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Accelerator R&D towards eRHIC. Yue Hao, C-AD For the eRHIC Team. eRHIC, linac-ring EIC. Linac=ERL, or the luminosity is negligible The first proposed linac-ring collider 250GeV (p) *15.9 ( e ) @1.5e33 cm-2 s-1 Why linac-ring Luminosity, remove the limitation of b-b parameter of e-beam

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Accelerator r d towards erhic

Accelerator R&D towards eRHIC

Yue Hao, C-AD

For the eRHIC Team

Erhic linac ring eic
eRHIC, linac-ring EIC

  • Linac=ERL, or the luminosity is negligible

  • The first proposed linac-ring collider

    • 250GeV (p) *15.9 (e) @1.5e33 cm-2 s-1

  • Why linac-ring

    • Luminosity, remove the limitation of b-b parameter of e-beam

    • High spin polarization (e-beam)

    • Easy to upgrade

    • Easier synchronization with various ion energy.

I. Ben-Zvi, J. Kewisch, J. Murphy and S. Peggs, Accelerator Physics Issues in eRHIC, NIM A463, 94 (2001), C-A/AP/14 (2000).

Erhic layout
eRHIC Layout


Defined by

PSR = 12 MW

Defined by xp = 0.015

Defined by

DQsp = 0.035

Beam synchronization detail
Beam Synchronization, Detail

  • Ion at sub-TeV energies is not ultra-relativistic,Change inenergyvelocityfrequency

  • Linac-ring scheme enable a trick to adjust the frequency of RF to sychronize electron and ion at discrete ion energies

  • Reduces the need of path lengthening.

  • Ring-ring scheme can not take the trick.

Erhic r d efforts
eRHIC R&D efforts

  • IR design, crab cavity and dynamic aperture

  • Beam cooling – major R&D efforts, high priority R&D

  • Polarization and Polarimetry (including electron polarimetry)

  • Polarized 3He production and acceleration

  • Polarized electron source

  • Superconducting RF system

  • Multipass ERL and related beam dynamics

  • FFAG energy recovery pass

  • Linac-ring beam-beam interaction

  • ......

Accelerator r d towards erhic

NS-FFAG Layout of the eRHIC

* 21GeV Design, Jan'14

Arc #2

#1 7.944 GeV

#2 9.266 GeV

#3 10.588 GeV

#4 11.910 GeV

#5 13.232 GeV

#6 14.554 GeV

#7 15.876 GeV

#8 17.198 GeV

#9 18.520 GeV

#10 19.842 GeV

#11 21.164 GeV

7.944 – 15.876 GeV

Injector 0.012 GeV

Linac 1.322 GeV

Arc #1

#1 1.334 GeV

#2 2.565 GeV

#3 3.978 GeV

#4 5.300 GeV

#5 6.622 GeV

Trajectory in ffag
Trajectory in FFAG

2.5819 m


BD=0.1932 T, Gd=-49.515 T/m

Bf= 0.1932 T,

Gf=49.515 T/m

Other half of QF magnet

Bmax[-0.013, 0.4215 T]

Bmax[-0.178, 0.442 T]

21.164 GeV

19.824 GeV

18.520 GeV

17.198 GeV

15.876 GeV

14.554 GeV

13.232 GeV



9.266 GeV

7.944 GeV







28.764 cm

28.764 cm

Half of

1.09855 m

Half of

1.09855 m

0.90805 m

θF=3.699017 mrad



ρD=296.985 m

Two alternative magnets



Accelerator r d towards erhic

  • With fewer BPMs than magnets, the space between some FFAG magnets could be used entirely by a BPM; this design produces “stretched” output pulses (from 13 ps rms bunches) intrinsically in the BPM in-vacuum hardware

  • long sampling platforms

  • 1.0 ns

  • 1.18 ns = ½ 422 MHz rf wavelength

  • = minimum FFAG bunch spacing

  • signal processing: use pair of 2 GSPS ADCs

  • triggered ~ 200 ps apart

Multi pass ffag prototype
Multi-pass FFAG Prototype

  • There is on-going plan to build a multi-pass FFAG Energy Recovery Linac prototype to prove the principle and the method of detecting and correcting the beam.

    • Energy of linac ~100MeV

    • # of passes: ~4

Ir design
IR design

Forward detector components

SC magnets




Ir and da
IR and DA

  • 10 mrad crossing angle and crab-crossing

  • 90 degree lattice and beta-beat in adjacent arcs (ATS) to reach beta* of 5 cm

  • Combined function triplet with large aperture for forward collision products and with field-free passage for electron beam

  • Only soft bends of electron beam within 60 m upstream of IP

Beam cooling cec pop
Beam cooling, CEC PoP

  • Traditional stochastic cooling does not have enough bandwidth to cool intense proton beams (~ 3×1011/nsec). Efficiency of traditional electron cooling falls as a high power of hadron’s energy. Coherent Electron Cooling has a potential for high intensity beams including heavy ions.

  • Research Goals:

    • Develop complete package of computer simulation tools for the coherent electron cooling

    • Demonstrate cooling of the ion beam

    • Validate developed model

    • Develop experimental experience with CeC system

Accelerator r d towards erhic

CEC PoP, cont’d





FEL Section

Helical Wigglers











Low Power

Beam Dump





Cec pop anticipated results

r.m.s. length of the cooled part 80-120 ps. The cooling effects can be observed with oscilloscope 2 GHz or more bandwidth or spectrum analyzer with similar upper frequency

Electron bunch – 10 psec

Ion bunch – 2 nsec

After 250 sec

After 60 sec

After 650 sec

Modeling of cooling is performed

with betacool by A. Fedotov

Cec timeline
CEC timeline

  • CECPoPRHICrampisdeveloped

  • Injectionsystem(112MHzgun,500MHzbuncher)wereinstalled.

  • Maincavity(704MHz)isfabricated.

  • CommissioninjectorsysteminJuly2014

  • Experimentstarts2015

Polarized e source
Polarized e-source

  • We are aiming at a high-current (50 mA), high-polarization electron gun for eRHIC.

  • The principle we are aiming to prove is funneling multiple independent beams from 20 cathodes.

  • External review was carried out in 2012.

  • Next week, first HV conditioning and possibly first beam!

5 cell srf cavity
5-cell SRF cavity

HOM high-pass filter

  • eRHIC will utilize five-cell 422 MHz cavities, scaled versions of the BNL3 704 MHz cavity developed for high current linac applications.

  • Stability considerations require cavities with highly damped HOMs.

  • The HOM power is estimated at 12 kW per cavity at a beam current of 50 mA and 12 ERL passes.

  • Apply funding to build prototype.

HOM ports

FPC port

Crab cavity
Crab Cavity

  • Development of a highly compact Double Quarter Wave Crab Cavity at 400 MHz.

  • Prototype to be tested in the CERN SPS in 2016- 2017.

Input power waveguides

Cryo jumper

Tuning system


Helium vessel




Thermal shielding

(80K – nitrogen)

Erl test facility
ERL test facility

  • The BNL ERL objectives 20 MeV at >100 mA (500 mA capability).

  • Experiment in progress, will see first photo-emission soon.

  • Loop in Oct, 2014, project completes in 2016.

All hardware in house, most installed

Electron beam disruption

Ion Beam

Electron beam disruption



  • There are many on-going simulation and experiment aiming on the challenge port of eRHIC.

  • The design now is based on extensive simulations.

  • R&D experiments are on-going, need few years to finish.