Recirculating pass optics V.Ptitsyn, D.Trbojevic, N.Tsoupas.
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Transcript of Recirculating pass optics V.Ptitsyn, D.Trbojevic, N.Tsoupas.
Recirculating pass optics
V.Ptitsyn, D.Trbojevic, N.Tsoupas
Recirculation passes in eRHIC designRecirculation passes in eRHIC design
At present design of eRHIC the beam passes the main linac five times during acceleration. Four of the beam recirculation passes will be placed in the tunnel. Lower energy pass can be put locally.
Possible location of therecirculation passes in the tunnel
Four recirculation passes
PHENIX
STAR
e-ion detector
eRHIC
Main ERL (1.9 GeV)
Low energy recirculation pass
Beam dump
Electronsource
Possible locationsfor additional e-ion detectors
The RHIC tunnel curvature defines average orbit radiusfor the passes. The dipole magnet strength is limited bysynchrotron radiation loss power.
Beam power loss due to synchrotron radiation for 0.26 A beam at 10 GeV versus dipole filling factor.
0
1
10
100
0 0.2 0.4 0.6 0.8 1 1.2
Dipole filling factor
Po
we
r lo
ss
, M
W
10 GeV pass
All 5 passes
Longitudinal transportLongitudinal transport
3rd harmonic cavities are used in both main and pre-accelerator linacs
R56=500 mm R56=20 mm
For acceleration on the crest the recirculating passes should be isochronous enough in order to have acceptable momentum spread after deceleration
-1.5
-1
-0.5
0
0.5
1
1.5
-15 -10 -5 0 5 10 15
z0, mm
dp
/p, 1
e-3 de/e_0
de/e_5
de/e_10
de/e_f
z, mm-30
-20
-10
0
10
20
30
40
-15 -10 -5 0 5 10 15
z0, mm
dp
/p, 1
e-3 de/e_0
de/e_5
de/e_10
de/e_f
z, mm
dp/p
, 1e-
3
dp/p
, 1e-
3
Basic cell for the recirculating passesBasic cell for the recirculating passes
FMC cell (D.Trbojevic)Dipole filling factor: 54%Reduced lengthTuned to ~0 momentum compaction
For 10GeV:Largest gradient: 7.7 T/mDipole field: 1.6 kGs
Dipole length: 5.5 mQuad length: 0.6 m
81 m
Summary of synchrotron radiationSummary of synchrotron radiation
I, mAI, mA E loss E loss on top on top pass,pass,
MeVMeV
E loss E loss on 5 on 5
passespasses
MeVMeV
Power Power loss on loss on
top top pass, pass, MWMW
Power Power loss on loss on
5 5 passespasses
MWMW
((p/p) p/p) rad,rad,
1e-31e-3
rad, rad, nmnm
10 GeV10 GeV 260260 4.34.3 6.76.7 1.11.1 1.71.7 0.020.02 0.040.04
20 GeV20 GeV 2626 6969 107107 1.81.8 2.82.8 0.130.13 1.31.3
Tunable RTunable R5656 parameter parameter
Should give at least +-0.3m tuning range for R56 on the whole pass.Beta_max change within 15%.
R56 versus gradient of QD2 quad (central quad)
For this basic cell there are also some other ways to tune R56.
-1.5
-1
-0.5
0
0.5
1
1.5
-0.25 -0.23 -0.21 -0.19 -0.17 -0.15
K(QD2),1/m^2
r56
per
cel
l,cm
Basic cell: beta-functionsBasic cell: beta-functions
Phase advances:_x = 1.6_y = 1.4
Arc latticeArc lattice
4 basic FMC cells+ matching sections
The whole arc transfer is achromatic.R56=0 and adjustable.
One sextantOne sextant
Arc+ straights with no IR
Separated functions:• R56 tuning: arcs• Phase trombone: straights• Path length tuning: in area of IR insertion (IR12)
Achromatic SpreaderAchromatic Spreader
N.Tsoupas
Beam parameters and dispersion for each line of the separatorBeam parameters and dispersion for each line of the separator
Interaction Straight LayoutInteraction Straight Layout
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-100 -50 0 50 100
H-plane V-plane
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-100 -50 0 50 100
Presently considered geometry of the interaction region straight.Ongoing work on the optics to minimize (or eliminate) dispersion at the IP.
SummarySummary
Optics of recirculation passes has been modified, Optics of recirculation passes has been modified, from FODO cell to FMC-cell based optics. from FODO cell to FMC-cell based optics. Isochronous lattice. Provides the flexible control of Isochronous lattice. Provides the flexible control of RR5656 parameter. parameter.
Initial separator/merger design has been Initial separator/merger design has been developed.developed.
Ongoing work: Ongoing work: Finalizing interaction region straight design.Finalizing interaction region straight design. Tracking with magnet errors/misalignments to study Tracking with magnet errors/misalignments to study
tolerances.tolerances.