Download - LHeC Linac-Ring Design

Operated by JSA for the U.S. Department of Energy

Thomas Jefferson National Accelerator Facility

Alex Bogacz 1

LHeC Linac-Ring Design

Alex Bogacz

for the LHeC Study Group

DIS'11, Newport News, April 12, 2011



Alex Bogacz 2

Linac-Ring LHeC – two options

60-GeV recirculating linac with energy recovery

straightlinac




Alex Bogacz 3

hgepp

pb HIN

eL

*

, 1

4

1

highest protonbeam brightness “permitted”(ultimate LHC values)

=3.75 mNb=1.7x1011

bunch spacing 25 or 50 ns

smallest conceivableproton * function: - reduced l* (23 m → 10 m)- squeeze only one p beam- new magnet technology Nb3Sn

*=0.1 m

maximize geometricoverlap factor- head-on collision- small e- emittance

c=0Hhg≥0.9

round beams

average e-

current !

Roadmap to 1033 cm-2s-1 Luminosity


Frank Zimmermann



Alex Bogacz 4

Pulsed linac for 140 GeV

140-GeV linacinjector

dump

IP7.9 km

• linac could be ILC type (1.3 GHz) or 720 MHz• cavity gradient: 31.5 MV/m, Q=1010

• extendable to higher beam energies• no energy recovery• with 10 Hz, 5 ms pulse, Hg = 0.94, Nb = 1.5x109 : <Ie> = 0.27 mA → L ≈ 4x1031 cm-2s-1

0.4 kmfinal focus




Alex Bogacz 5

Baseline:Energy Recovery Linac60 GeV, Power 100MW

Linac-Ring Configuration

J. Osborne

LHC p

1.0 km

2.0 km

10-GeV linac

10-GeV linac injector

dump

IP

comp. RF

e- final focus

tune-up dump

0.26 km

0.17 km

0.03 km

0.12 km

comp. RF

10, 30, 50 GeV

20, 40, 60 GeV

total circumference ~ 8.9 km

J. Osborne




Alex Bogacz 6

Design Parameters

electron beam LR ERL LRe- energy at IP[GeV] 60 140luminosity [1032 cm-2s-1] 10 0.44polarization [%] 90 90bunch population [109] 2.0 1.6e- bunch length [mm] 0.3 0.3bunch interval [ns] 50 50

transv. emit. x,y [mm] 0.05 0.1

rms IP beam size x,y [m] 7 7

e- IP beta funct. *x,y [m] 0.12 0.14

full crossing angle [mrad] 0 0

geometric reduction Hhg 0.91 0.94

repetition rate [Hz] N/A 10

beam pulse length [ms] N/A 5

ER efficiency 94% N/A

average current [mA] 6.6 5.4

tot. wall plug power[MW] 100 100




Alex Bogacz 7

Energy Recovering Linacs (ERL)

High energy (60 GeV), high current (6.4 mA) beams: (384 MW beam power) would require sub GW (0.8 GW)-class RF systems in conventional linacs .

nvoking Energy Recovery alleviates extreme RF power demand (power reduced by factor (1

ERL) ⇨ Required RF power becomes nearly independent of beam current.

Energy Recovering Linacs promise efficiencies of storage rings, while maintaining beam quality of linacs: superior emittance and energy spread and short bunches (sub-pico sec.).

GeV scale Energy Recovery demonstration with high ER ratio (ERL

= 0.98) was

carried out in a large scale SRF Recirculating Linac (CEBAF ER Exp. in 2003)

No adverse effects of ER on beam quality or RF performance: gradients, Q, cryo-load observed – mature and reliable technology (next generation light sources)




Alex Bogacz 8

CEBAF ER Exp. 2003

~ 55 MeV Decelerating beam

~ 1 GeV Accelerating beam

0.20

0.15

0.10

0.05

0.00

-0.05

-0.10

-0.15

Volts

350300250200150100500Time(s)

250 s

with ERwithout ER

RF Response to Energy Recovery




Alex Bogacz 9

LHeC Recirculator with ER

10 GeV/pass

Linac 1

Linac 2

Arc1, 3, 5 Arc 2, 4 Arc 6

10 GeV/pass

LHC

IP

0.5 GeV

60.5 GeV




Alex Bogacz 10

Linac RF parameters

ERL 720 MHz ERL 1.3 GHz Pulsedduty factor cw cw 0.05RF frequency [GHz] 0.72 1.3 1.3cavity length [m] 1 ~1 ~1energy gain / cavity [MeV] 18 18 31.5R/Q [100 W] 400-500 1200 1200 Q0 [1010] 2.5-5.0 2 ? 1power loss stat. [W/cav.] 5 <0.5 <0.5power loss RF [W/cav.] 8-32 14-31 ? <10power loss total [W/cav.] 13-37 (!?) 14-31 11“W per W” (1.8 k to RT) 700 700 700power loss / GeV @RT [MW] 0.51-1.44 0.6-1.1 0.24length / GeV [m] (filling=0.57) 97 97 56




Alex Bogacz 11

Required Power & Cryo-load




Alex Bogacz 12

The eRHIC-type cryo-module containing six 5-cell SRF 703 MHz cavities.

Model of a new 5-cell HOM-damped SRF

703 MHz cavity.

I. Ben-Zvi

RF cavities


Ilan Ben-Zvi



Alex Bogacz 13

560

0.5

0P

HA

SE

_X&

Y

Q_X Q_Y560

150

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]

BETA_X BETA_Y DISP_X DISP_Y

Linac Optics 1300 FODO Cell

phase adv/cell: x,y= 1300

720 MHz RF:

Lc =100 cm

5-cell cavity

Grad = 17.361 MeV/m

E= 555.56 MV

linac quadrupoles

Lq=100 cm

GF= 0.103 Tesla/m

GD= -0.161 Tesla/m

E = 0.5 GeV

2×8 cavities 2×8 cavities




Alex Bogacz 14

Linac 1 Focusing profile

18 FODO cells (18 × 2 × 16 = 576 RF cavities)

E = 0.5 10.5 GeV

10080

200

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


quad gradient




Alex Bogacz 15

Linac 3 (Linac 1, pass 2) Optics

10080

0.5

0P

HA

SE

_X&

Y

Q_X Q_Y

betatron phase advance

10080

500

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


E = 20.5 30.5 GeV

min

1ds

E L E




Alex Bogacz 16

Linac 2 Focusing profile

E = 10.5 0.5 GeV (ER)

10080

200

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


quad gradient


Linac 2 multi-pass optics with ER mirror symmetric to Linac 1

18 FODO cells (18 × 2 × 16 = 576 RF cavities)



Alex Bogacz 17

Linac 1 and 2 Multi-pass ER Optics


60480

800

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]

BETA_X BETA_Y DISP_X DISP_Y 60480

800

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


Linac 1 Linac 2

60.5 GeV

50.5 GeV

40.5 GeV

30.5 GeV

20.5 GeV

10.5 GeV

0.5 GeV

0.5 GeV

10.5 GeV

20.5 GeV

30.5 GeV

40.5 GeV

50.5 GeV

60.5 GeV



Alex Bogacz 18

10080

1500

0

50

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


‘weak’ vs ‘strong’ Linac focusing

E = 0.5 10.5 GeV


Zero quad gradient

10080

1500

0

0.5

-0.5

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


1300 FODO

/

12.9 /12.7 /x y

cm MeVE

/

1.8 /1.6 /x y

cm MeVE

Wake field effects more severe ~ 8 timesDaniel Schulte



Alex Bogacz 19

ERL configuration


total circumference ~ 8.9 km

Daniel Schulte



Alex Bogacz 20

52.35990

150

0

0.3

-0.3

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


Quasi-isochronous FMC Cell

Emittance dispersion

〈 H 〉 avereged over

bends

2 22 ' 'H D DD D

Momentum compaction

56 bend

DM ds D

356 1.16 10 mM

factor of 27 smaller than FODO factor of 2.5 smaller than FODO

3 8.8 10 H m




Alex Bogacz 21

52.35990

500

0

0.5

-0.5

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]

BETA_X BETA_Y DISP_X DISP_Y52.35990

500

0

0.5

-0.5

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]

BETA_X BETA_Y DISP_X DISP_Y52.35990

500

0

0.5

-0.5

BE

TA

_X&

Y[m

]

DIS

P_X

&Y

[m]


Arc Optics – Emittance growth

total emittance increase (all 5 arcs): xN = 1.25 × 4.5 m rad =5.6 m rad

Arc 1 , Arc2

6 2 20 2

2, 2 ' '

3N

qC r H H D DD D

TEM-like Optics DBA-like Optics Imaginary t Optics

Arc 3 Arc 4 , Arc5, Arc 6

3 1.2 10 H m 3 8.8 10 H m 3 2.2 10 H m factor of 18 smaller than FODO


emittance growth due to disruption in the collision 15%-180% (without/with rematch the outgoing optics)



Alex Bogacz 22

Alternative Arc Optics BNL FMC Cell

Flexible Momentum Compaction


Dejan Trbojevic



Alex Bogacz 23

Recirculator Magnets

# Field M.Length # Gradient M.Length # Gradient M.Length # Gradient M.Length # Gradient M.LengthLINAC 1 18 2.200 1.000 18 -2.200 1.000LINAC 2 18 2.200 1.000 18 2.200 1.000Arc 1 600 0.046 4.000 60 -3.179 1.000 60 10.515 1.000 60 -11.053 1.000 60 10.535 1.000Arc 2 600 0.089 4.000 60 -6.206 1.000 60 20.529 1.000 60 -21.579 1.000 60 20.568 1.000Arc 3 600 0.133 4.000 60 12.397 1.000 60 17.493 1.000 60 -24.576 1.000 60 17.918 1.000Arc 4 600 0.177 4.000 60 16.462 1.000 60 23.228 1.000 60 -32.633 1.000 60 23.792 1.000Arc 5 600 0.221 4.000 60 29.227 1.000 60 28.904 1.000 60 -40.791 1.000 60 29.667 1.000Arc 6 600 0.264 4.000 60 35.014 1.000 60 34.627 1.000 60 -48.868 1.000 60 35.541 1.000

60.5 GeV LHeC Recirculator: Linac FODO, Arcs FMC optics

Units: meter (m), Tesla (T), T/m

Q2 Q3Dipoles (R=764 m) Q0 Q1

Proposed solution: One type of bending magnets, possibly with different conductors

Two types of quadrupoles, same cross section, different length: Q2 1200 mm, Q0-Q1-Q3 900 mm; possibly with different conductors, radius 20 mm

Davide Tommasini




Alex Bogacz 24

Quadrupoles for 10 GeV Linacs

Parameters for Quadrupoles

Number of magnets 72

Aperture radius [mm] 20

Field gradient [T/m] 4.4

Magnetic Length [mm] 500

Weight [kg] 150

Number of turns/pole 18

Current [A] 40

Conductor material Copper

Current density [A/mm2] 1.5

Resistance [mW] 60

Power [kW] 0.1

Inductance [mH] 9

Cooling Air25 cm

Davide Tommasini




Alex Bogacz 25

Bending for 60 GeV Recirculator

Magnet Parameters L-R

Beam Energy [GeV] 70

Magnetic Length [m] 5.0

Magnetic field [Gauss] 3300

Number of magnets 6*600

Vertical aperture [mm] 25

Pole width [mm] 80

Number of coils 2

Number of turns/coil 1

Current [A] 2750

Conductor material copper

Magnet Inductance [mH]

0.12

Magnet Resistance [mW]

0.13

Power per magnet [kW] 1

Cooling Air or water

23 cm

Davide Tommasini




Alex Bogacz 26

Quadrupoles for 60 GeV Recirculator

Parameters for Quadrupoles

Number of magnets 1440

Aperture radius [mm] 20

Field gradient [T/m] 41

Magnetic Length [mm] 900-1200

Weight [kg]

Number of turns/pole 17

Current [A]

Conductor material Copper

Current density [A/mm2]

Resistance [mW]

Power [kW]

Inductance [mH]

Cooling

35 cm

Davide Tommasini




Alex Bogacz 27

Three-beam IR layout


Rogelio Tomas

IR with a schematic view of synchrotron radiation – beam trajectories with 5 and 10 envelopes

Half quadrupole with field-free region

Stephan Russenschuck



Alex Bogacz 28

The presence of a strong synchrotron radiation has two major implications for the vacuum system:

it has to be designed to operate under the strong photon-induced stimulated desorption while being compatible with the significant heat loads onto the beam pipes.

synchrotron radiation will dramatically enhanced the electron cloud build-up and mitigation solutions shall be included at the design stage.

Photon-induced desorption rate depends on critical energy of the synchrotron

light

E0 = 5.10-4 GeV for electrons, EB is the energy of the beam and R the bending radius

For the Linac-Ring option (bending sections and by-passes), the linear photon flux is expected to be 5 times larger than in LHC.

Vacuum requirements


Miguel Jimenez

2

431024.1/IE

mWP

10337

o

Bc E

E

ReV



Alex Bogacz 29

Scattering of particles on the molecules of the residual gas, dominated by the Bremsstrahlung on the nuclei of gas molecules ⇨ depends on partial pressure, weight of the gas species and radiation length

The beam-gas interactions are responsible for machine performance limitations such as;

reduction of beam lifetime (nuclear scattering)

machine luminosity (multiple Coulomb scattering)

intensity limitation by pressure instabilities (ionization)

Vacuum engineering issues

Pumping

Diagnostics

Sectorization

HOM and Impedance implications

Bake-out of vacuum system

Shielding

Vacuum mitigation


Miguel Jimenez



Alex Bogacz 30

Conclusions


High luminosity Linac-Ring option ERL

RF power nearly independent of beam current.

Multi-pass linac Optics in ER mode

Choice of linac RF and Optics 720 MHz SRF and 1300 FODO

Linear lattice: 3-pass ‘up’ + 3-pass ‘down’ (single-pass wake-field effects)

Arc Optics Choice Emittance preserving lattices

Quasi-isochronous lattices

Flexible Momentum Compaction

Acceptable level of emittance dilution & momentum spread

Magnet design

Quad and dipole prototypes

Vacuum requirements

Mitigations and engineering issues



Alex Bogacz 31

Special Thanks to:


Frank Zimmermann

Daniel Schulte

and

Max Klein