A proposal for the first facility to be installed at ELI Romanian pillar:

A simple, compact and very bright 1-30 MeV gamma ray source based on Compton scattering

Guy WormserLAL Director

LAL-Orsay. IN2P3-CNRS

Everything said in one slide• We have learned that ELI could be interested in a 1-30 MeV intense

Compton source• It so happens that LAL Orsay with a strong team of collaborators is

presently designing the most ambitious X ray Compton source in the world (10**13 photons per second in the 100 keV range)– Very detailed Conceptual Design Report now available – Top level expertise in laser, cavity, accelerator– Technical Design Report ready by end 2010– Experimental results on 1.3 GeV ring in Japan starting from summer

2010• Our X ray source design can be easily adapted to produce 1-30

MeV photons with similar performance– Ease the ring design and dynamics (250 MeV-1 GeV ring)

• If there is interest from your side, we are happy to explore collaboration possibilities to build such a machine for/with you.

Our general idea

• There will be a photonuclear program in ELI nuclear physics pole

• Ultimaltely the Compton source will be produced by the 10 PW laser, coupled with a electron source from an accelerator or another laser (or the same laser)

• One should not perform difficult measurements with a new source being commissioned at the same time

• Seems therefore very wise to start the experimental program with a good performance stable « classical »  source of moderate cost 

• Ideal first step : Ring based Compton source, totally decoupled from the PW laser program

Why this presentation• Extract from ELI scientific committee• [c] Photonuclear physics• Methods to produce monoenergetic directed brilliant pulsed gamma-

rays have been already discussed earlier in Subsecs.[a] and [b]. The principal approach is to utilize the intense laser backscattered on high energy electron bunch to produce such gamma-rays by the Compton backscattering process. This method is proven and has been already employed several laboratories around the world to produce some promising results in exploring nuclei by high energy photons. In this technique, for example, a large amount of MeV gamma-rays with the above characteristics may be generated. MeV is the energy range where typical nuclear reactions and nuclear excitations take place.

• We are currently designing a compact X ray source ThomX capable of delivering 10**13 100 keV photons per second!

• We know how to build a very intense MeV Compton source!

Brief LAL Orsay presentation

• LAL Orsay is the largest CNRS/IN2P3 laboratory devoted to particle physics and cosmology

• LAL is a Joint Research Unit between CNRS and Paris Sud 11 University

• 100 physicists, 220 Engineers and technicians• Annual consolidated budget: 20 M€

– Mostly coming from IN2P3 but now with important funds coming from other sources as well: European Union, National Research Agency, Paris region, etc….

• Strong implication in HEP experiments across the world with large technical contributions

• No more local accelerators but many accelerator R&D activities

LAL technical know-how

• Mechanics– 60 technicians and engineers with a strong local workshop– Very large construction hall (Hall André Lagarrigue)

• Electronics– 60 technicians and engineers, 50 cards per year– Microelectronics excellence pole

• 10 ASIC top level designers

• Computing– A Tier2 Node for LHC– Local software development (CMT, graphics, databases,..)

• Accelerator R&D (70 people including 20 acc. Specialists)

• Administration

LAL Accelerator projects

• XFEL (DESY) : delivery of all 800 power couplers for LINAC

• CTF3 (CERN) : Delivery of Drive beam and Probe beam photo-injectors

• PHIL (LAL) : Photo-injector test bench: 10 MeV Linac

• ILC-GDE : Power couplers, Beam Delivery system

• ATF2 (KEK) : Optics study at the IP• SuperB (Frascati) : Positron source, vacuum, IP

studies

Outline of this talk

• Presentation of Compton sources• ThomX: a vey bright compact X ray source

– General design– Laser system– Resonant cavity– Accelerator system– Cost and schedule

• Some results from ATF ring• Adaptation to MeV source• How to proceed• Conclusion

ThomX CDR now availablehttp://publication.lal.in2p3.fr/2009/LALRT0928.pdf

The ThomX Team• LAL CNRS, Université Paris-Sud 11, Batiment 200,

91898 Orsay, France: C.Bruni, R.Chiche, R.Cizeron, Y.Fedala, J.Haissinski, M.Jacquet, D.Jehanno, M.Lacroix, L.Meignien, B.Mercier, B.Mouton, Y.Peinaud, C.Prevost, R.Roux, V.Soskov, A.Variola, G.Wormser, F.Zomer,

• Synchrotron-SOLEIL,Saint-Aubin, France : P.Brunelle, M.E.Couprie, J.C.Denard, J.M.Filhol, N.Guillotin, P.Lebasque, A.Loulergue, P.Marchand, O.Marcouillé, F.Marteau, R.Nagaoka,

• Centre Lasers Intenses et Application, CNRS – Université de Bordeaux 1: P.Balcou, E. Cormier, M.C. Nadeau,

• C2RMF-UMR171 du CNRS/Ministère de la Culture : P.Walter,

• ILE, Ecole Polytechnique, CNRS, Palaiseau, France : N. Artemiev,

• L.M.A. CNRS, 7, Avenue Pierre de Coubertin VILLEURBANNE, France : R. Flaminio, C. Michel, L. Pinard, B. Sassolas,

• THALES : J.P. Brasile

The Compton effect : its use for X, rays sources

Compton backscattering is the most efficient « frequency amplifier » diff=42 laser, ThomX =>

but very weak cross section: 6.6524 10-25 cm2

Therefore for a powerful light source, one needsbeaucoup d’électrons qui collisionnent avec beaucoup

-lots of electrons-lots of photons-very small collision volume-very high repetition frequency

electron

Laserlaser

Rayon X : diff

(scattered electron)

=Eélectron/mec2

diff

Main features of the Compton effect between 1 electron and 1 photon1) Outgoing photon frequency = Laser frequency* 42

(tunability thru either laser or electron energy)2) Directivity= > around the electron direction3) Energy/angle dependance => monochromaticity thru

diaphragm4) Polarisation if needed5) Further tunability by relationship between electron and

laser collision angle

0

2

4

6

8

1015

2025

3035

4045

50

5.0x103

1.0x104

1.5x104

2.0x104

2.5x104

3.0x104

X-R

ay

Flu

x, [p

h/m

rad2 ]

0

2

4

6

8

010

2030

4050

60

0.0

5.0x103

1.0x104

1.5x104

2.0x104

2.5x104

3.0x104

X-R

ay F

lux,

[ph/

mra

d2 ]

Collis

ion

angl

e, [d

eg]

Time Delay Between Pulses, [ps]

2.0x104 2.5x104 3.0x104 3.5x104 4.0x104 4.5x104 5.0x104

-2.0x102

0.0

2.0x102

4.0x102

6.0x102

8.0x102

1.0x103

1.2x103

1.4x103

100m

90m

80m

70m

60m50m40m

X-R

ay F

lux,

[ph/

shot

/mra

d2/0

.1%

BW

]

X-Ray Energy, [eV]

NxRTX Spectra for various electron fucus size

30m

But: Collision imply an electron bunch and a laser pulse.

Everything gets somewhat smeared and coupled:a) energy, angles, polarisation, (convolution)b) effect of the collision angle (luminosity loss, energy shift, jitter) c) Focalisation => hourglass effect

N.Artemiev

The ThomX project

• compact electron ring = e bunches withy a high rep rate• laser system with similar high frep and large AVERAGE

power coupled to a high finesse Fabry-Prot resonator

Source

X energy 50-90 keV*

Flux 1011 – 1013 ph/s

Frequency width 10 %**

Divergence  < 2 mrad

Cost (excluding Manpower)

< 5 M€

Accélerator and laser

Ring and injector energy 50 MeV

Charge  1 nC

Emittance (rms normalised)

< 5 mm mrad

*  10 cm =>IP ~ 70 m

Average power inside cavity

> 100 kW

Bunch length, rms 5-10 ps*

Compton frep 50-200 MHz

Collaboration between: LAL Orsay, SOLEIL, CELIA Bordeaux, ILE, LMA, Thales

A compact X ray source

Compton source characteristics

• Photon flux : 10**13 /s• Laser characteristics : 50 MHz, 1 micron, 100 W,

5 ps (fiber-doped)• Time structure: 1 bunch every 20 ns (50 MHz)• Energy: 1-30 MeV• Natural energy spread : 2-3%

– Possibility of collimation down to 0,1%– Linear loss on the rate

• Beam spot at the IP : 50 microns• Beam divergence at the IP : few mrads

Laser beam Linac +RF gun

Electron beam pipe

Electron Storage ring

Collision point

Electron beam dumpFour mirrors Fabry Perot cavity

X rays ThomX general scheme

Comparison with other light sourcesFlux is of course smaller than in large (and expensive) synchrotron sources,but in this energy range, very important applications fora compact source

M.E.Couprie, O.Marcouille

≈ n*10 MHz, n*102 W (amplification inside cavity 10000) => 100kW -MW!!!!!!!

Fabry-Perot cavity 2 Super mirrors 4 for mech stability

Electron bunch

The Fabry Perot resonator

Resonant pile-up Fréquence du laser frequency= c/2 L

(L = cavity length)

Laser pulse a few ps

E

beam

n*10

n*10

F.Zomer

M3

M4

telescopeλ/4

Glan

Cavity

EOMFITi:SaVERDI

FS

λ/4

M1Digital Feedback Grating

PD1

M2

PD2

Glan

PDtr

PDH1

PDH2

M3

M4

telescopeλ/4

Glan

Cavity

EOMFITi:SaVERDI

FS

λ/4

M1Digital Feedback Grating

PD1

M2

PD2

Glan

PDtr

PDH1

PDH2

30000 finesseDec 08 : World record! Previous world record: by LAL:3000

Test bench cavity results at LAL

OscillatorOscillator

LDLDVBGVBG VBGVBG

Output to Output to FPFP

ANR MightyLaser goal 200 WTo get amplified in the Fabry perot cavityVery high quality beam, monomde, small phase jitter

P.Balcou, E.Cormier

Two Prototype Cavities4-mirror cavities w/LAL

2-mirror cavity

high enhancementsmall spot sizesophisticated control

moderate enhancementmoderate spot sizesimple control

(Hiroshima / Weseda / Kyoto / IHEP / KEK)

demonstration of ray gen.accum. exp. w/ cavity and acc. intense ray generation

The most delicate : putting everything togetherStabilisation of the cavity frequency (40 MHz with a few mHz precision)Integration in an accelerator environmentDigital feedback system

F.Zomer, P.Balcou

Integration in the electron ring optimised to limit the impact of the photon beam divergence

M.Lacroix

Energy (MeV) 70.4

Normalized emittance (mm.mrad)

4.5

Transverse size (mm) 0.9

Bunch length (ps) 4.5

Energy spread (%) 0.57

Energy (MeV) 50.4

Normalized emittance (mm.mrad)

4.2

Transverse size (mm) 1.2

Bunch length (ps) 4.5

Energy spread (%) 0.68

50 MeV => ~40 keV

Photoinjector new design

70 MeV => ~80 keV

R.Roux

The Accelerator system : The linac

Injection and transport lineNo time for damping !

R.Roux

Circumference (m) 14.47

Nominal energy (MeV) 50

Betatron tunes x, z 3.4 / 1.4

Beta max x,z (m) 11 / 11

Dispersion max (m) 0.9

Beta, dispersion @ IP (m) 0.1 / 0.1 / 0

Momentum Compaction Factor 0.0148

RF frequency (MHz) 500

RF harmonic 24

RF voltage (kV) 300

Period (ns) / Revolution frequency (MHz) 48.5 / 20.6

Natural chromaticities -3.2 / -8.2

Dipole number, family & field (T) 8 / 1 / 0.5

Quadrupole number, families & field (T/m)

24 / 6 / <3

Sextupole number, families & field (T/m2) 12 / 2 / <30

A.Loulergue, C.Bruni

Characteristics of the electron ring

3 m diameter!!

Dynamics and Instability studies

2 1013

C.Bruni, A.Loulergue

Désadaptation résiduelle=> Effets collectifs

Zone « stabilisée »

Wake fields

…………….interaction Compton

Magnetic systems

Novel idea of the cavity integration into the ringSolves many problems!

A.Loulergue, P.Lebasque

RF systems

ttob

o

fI

eE

...

/2

t = 20 ms

Fig. 3 : shape of the 500 MHz ELETTRA-type cavity with a cut-off pipe diameter of 60 mm.

C RF cavity (300-500 kV at 500 MHz) to reduce the compression factor and limit the bunch lenghtening induced by the Compton scatteringCritcial to lwoer HOM impact to stabilise the electron beam

P.Marchand

Detailed layout of the THomX machine

7m

10

m

Canon RF a forte brilliance LINAC 3 GHz – 50 / 70 MeV

Anneau de stockage

Zone d interaction Compton

Cavité et laser

Utilisateurs

Y.Peinaud, M.Lacroix

Cost and Manpower

Photoinjector 422

LINAC 1176

Transport line 219

Ring 1919

Fabry Perot 339

Laser 246

control systems and synchro 490

Infrastructure and cabling 200

Extraction and caracterisation of X rays 200

Spares 222

Total (k€ - HT) [1] 5433

Machine Cost (Preliminary)

FTE FTE (BE)

Photoinjector 1.2 0.5

LINAC 1.4 0.4

Ring and transport line 2.8 0.6

Fabry Perot 0.1 0.1

Laser 2.2 0.2

Control systems 1.0

Infrastructure, support & câblage 1.6 0.8

Total 10 2.6

~70% of this manpower has been identified

TDR phase personnel needs

ThomX Planning

Start

9 MOIS

2 ANS

1 AN

Detailed study Machine constructionExperimental Hall

Assembly, test, commissioning, X ray characterisation

Jan2010 Jan 2013 Oct 2013

Oct 2010

Experimental R/D in ATF

.

Make a fist prototype 2-mirror cavity

Put it in ATF ring

Hiroshima-Waseda-Kyoto-IHEP-KEK

Lcav = 420 mm

Laser Power enhancement 250

Flat mirror

Flat mirror

Spherical mirror

8°

Central support

Spherical mirror

R. CizeronLAL 30/01/2008

Staus of the LAL cavity

French colleagues visited KEK in July.discussed detail of the installation procedure

setting up at the ATF beam line

The cavity will be installed on ATF ring in summer 2010 (2 GeV e-) and will produce 100 MeV photons

• If we want 1 MeV photons the best way is to increase the beam energy (we should also reduce the laser wavelength but remember that for a ring =>higher the energy easier the operation due to Touschek, gas scattering, instabilities….)

• So with an easy scaling for 1 MeV photons we need 250 MeV electrons.

• This will imply also a lower B field in the Q poles for the focalisation sections.

• The emission cone will be reduced from 10 mrad to 2 mrad (sigma) with a consequent increasing of the brillance. But remember that the 1 MeV photons will be located close the axis.

• Diaphragm effects on the energy spectrum are expected close to the 50 MeV case

• The expected flux is bigger (> 1013 /s)or equivalent to the ThomX one

• Dynamics will be different !!!!! Maybe we can use the Syncrotron damping with an important gain in stabilization. If this is the case we can reduce the frequency of injection to reduce the Linac cost that will be increase by the bigger required injection energy

Extension to 1 MeV source

MC simulations – e beam at 250 MeV, laser ~1.37eV

Emitted photons emittance

Emitted spectrum

Photon tracking without andWith diaphragm

Photons angle energy correlation

Energy cut ~ 1.25 MeV

Potential use

• Fundamental studies– Photonuclear scienecs on stable nuclei

• Photonuclear sciences on instable nuclei– Waste material– Coupling with accelerators to excite nuclei ???

• Applied science

Potential collaborations

• C.J. Barty et al. (GRLS)

Energy range

• 1 MeV gamma : 250 MeV electron ring

• 16 MeV gamma : 1 GeV electron ring– Similar to many damping rings (PEP-II)– 30 m circonference

• 32 MeV gamma : 1 GeV electron ring and 500 nm laser

How to proceed !• Is there an interest for ~1 MeV Compton source?• Critical : Main specifications

– Energy (Nominal-Range-Tunability)– Energy width (in %)– Photon intensity– Temporal characteristics (pulse width-Frequency)– Spatial characteritics (beam spot)

• What we can offer– If confirmed interest from ELI , make a complete study for such a machine

in 2010-2011 (cost ~0,5 M€)– Full experimental tests in summer 2010 at KEK of the laser/cavity system– Build a 1 MeV Compton source – Commissionning (in Orsay or in Romania?)– Transport to Romania– Could be ready in 2015– Cost not known yet

• Cooperation agreement would need to be worked out

Conclusion• We have learned that ELI could be interested in a 1 MeV intense

Compton source• It so happens that LAL Orsay with a strong team of collaborators is

presently designing the most ambitious X ray Compton source in the world– Lot of expertise in laser (CELIA), cavity-accelerator (LAL), ring (Soleil)– End of technical design report fall 2010– Experimental results on 1,3 GeV ring in Japan starting from summer

2010• Our X ray source can be easily adapted to produce 1 MeV photons

– Ease the ring design and dynamics (250 MeV ring)– Cost not known yet– 4 year construction time

• If there is interest from your side, we are happy to explore collaboration possibilities to build such a machine for you.