high resolution cavity bpms from rhul
DESCRIPTION
High resolution Cavity BPMs from RHUL. N Joshi* , S Boogert, F Cullinan, A Lyapin, et al. *[email protected] JAI at Royal Holloway University of London, A Morgan, G Rehm et. al. DIAMOND L ight S ource. DITANET topical workshop on BPM , CERN, January 16, 2012. - PowerPoint PPT PresentationTRANSCRIPT
High resolution Cavity BPMs from RHUL
N Joshi*, S Boogert, F Cullinan, A Lyapin, et al.*[email protected]
JAI at Royal Holloway University of London,
A Morgan, G Rehm et. al.
DIAMOND Light Source
DITANET topical workshop on BPM , CERN, January 16, 2012
JAI - John Adams Institute(NOT Japanese Accelerator Institute!)
RHUL – Royal Holloway, University of London
BPM work at JAI/RHUL
ATF• Running the BPM system• Provided electronics for the S-band system• Initiated both the S- and C-band designs• Main running system with ~40 BPMs• Resolution and stability studies• Will be covered in our talk tomorrow
CLIC• Have just established the collaboration with CERN
and Fermilab• The first prototype built at CERN, measurements at
RHUL• Details in Andrei Lunin’s talk
Diamond Light Source• Trying to come up with an improved solution for
CBPMs• More in the following slides
Working principle: Cylidrical cavity BPM
R
jmnmn
00
1
LQ2
Vcavity
x
x dVE
LE
W
V
Q
R
2011
20
1111
211
,11
20
losso PWQ
extoL QQQ
111
Basic equations
Transverse Resonance mode frequency:
Quality factor:
Loaded quality factor:
Decay time constant:
Normalized shunt impedance
Typical power spectrum of modes excited inside the resonance cavity.
2cos
2 00,1,1
1 z
extd
k
x
xq
Q
R
Q
ZA
Voltage induced by position offset:
)( 0 ti
t
dd eeAV
Computation and EM simulation codes
Advanced Computational Electromagnetic-3P (ACE3P) suit, SLAC, USA. Parallel, higher order, finite element based. Runs on NERSC super computers.
o Omega3P : Eigenmode solver to find normal modes of the cavity.
o T3P : Time domain solver to calculate transient response.
o S3P : S-parameter solver for transmission properties.
Electromagnetic (EM) simulation codes.
GdfidL : 3D EM simulation code written in Fortran. Finite difference time domain (FDTD) solver at core. Runs on a cluster of 61 nodes at RHUL. Solvers:
o Eigen-mode solver o Time domain solver
Cavity BPM project for NLS-DIAMOND
Science disciplines utilizing DIAMOND light source.o Chemistryo Cultural heritageo Earth scienceo Engineering
o Environmental science
o Life scienceo Physics and material
science
Major parameters:o Accelerated particle : e-
o Particle energy : 3GeVo Circumference : 561.6 mo Beam current : 300 mAo Bunch repetition rate: 500kHz
DIAMOND BPM: RF design and simulation
BPM development project at DIAMOND1:
BPM cavity with beam pipe andcoupler with feed-through
Waveguide coupler with feed-through
Basic design considerations :
oDipole frequency in C-Band range.oRelatively high Qo Frequency separation in XY to
improve isolation via different slot size in X and Y
oNo tuning.
Waveguide coupler
DIAMOND Cavity BPM: simulation
DIAMOND Cavity BPM: simulation
o Monopole frequency : 4.5 GHzo Monopole reduction by waveguide
fcut-off (Waveguide ) > fmonopole (Cavity)
o Dipole frequency : 6.47 GHzo Dipole coupling into the waveguide
fcut-off (Waveguide ) < fdipole
(Cavity)
Eigen mode solution : Monopole
Eigen mode solution : Dipole
S-parameter simulation CST
DIAMOND Cavity BPM: simulation
A. Morgan, DLS
DIAMOND Cavity BPM: Time domain simulation
Field Propagation Output signal.
oSimulated using T3P. oBeam offset by 1mm in X and Y both.
DIAMOND BPM simulation resultsMonopole frequency 4.5 GHz
Monopole suppression > 55 dB
Dipole frequency 6.457 GHz
Frequency separation between X and Y position data
~ 5 MHz
X and Y plane isolation ~ 50 dB
QL (decay time constant ) Y-plane ~ 3000 (0.073 s)
Expected sensitivity ~ 0.5 V/mm/nC
DIAMOND Cavity BPM: simulation
o Cavities were fabricated by FMB Berlin.
RF Measurements
o Peak Frequency S11: 6.376GHzo Peak Frequency S22: 6.371GHzo Coupling loss: ~ -10
dB o XY isolation : ~ -15
dBo Monopole suppression: > -
55 dBo Qload : 2892
RF Measurements
S-parameter simulation ACE3P
DIAMOND Cavity BPM: simulation
DIAMOND Cavity BPM: RF Measurements (Mode orientation)
Dipole : Rotation angle= ~13
o -4…4 mm scan in 0.2 mm steps.
o Movers and VNA were remote controled and synchonised using USB and VISA over LAN.
o All S-parameters are recorded during single frequency sweep
o 6400 S-para files were processed in parallel mode on cluster.
o Rotation agrees with isolation.
o Perhaps, can use external tuners to tune the X-coupling?
o May also be an interesting study case for advanced analysis
DIAMOND Cavity BPM: Beam testing in ATF2
Cavity Installation:
o The cavity has been installed on a mover system.
o Can be moved irrespective of other system in transversally in X and Y by +/- 1.5 mm
Signal detection with diode:
o Cavity outputs from one port for X and Y each is connected to a Shottky diode.
o Dioe out digitized using network scope located outside the tunnel.
The main installation (3 BPMs) is at Diamond, but there dedicated time is needed for tests due to long bunches. 1 BPM was installed at ATF2 where it can be compared to the rest of the BPMs in the beamline and worked on parasitically.
DIAMOND Cavity BPM: Beam testing on ATF2 o Cavity moved in 50 µm steps.o Sx = 0.4735 µV/µmo Sy = 0.427 µV/µmo Seems too lowo Checking…