Yellow: Your Tasks T1 – T4

Calibration ofButton Type Beam Position Monitors

Simulation

Linéarité X - Y

-20

-16

-12

-8

-4

0

4

8

12

16

20

-20 -16 -12 -8 -4 0 4 8 12 16 20

X [mm]

Y [

mm

]

Position Linéarisée sur les Axes X et Y

-20

-16

-12

-8

-4

0

4

8

12

16

20

-20 -16 -12 -8 -4 0 4 8 12 16 20

X [mm]

Y [

mm

]

Position Linéarisée

-20

-16

-12

-8

-4

0

4

8

12

16

20

-20 -16 -12 -8 -4 0 4 8 12 16 20

X [mm]

Y [

mm

]

Electrostatic Pick-up – ButtonNon-linear

– requires correction algorithm when beam is off-centre

– vacuum chamber not rotational symmetric (SR-source)

Area A

r

411

521

31

61

31

551

5 1053.11053.7035.11070.31030.2 YXYXXXXX

Rhodri Jones –CERN Beam Instrumentation Group

courtesy: A.Delfs (DESY)

beam

pump

channel button pickup

(cut)

PETRA-III BPM close to ID

-10 -8 -6 -4 -2 0 2 4 6 8 10-10

-8

-6

-4

-2

0

2

4

6

8

10

Horizontal Position [mm]

Ver

tica

l P

osi

tio

n [

mm

]

Position Map

Dr. Rhodri Jones – CERN Beam Instrumentation Group Introduction to Beam Instrumentation - CAS 2015

-- - - -+

+ + ++-

++

+- -+ -+

+

-- +

-- ++- + -

-- - - - -+ +

++- +

+ +- -+

-++- -+ -+ -

- -- - - -+

+ ++-

++

+- -+ -+

+

-- +

-- ++-+-

V

- - - - - - -

-+

+ ++

+-

-+ -

+ - +- + -

- - -+ ++

- ++ -+ - -+ -+

- -- - -

++ + -

++

--+-

-

-

-

-

-

-

Electrostatic Beam Position Monitor

40.5 mm

Position ReconstructionTwo common monitor geometries

Gero Kube & Kay Wittenburg, DESY / MDI EDIT 2015, Frascati (Italy), 23./27.October 2015

x

y

beam

linac-type

x = Kx

P1 – P3

P1 + P3

y = Ky

P2 – P4

P2 + P4

storage ring-type

x = Kx

(P1+P4) – (P2+P3)P1+P2+P3+P4

y = Ky

(P1+P2) – (P3+P4)P1+P2+P3+P4

x

y

beam

difference in position reconstruction

requires knowledge of monitor constant Kx, Ky

Position Information

r

α→ rule of thumb (circular duct)

sin2

sin2

,

,

rK

rK

yx

yx

linac-type

storage ring-type

KPositionor sum-over-difference Beampipe: round: r = 20.25 mm

Button Diameter: d =16.0 mm

sin() =

=

Kx =

T1) Calculate Kx,

for Linac type

1.3 GHz sine wave generator

Tasks: BPMs

Signal generation by button BPM

calculate monitor constants for BPMs

use rule-of-thumb formulae

measure XFEL BPM monitor constants

T2) define electrical center of both planes and calibrate movers

T3) perform 1-dim. scan along one axis → max. wire position: ± 15 mm (!!!)

→ 3a) measure signal amplitudes from each button (x-plane only)

→ 3b) calculate Δ/Σ from measured signals

→ 3c) plot Δ/Σ versus wire position

T4) determine monitor constant from slope at origin and compare with rule-of-thumb

Monitor Constant Calculation

-20 -15 -10 -5 0 5 10 15 20-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Beam Displacement [mm]

/

Sensitivity

sensitivity Sx,y

sensitivity: slope at origin

monitor constant: Kx,y = Sx,y-1

= Kx * /

Please stay in

the middle of

Chamber!!!!-

Maximum

± 15 mm

(more might

damage the

antenna)

• End

From CST Simulation

Position ReconstructionTwo common monitor geometries

Gero Kube & Kay Wittenburg, DESY / MDI EDIT 2015, Frascati (Italy), 23./27.October 2015

x

y

beam

linac-type

x = Kx

P1 – P3

P1 + P3

y = Ky

P2 – P4

P2 + P4

storage ring-type

x = Kx

(P1+P4) – (P2+P3)P1+P2+P3+P4

y = Ky

(P1+P2) – (P3+P4)P1+P2+P3+P4

x

y

beam

difference in position reconstruction

requires knowledge of monitor constant Kx, Ky

Position Information

r

α→ rule of thumb (circular duct)

sin2

sin2

,

,

rK

rK

yx

yx

linac-type

storage ring-type

KPositionor sum-over-difference Beampipe: round: r = 20.25 mm

Button Diameter: d =16.0 mm

sin() = 0.367

= 0.376

Kx = 10.367 mm (linac)

T1) Calculate Kx,

for Linac type

Input at x and z

out W = x+z, out Y = x-z

180 deg Hybrids

Phase, Noise, and Drifts (Stability)

Problem: Electronic drift: 0.2 mm/0C

Sensitivity

Simulation

-100% to 100% means the ± radius => x=10 => x= 40.5 mm

Kx = 1/S = 4.05 / 0.40 = 10.15

y=S*x, xfull scale = position variation, S=y/x

Multiply to the Scale a factor 2!

=0.4