Accelerators and Photons

Accelerators and Photons.

Trends, challenges, opportunities

Reinhard Brinkmann, DESY

Reinhard Brinkmann | Director Accelerator Division | EuroNNAc Workshop| CERN, 4. May, 2011 | page 2

Synchrotron radiation storage rings – the flagships

ESRF SPring 8

APS PETRA IIIPETRA III


Storage rings – basic parametersESRF SPring 8 APS PETRA

IIIE/GeV 6 8 7 6

C/m 844 1434 1104 2304

x/nm 4 3 3 1

y/x 0.1 – 0.2% 0.2% 0.3 - 1% ~1%

Ibeam/mA 200 100 100 – 300 100

0 10 20 30 40 50 60 70 80 90 1001E18

1E19

1E20

1E21

Diamond U46

SLS U19

Petra U1 (20m, 200mA)

MT.

23.0

5.02

Petra U1 (5m, 200mA)

Bril

lianc

e [s-1

mm

-2m

rad-2

0.1%

BW

-1]

Photon energy [keV]

ESRF ID16 (5m)

APS Und.A (5m)

Spring8 BL46


The future: Ultimate storage ring

Invited paper at EPAC2000, Vienna:

Intensive work towards ultimate performance started > 10years ago with the ESRF group and Pascal Elleaume† being a strong driving force


Ultimate storage ring – emittance challenge

> Ultimate performance requires e-beam emittance comparable to photon beam emittance („diffraction limit“) e ph = ph/4

Beam emittance 10pm*rad for 1Å wavelength!> TME multi-bend achromat lattice with large # of dipole magnets

> Compromise for dynamic aperture Relax focusing, ~ factor 3 above

theoretical limit M. Borland et al, 2010

𝐶𝑞

2𝐷❑ 3

12√15 𝐽 𝑥

𝜀≈1𝑛𝑚 ∙( 𝐸6𝐺𝑒𝑉 )

2

∙ ( 100𝑛𝐷𝑖𝑝 )3


Strong sextupoles – small dynamic acceptance

Analytical scaling estimate : Ax ~ x2/3 …. x


Intrabeam – effects: round beams

> For extremely dense bunches, Touschek lifetime drops strongly & emittance grows due to IBS don‘t aim for y << x

Operate on x-y coupling resonance y = x

Gain a factor almost 2 in zero-current x and reduce growth due to IBS

A. Xiao, IBS calculations for USR7 (2009)


U.S.R.‘s cont‘d

> Storage ring near ~10pm*rad very challenging, but not impossible with state-of-the-art technology

Top-up mode with accumulation of small

Portions of beam unlikely to work fast on-axis

kicker concept

Very large rings advantageous: practicalities

(many magnets!), effective use of damping

Wigglers, for given lattice type acceptance

proportional to circumference ( usage of existing infrastructure PEP, PETRA, HERA)

> USR with even somewhat relaxed parameters (~50pm) has normalised emittances <1mm*mrad competitive with linac-driven sources !?

Longitudinal emittance much too large/peak current much too low (factor ~100) to drive hard x-ray SASE FEL

Partial lasing conceivable: Lg ~100m for Ipk = 50A – use K-J Kim et al. XFEL-oscillator concept?? (proposed for an ERL!)

Top-up operation in PETRA-III


Storage rings advanced-I: round-beam insertion

> Consider „conventional“ ring with e.g. 2GeV, x = 1nm, y = 0.01nm, want diffraction limited beam at 1nm wavelength

Instead of coupling resonance where , x +y = const, use transformation flat-to-round beam in an undulator insertion where x y = const = 2, = 0.1nm (R.B. EPAC 2002)

Possible with skew quad transformation + solenoid field (in practice: s.c. solenoid + helical undulator in one device) (transformation concept originally proposed by Y. Derbenev for e-cooling 1998)

> Could provide diffraction limited 1nm soft X-rays in an (almost) existing ring

Has not made it into practice…(yet?): solenoid/undulator device not easy to design & build, concerns keeping the flat-round-flat transformation perfectly closed, cost. schedule, user interest…

skew triplet skew triplets.c. solenoid & undulator


Storage rings advanced-II: fs pulses/slicing

Selection of short photon pulse by energy modulation + transverse displacement

idea: A. Zholents, M. Zolotorev, PRL 76 (1996), 912first experiment (ALS): R. W. Schoenlein et al., Science 287 (2000), 2237

Courtesy Shaukat Khan, TU Dortmund

Recent idea at DELTA/Dortmund: use seeding for coherent generation & possibly EEHG scheme to produce VUV radiation pulses


Storage rings advanced-III: ps pulses/rf deflection

Photon pulse shortening by long.-vertical correlation with deflecting mode cavity

idea: A. Zholents et al. NIM A425 (1999), 385

(From K. Harkay et al., PAC2005)


FELs – operational & under construction/commissioning

LCLS-2009

EU-XFEL-2015

FLASH-2005

… + FEL projects in Italy, Korea, Switzerland, …

2011


FEL parameters – SASE operation

FLASH LCLS XFEL@Spring 8

EU-XFEL

E/GeV 1.25 13.6 8 17.5

L/km 0.3 1.5 0.8 3.4

ph/nm 4 - 60 0.15 – 1.5 0.1 - 1 0.05 – 1.6

/10-6m 1 – 1.5 0.4 0.8 0.4 – 0.8

Pulse rate /Hz

3,000 (50,000)

120 (+ mb option)

60 ( 3,000 mb option)

27,000


Peak brilliance in entirely new regime

ã Firmenam e (Referentennam e)28

Coulomb explosion of lysozyme (50 fs)Coulomb explosion of Lysozyme LCLS

Radiation damageinterferes with atomicscattering factors and

atomic positions

50 fs3x1012 photons/100 nm spot12 keV

Neutze, Wouts,van der Spoerl, Weckert, Hajdu: Nature 406 (2000) 752-757

t=50 fsec

t=100 fsec


Remarkable agreement of performance with predictions

> Excellent injector performance and very small emittance dilution in linac & bunch compressors

> Built-in safety margins not really necessary – saturation reached over ~half of total undulator length

> LCLS (& EU-XFEL) can reach performnce well beyond design specs

> for given wavelength design goal, beam energy can be lowerFrom P. Emma, PAC2009

LCLS commissioning April 2009:


Parameter scaling – beam energy, emittance

(parametrisation of studies by Saldin, Schneidmiller, Yurkov)

Not gain length, but coherence (and peak brilliance ~Ebeam) strongly dependendent on energy (via absolute emittance)

Injector performance is the crucial element for FEL facility cost (Energy!) & performance


Injector R&D – example PITZ @ DESY-Zeuthen


“core” emittance for different bunch charges

Idea: Cut low intensity region of MEASURED phase space (no lasing)

100% of 1nC: εx = 0.92 mm mrad, εy = 0.84 mm mrad

*LCLS results: projected emittance, 95% RMS values.D. Dowell + P. Emma, priv. commun. + FEL2009

xx´ yy´preliminary

Why not start with higher charge and collimate the bunch?

(looks like could gain factor 2…3 in emittance, but: wakefields, radiation protection, …)


Towards single spikes with low-charge, short bunches

14,3 14,4 14,5 14,6 14,7 14,8 14,90

200

400

600

800

Inte

nsity

, a.u

Wavelength, nm

ss1 ss2 ss3 ss4 aver 800 shots

Bandwidth 1.3%

150 pC500 pC

14,3 14,4 14,5 14,6 14,7 14,8 14,90

5000

10000

Inte

nsity

, a.u

Wavelength, nm

ss7 ss8 ss9 ss10 aver 800 shots

Bandwidth 1.8 %

FLASH 2011

ph ~ 15fs

LCLS simulation at 1.5nm, 20pC bunch charge (from Y. Ding et al., PAC09)

FEL operation @20pC successfully demonstrated


Alternative to SASE FEL: seeding concepts

> HGHG: modulation with optical laser amplification of higher harmonics in several stages

> HHG: modulation with high harmonics of optical laser generated by interaction with a gas (or combination of both)


New idea: echo-enabled harmonic generation

laser 1 1

laser 22

VUV pulse /n

modulator 1 modulator 2 radiator

simulations by D. Xiang and G. Stupakov (2009)

- proposed: G. Stupakov, PRL 102 (2009), 074801- 1st experimental results at SLAC, D. Xiang et al. IPAC10

Courtesy Shaukat Khan, TU Dortmund


Energy recovery linacs

> 1st idea (for superconducting linear collider) by M. Tigner, Nuovo Cimento 1965

> Rapidly growing interest in ERL concepts & projects over past ~10 years (JLAB, Cornell, BNL, BINP, KEK, HZB, DESY, …)

EU-XFEL Cornell ERL

Storage rings today

Ultimate rings

E/GeV 17.5 (6cw) 5 6 - 8 5 - 8

av Ibeam/mA 0.05 (0.5cw) 25 – 100! ~100 100 - 500

ph/ps 0.01 – 0.1 0.1 - 2 >20 >20

/10-6m 0.4 – 0.8 0.1 – 1! 10 - 40 0.2 - 1

!: Cornell injector prototype achieved: 4mA, 0.4 – 1.5mm*mrad(I. Bazarov et al. PAC09)


R&D on CW-injectors crucial – synergy with s.c. FELs

Trend for future s.c. FELs (or upgrades) goes towards cw-operation – overlap with development programme for ERLs

(Examples, not exhaustive)


Option for ERLs (or s.c. FELs): XFEL oscillator

R. Colella, A. Luccio, Optics Comm. 50 (1984), K.-J. Kim, Y. Schvydk‘ov and S. Reiche, Phys. Rev. Lett. 100 (2008)

Courtesy Johann Zemella, Univ. Hamburg

Build-up of FEL radiation towards steady-state over severals 10s of pulsesExtremely narrow line 10-5 – 10-6/high spectral brightness


Photon sources with plasma acceleration?

Emittance from LPWA with m source size and mrad rms divergence can be of same order as from conventional beam source:

L = focal length

0 p/p

Chromatic emittance dilution is not negligible!


Synergies and opportunities

> Accelerator physics and technology developed for photon sources as well as available infrastructure have overlap with developments of plasma acceleration – opportunities to use synergies and jointly advance this field of accelerator research Generation & dynamics of fs-beams Fs-synchronisation & diagnostics Usage of test facilities & accelerator infrastructures for plasma

acceleration experiments …


Example: using PITZ for plasma-wakefield experiment

(similar to idea of comb-beam by M. Ferrario et al.)

OSS signal (UV)

temperature

controlled birefringen

t crystal

motori

zed rotatio

nstage

Will, Klemz, Optics Express 16 (2008) , 4922-14935

FWHM ~ 20 ps

Simulated pulse-stacker FWHM ~ 24 ps

FWHM ~ 24 ps

Pulse shaper laser by MBI

Bunch structure with e.g. 5 or 6 spikes and approximately linear increase in bunch charge should be possibleCompression of this structure to match plasma wavelengthDemonstration of large transformer ratio with plasma wakefield experiment conceivable


Example: using FLASH (II) to test LPWA with externally injected beam

Civil construction for FLASH-II starts this year

Use one bunch per linac pulse of extracted FLASH-II beam for plasma acc experiments


Thank you for your attention!

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Accelerators and Photons