The Cavity Beam Position Monitor (BPM) Massimo Dal Forno

Transcription

1 The Caviy eam Posiion Monior (PM) Massimo Dal Forno Paolo Craievich, Raffaele De Mone, Thomas orden, Andrea orga, Mauro Predonzani, Mario Ferianis, Robero Vescovo

2 Conens Inroducion: The Caviy PM HFSS Simulaions CST Simulaions The new elecronic sysem The in-unnel es Oulook of he fuure work

3 Inroducion: The Caviy PM Devices able o deermine he X and Y posiion of he elecron beam in he beam pipe ased on a resonan caviy Resonan Caviy Waveguides Good resoluion (~1μ arge for FERMI@Elera), High signal level in single sho

4 The dipole mode: TM 110 I is he posiion sensing mode Is inensiy is proporional o he beam offse There are wo differen polarizaions: verical and horizonal Working Frequency: ~6.5 GHz The separaion of he monopole and of he wo polarizaions is achieved wih he caviy-waveguide coupling

5 Separaion of he wo dipole polarizaions The magneic coupling is described by H R (radial componen of H) Allows he separaion of he wo polarizaions Propagaion H R X polarizaion por 1, 3 Y polarizaion por, 4

6 Signal processing The signal of por 1, 3 is proporional o he X posiion The signal of por, 4 is proporional o he Y posiion An addiional signal is used as reference signal, o: Obain a bipolar oupu signal (for +X, +Y), Separae he offse from he il componen

7 eam offse and il effecs on he oupu signals Only offse V acc, offse E z e jkz dz C j11t R dr l Purely real Only il V acc, il E z e jkz dz jc j11g k a sin kl kl cos kl Purely immaginary The elecronics mus even separae he offse from he il componen in quadraure (IQ demodulaion or our approach)

8 HFSS Simulaions Aim: Simulaing he RF parameers of he caviies wih 90, 180 and no symmery planes: Reference caviy PM caviy Aim: Esimaing he oupu signal levels wih 1 nc of bunch charge, he volage is given by he following relaion: V Z k OUT QEXT q

9 HFSS Simulaions resuls Workbench measured frequencies: The simulaion resul is 19 MHz differen from he measured value

10 CST Simulaions Aim: Simulaing he oupu signal levels wih 1 nc of bunch charge Summary of he sigal levels:

11 The new elecronic sysem Aim: designing a new elecronic sysem ha avoids he IQ demodulaion Firs ype of circui ) ( ) ( ) ( ) ( ) sin( ) )cos( ( ) sin( ) )cos( ( ) cos( )) sin( ) cos( ( R R R R R D D RIF PM e e Ae e e Ae e e Ae e e Ae e A V e V The il componen mus be negligible wih respec o he offse (for 1μm, he il mus be < 0.1 mrad)

12 The new elecronic sysem Advanages: eam in he cenre High oupu signal level ( =Δ) Calibraion sysem V V PM RIF 0 Acos( ) e R D Ae Ae Ae R R cos( cos( R ) ) Calibraion Marix A cal A Δ cal D Ae R

13 The new elecronic sysem Second ype of circui The il componen is rejeced: d A d D 4A D 4A e R e Anologous resul o he coheren demodulaion

14 The in-unnel es The prooype has been insalled in unnel during he las commissioning Aim: deermining he oupu volage wih 1 nc of bunch charge Signal levels: Reference caviy:.5 V Caviy PM, X offse: 0.33 Vmm Caviy PM, Y offse: 0.30 Vmm

15 The in-unnel es Specrum (FFT) of he PM oupu signal Dipole mode f = GHz Quadrupole mode f= GHz Recangular waveguide f= 7.7 GHz Dipole of he reference f = 8.47 GHz

16 Oulook of he fuure work 10 caviy PMs have been insalled in he undulaor hall Each one has a mover (Encoder resoluion: 1 μm) Tesing he RF fronend Measuremens of he resoluion

17 Thank you for your aenion Quesions?

18 The resonan modes of he caviy The elecron beam excies he resonan modes of he caviy The firs four resonan modes are he following: TM 010 TM 110 TM 10 TM GHz 6.5 GHz 9.04 GHz 10.5 GHz (Frequencies of he PM) 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30

19 The monopole mode: TM 010 I is an unwaned mode Is signal volage is only proporional o he beam inensiy and does no depend on he beam posiion. Working Frequency: 4.63 GHz Rejecion achieved wih: Cu-off frequency of he recangular waveguide Caviy-Waveguide Coupling and pass filer cenred on he dipole frequency 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30

20 Rejecion of he TM 010 mode: Cu-off frequency of he waveguide Waveguides behave as high-pass filer Cu-off frequency for he fundamenal mode (TE10): c f L 5 GHz a The monopole, a 4.63 GHz is under cu-off 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30

21 Rejecion of he TM 010 mode: Caviy-Waveguide Coupling Magneic coupling: only he magneic field (Hr) of he dipole will couple wih he waveguide Radial componen of H (Hr) 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30

22 Rejecion of he TM 010 mode: Caviy-Waveguide Coupling The monopole does no couple wih he waveguide 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30

23 Caviy-Waveguide Coupling: Separaion of he wo dipole polarizaions However, due o he mechanical olerances, he wo polarizaions are no perfecly orhogonal The orhogonal pors are no isolaed beween hem This phenomena is called Cross-Talking 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30

24 Rejecion of he TM 010 mode: Caviy-Waveguide Coupling Consequences of he caviy-waveguide coupling The monopole does no couple wih he waveguide I separaes he verical and he horizonal polarizaions An addiional band-pass filer is placed o have only he dipole signal and o rejec he higher modes 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30

25 Vou Energy U k q Pex U Qex Qex k q Vou Z Pex Z Qex k q Z Qex R Q q 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30

26 Vacc, Energy, essel, Lineariy 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30

27 Offse, Til 14h ESLS RF Workshop ELETTRA Triese, Ialy 010 Sepember 9 30