berlinpro an erl demonstration facility at the ......berlinpro: an erl demonstration facility at the...

BERLinPro

An ERL Demonstration facility at theHELMHOLTZ ZENTRUM BERLIN

March, 1st, 2010, Bettina Kuske, FLS 2010, SLAC, USA

BERLinPro: An ERL demonstration facility at the HELMHOLTZ ZENTRUM BERLIN

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Main components:

100MeV, 100mA beam Small emittance, rel. short bunches High current: to address needs of storage ring users Show energy recoveryExplore limits of ERL (multiturn, injection energy)Show different operational modes: high current (100mA, 2ps), short pulses (10mA, 100fs), ??, => superiority of the ERL concept to storage rings

BERLinPro: ERL demonstration facility to prepare the ground for a few GeV ERL @ Berlin-Adlershof

Goal:

•SC-RF gun•Booster module – Cornell development with minor modifications•Merger: C-chicane, 4 rectangular dipoles•Linac: based on Tesla technology, modified for high current•Return arc: TBA•Second loop option



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Finances and time table :

• ‚go ahead‘ for gun development• R&D money for gun development secured• Further approval process for entire budget

2010 beam from 1.6 cell gun cavity in HoBiCaTConceptual design

2011Technical layout (TDR)

5 years after approval: first recirculated electrons



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GUN DEVELOPMENT

SRF Gun

Return Arc

Merger SectionMain Linac SRF Module

Spent Beam

Beam Dump

SRF Booster

1.5 MeV

5-10 MeV100 MeV

Beam Manipulation Undulator tests



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BERLinPro gun: Staged approachA high brightness source which can deliver high

average current and short pulses.

Stage 1-Beam Dynamics: Produce beam with cold gun in existing HoBiCaT cryomodule.Nb cavity with Pb-coated cathode (J. Sekutowicz & Co), UV laser (MBI), sc solenoid and beam diagnostics.

Stage 2-Cathode integration: Extend HoBiCaT bunker, new cryomodule, cathode preparation infrastructure. Produce 1 to 10 mA with CsK2Sb cathode, green laser (MBI). In parallel, test gun cavities and new RF coupler (>100kW) in HoBiCaT.

Stage 3-High current operation: Build SRF gun for BERLinPro (high rep. rate) Fr

om J

. Sek

utow

icz,

Pr

oc. o

f PA

C09

Courtesy of Thorsten Kamps



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Stage 1 setup in HoBiCaT

1.6 cell cavity, sc-solenoid,Helium supply

Stage 1 diagnostic beam line

View screens, stripline, current monitor, emittance measurement, energy measurement



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HoBiCat preparations:



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MERGER DESIGN CONSIDERATIONS

SRF Gun

Return Arc


Spent Beam

Beam Dump

SRF Booster

1.5 MeV

5-10 MeV100 MeV




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Zigzag chicane:(Brookhaven)

Space charge forces: compatible with emittancecompensation scheme

Higher order dispersion: intrinsically cancelled by C-chicane with rectangular magnets

• equal focussing in both planes• 2. order dispersion not 0• Small trajectory displacement• Fixed relation D1/D2• „Geometrically challenging“(vertical construction in Brookhaven)

• Easier to incorporate in machine• Flexible drift lengths• Offset adjustable by drift length• Vertical focussing

C-chicane:



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ASTRA: Emittance for Zigzag / C- chicane for increasing bunch charge and different energy spread (correlated)

C-chicane

Zigzag

Gaussian bunch:ε x,y = 1.0 π mradσ x,y = 1.0 mmσ z = 1.0 mmβ x,y = 20.0 mα x,y = 0



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Bunch lengthening in merger due to energy spread / space charge

Effect is reduced when goingto 10 MeV injection energy.



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Emittance vrs. bunch length

Gaussian bunch:E = 10 MeVε x,y = 1.0 π mradσ x,y = 1.0 mmβ x,y = 20.0 mα x,y = 0σ E = 20keV

Emittance depends strongly on bunch length:

Charge σz Compression77pC 6ps 3 or more10pC 1ps 10 or more77pC

10pC



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Lambertson magnet: Good idea??

Last merger dipole deflects high energy beam by up to 4°

=> extra chicane necessary

Lambertson: High energy beam travels infield free region, injected low energy beam runs parallel

Lambertson would reduce 4° to less than 0.14°, which is rather an orbit correction

By Lars-Johan Lindgren, MAX-lab



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L1

dα

d \ L2 0.4m 0.8m 1.2m

10mm 1.4 0.7 0.5

20mm 2.9 1.4 0.7

30mm 4.3 2.1 1.4

α [°] as a function of d, L1

0.025rad = 1.432deg.High energy beam deflected by 1/10: 0.14° mean 2.5cm offset after 10m linac⇒Steering for HE beam is necessary⇒Place for HE optical elements before Lambertson

SteererLast merger dipoleLambertson?



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Linac:

SRF Gun

Return Arc


Spent Beam

Beam Dump

SRF Booster

1.5 MeV

5-10 MeV100 MeV




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100 MeV Linac:

•1.3 GHz•Start with multicell TESLA and adapt this for CW and high current •Single cryomodule with 6-7 cavities•7 cells/cavity (?)•Application „Verbundforschungsantrag“: federal funding for a collaboration

with Univ. Rostock and Dortmund for the calculation of HOMOptions for HOMs: Ferrite loads, waveguide dampers

•HoBiCaT test



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RECIRCULATOR - ARC

SRF Gun

Return Arc


Spent Beam

Beam Dump

SRF Booster

1.5 MeV

5-10 MeV100 MeV




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Path length management:•Short bunches require pathlength adjustment•Second loop option:

100MeV: 1. turn: L=(n+1/2) λrf 200MeV: 1. turn: L= n λrf (λrf/2=12cm)

•Variable injection energy alters path length in merger & splitter for HE beam20o bend @ 5-20MeV = 1-4o @ 100MeV => 0.5cm

t

EE = E0 cos (ωt +φ0)

X∆φ = π – 2 φ0

∆φ = π

head with higher Egives compression with “normal” arc R56

chirp at decelerationdoubles inacceptableenergy spread

∆L = 2 φ0/2π∗λrf =2-3cmφ0 =20deg.

Courtesy of Michael Abo-Bakr



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3 Approaches to pathlength adjustment:1 - Brookhaven: Build arc on sledge, mechanical adjustment

very precise expensive slow

2 - C-chicanelong @ 100MeV: 2-3mCSR – bunches are short

3 - Incorporate into the arc

ρ1

ρ0φ0

φ1ψK

SB

X0

X1

D0

Dϕ1,3[°] ϕ2[°] ψK[°] ∆xmax/cm

60 60 4.8 6.3

45 90 2.9 4.5

Angle and offset for 6cm additional pathlength

Courtesy of Michael Abo-Bakr



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Radiation safety requirements:

Different ‚league‘ than storage ringsDrive costs

=>drive beamloss requirements Permissable beamloss:<1e-5?

=> Too little space for shielding above ground=> Consider construction underground

reduced shielding, vibrations and temperature fluctuationsat comparable costs



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BESSY II

Cryogenic plant



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Building: All dimensions preliminary

55m 6.4m

6.0m

15m

Storage Ring Hall

berlinpro an erl demonstration facility at the ......berlinpro: an erl demonstration facility at the...

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