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Laser Pulse Circulation System for Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Monochromatic Hard-X-ray Source Haruyuki OGINO [email protected] The University of Tokyo, Japan The Physics and Applications of High Brightness Electron Beams, ICFA Workshop Atsushi FUKASAWA 1 , Fumito SAKAMOTO 1 , Tomohiko YAMAMOTO 1 , Kazutaka TAKAO 1 , Meng De 1 , Katsuhiro DOBASHI 2 , Toshinobu MIYOSHI 2 , Mitsuru UESAKA 1 1) University of Tokyo, nuclear professional school, school of engineering 2-22 Shirakata-shirane, Tokai, Naka, Ibaraki 319-1188 JAPAN 2) National Institute of Radiological Sciences 4-9-1 Anagawa, Inage, Chiba, Chiba, 263-8555 JAPAN

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Page 1: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

Laser Pulse Circulation System forLaser Pulse Circulation System for

Monochromatic Hard-X-ray SourceMonochromatic Hard-X-ray Source

Haruyuki OGINO

[email protected]

The University of Tokyo, Japan

The Physics and Applications of High Brightness Electron Beams, ICFA Workshop

Atsushi FUKASAWA1, Fumito SAKAMOTO1, Tomohiko YAMAMOTO1,

Kazutaka TAKAO1, Meng De1, Katsuhiro DOBASHI2, Toshinobu MIYOSHI2,

Mitsuru UESAKA1

1) University of Tokyo, nuclear professional school, school of engineering

2-22 Shirakata-shirane, Tokai, Naka, Ibaraki 319-1188 JAPAN

2) National Institute of Radiological Sciences

4-9-1 Anagawa, Inage, Chiba, Chiba, 263-8555 JAPAN

Page 2: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

Background for medical useBackground for medical useTunable Monochromatic Hard-X-ray-SourceTunable Monochromatic Hard-X-ray-Source

Synchrotron radiation facility

•High intensity(1011!1013photons/s), but huge

size and high cost, difficulty in diffusion

•It takes about a few minutes when we change

the X-ray energy

Unfavorable for vital observation Spring-8, Japan

40 keV

Monochromatic X-ray

80 keV

Monochromatic X-ray

40 keV CT

80 keV CT

sampleElectron density

distribution

Effective atomic number

distribution

detector

We need more smaller system for vital observationWe need more smaller system for vital observation

For cancer radiotherapy

Page 3: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

Laser Electron Compton ScatteringLaser Electron Compton Scattering

Tunable Monochromatic Hard-X-ray SourceTunable Monochromatic Hard-X-ray Source

X-band LinacElectron(35MeV)

Monochromatic X-ray(44.5keV)

Laser (!=532nm)

Collision

Two laser system will be installed and they collide with 35MeV

electron beam by turns and it takes about 40ms to change the

laser wavelength, then the 44.5keV and 22.5keV X-ray will be

generated by turns.The intensity will be 108photons/s.

X-band LinacElectron(35MeV)

Monochromatic X-ray(22.5keV)

Laser (!=1064nm)

Collision

The X-ray energy is depend on electron energy and laser wavelengh.

Same electron energy "#different laser wavelength = different monochromatic X-

ray

Page 4: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

1064nm

532nm

Hard X-ray

Electron Bunch

Laser Pulse#(1064 nm)

Laser Pulse#(532 nm)

Constant Electron Energy (35MeV)

Different laser wavelength (532nm,1064nm)

$

Dual X-ray EnergyDual X-ray Energy44.5keV#,#22.5keV

Xband Linac

Electron and laser

Beam size

" =100µm

The smaller system for vital observationThe smaller system for vital observation

Page 5: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

Final goalFinal goalNow we are developing the experiment

proof of laser electron Compton scattering

X-ray source.

Our final goal is shown below, it can be

installed inside the hospital room.

Smaller system

Page 6: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

What is laser pulse circulation system?What is laser pulse circulation system?

The LPCS (Laser Pulse Circulation System) can make the laser

Pulse overlap with the electron beams at transverse and

longitudinal direction. It will lead to the stable and efficient

X-ray generation at the laser electron collision experiment.

Longitudinal

direction

Transverse

direction

Laser pulse(10ns,FWHM) is blocked into the circuit (5m) and it

collides with electron beams(1µs).The collision period is about

20ns.

%The recycle of laser pulse (one laser pulse collides 50times)

It is more difficult to modify the position of electron beams

because we have to change the magnet parameter, so we

modify the position of laser from outside the circuit.

%We change the transverse laser position and beam size(rms).

The X-ray intensity is calculated to be 108photon/s without LPCS.

LPCS can intensify it 10times stronger, that is 109photons/s.

Page 7: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

Longitudinal LPCS by changing its polarizationLongitudinal LPCS by changing its polarization

From injection to 2nd lap

During 2nd lap

From 2nd lap to the end

In this case, only 2 laps

After 2nd lap, pockels cell HV ON

Page 8: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

LPCS at the longitudinal directionLPCS at the longitudinal direction

Page 9: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

Transverse LPCS by shifting the lens positionTransverse LPCS by shifting the lens position

The distance of lens adjustment The distance of collision point

Same resolution

The position of laser collision point can be changed with µm

order, and the laser keeps the same condition without reference

to the lens adjustment.

Page 10: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

LPCS at the transverse directionLPCS at the transverse direction

electron & laser

beam size"=100µm

Page 11: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

• PurposeLPCS principle experimentLPCS principle experiment

To establish by proof of Laser Pulse Circulation System for

longitudinal and transverse direction.

Low energy laser

(MAX:25mJ/pulse)

second harmonic wave

(!=532nm)

532nm

25mJ/pulse

10Hz

Longitudinal direction To make the laser circulate by changing its polarization.

To measure the LPCS and calculate the transfer

efficiency and energy intension.

Q-switch Nd:YAG Laser

Transverse direction To change the laser position by moving four lenses

and to keep the circulation condition.

PHOTONIC SOLUTIONS, MINILITE2Fundamental wave experimentFundamental wave experiment

will be held on 2005.12will be held on 2005.12!!

Page 12: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

LPCS principle experimentLPCS principle experimentLow energy laser(532nm) and no electron beamLow energy laser(532nm) and no electron beam

• Experimental setup

Circuit length 5m, Nd:YAG Laser,

!=532nm(second harmonic wave), 25mJ/pulse, 10ns(FWHM),10pps

• How to measure the LPCS

Longitudinal LPCS % Photo multiplier

Transverse LPCS % CCD camera (laser position and beam size)

To avoid

the air ionization.

Page 13: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

LPCS experiment result, longitudinal directionLPCS experiment result, longitudinal direction

!=

"

"

"

"==

+######+++=

n

k

n

k

n

n

n

A

AIAII

AIAIAIII

1

0

1

0

1

0

2

000

1

1 I0: Incident laser pulse energy.

In: Laser intensity in the laser pulse

circulation system.

A: Transmission efficiency per one cycle.

n: Total number of the collisions.

1st lap =0.42

15th lap = 0.10

Then, A=0.90

A=0.90, n=50

Then, 10times higher intensity10times higher intensity

Page 14: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

LPCS experiment result, transverse directionLPCS experiment result, transverse direction

It can be proved that the transverse position of laser can be controlled

independently with the same resolution of four convex lenses shifting

(µm order). Laser can keep beam size while shifting its position.

horizontal direction vertical direction

Page 15: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

LPCS for laser electron ComptonLPCS for laser electron Compton

scattering experimentscattering experiment

• High power Laser

Nd:YAG Laser, 1.4J/pulse,532nm,10ns(FWHM),10pps

Principle experiment % Nd:YAG Laser, 25mJ/pulse,532nm,10ns(FWHM),10Hz

High power laser for Compton scattering

Spectra Physics Quanta-ray Pro-290

Both Q-switch Nd:YAG Laser

PHOTONIC SOLUTIONS, MINILITE2

Principle experiment

25mJ/pulse

1.4J/pulse

Page 16: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

LPCS for laser electron ComptonLPCS for laser electron Compton

scattering experimentscattering experiment

•Experimental Setup

What is the difference between principle experiment and this high power LPCS?

•Laser energy 25mJ/pulse%1.4J/pulse

•No need for !/2 waveplate

At the 1st lap, the polarization will be changed

from p to s, and the HV will be off quickly after

that. So the laser keeps s polarization, at alltimes then we don’t need !/2 waveplate.

The voltage of pockels cell

On%Off at the 1st lap

Page 17: Laser Pulse Circulation System for Monochromatic Hard-X ... · Laser Pulse Circulation System for Monochromatic Hard-X-ray Source Haruyuki OGINO ogino@nuclear.jp The University of

SummarySummary• Electron laser Compton scattering monochromatic hard

X-ray source are now under construction at the Univ.

of Tokyo, Japan.

• LPCS proof experiment has proved that the 25mJ laser

could be blocked into the circuit by changing its

polarization and its energy could be intensified 10timeshigher and could be changed its position with µm

order.

• LPCS will be installed to the X-ray source in order to

make 1.4J laser collide with the electron efficiently and

intensify the X-ray yields from 108 to 109 photons/s.