‘multi-pass-droplet’ experiment
DESCRIPTION
‘Multi-pass-Droplet’ Experiment. Kevin Beard, Alex Bogacz , Vasiliy Morozov, Yves Roblin. Discussion. Why multi-pass arcs? Recent development of Dogbone RLAsAlex15 min. Proof-of-principle optics for a two-pass arc Vasiliy 15 min. - PowerPoint PPT PresentationTRANSCRIPT
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
‘Multi-pass-Droplet’ Experiment
1
Why multi-pass arcs? Recent development of Dogbone RLAs Alex 15 min.
Proof-of-principle optics for a two-pass arc Vasiliy 15 min.
Scaled super-cell test with electrons Yves 25 min.
Discussion All 20 min.
Why?
How?
What?
????
Kevin Beard, Alex Bogacz, Vasiliy Morozov, Yves Roblin
Discussion
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Why multi-pass arcs?
Recent development of Dogbone RLAs
2
Alex Bogacz
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
A Decade of Muon RLAs
Racetrack RLA – NF Study I (2000) (Bogacz/Lebedev)
Switchyard (single bend, horizontal)
Individual energy return Arcs for recirculation
Dogbone RLA – NF Study II (2005) (Bogacz)
Better separation of passes
Compact arcs, saving on beamlines
Simultaneous acceleration of both charge species
Increasing number of passes (ISS/IDS-NF):
Bi-sected linac Optics (2006) (Bogacz)
Ramped linac quads (2007) (Johnson)
Reducing number of return Arcs – Multi-pass Arcs (IDS-NF):
Non-scaling FFAG arcs with sextupoles (2008) (Trbojevic/Bogacz/Wang)
Linear Non-scaling FFAG arcs (2010) (Morozov)
Arcs based on combined function magnets (2011) (Morozov)
3
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Racetrack vs ‘Dogbone’ RLA
E/2
E/2
E
E
E
the droplets can be reduced in size according to the required energy
better orbit separation at linac’s end ~ energy difference between consecutive passes (2E)
allows both charges to traverse the Linac in the same direction (more uniform focusing profile)
both charge signs can be made to follow a Figure-8 path (suppression of depolarization effects)
4
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Dogbone RLA – IDS
244 MeV 900 MeV
0.9 GeV 3.6 GeV
86 m0.6 GeV/pass
5
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Pre-Linac and RLA I to RLA II …
3 GeV
1.8 GeV
1.2 GeV
3.6 GeV
244 MeV
900 MeV
2.4 GeV
6
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Injection/Extraction Chicane
FODO lattice:
900/900 (h/v) betatron phase adv. per cell
7
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Droplet Arcs
top view
side view
2.4 GeV1.2 GeV
1.2 GeV
2.4 GeV
1 m
8
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
(out = in and out = -in , matched to the linacs)
Mirror-symmetric ‘Droplet’ Arc – Optics
10 cells indisp. sup. cells out
2 empty transition cells
disp. sup. cells out
2 empty transition cells
130.6180
20
0
3-3
BE
TA
_X&
Y[m
]
DIS
P_
X&
Y[m
]
BETA_X BETA_Y DISP_X DISP_Y
2 vertical steps 2 vertical steps
9
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Switchyard - Arc 1 and 3
1.2 GeV
1.2 GeV
2.4 GeV
10
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Switchyard - Arc 1 and 3
2.4 GeV1.2 GeV
1.2 GeV
11
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
78.91030
150
50
BE
TA
_X&
Y[m
]
DIS
P_X
&Y
[m]
BETA_X BETA_Y DISP_X DISP_Y
39.91030
150
50
BE
TA
_X&
Y[m
]
DIS
P_X
&Y
[m]
BETA_X BETA_Y DISP_X DISP_Y
Multi-pass Linac Optics – Bi-sected Linac
1-pass, 1200-1800 MeV
‘half pass’ , 900-1200 MeV initial phase adv/cell 90 deg. scaling quads with energy
mirror symmetric quads in the linac
quad gradient
quad gradient
6 meter 90 deg. FODO cells17 MV/m RF, 2 cell cavities
12
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Multi-pass bi-sected linac Optics
389.3020
300
50
BE
TA
_X&
Y[m
]
DIS
P_X
&Y
[m]
BETA_X BETA_Y DISP_X DISP_Y
1.2 GeV0.9 GeV 3.0 GeV2.4 GeV1.8 GeV 3.6 GeV
Arc 4Arc 3Arc 2Arc 1
x = 3.2 m y = 6.0 mx =-1.1 y =1.5 x,y → x,y
xy → xy
x,y → x,y
xy → xy
x,y → x,y
xy → xy
x,y → x,y
xy → xy
x = 6.3 m y = 7.9 mx =-1.2 y =1.3
x = 7.9 m y = 8.7 mx =-0.8 y =1.3
x = 13.0 m y = 14.4 mx =-1.2 y =1.5
quad grad.
length
13
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
254.6510
100
0
50
BE
TA
_X&
Y[m
]
DIS
P_X
&Y
[m]
BETA_X BETA_Y DISP_X DISP_Y
254.6510
100
0
50
BE
TA
_X&
Y[m
]
DIS
P_X
&Y
[m]
BETA_X BETA_Y DISP_X DISP_Y
‘Fixed’ vs ‘Pulsed’ linac Optics (8-pass)
Pulsed
Fixed
14
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
‘Dogbone’ RLA with 2-pass Arcs
15
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
A Decade of Muon RLAs
Racetrack RLA – NF Study I (2000) (Bogacz/Lebedev)
Switchyard (single bend, horizontal)
Individual energy return Arcs for recirculation
Dogbone RLA – NF Study II (2005) (Bogacz)
Better separation of passes
Compact arcs, saving on beamlines
Simultaneous acceleration of both charge species
Increasing number of passes (ISS/IDS-NF):
Bi-sected linac Optics (2006) (Bogacz)
Ramped linac quads (2007) (Johnson)
Reducing number of return Arcs – Multi-pass Arcs (IDS-NF):Reducing number of return Arcs – Multi-pass Arcs (IDS-NF):
Non-scaling FFAG arcs with sextupoles (2008) Non-scaling FFAG arcs with sextupoles (2008) ((Trbojevic/Bogacz/WangTrbojevic/Bogacz/Wang))
Linear Non-scaling FFAG arcs (2010) Linear Non-scaling FFAG arcs (2010) ((MorozovMorozov))
Arcs based on combined function magnets (2011) Arcs based on combined function magnets (2011) ((MorozovMorozov))
16
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
2-pass ‘Droplet’ Arc
* Trajectories are shown to scale
B 1 .7 Tesla
G 28 Tesla/m
17
Dipole and quadrupole field components of the remaining magnets adjusted so that at both momenta
Each super-cell has periodic solutions for the orbit and the Twiss functions
At the cell’s entrance and exit, periodic orbit offset, dispersion and their slopes are all zero
Vasiliy Morozov
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Proof-of-principle optics for a two-pass arc
18
Vasiliy Morozov
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
RLA with Two-Pass Arcs
244 MeV
0.6 GeV/pass3.6 GeV
0.9 GeV
146 m
79 m
2 GeV/pass
264 m
12.6 GeV
Two or potentially more regular droplet arcs replaced by one multi-pass arc
Simplified scheme
No need for a complicated switchyard
Compactness
More efficient use of RF by maximizing the number of passes
Potentially cheaper
Potential for other applications
79 m
RLA with FFAG Arcs
Alex Bogacz
19
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
60
300
simple closing of geometrywhen using similar cells
= 41.3 m
C = 302.4 m
Schematic Layout of a Two-Pass FFAG Arc
20
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Non-Linear FFAG: 1.2 GeV/c Linear Optics of Unit Cell
Combined-function bending magnets are used
1.2 GeV/c orbit goes through magnet centersLinear optics controlled by quadrupole gradients in symmetric 3-magnet cellDispersion compensated in each 3-magnet cell
3-magnet cell
MAD-X (PTC)
in + out + in = in
21
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
sextupole and octupole components
Non-Linear FFAG: 2.4 GeV/c Linear Optics of Unit Cell
Unit cell composed symmetrically of three 3-magnet cellsOff-center periodic orbitOrbit offset and dispersion are compensated by symmetrically introducing sextupole and octupole field components in the center magnets of 3-magnet cells
symmetric unit cell
MAD-X (PTC)
22
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Cell Matching1.2 GeV/c 2.4 GeV/c
outward inward outward inward
23
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Issues with Non-Linear FFAG Arcs
Small dynamic aperture and momentum acceptance
Compensation of non-linear effects is complicated
Matching to linac is difficult
Hard to control the orbit lengths and therefore the difference in the times of flight of the two momenta
Combined function magnets with precise control of field components up to octupole
24
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Two-Pass Linear FFAG Arcs
Same concept as with the non-linear FFAG arcs
Droplet arcs composed of symmetric FFAG cells
Each cell has periodic solution for the orbit and the Twiss functions
For both energies, at the cell’s entrance and exit:
Offset and angle of the periodic orbit are zero
Alpha functions are zero
Dispersion and its slope are zero
Outward and inward bending cells are automatically matched
25
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Two-Pass Linear FFAG Arcs
Combined function magnets with dipole and quadrupole field components only
Much greater dynamic aperture expected than in the non-linear case
Easier to adjust the pass length and the time of flight for each energy
Easier to control the beta-function and dispersion values
Initial beta-function values chosen to simplify matching to linac
Much simpler practical implementation without non-linear fields
More elements are used in each unit cell to satisfy the diverse requirements and provide enough flexibility in the orbit control
26
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Linear FFAG: Linear Optics of Unit Cell Initial conditions set; orbit, dispersion and -function slopes zero at the centerPath lengths adjusted to give time of flight difference of one period of RF1.2 GeV/c 2.4 GeV/c
27
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Dynamic Aperture
28
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Design Based on Linear Combined-Function Magnets
Same concept as the linear FFAG design
Linear combined-function magnets
Droplet arc composed of symmetric super cells
Each super-cell has periodic solutions for the orbit and the Twiss functions
At the cell’s entrance and exit, periodic orbit offset, dispersion and their slopes are all zero
Two cells bending in the same or opposite directions automatically matched at both momenta
First few magnets of the super cell have dipole field component only, serving as spreader/recombiner
Both dipole and quadrupole field components of the remaining magnets used as parameters to meet the constraints
Synchronization with linac accomplished using path-length adjusting chicanes and/or vertical beam bypasses
29
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Advantages of New Arc Design
All the advantages of a linear FFAG at a greater compactness
Alternating in-out-in or out-in-out pattern no longer required
Variation of the bending angles increases the number of available parameters and reduces the number of magnets required
Reduced orbit excursion
Spreader/recombiner incorporated into the arc design
Large dynamic aperture and momentum acceptance expected
Simple linear combined-function magnet design
30
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
60
300
C = 117.6 m
Arc Layout
Still simple closing of arc geometry when using similar super cells
1.2 / 2.4 GeV/c arc design used as an illustration can be scaled/optimized for other momenta preserving the factor of 2 momentum ratio of the two passes
B 1 .7 Tesla
G 28 Tesla/m
31
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Super-Cell Optics for P2 / P1 = 2P 2xP
32
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Droplet Arc Spreader/Recombiner
First few magnets of the super cell have dipole field component only, serving as Spreader/Recombiner
* Trajectories are shown to scale
33
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Two 2-Pass Arc Switchyard
Two 2-pass arcs
Lower momentum arc is the most challenging because of the highest momentum ratio; have a solution but still plenty of room for optimization
* Trajectories are shown to scale
34
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Future Studies and Optimization Paths
Lower momentum ratio
In case of a race-track design or in the inner droplet super cells, quadrupole field component can be used in the super-cell’s first magnets
Introduce sextupole component in the spreader/recombiner to control orbit deviation
Study the possibility of more than two passes
Study sextupole compensation of chromatic effects
Study error sensitivity
Tracking using realistic field maps
35
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Scaled super-cell test with electrons
36
Yves Roblin
Operated by JSA for the U.S. Department of Energy
Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
goal of the project
•Validate the concept of combined function magnet return arcs
•Demonstrate feasibility, establish leadership
•The scaled down test is a fertile ground for beam physics:• Dynamic aperture,•Effect of non linearities,•Tunability,•Envelope control,•Exploring the range of momenta that can be transported•Etc..etc..
37
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Closed orbit in cell
20cm aperture
38
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scope
Build a fully functional half-cell (first phase) and eventually a full arc using electrons rather than muons.
Use this arc to characterize and demonstrate the concept for the MAP program
Great teaching tool. Can partner with local universities (ODU Beam physics program)
39
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
feasibility
Electron is 206 times lighter than muon. We only need a few MeV to 10’s of MeV to carry out the tests. Canonical 2.4 GeV/c lattice requires 11.6 MeV/c electrons.
Real arc will have superconducting magnets. We can build small normal conducting magnets in house to test the concept (more about this later)
We have the expertise with electron beams and can deliver the needed beam
We have the room at JLAB (see next slides) for testing a half cell, maybe even a full cell and later a full arc.
40
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Testing a Half-Cell with Electrons
Cell with 12 combined function magnets bending a totalof 30 degrees.
Each magnet is a dipole+quad+sextupole.L=50cm, aperture=20cm
Need instrumentation between each magnet (beam position monitors and means of measuring beam profile at some locations)
Low current is adequate.5 to 40 MeV/c of electron beam is good
41
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Footprint of the apparatus
Full cell
About 8x3 meters on floor for the half cell.
42
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Possible Locations at Jefferson Lab
Where 0L07 spectrometer is.
In a Hall after setting up CEBAF in energy recovery mode to get aLow energy beam. Good option if one want to test a bigger device.
In the test lab !! Using the injector group test gun along with a cavity to bring beam to 5 MeV. Maybe some paperwork involved..
43
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Magnet specifications
Aperture of 20 cm, length of 50 cm.
The real thing will have to provide around 1.8 Tesla.
Our prototype only needs to put out 1.8/206 or about 87 Gauss.
These magnets can be easily (maybe??) made in house.
44
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Printed Circuit design(cont)
And it works..
Phys. Rev. ST Accel. Beams 3, 122401 (2000)
45
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Printed Circuit design
BackFront
That’s a quad !
46
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Muons, Inc.Multi-Pass Arc Experiment Meeting, October 28, 2011
Full scaled down simulation of RLA with return arcs
Eventually two of these return arcs can be build.
A small recirculating linac would accelerate from 11.6 GeV to 46.4 GeV/c over several recirculations.
This would be a full scaled down test of the neutrino factoryand/or muon colliders.
47