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Spectrometer compensation in IR2 and IR8 during the 450 GeV
collision run
September 11, 2006
LOC meeting
Y. Papaphilippou
Thanks to S. Fartoukh, W. Herr, B. Jeanneret, M. Giovannozzi
LOC meeting, Y. Papaphilippou 211/09/2006
Can the spectrometer magnets of IR2 and IR8 have their maximum (corresponding to 7TeV) field during the 450 GeV collisions run? (LTC action)
IR2/8 nominal injection optics and crossing schemes IR2/8 spectrometer magnets and internal crossing angles Nominal aperture with different configurations
With/without external crossing With + or – spectrometer polarities
Available aperture when spectrometer ramped to its max value at 450 GeV.
Analytical estimates and MADX simulations
Outline
LOC meeting, Y. Papaphilippou 311/09/2006
Two high luminosity experiments ATLAS in IP1 (vertical crossing) CMS in IP5 (horizontal crossing)
B-physics with lower luminosity in asymmetric IP8
LHCb (horizontal crossing) Injection of beam 2
Heavy ion experiment (and p-p collisions with offset beams)
ALICE (vertical crossing) Injection of beam 1
LHC experimental IRs
LOC meeting, Y. Papaphilippou 411/09/2006
β*=10m, vertical crossing angle of ±150μrad and horizontal parallel separation of ± 2mm
External angle of ±80μrad for reducing the long range beam-beam effect
Internal angle of ±70μrad for compensating spectrometer orbit distortion
IR2 Injection optics (O. Brüning et al. LHC Project rep 367)
Beam 1 Beam 2
Beam 2
Beam 1
Horizontal separation positive for Beam 1 and negative for Beam 2
Angle sign can be chosen arbitrarily (following spectrometer polarity)
LOC meeting, Y. Papaphilippou 511/09/2006
3m-long spectrometer dipole (MBAW) @ 10m to the right of the IP
Vertical deflection with nominal integrated field of 3Tm (deflection of 130μrad @ 7TeV)
The resulting orbit deflection is compensated by three dipole magnets
Two 1.5m-long magnets of type MBXWT @ 20m left and right of the IP
One 2.6m-long magnet of type MBWMD @ 10m to the left of the IP
Two Beam Position Monitors (BPMWS) are located upstream and downstream of the two MBXWT to monitor the internal bump closure
ALICE dipole magnet and its compensatorsD. Swoboda, TS/LEA
LOC meeting, Y. Papaphilippou 611/09/2006
Injection optics around the IR2
0
10
20
30
40
50
60
βx,
y [
m]
BEAM 1
BEAM 2
IP2
MBXWTMBXWTMBWMD MBAW
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
3305 3310 3315 3320 3325 3330 3335 3340 3345 3350 3355 3360
S [m]
dx
,y [
m]
BEAM 1 - hor
BEAM 2 - hor
BEAM 1 - ver
BEAM 2 - ver
IP2
MBXWT
Equipment Aperture [m] β [m]
BPMSW.1L2 0.030 57
MBXWT.1L2 0.02656 - 48
MBWMD.1L2 0.03024 - 19
IP2 0.029 10
MBAW.1R2 0.15117 - 23
MBXWT.1R2 0.02648 - 56
BPMSW.1R2 0.030 57
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
3300 3310 3320 3330 3340 3350 3360S [m]
aper
ture
[m
]
BEAM 1BEAM 2
IP2MBXWT MBXWTMBWMD
MBAW
LOC meeting, Y. Papaphilippou 711/09/2006
Internal crossing angle of ±70μrad in the vertical plane (maximum deflection of ±0.7mm at MBWMD)
External crossing angle follows spectrometer dipole polarity
Internal crossing bump of IR2
-8.E-04
-6.E-04
-4.E-04
-2.E-04
0.E+00
2.E-04
4.E-04
6.E-04
8.E-04
3305 3310 3315 3320 3325 3330 3335 3340 3345 3350 3355 3360
S [m]
δy
[m]
BEAM 1
BEAM 2
IP2
MBXWT MBXWTMBWMD MBAW
3310 3315 3320 3325 3330 3335 3340 3345 3350 3355-8
-6
-4
-2
0
2
4
6
8
s [m]
y [
]
- ext, - int- ext, 0 int- ext, + int0 ext, - int0 ext, 0 int0 ext, + int+ ext, - int+ ext, 0 int+ ext, + int
External crossing angle of ±80μrad in the vertical plane added giving an effective crossing angle of ±150μrad, when polarity of spectrometer follows the sign of the external angle
Beam size varies between 0.8 and 0.3mm
Deflection maximum of 6σ at MBWMD
Nominal injection crossing bump of IR2
3310 3315 3320 3325 3330 3335 3340 3345 3350 3355-4
-3
-2
-1
0
1
2
3
4x 10
-3
s [m]
y
[m]
- ext, - int- ext, 0 int- ext, + int0 ext, - int0 ext, 0 int0 ext, + int+ ext, - int+ ext, 0 int+ ext, + int
BEAM 1
3310 3315 3320 3325 3330 3335 3340 3345 3350 3355
3
4
5
6
x 10-4
[m
]
s [m]
3310 3315 3320 3325 3330 3335 3340 3345 3350 33550
0.02
0.04
0.06
0.08
0.1
s [m]n 1 [
mm
]
BEAM 1
MBXWT MBXWTMBWMD IP2
MBAW
Aperture varies for less than 3σ between the scheme with only internal and full crossing scheme
Around half of the available aperture is lost for all compensators and 40% for the spectrometer (but a lot of margin in that area)
Nominal injection aperture in IR2
3310 3315 3320 3325 3330 3335 3340 3345 3350 33550
50
100
150
200
250
300
s [m]
n 1 []
Equipmentn1 [σ]
n1 [m]
n1 [%]
BPMSW.1L2 20 0.014 47
MBXWT.1L2 17 0.011 42
MBWMD.1L2 33 0.014 47
IP2 53 0.015 52
MBAW.1R2 221 0.093 58
MBXWT.1R2 17 0.011 42
BPMSW.1R2 20 0.014 47
LOC meeting, Y. Papaphilippou 1011/09/2006
Internal crossing angle of ±1089μrad in the vertical plane Maximum deflection of ±0.011m at MBWMD, corresponding to 25σ,
as compared to 0.0007m (1.6σ) of the nominal bump
Internal crossing bump of IR2 with collision strength for the spectrometer dipole
-0.012
-0.01
-0.008
-0.006
-0.004
-0.002
0
0.002
0.004
0.006
0.008
0.01
0.012
3305 3310 3315 3320 3325 3330 3335 3340 3345 3350 3355 3360
S [m]
δy
[m]
BEAM 1
BEAM 2
BEAM 1 - nominal
BEAM 2 - nominalIP2
MBXWT MBXWTMBWMD MBAW
3310 3315 3320 3325 3330 3335 3340 3345 3350 3355-30
-20
-10
0
10
20
30
s [m]
y
[]
Maximum beam excursion of 0.012m (30σ) at MBWMD, as compared to 0.0004m (6σ) for the nominal scheme
When polarity and external crossing angle sign are mismatched, two additional crossings occur ~15m left and right of the IP (W. Herr, Chamonix 2006)
Crossing bump in IR2 at injection with collision strength for the spectrometer dipole
BEAM 1
3310 3315 3320 3325 3330 3335 3340 3345 3350 3355-0.015
-0.01
-0.005
0
0.005
0.01
0.015
s [m]
y
[]
3310 3315 3320 3325 3330 3335 3340 3345 3350 3355-8
-6
-4
-2
0
2
4
6
8
s [m]
y
[]
- ext, - int- ext, 0 int- ext, + int0 ext, - int0 ext, 0 int0 ext, + int+ ext, - int+ ext, 0 int+ ext, + int
3310 3315 3320 3325 3330 3335 3340 3345 3350 33550
0.02
0.04
0.06
0.08
0.1
s [m]
n 1 [m
m]
BEAM 1
MBXWT MBXWTMBWMDIP2
MBAW
Biggest loss in aperture around MBWMD
n1 takes equivalent values with MBWXT and IP2 in σ and even smaller in mm
Aperture in IR2 with full spectrometer dipole strength
3310 3315 3320 3325 3330 3335 3340 3345 3350 33550
50
100
150
200
250
300
s [m]
n 1 []
Not important impact in any element apart MBWMD Available aperture of 9mm (with respect to 14mm), corresponding to
13σ of aperture loss Remaining aperture is 30% of the available
Aperture loss in IR2 by element
Equipment
n1 nominal
[σ] n1 full [σ]
n1 nominal
[m]n1 full
[m]
n1 nominal
[%]n1 full
[%]
BPMSW.1L2 20 20 0.014 0.014 47 47
MBXWT.1L2 17 17 0.011 0.011 42 42
MBWMD.1L2 33 20 0.014 0.009 47 30
IP2 53 53 0.015 0.015 52 52
MBAW.1R2 221 217 0.093 0.088 62 58
MBXWT.1R2 17 17 0.011 0.011 42 42
BPMSW.1R2 20 20 0.014 0.014 47 47
LOC meeting, Y. Papaphilippou 1411/09/2006
β*=10m, horizontal crossing angle of ±200 or ±75 μrad depending on the polarity and vertical parallel separation of ± 2mm
External angle of ±65 (- polarity) or ±210 μrad (+ polarity)
Internal angle of ±135 μrad for compensating spectrometer orbit distortion
IR8 Injection optics (O. Brüning et al. LHC Project rep 367)
Horizontal crossing angle always negative for Beam 1 and positive for Beam 2
Vertical separation sign can be chosen arbitrarily
Beam 2Beam 1
Beam 2
Beam 1
LOC meeting, Y. Papaphilippou 1511/09/2006
LHCb dipole magnet
D. Swoboda, TS/LEA
1.9m-long spectrometer dipole (MBLW) @ 4.9m to the right of the IP Horizontal deflection with nominal integrated field of 4.2Tm (deflection of
180μrad @ 7TeV) The resulting orbit deflection is compensated by three dipole magnets
Two 0.8m-long magnets of type MBXWS @ 20m left and right of the IP One 3.4m-long magnet of type MBXWH @ 5m to the left of the IP
Two Beam Position Monitors (BPMWS) are located upstream and downstream of the two MBXWS to monitor the internal bump closure
LOC meeting, Y. Papaphilippou 1611/09/2006
Injection optics around the IR8
0
10
20
30
40
50
60
βx,
y [m
]
BEAM 1
BEAM 2
IP8
MBXWSMBXWS
MBXWH MBLW
-0.025
-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
0.025
0.03
23290 23295 23300 23305 23310 23315 23320 23325 23330 23335 23340
S [m]
dx
,y [
m]
BEAM 1 - hor
BEAM 2 - hor
BEAM 1 - ver
BEAM 2 - ver
Equipment Aperture [m] β [m]
BPMSW.1L8 0.030 57
MBXWS.1L8 0.02655 - 52
MBXWH.1L8 0.02615 - 12
IP8 0.030 10
MBLW.1R8 0.06412 - 14
MBXWS.1R8 0.02652 - 55
BPMSW.1R8 0.030 57
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
23290 23300 23310 23320 23330 23340S [m]
I P8MBXWS MBXWSMBXWH
MBLW
LOC meeting, Y. Papaphilippou 1711/09/2006
Internal crossing angle of ±135μrad in the horizontal plane (maximum deflection of ±0.6mm at MBXWH)
External crossing angle does not follow spectrometer dipole polarity Note additional crossing at the edge of MBXWH(???)
Internal crossing bump of IR8
-8.E-04
-6.E-04
-4.E-04
-2.E-04
0.E+00
2.E-04
4.E-04
6.E-04
8.E-04
23290 23295 23300 23305 23310 23315 23320 23325 23330 23335 23340
S [m]
δx
[m]
BEAM 1
BEAM 2
IP8
MBXWS MBXWSMBXWH MBLW
2.329 2.33 2.331 2.332 2.333 2.334
x 104
-6
-4
-2
0
2
4
6
s [m]
x [
]
- ext, - int- ext, 0 int- ext, + int0 ext, - int0 ext, 0 int0 ext, + int+ ext, - int+ ext, 0 int+ ext, + int
2.329 2.33 2.331 2.332 2.333 2.334
x 104
-5
0
5x 10
-3
s [m]
x
[m]
- ext, - int- ext, 0 int- ext, + int0 ext, - int0 ext, 0 int0 ext, + int+ ext, - int+ ext, 0 int+ ext, + int
External crossing angle of ±65 or ±210μrad in the horizontal plane added giving an effective crossing angle of ±200 or ±75μrad, and polarity of spectrometer does not follow the sign of the external angle
Beam size varies between 0.7 and 0.3mm
Deflection maximum of 6σ at MBXWS
Nominal injection crossing bump of IR8BEAM 1
2.329 2.33 2.331 2.332 2.333 2.334
x 104
2
3
4
5
6
7
8x 10
-4
s [m]
[
m]
2.329 2.33 2.331 2.332 2.333 2.334
x 104
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
s [m]n 1 [
m]
BEAM 1
MBXWS MBXWSMBXWHIP8
MBLW
2.329 2.33 2.331 2.332 2.333 2.334
x 104
0
50
100
150
s [m]
n 1 []
Differences with respect to IP2 on the 2nd compensator (smaller β) and spectrometer (smaller β and aperture)
Aperture varies for less than 3σ between the scheme with only internal and full crossing scheme
Around 50-60% of the available aperture is lost for all compensators and 40% for the spectrometer
Nominal injection aperture in IR8
Equipmentn1 [σ]
n1 [m]
n1 [%]
BPMSW.1L8 20 0.014 45
MBXWS.1L8 16 0.010 40
MBXWH.1L8 34 0.012 45
IP8 56 0.016 52
MBLW.1R8 111 0.037 58
MBXWS.1R8 16 0.010 40
BPMSW.1R8 20 0.014 45
LOC meeting, Y. Papaphilippou 2011/09/2006
Internal crossing angle of ±2100μrad in the horizontal plane! Deflection of ±0.010m at MBXWH, corresponding to 29σ, as
compared to 0.0006m (2σ) of the nominal bump
Internal crossing bump of IR8 with collision strength for the spectrometer dipole
-1.2E-02
-8.0E-03
-4.0E-03
0.0E+00
4.0E-03
8.0E-03
1.2E-02
23290 23295 23300 23305 23310 23315 23320 23325 23330 23335 23340
S [m]
δx
[m]
BEAM 1 - nom
BEAM 2 - nom
BEAM 1
BEAM 2
IP8
MBXWS MBXWSMBXWH MBLW
Beam excursion of 0.011m (33σ) at MBXWH, as compared to 0.0004m (6σ) for the nominal scheme
When polarity and external crossing angle sign are mismatched, two additional crossings occur ~15m left and right of the IP (in total 4 crossings)
Crossing bump in IR8 at injection with collision strength for the spectrometer dipole
BEAM 1
2.329 2.33 2.331 2.332 2.333 2.334
x 104
-40
-30
-20
-10
0
10
20
30
40
x
[]
s [m]
2.329 2.33 2.331 2.332 2.333 2.334
x 104
-6
-4
-2
0
2
4
6
s [m]
x
[]
- ext, - int- ext, 0 int- ext, + int0 ext, - int0 ext, 0 int0 ext, + int+ ext, - int+ ext, 0 int+ ext, + int
2.329 2.33 2.331 2.332 2.333 2.334
x 104
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
s [m]
x
[m]
2.329 2.33 2.331 2.332 2.333 2.334
x 104
0
50
100
150
n 1 []
s [m]
BEAM 1
MBXWS MBXWSMBXWH
IP8
MBLW
Biggest loss in aperture around MBXWH
n1 correspond to even smaller values than MBWXS in mm
Aperture in IR8 with full spectrometer dipole strength
2.329 2.33 2.331 2.332 2.333 2.334
x 104
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
s [m]
n 1 [] [m
]
Not important impact in any element apart MBXWH Available aperture of 6mm (with respect to 12mm), corresponding to
15σ of aperture loss Remaining aperture corresponds 24% of the available
Aperture loss in IR8 by element
Equipment
n1 nominal
[σ] n1 full [σ]
n1 nominal
[m]n1 full
[m]
n1 nominal
[%]n1 full
[%]
BPMSW.1L8 20 20 0.014 0.014 45 45
MBXWS.1L8 16 16 0.010 0.010 40 40
MBXWH.1L8 34 19 0.012 0.006 45 24
IP8 56 56 0.016 0.015 52 52
MBLW.1R8 111 95 0.037 0.031 58 50
MBXWS.1R8 16 16 0.010 0.010 40 40
BPMSW.1R8 20 20 0.014 0.014 45 45
LOC meeting, Y. Papaphilippou 2411/09/2006
Summary Main limitations in IR2 and 8 in the aperture of 2nd compensator
magnets MBWMD in IR2
Available aperture of 9mm (with respect to 14mm), corresponding to 13σ of aperture loss
MBXWH in IR8 Available aperture of 6mm (with respect to 12mm), corresponding to 15σ of
aperture loss
In both cases, n1 above 7σ, but available aperture quite small, especially in IR8
Any decision should be based on the ability to control the orbit and optics within the tolerances given for computing the available aperture