V . P T I T S Y N

O N B E H A L F O F E R H I C D E S I G N T E A M : E . A S C H E N A U E R , M . B A I , J . B E E B E - W A N G , S . B E L O M E S T N Y K H , I . B E N - Z V I , M . B L A S K I E W I C Z , R . C A L A G A , X . C H A N G , A . F E D O T O V , D . G A S S N E R , L . H A M M O N S , H . H A H N , Y . H A O , P . H E , W . J A C K S O N , A . J A I N , E . C . J O H N S O N , D . K A Y R A N , J . K E W I S C H , V . N . L I T V I N E N K O , Y . L U O , G . M A H L E R , G . M C I N T Y R E , W . M E N G , M . M I N T Y , B . P A R K E R , A . P I K I N , T . R A O , T . R O S E R , J . S K A R I T K A ,

B . S H E E H Y , S . T E P I K I A N , Y . T H A N , D . T R B O J E V I C , N . T S O U P A S , J . T U O Z Z O L O , G . W A N G , S . W E B B , Q . W U , W E N C A N X U ,

A . Z E L E N S K I ( B N L ) E . P O Z D E Y E V ( F R I B , M S U ) , E . T S E N T A L O V I C H ( M I T - B A T E S )

Accelerator Design of High Luminosity Electron-Hadron

Collider eRHIC

From RHIC to eRHIC 2

RHIC + Electron accelerator = eRHIC

eRHIC

Quark splits into gluon splits into quarks …

Gluon splits into quarks

Increasing resolution

High precision microscope for the nucleons and nuclei:

 resolving nucleon spin puzzle  3-D tomography of nucleons   non-linear QCD regime of high gluon densities (saturation)

PANIC 2011

Design choices 3

Compared with HERA eRHIC will have: • Polarized proton and 3He • Heavy ion beams • Wide variable center-of mass energy range • Considerably higher luminosity

Lpeak, cm-2s-1 ~5 1031

HERA

• 10 GeV storage ring • ZDR in 2004 • Fundamental luminosity limits:

o Beam-beam o SR power loss (total and per m)

RHIC

~4 1032

eRHIC ring-ring

• Large allowed beam-beam on electrons • Electron energy beyond 10 GeV • Simple energy staging by increasing the linac length • No e-polarization issues with spin resonances

RHIC

up to 1.5 1034

eRHIC linac-ring

€

ξe ~ 1

PANIC 2011

Luminosity 4

Reaching high luminosity: • high average electron current (50 mA = 3.5 nC * 14 MHz):

• energy recovery linacs; SRF technology • high current polarized electron source

• cooling of the high energy hadron beams (Coherent Electron Cooling) • β*=5 cm IR with crab-crossing

Protons

Electrons

E, GeV 50 75 100 130 250 325

5 0.077 0.26 0.62 1.4 9.7 15

10 0.077 0.26 0.62 1.4 9.7 15

20 0.077 0.26 0.62 1.4 9.7 15

30 0.019 0.06 0.15 0.35 2.4 3.8

Polarized e-p luminosities in 1033 cm-2 s-1 units

Limiting factors: - hadron ΔQsp ≤ 0.035 - hadron ξ ≤ 0.015 - polarized e current ≤ 50 mA - SR power loss ≤ 8 MW

PANIC 2011

 All-in tunnel staging approach uses two energy recovery linacs and 6 recirculation passes to accelerate the electron beam.

 Staging: the electron energy will be increased in stages, from 5 to 30 GeV, by increasing the linac lengths .

 Up to 3 experimental locations

ERL-based eRHIC is multiple IP collider 5

PANIC 2011

eSTAR

New detector

30 GeV

27.55 GeV

22.65 GeV

17.75 GeV

12.85 GeV

3.05 GeV

7.95 GeV

25.1 GeV

20.2 GeV

15.3 GeV

10.4 GeV

30.0 GeV

5.50 GeV

27.55 GeV

0.60 GeV

Compact magnets 50 mA polarized electron source

  Mechanical design has been developed   Ready for prototype construction

  Alternative development by MIT: large cathode gun (E. Tsentalovich).

Also ready to built the prototype

6

eRHIC R&D items

Gap 5 mm total 0.3 T for 30 GeV

BNL Gatling Gun the current from multiple cathodes is merged

Y.Hao, G.Mahler, V.Litvinenko

  More than 14000 magnets in electron beam lines   Small gap -> efficient and inexpensive-> low cost

eRHIC   Dipole, quadrupole and vacuum chamber

prototypes have been constructed   Magnetic measurements : dipole prototype

meets specification

merger

PANIC 2011

I. Ben-Zvi X. Chang

PoP of Coherent Electron Cooling Energy Recovery Linac

  CEC- revolutionary beam cooling technique   PoP experiment in RHIC by the collaboration:

BNL, Jefferson Lab, Tech-X Corporation   Projected dates: 2013-2014   Aim : demonstration of cooling of 40 GeV Au ion

beam

  ERL test facility. E=20 MeV   The energy recovery with high

beam current (up to 0.5 A CW )   First tests start later this year

7

R&D test facilities

Cryo-module

e- 15 – 20 MeV

SC RF Gun

e- 4-5MeV Beam dump

50 kW 700 MHz transmitter

Magnets, vacuum

Controls & Diagnostics

Laser 1 MW 700 MHz Klystron

e- 4-5 MeV

PANIC 2011

Design Study Highlights 8

• Energy loss and energy spread compensation. • How small can be beam pipe size? •  Surface roughness effect (extruded Al pipe)

• Measurements of CSR shielding effect on the energy spread (V. Yakimenko, et al. )

 HOM tolerances from BBU simulations  Up to 12.3MeV/m real estate gradient  Compact cryomodule; No quadrupoles in the linacs

New design of 704 MHz cavity (BNL III): -reduced peak surface magnet field -strong HOM damping (I. Ben-Zvi, et al.)  

Beam-beam simulations: disruption, kink instability, parameter fluctuations.

Hadron beam kink instability feedback (Y. Hao, et al.)

0

500

1000

1500

2000

2500

3000

3500

4000rms effective emittance ellipse

6 rms effective emittance ellipserms geometric emittance ellipse

6 rms geometric emittance ellipse

-0.00015 -0.0001 -5e-05 0 5e-05 0.0001 0.00015x [m]

-0.002

-0.0015

-0.001

-0.0005

0

0.0005

0.001

0.0015

0.002

xp [r

ad]

Disruption simulations; D=140

PANIC 2011

Electron polarization in eRHIC

PANIC 2011

9

  High polarized beam current produced by the e-gun.

(DC gun with strained-layer super-lattice GaAs-photocathode)

  Direction of polarization are switch by changing helicity of laser photons in and arbitrary bunch-by-bunch pattern

  Linac accelerator -> No depolarizing resonances!   Only longitudinal polarization is needed in the

experimental detector(s)

• Beam polarization vector rotates in the horizontal plane during the acceleration. • The conditions for the longitudinal polarization orientation in possible experimental points:

• IP8: Ee =N*0.077922 GeV • IP6: Ee = N*0.075690 GeV

Polarized e-gun

ϕd, γd

ϕ0, γ0

ϕ

stays in horizontal plane and rotates in arcs around vertical direction

!

! v e

!

! p e

!

! p e

! !( )=!0+" # $( )0

!

" d$

The design of high-lumi IR with β*=5 cm 10

!"#"##$%$

&'%%(%!$)$

*+$ ,+$*%$

-&'&(.&!$)$

/&'&++-$)$

#&$

&'0+(0$$)

$

!$)$

!-'-($)$

!1#&'!0++

$)234$

#&$)234$

&'!#+.0/$)

$!&$0&$

!1&'&&!/.%+$)234$

•  10 mrad crossing angle and crab-crossing •  High gradient (200 T/m) large aperture Nb3Sn focusing magnets •  Arranged free-field electron pass through the hadron triplet magnets •  Integration with the detector: efficient separation and registration of low angle

collision products •  Gentle bending of the electrons to avoid SR impact in the detector •  Easy to vary the beam energies in wide ranges.

© D.Trbojevic, B.Parker, J. Beebe-Wang

e

p

PANIC 2011

Arranged free-field electron pass

Summary 11

  The design of eRHIC is well advanced.

  The eRHIC luminosity in ERL-based design reaches above 1034 cm-2 s-1.

  The electron lattice and interaction region design have been developed, and critical beam dynamics issues have been evaluated.

  Considerable progress on crucial R&D items has been achieved: polarized source; compact magnets; cavities and cryomodule.

  Important conceptual tests are in preparation: CeC and the ERL facility.

  Detailed cost estimate to the end of 2011.

PANIC 2011