Spectrometer compensation in IR2 and IR8 during the 450 GeV collision run

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


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


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)


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


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


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]


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


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

[]


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


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


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


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


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 [

]


2.329 2.33 2.331 2.332 2.333 2.334

x 104

-5

0

5x 10

-3

s [m]

x

[m]


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


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

[]


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


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

Spectrometer compensation in IR2 and IR8 during the 450 GeV collision run

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