Bruce DunhamOct 12, 2017

SLAC Expertise and Technologies for Electron-Ion Colliders

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Outline of Topics

• Interaction Region Design• Impedance Budget• Beam-Beam Effects• Lattice Design• LLRF and Feedback Systems• Crab Cavities• Coherent Electron Cooling• Polarization Tracking• Electron Sources• Fast Kickers• PEP-II Hardware

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Interaction Region Design(M. Sullivan, A. Novokhatski)

• We have already guided the JLEIC IR design to minimize the Synchrotron Radiation backgrounds in the detector

• More needs to be done to actually get background numbers in the detector from various SR sources and to optimally minimize these backgrounds

• The JLEIC detector team hopes to measure the electron beam polarization in a chicane downstream from the collision point. More work is needed to develop a polarization detector that will not be swamped by backgrounds.

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5

0

-5

-100 1 2-1-2 m

cm BeCu Be Cu

Central detectorbeam pipe +/-12.5 cm in Z

radius=15 mm

Central detector SA inside +/-150 mrad

NEG pump NEG pump

HOM Abs HOM Abs

BPMS BPMS

Beam Chamber for FCC IR

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Interaction Region Design

• The central beam pipe of the detector is still under study and needs serious evaluation in order to satisfy the detector requirements.

• We will need to maintain the close cooperation between the accelerator and the detector teams we have had in the past in order to achieve this goal.

• The detector team wants to use a zero-degree luminosity detector and this effort would greatly benefit from guidance gained by the SLAC PEP-II experience

Q1Q2 Q3

Q1Q2Q3Q4

Q1

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75 100 100 75

40

e-

P+

0-2 2 4 6-4-6

0

10

20

30

-10

-20

-30

X(cm)

Z (m)

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Collective Effects and Impedance Budget (A. Novokhatski, J. Seeman, M. Sullivan)

The prime goal of this activity is to mitigate the collective effects in EIC based

on our experience with high currents at the SLAC PEP-II B-factory

• Analytical estimate of the current limit for various instabilities.

• Model the wake function for simulations of the beam stability in the machine.

• Design and RF simulations of vacuum chambers

• Final simulation of beam stabilities and bunch lengthening.

• HOM heating calculations and specification for HOM absorbers

• Impedance budget of all important elements

• Summary with recommendations on the beam pipe geometry.

PEP-II HOM absorbers

Beam Chamber for FCC IR

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Beam-Beam Effects(Y. Cai)

Bunch Luminosity Specific Luminosity

• Apply the benchmarked code at PEP-II and KEKB to study the beam-beameffects in the ion and electron collider

• Investigate the methods of mitigation in the beam-beam interaction, for example, traveling focusing

Electron ring lattice with non-linear chromaticity correction blocks (CCB)

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Lattice Design and Single Particle Dynamics(Y. Nosochkov, Y. Cai)

• SLAC has extensive expertise in design and operation of colliders (PEP-II, MAP, ILC, FCC), including design of low-bIR optics, low emittance optics, non-linear compensation schemes, particle tracking, maps, error analysis, tolerance specifications

• In the past 3 years, SLAC team has already contributed to the JLEIC design of the ion and electron collider lattice, compensation of non-linear chromaticity, evaluation of dynamic aperture and error effects

• Future effort may include- Finalizing lattice designs of both rings- Compensation of detector solenoid in electron ring

- Injection optics- Orbit diagnostic and correction in electron ring

- Dynamic aperture optimization- Specification of field quality and error tolerances

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LLRF and Beam Loading(J. Fox)

SLAC can contribute:• Investigate the operational limits and impact on beam dynamics from

impedance controlled RF systems.• Time-domain non-linear simulations of beam dynamics incorporating

the technology of LLRF systems• Modeling and studies of new control techniques, based on experience

gained from PEP-II and LHC• Develop RF system tools and methods to optimize performance• Synergistic with ongoing US-Japan high beam-loading studies for

SuperKEK-B. Also have experience applying techniques at LHC and for HL-LHC studies.

• EIC designs have challenging goals for stored current

• The two rings have completely different RF systems and longitudinal dynamics

• Interactions of beam gaps with the RF systems lead to modulations of synchronous phase at the IP

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Beam Instability Feedback(J. Fox)

SLAC can expand models (from PEP-II and SuperKEKB) to include the technical features of an EIC RF system

• Estimate growth/damping rates for all modes versus current fill patterns• Use estimates/measurements of cavity HOM’s to study coupled bunch

motion• Estimate required system gains and bandwidths for transverse and

longitudinal feedback• Understand interaction of modes within the LLRF loop bandwidth and

broadband system bandwidth• Research new control techniques for colliders

SLAC has a long history with beam instability feedback, and has developed technology and techniques that are used at accelerators around the world

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Crab Cavities – Normal and Super-conducting(Z. Li, A. Ratti)

At SPEAR3, we are considering a crabbing scheme to produce short photon pulse:

• RF Crab cavity produces a rotation to the electron bunch, resulting in transverse spread of the emitted photon bunch

• A slit downstream allow a small slice to pass through producing a short photon pulse

• Kick voltage required within reach with CW NCRF technology• Recent advances in RF technology developed at SLAC make

CW NCRF approach much more affordable • Larger aperture required to suppress short-range wakefield• Multi-cell standing wave structure with elliptical cell shape was

chosen for SSRL

Damping of HOM’s

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.5E+09 3.5E+09 5.5E+09 7.5E+09 9.5E+09

(R:O

hm,R

_X:O

hm/m

)

F(Hz)

a20mm,T14mm,22/27mohm,LOM70mmV3R

R_X

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Crab Cavities – Normal and Super-conducting

SLAC’s contribution to RFD crab cavity collaboration for HL-LHCCavity RF design optimization, Input power and HOM coupler designMultiphysics analysis – LFD, multi-pacting, tolerancesEngineering design supportProject coordination and system integration support

E B

• Compact design to fit into existing beam line

• Deflect mostly by E field

• No lower-order mode• Minimized higher

multipole fields

Prototype cavity tested at JLab and FNAL -Achieved gradient well above design requirement

availablespace: 194 mm

140.5 mm

second beam pipe42mm radius

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Microbunching instability-based Coherent Electron Cooling(D. Ratner, G. Stupakov)

Goal: Use microbunching instability as an amplifier in CeC• Relatively simple technically (requires only drifts and bends)• Potential for very large bandwidth/fast cooling

SLAC Role:• Theoretical studies to derive simple scaling formulas for cooling rate• Support design of practical implementation, including proof-of-principle

(e.g. Lm, Lk, R56, electron current, etc.)• Support simulations for design and tests

Lm

DispersionSpace Charge

e- Path

Ion Path

Kicker

Ion+++

+++

++

+

Lk

+ + +

+E

-E

Eion

e-

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Spin Tracking(C. Mayes)

• Bmad is a well-developed software library for charged particles.

• It has been used for spin simulation studies for:• Fermilab g-2 ring• ILC• Julich COSY ring for future electric

dipole moment (EDM) measurements• It can be used for efficient long term

tracking using one-turn symplectic maps, map normal form analysis, resonance strength analysis, spin invariant map analysis, analysis of chromatic aberrations, etc. Fig. 4.19 from Hoffstaetter “High-

Energy Polarized Proton Beams: A Modern View” Springer, 2006

Validation with HERA-p calculationDots: BmadLines: Hoffstaetter

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Spin Tracking

• Bmad and PTC (integrated into Bmad) can track a particle’s spin including EDM and fringe fields.

• Bmad can track through arbitrary fields.• PTC can produce transfer maps which include spin.

Out Coef Exponents Order -----------------------------------------------------1: -0.600000000000 0 0 0 0 0 0 0 1: 1.000000000000 1 0 0 0 0 0 11: 0.145000000000 2 0 0 0 0 0 2-----------------------------------------------------2: -0.185000000000 0 0 0 0 0 0 0 2: 1.300000000000 0 1 0 0 0 0 12: 3.800000000000 2 0 0 0 0 1 3-----------------------------------------------------3: 1.000000000000 0 0 1 0 0 0 13: 1.600000000000 0 0 0 1 0 0 13: -11.138187077310 1 0 1 0 0 0 2-----------------------------------------------------4: 1.000000000000 0 0 0 1 0 0 1-----------------------------------------------------5: 0.000000000000 0 0 0 0 0 0 05: 0.000001480008 0 1 0 0 0 0 15: 1.000000000000 0 0 0 0 1 0 15: 0.000000000003 0 0 0 0 0 1 15: 0.000000000003 2 0 0 0 0 0 2-----------------------------------------------------6: 1.000000000000 0 0 0 0 0 1 1

Phase Space MapOut Coef_Sx Coef_Sy Coef_Sz Exponents Order-------------------------------------------------------------------------------Sx: 0.99757886 -0.02372254 -0.06537314 0 0 0 0 0 0 0Sx: 0.04802411 0.22401654 0.65154583 1 0 0 0 0 0 1Sx: 0.07391383 3.77338795 -0.24137562 0 1 0 0 0 0 1Sx: 0.00008802 -0.17584738 0.06515458 0 0 1 0 0 0 1Sx: 0.01148244 -0.20322945 0.24896717 0 0 0 1 0 0 1Sx: -0.00457076 -0.22322148 0.01125358 0 0 0 0 0 1 1-------------------------------------------------------------------------------Sy: -0.02460178 0.75885811 -0.65079114 0 0 0 0 0 0 0Sy: 0.25039365 -0.04801091 -0.06544895 1 0 0 0 0 0 1Sy: -3.02631629 -0.07739091 0.02416143 0 1 0 0 0 0 1Sy: 0.17584738 0.00008802 -0.00654489 0 0 1 0 0 0 1Sy: 0.47579058 1.59361755 1.84025908 0 0 0 1 0 0 1Sy: 0.13046518 -0.46155512 -0.54313051 0 0 0 0 0 1 1-------------------------------------------------------------------------------Sz: 0.06504736 0.65082378 0.75643719 0 0 0 0 0 0 0Sz: -0.64180483 0.06414595 0.00000000 1 0 0 0 0 0 1Sz: -2.27815007 0.22777762 -0.00007328 0 1 0 0 0 0 1Sz: 0.06515785 -0.00651227 0.00000000 0 0 1 0 0 0 1Sz: 0.00385332 -1.86555986 1.60475990 0 0 0 1 0 0 1Sz: 0.11944181 0.53003513 -0.46630288 0 0 0 0 0 1 1

Spin Map

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SLC polarized source/high brightness sources

• The SLC Gun delivered 16nC @120 Hz

•SLAC still has expertise in polarized electron sources and other high brightness, high current sources, and can contribute to EIC needs•SLAC linac cavities are available for full injector

We are also starting to develop ultra-high brightness sources for future FEL’s – an emittance of < 0.1 um at 100 pC is required!

Quarter-wave SRF guns are our top choice for this project

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Fast Kickers(T. Beukers, A. Krasnykh)

• An ultrafast kicker is in development to separate bunches spaced five to ten nanoseconds apart for LCLS-II. One bunch is steered to the SXR undulator and the other to the HXR undulator. The resulting x-rays, of different color, are recombined for pump-probe experiments.

• The kick will be the sum of kicks imparted from multiple TEM mode structures.

• The ultrafast rise/fall time formation is enabled by DSRD topology. The pulser will develop 5-10 kV pulses with greater than 100pm repeatability at 10kHz.

• A development effort is underway to demonstrate these parameters, and in the future 1 MHz and up to 20 kV

Demonstration Waveform @60 Hz

Driver circuit in development FY17

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PEP-II and Linac Hardware(J. Seeman)

Permanent magnet construction(~1000 kg scale)

Klystrons >1 MW CWHigh power Cu Cavities + HOMsHigh power vacuum chambersDipole magnets Quadrupole magnets ready to useBeam diagnosticsFeedback electronicsLuminosity monitor (~1% at 1Hz)SLAC linac sections

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Summary

The accelerator staff at SLAC is ready to contribute to EIC R&D activities!