1. JLEIC Forward Ion Detection Region
Machine Parameters
V.S. Morozov
JLEIC Forward Ion Detection Region
October 28, 2016
F. Lin

2. JLEIC Layout 2015 Electron complex CEBAF Electron collider ring
Ion complex
Ion source
SRF linac (285 MeV/u for protons)
Booster
Ion collider ring
Optimum detector location for minimizing background
3-10 GeV
8-100 GeV
8 GeV
2015
arXiv:

3. JLEIC Layout & Detector Location
Cold Ion Collider Ring
(8 to 100 GeV)
Two IP locations:
One has a new detector, fully instrumented
Second is a straight-through, minor additional magnets needed to turn into IP
Ion Source
Booster
Linac
Warm Electron
Collider Ring
(3 to 10 GeV)
Considerations:
Minimize synchrotron radiation
IP far from arc where electrons exit
Electron beam bending minimized in the straight before the IP
Minimize hadronic background
IP close to arc where protons/ions exit

4. Beam Parameters p e Beam energy GeV 100 5 Collision frequency MHz 476
Particles per bunch
1010
0.98
3.7
Beam current A
0.75
2.82
Polarization
>70%
Bunch length, rms cm
1.2
Norm. emittance, x/y m
0.5/0.1
70/14
x/y *
6/1.2
4/0.8
Vert. beam-beam param.
0.015
0.053
Laslett tune shift
0.048
Small
Detector space, up/down m
3.6/7
2.4/1.6
Hourglass (HG) reduction
0.80
Lumi./IP, w/HG, 1033
cm-2s-1
19.5

5. e-p Collision Luminosity
Design point (CM)
p energy (GeV)
e- energy (GeV)
Main luminosity limitation
low 30 4
space charge
medium
100 5
beam-beam
high 10
synchrotron radiation

6. Detector Region Design Ingredients
Detector requirements
Acceptance
Large detector space
Forward tagging
Emittance
Background
Dynamic requirements
Magnet strengths
Optical integration
Magnet multipoles
Non-linear dynamics
Chromaticity compensation
Dynamic aperture
Geometric integration
Crossing angle
Matched beam-line footprints
IR magnet dimensions
Ring geometry decoupled from IR design

7. IR & Detector Concept
Ion beamline
Electron beamline
Possible to get ~100% acceptance for the whole event
Central Detector/Solenoid
Dipole
Forward (Ion) Detector
Scattered Electron
Particles Associated
with Initial Ion
Particles Associated with struck parton

8. Full-Acceptance Detector
50 mrad crossing angle
Improved detection, no parasitic collisions, fast beam separation
Forward hadron detection in three stages
Endcap
Small dipole covering angles up to a few degrees
Far forward, up to one degree, for particles passing through accelerator quads
Low-Q2 tagger
Small-angle electron detection

9. Detector Region IP e ions p e
Integrated detector region design developed satisfying the requirements of
Detection – Beam dynamics – Geometric match
GEANT4 detector model developed, simulations in progress IP e
Compton polarimetry
ions
forward ion detection
forward e detection
dispersion suppressor/
geometric match
spectrometers p
(top view in GEANT4) e
low-Q2 electron detection
and Compton polarimeter
Forward hadron spectrometer
ZDC

10. Detector Region Geometry
Overall geometry fixed: the beam position and angle at the end point are fixed
e beam
i beam
2nd spectrometer dipole
56 mrad ( GeV)
“3rd” spectrometer dipole
-56 mrad ( GeV)
length of this straight
controls overall length
controls overall height
Three dispersion-suppression/
geometry-control dipoles
|56 mrad| ( GeV)
cannot be much smaller
geometrically fixed point

11. Ion IR *x,y = 10 / 2 cm, D* = D* = 0 Three spectrometer dipoles (SD)
Large-aperture final focusing quadrupoles (FFQ)
Secondary focus with large D and small D
Dispersion suppressor geometric match
geom. match/
disp. suppression IP
SD1
SD2
SD3
FFQ
~14.4 m
4 m
D = 0, D’ = 0
D’ ~ 0
forward detection
x , y < ~0.6 m
middle of straight
limit x and y

12. Downstream Ion IR Layout
Blue – dipoles, green – vertically focusing quads, red – horizontally focusing quads, grey – corrector packages
Element sizes, center coordinates, and angular orientations are specified in the Excel file
All elements are approximately cylindrical
Detector and anti solenoids are not shown
rbffb
sp. dip. #1
sbffb
sp. dip. #2
bxspds01r
sp. dip. #3
qffb1 x
 = 50 mrad
qffb2
qffb3 e-
QSPDS01
1st machine element z IP
1.5 m
ions
FF quads
14.4 m

13. IR Ion Magnet Parameters
Assuming 100 GeV/c
Parameters are determined primarily by detection requirements rather than beam dynamics
Bottom-up study of multipole requirements in progress
Note: parameters are still being fine-tune but no major changes
Name
Type
Length [m]
Good-field radius [cm]
Inner radius [cm]
Outer radius [cm]
Min. beam separation [cm]
Strength [T or T/m]
Pole-tip field [T]
QFFB3_US
Quad [T/m] 1 3 4 12
36.0
-116
-4.6
QFFB2_US
1.5
26.5
149 6
QFFB1_US
1.2 2 10
18.0
-141
-4.2
SB1
Dipole [T] 17 24
25.0 -2
QFFB1
6.8
17.1
35.9
-88 -6
QFFB2
2.4
11.8
24.7
48.2 51
QFFB3
26.7
67.2
-35
SB2 40 90
102
4.7
-4.7

14. Ion Beam Envelope & 99%p Trajectory
Assuming beam momentum of 100 GeV/c, ultimate normalized x/y emittances xN/yN of 0.35/0.07 m, and ultimate momentum spread p/p of 310-4
The horizontal size includes both betatron and dispersive components
2nd focus IP

15. Far-Forward Acceptance for Charged Fragments
Δp/p = -0.5
Δp/p = 0.0
Δp/p = 0.5
(protons rich fragments)
(exclusive / diffractive recoil protons)
(tritons from N=Z nuclei)
(spectator protons from deuterium)
(neutron rich fragments) 15

16. Far-Forward Ion Acceptance
Transmission of particles with initial angular and p/p spread
Quad apertures = B max / (fixed field 100 GeV/c)
Uniform particle distribution of 0.7 in p/p and 1 in horizontal angle originating at IP
Transmitted particles are indicated in blue (the box outlines acceptance of interest)
More accurate simulations are in progress
6 T max
 electron beam 16

17. Far-Forward Ion Acceptance for Neutrals
Transmission of neutrals with initial x and y angular spread
Quad apertures = B max / (fixed field 100 GeV/c)
Uniform neutral particle distribution of 1 in x and y angles around proton beam at IP
Transmitted particles are indicated in blue (the circle outlines 0.5 cone)
6 T max
 electron beam 17

18. Ion Momentum & Angular Resolution
Protons with p/p spread are launched at different angles to nominal trajectory
Resulting deflection is observed at the second focal point
Particles with large deflections can be detected closer to the dipole
 electron beam
±10 @ 60 GeV/c
|p/p| > x,y = 0 18

19. Ion Momentum & Angular Resolution
Protons with different p/p launched with x spread around nominal trajectory
Resulting deflection is observed 12 m downstream of the dipole
Particles with large deflections can be detected closer to the dipole
|x| > 3 p/p = 0
 electron beam
 electron beam
±10 @ 60 GeV/c 19

20. Parameter Choice
Impact of * and  on luminosity and detector acceptance
Luminosity
Smaller * and   higher luminosity
nx,y = 1 / 0.5 m  0.5 / 0.1 m  a factor of 3 increase in L
*x,y = 10 / 2 cm  6 / 1.2 cm  another factor of 1.7 increase in L
Fundamental limit on detector angular acceptance
nx,y = 1 / 0.5 m, *x,y = 10 / 2 cm  min > 3-5 mrad at 100 GeV/c
nx,y = 1 / 0.5 m  0.5 / 0.1 m  a factor of reduction in min
*x,y = 10 / 2 cm  6 / 1.2 cm  a factor of 1.3 increase in min

21. Parameter Choice
Fundamental limit on momentum acceptance at the secondary focus
Roman pot at the secondary focus has finite length l , therefore where sx is the  function at the secondary focus
Smaller x  smaller (p/p)min
Optimum is when sx = l / 2 (similar to the hour-glass effect)
Currently, sx ~ 0.6 m, it changes proportionally to *x
In our case, the beam size is dominated by Dx , changes in *x and sx have very little effect
Assume l = 2 m, nx = 1 m, sx = 0.6 m, Dx = 1 m,  = 5 10-4  (p/p)min > 510-3

22. Summary & Outlook
Detector region design is fairly complete from the accelerator integration point of view
Most detector optimization does not affect the beam dynamics significantly
Ongoing work
Quantification of detector performance
Background simulations
Need to better define
Solenoid compensation elements
Orbit diagnostics and correction elements in the detector region
Engineering parameters of detector region magnets