Transcript Slide 1

LHeC Linac-Ring Design
Alex Bogacz
for the LHeC Study Group
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex
Bogacz News, April 12, 2011
DIS'11,
Newport
1
Linac-Ring LHeC – two options
60-GeV recirculating linac
with energy recovery
straight
linac
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
2
Roadmap to 1033 cm-2s-1 Luminosity
round beams
Frank Zimmermann
1 Nb, p 1
L
I H hg
* e
4e  p  p
highest proton
beam brightness “permitted”
(ultimate LHC values)
g=3.75 mm
Nb=1.7x1011
bunch spacing
25 or 50 ns
average ecurrent !
smallest conceivable
proton * function:
- reduced l* (23 m → 10 m)
- squeeze only one p beam
- new magnet technology Nb3Sn
*=0.1 m
maximize geometric
overlap factor
- head-on collision
- small e- emittance
qc=0
Hhg≥0.9
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
3
Pulsed linac for 140 GeV
7.9 km
injector
IP
140-GeV linac
dump
0.4 km
final focus
• 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
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
4
Linac-Ring Configuration
J.J.Osborne
Osborne
Baseline:
Energy Recovery Linac
60 GeV, Power 100MW
tune-up dump
comp. RF
10-GeV linac
0.12 km
comp. RF
injector
0.17 km
1.0 km
20, 40, 60 GeV
total circumference ~ 8.9 km
2.0 km
LHC p
10, 30, 50 GeV
dump
10-GeV linac
0.03 km
0.26 km
IP
e- final focus
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
5
Design Parameters
electron beam
e- energy at IP[GeV]
luminosity [1032 cm-2s-1]
polarization [%]
bunch population [109]
e- bunch length [mm]
bunch interval [ns]
transv. emit. gx,y [mm]
LR ERL
60
10
90
2.0
0.3
50
0.05
LR
140
0.44
90
1.6
0.3
50
0.1
7
7
0.12
0.14
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
rms IP beam size sx,y [mm]
e- IP beta funct. *x,y [m]
full crossing angle [mrad]
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
6
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 .
Invoking Energy Recovery alleviates extreme RF power demand (power reduced by
factor (1 - hERL) ⇨ 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 (subpico sec.).
GeV scale Energy Recovery demonstration with high ER ratio (hERL = 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, cryoload observed – mature and reliable technology (next generation light sources)
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
7
CEBAF ER Exp. 2003
~ 1 GeV Accelerating beam
RF Response to Energy Recovery
0.20
0.15
Volts
0.10
~ 55 MeV Decelerating beam
0.05
0.00
250 ms
-0.05
-0.10
without ER
with ER
-0.15
0
50
100
150
200
Time(ms)
250
300
350
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
8
LHeC Recirculator with ER
Linac 1
0.5 GeV
10 GeV/pass
Arc1, 3, 5
Arc 2, 4
Arc 6
Linac 2
10 GeV/pass
IP
60.5 GeV
LHC
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
9
Linac RF parameters
ERL 720 MHz
duty factor
RF frequency [GHz]
cavity length [m]
energy gain / cavity [MeV]
R/Q [100 W]
Q0 [1010]
power loss stat. [W/cav.]
power loss RF [W/cav.]
power loss total [W/cav.]
“W per W” (1.8 k to RT)
power loss / GeV @RT [MW]
length / GeV [m] (filling=0.57)
ERL 1.3 GHz
Pulsed
cw
cw
0.05
0.72
1
18
400-500
2.5-5.0
5
8-32
13-37 (!?)
700
0.51-1.44
97
1.3
~1
18
1200
2?
<0.5
14-31 ?
14-31
700
0.6-1.1
97
1.3
~1
31.5
1200
1
<0.5
<10
11
700
0.24
56
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
10
Required Power & Cryo-load
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
11
RF cavities
The eRHIC-type
cryo-module
containing six 5-cell
SRF 703 MHz
cavities.
I. Ben-Zvi
Ilan
Ben-Zvi
Model of a new 5-cell
HOM-damped SRF
703 MHz cavity.
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
12
Linac Optics - 1300 FODO Cell
0.5
150
5
E = 0.5 GeV
0
BETA_X
BETA_Y
DISP_X
DISP_Y
2×8 cavities
DISP_X&Y[m]
PHASE_X&Y
0
0
0
BETA_X&Y[m]
phase adv/cell: Dfx,y= 1300
56
2×8 cavities
0
Q_X
Q_Y
56
720 MHz RF:
linac quadrupoles
Lc =100 cm
Lq=100 cm
5-cell cavity
GF= 0.103 Tesla/m
Grad = 17.361 MeV/m
GD= -0.161 Tesla/m
DE= 555.56 MV
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
13
Linac 1 - Focusing profile
5
200
E = 0.5 - 10.5 GeV
0
0
DISP_X&Y[m]
BETA_X&Y[m]
quad gradient
0
BETA_X
BETA_Y
DISP_X
DISP_Y
1008
18 FODO cells (18 × 2 × 16 = 576 RF cavities)
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
14
5
500
Linac 3 (Linac 1, pass 2) - Optics
DISP_X&Y[m]
BETA_X&Y[m]
E = 20.5 - 30.5 GeV
1 

   ds 
E
L E
min
0
0

BETA_X
BETA_Y
DISP_X
DISP_Y
1008
0.5
0
0
PHASE_X&Y
betatron phase advance
0
Q_X
Q_Y
1008
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
15
Linac 2 - Focusing profile
5
200
E = 10.5 - 0.5 GeV (ER)
0
0
DISP_X&Y[m]
BETA_X&Y[m]
quad gradient
0
BETA_X
BETA_Y
DISP_X
DISP_Y
1008
18 FODO cells (18 × 2 × 16 = 576 RF cavities)
Linac 2 multi-pass optics with ER - mirror symmetric to Linac 1
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
16
0
0.5
GeV
BETA_X
BETA_Y
DISP_X
DISP_Y
10.5
GeV
20.5
GeV
30.5
GeV
40.5
GeV
50.5
GeV
0
60.5 60.5
GeV GeV
5
DISP_X&Y[m]
BETA_X&Y[m]
0
6048
Linac 2
0
DISP_X&Y[m]
0
0
BETA_X&Y[m]
Linac 1
800
800
5
Linac 1 and 2 - Multi-pass ER Optics
BETA_X
50.5
GeV
BETA_Y
DISP_X
DISP_Y
40.5
GeV
30.5
GeV
20.5
GeV
6048
10.5
GeV
0.5
GeV
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
17
‘weak’ vs ‘strong’ Linac focusing
5
1500
E = 0.5 - 10.5 GeV
BETA_X&Y[m]
E
Zero quad gradient
 12.9 /12.7cm / MeV 
DISP_X&Y[m]

x/ y
Wake field effects more severe ~ 8 times
0
0
Daniel Schulte

DISP_Y
1008
 1.8 /1.6cm / MeV 
1300 FODO
x/ y
-0.5
E
DISP_X
0.5
BETA_Y
DISP_X&Y[m]
BETA_X
0
BETA_X&Y[m]
1500
0
0
BETA_X
BETA_Y
DISP_X
DISP_Y
1008
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
18
ERL configuration
total circumference ~ 8.9 km
Daniel Schulte
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
19
150
0.3
BETA_X&Y[m]
DISP_X&Y[m]
Quasi-isochronous FMC Cell
Emittance dispersion
Momentum compaction
0
-0.3
〈H〉avereged over bends
0
BETA_X
BETA_Y
DISP_X
H  g D2  2 DD '  D '2
DISP_Y
52.3599
M 56  - 
H  8.8  10-3 m
D

ds  -qbend D
M56  1.16  10-3 m
factor of 2.5 smaller than FODO
factor of 27 smaller than FODO
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
20
Arc Optics – Emittance growth

,H  g D 2  2 DD '  D '2
2

BETA_X
BETA_Y
DISP_X
52.3599
DISP_Y
0
BETA_X
BETA_Y
DISP_X
52.3599
DISP_Y
H  2.2  10-3 m
H  8.8  10-3 m
0
DISP_X&Y[m]
TEM-like Optics
-0.5
0.5
DISP_X&Y[m]
BETA_X&Y[m]
-0.5
DBA-like Optics
500
Arc 4 , Arc5, Arc 6
0
500
BETA_X&Y[m]
0
0
0
DISP_X&Y[m]
Imaginary gt Optics
-0.5
0.5
Arc 3
BETA_X&Y[m]
500
Arc 1 , Arc2
0.5
2
3
D N  Cq r0 g 6  H 
BETA_X
BETA_Y
DISP_X
DISP_Y
52.3599
H  1.2  10-3 m
factor of 18 smaller than FODO
total emittance increase (all 5 arcs):
DxN = 1.25 × 4.5 mm rad =5.6 mm rad
emittance growth due to disruption in the collision 15%-180% (without/with rematch the outgoing optics)
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
21
Alternative Arc Optics - BNL FMC Cell
Flexible Momentum Compaction
Dejan Trbojevic
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
22
Recirculator Magnets
60.5 GeV LHeC Recirculator: Linac FODO, Arcs FMC optics
Dipoles (R=764 m)
Q0
Q1
Q2
#
LINAC 1
LINAC 2
Arc 1
Arc 2
Arc 3
Arc 4
Arc 5
Arc 6
Field
600
600
600
600
600
600
0.046
0.089
0.133
0.177
0.221
0.264
M.Length
4.000
4.000
4.000
4.000
4.000
4.000
#
Gradient M.Length
18
18
60
60
60
60
60
60
2.200
2.200
-3.179
-6.206
12.397
16.462
29.227
35.014
#
Gradient M.Length
#
1.000
1.000
1.000
60 10.515
1.000
1.000
60 20.529
1.000
1.000
60 17.493
1.000
1.000
60 23.228
1.000
1.000
60 28.904
1.000
1.000
60 34.627
1.000
Units: meter (m), Tesla (T), T/m
Q3
Gradient M.Length
18
18
60
60
60
60
60
60
-2.200
2.200
-11.053
-21.579
-24.576
-32.633
-40.791
-48.868
#
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Gradient M.Length
60
60
60
60
60
60
10.535
20.568
17.918
23.792
29.667
35.541
1.000
1.000
1.000
1.000
1.000
1.000
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
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
23
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]
Cooling
9
Air
25 cm
Davide Tommasini
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
24
Bending for 60 GeV Recirculator
Magnet Parameters L-R
Beam Energy [GeV]
70
Magnetic Length [m]
5.0
Magnetic field [Gauss]
Number of magnets
3300
6*600
Vertical aperture [mm]
25
Pole width [mm]
80
Number of coils
2
Number of turns/coil
1
Current [A]
Conductor material
2750
copper
Magnet Inductance [mH]
0.12
Magnet Resistance [mW]
0.13
Power per magnet [kW]
Cooling
23 cm
1
Air or water
Davide Tommasini
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
25
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
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
26
Three-beam IR layout
IR with a schematic view of synchrotron radiation – beam
trajectories with 5s and 10s envelopes
Half quadrupole with field-free region
Stephan Russenschuck
Rogelio Tomas
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
27
Vacuum requirements
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.
P W / m  1.24103
E4I
Miguel Jimenez
2
Photon-induced desorption rate depends on critical energy of the synchrotron
light
3 10-7  E B

 c eV  
R  Eo



3
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.
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
28
Vacuum mitigation
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
Miguel Jimenez
HOM and Impedance implications
Bake-out of vacuum system
Shielding
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
29
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
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
30
Special Thanks to:
Frank Zimmermann
Daniel Schulte
and
Max Klein
Thomas Jefferson National Accelerator Facility
Operated by JSA for the U.S. Department of Energy
Alex Bogacz
DIS'11, Newport News, April 12, 2011
31