one needs a low emittance, low energy spread electron beam with a  high charge density in conjunction with a very precise magnetic field and accurate beam steering through the undulator. **

** ****Unfortunately, because of the absence of efficient large incidence angle mirrors at shorter wavelengths, the highest frequency achievable with the conventional FEL scheme is limited to the near-UV.**

## FLASH already in operation!

**FLASH already in operation!**

##  In the Cornell University-Jefferson Lab proposal for example, they describe a single pass machine based on a superconducting linac and a one-turn return arc that re-circulate the “used” beam back into the linac for recovering the beam energy.  The 5 to 7 GeV, 10 to 200 mA ERL machine could produce electron beams with very low emittances (8 to 100 pm) in both the planes.  Small gap undulators in the arc can produce ultra-high brilliance x-ray beams with many desirable characteristics, including: transversely coherent, diffraction-limited hard x-rays of very short duration (~20 fs to 2 ps). Additionally, the recovery of the energy should allow for very high repetition rates (1.3GHz).

** ****In the Cornell University-Jefferson Lab proposal for example, they describe a single pass machine based on a superconducting linac and a one-turn return arc that re-circulate the “used” beam back into the linac for recovering the beam energy.  The 5 to 7 GeV, 10 to 200 mA ERL machine could produce electron beams with ****very low emittances (8 to 100 pm)**** in both the planes.  Small gap undulators in the arc can produce ultra-high brilliance x-ray beams with many desirable characteristics, including: ****transversely coherent, diffraction-limited hard x-rays of very short duration (~20 fs to 2 ps). ****Additionally, the recovery of the energy should allow for**** very high repetition rates (1.3GHz)****.**

** ****The main limitation of storage rings as synchrotron light sources is paradoxically due to the emission of synchrotron radiation (SR) itself . In fact, it is the quantum excitation during the SR process that limits the minimum emittance and bunch length achievable in the ring.**

** ****A new type of synchrotron radiation machine that can potentially overcome these limits while maintaining the “good” qualities of storage rings, is the ****Energy Recovery Linac**** (ERL). **

##  Technical Design Report (TDR) for TESLA, Part V The X-ray free electron laser 

** ****Technical Design Report (TDR) for TESLA, Part V *****The X-ray free electron laser***** **

**Thanks to Herman Winick and David Robin for sharing their viewgraphs.**

##  Calculate the critical energy in eV for the ALS superbends knowing that the electron beam energy is 1.9 GeV, the field is 5 T and the total deflection angle for the magnet is 10 deg. Remember that the photon energy is given by hf (with h the Planck constant, 6.626068 × 10-34 m2 kg / s, and f the photon frequency)

** ****Calculate the critical energy in eV for the ALS superbends knowing that the electron beam energy is 1.9 GeV, the field is 5 T and the total deflection angle for the magnet is 10 deg. Remember that the photon energy is given by *****hf***** ****(with *****h***** the Planck constant, 6.626068 × 10****-34**** m****2**** kg / s, and *****f***** the photon frequency)**

** ****Always for the ALS case, calculate the critical energy for the normal bends knowing that the bending radius is 4.957 m and the total deflection angle for the magnet is 10 deg.**

** ****Using the universal spectrum for the bending magnet radiation, calculate for both the above cases, the maximum radiated power in 0.1% bandwidth when 400 mA electrons are stored ( the ring length is 197 m). Indicate at which photon energy is the maximum located.**