CALIFES linac
description
Transcript of CALIFES linac
1C. Simon CTF3 Meeting
CavityBPM for CALIFES
C. Simon, M. Luong, D. Bogard, W. Farabolini,
J. Novo
CTF3 Meeting – 27-29 January 2009
227/01/09 CTF3 Meeting
CALIFES linac
CA
.BH
B 0
40
0
CA
.SN
H 0
11
0
CA
.SN
I 0
12
0
CA
.VV
S 0
10
0 CA
.DH
G/D
VG
01
30
CA
.VV
S 0
20
0C
A.M
TV
02
15
CA
.BP
M 0
22
0C
A.D
HG
/DV
G 0
22
5
CA
.SN
G 0
23
0
CA
.SN
G 0
25
0
CA
.BP
M 0
24
0
CA
.BP
M 0
26
0
CA
.BP
M 0
31
0
CA
.BP
M 0
38
0
CA
.DH
G/D
VG
02
45
CA
.DH
G/D
VG
02
65
CA
.DH
G/D
VG
03
20
CA
.DH
G/D
VG
03
85
CA
.DH
B/D
VB
02
70
CA
.IC
T 0
21
0
CA
.VV
S 0
30
0
CA
.QF
D 0
35
0
CA
.QF
D 0
36
0
CA
.QD
D 0
35
5
CA
.BP
R 0
37
0
CA
.BP
M 0
41
0CA
.MT
V 0
39
0
CA
.MT
V 0
42
0C
A.V
VS
05
00
CA
.SD
H 0
34
0
CA
.DH
B/D
VB
02
30
CA
.DH
B/D
VB
02
50
ACS 0230 ACS 0250 ACS 0270
DUM
0450
TBTS
ITL
CA
.MT
V 0
12
5(v
irtu
al c
ath
od
e)
CA
.FC
U 0
43
0
6 BPMs are installed on the CALIFES linac
327/01/09 CTF3 Meeting
Reentrant Part
Reentrant Cavity BPM for CALIFES
Bent coaxial cylinder designed to have:
- a large frequency separation between monopole and dipole modes
- a low loop exposure to the electric fields
• It is operated in single and multi-bunches modes
• The cavity is fabricated with titanium and is as compact as possible :
~125 mm length and 18 mm aperture 4 mm gap
427/01/09 CTF3 Meeting
RF characteristics
Eigen modes
F (MHz) Ql (R/Q) (Ω) (R/Q) (Ω)
Calculatedwith HFSS
in eigen mode
Measured in the CLEX
Calculatedwith HFSS
in eigen mode
Measuredin the CLEX
CalculatedOffset 5
mm
CalculatedOffset 10
mm
Monopole mode
3991 3988 24 26.76 22.3 22.2
Dipole mode
5985 5983 43 50.21 1.1 7
• RF characteristics of the cavity: frequency, coupling and R/Q
Due to tolerances in machining, welding and mounting, some small distortions of the cavity symmetry are generated.
This asymmetry is called cross talk and the isolation is evaluated > 26 dB.
BPM
• Similar results from one BPM to another, and in-situ results
are comparable to Saclay in-lab measurements
Monopole and dipole transmission measured by the network analyzer
Monopole and dipole reflection measured by the network analyzer
527/01/09 CTF3 Meeting
Signal Processing Hybrids installed close to BPMs in the CLEX
Multiport switches used to have one signal processing electronics to control six BPMs.
Analog electronics with several steps to reject the monopole mode
BPMs in the probe beam linac tunnel
beam positionmonitor 1
x1
x2
y2
y1
180°hybrid
180°
hybrid
phaseshifter
3 dBcombiner
beam positionmonitor 6
x1
x2
y2
y1
180°hybrid
180°
hybrid
3 dBcombiner
.
.
.
6 to 1multiportswitch
phaseshifter
x
y
6 dB
6 dB
18 dBm leak.
18 dBm leak.
Filter 5997 MHz600 MHz BW
0 to 70 dB
0 to 70 dB
18 dBm leak.
Lowpass Filter120 MHz
0 to 70 dB
3 dBsplitter
reference2.891 GHz
14 dBm
RF electronics in the hall
8channel
videoamp
Gv = 10
4channel10 bits2 Gs/sADC
2channel10 bits2 Gs/sADC
DAQ in the hall
control unit
VME Crate
signals for switchesand variable
attenuators control
Ix
Qx
Iy
Qy
Filter 5997 MHz600 MHz BW
RF
LO
II-Q
demodulator
Q
RF
LO
II-Q
demodulator
Q
Lowpass Filter200 MHz
Filter 3990 MHz400 MHz BW
AcqirisDigitizers
Hybrid
couplers
RF electronics used synchronous detection with an I/Q demodulator.
627/01/09 CTF3 Meeting
Control Command of BPMs1/Sampling with acqiris boards and readout signals on OASIS
3/Results sent on graphic windows under JAVA and in a file to be used with Matlab
6 BPMs implemented
sincos QI
2/Signal processing: Digital Down Conversion
- raw waveform multiplied by a local oscillator of the same frequency to yield a zero intermediate frequency - real and imaginary parts of each IF are then multiplied by a 60 coefficient, symmetric, finite impulse response (FIR), low pass filter with 40MHz 3dB bandwidth
P
A
Qsin
22 QIA
Beam position
A
Icos
727/01/09 CTF3 Meeting
Signal in 32 bunches mode behind RF electronics
Signal in single bunch mode behind RF electronics
Signal voltage determined by the beam’s energy loss to the dipole mode.
Dipole mode signal depends on frequency fi and external coupling Qi of this mode
Simulations (1)
Φ(t) = heaviside function, q = bunch charge, R0 = 50 Ω, (R/Q)i = coupling to the beam and ζi = 2 (dipole mode)
iaiQ
tiatiiQ
tiVtiS
ii..2
).sin(...cos)
.2
.exp()(
iQ
RqQRiV
i
oii
.
..)/.( 22
24
11
iQiia
single bunch
Sd(n)
Dipole mode signal in 32 bunches mode
Dipole mode signal in single bunch mode
~ 30 ns~10 ns
Rdn
0
32
I
Phi n Te( )
Vod e
2 Fd1n Te
2 Qd1
cos ad1 n Te( ) 2 Fd1sin ad1 n Te( )
2 Qd1 ad1
32 bunches
827/01/09 CTF3 Meeting
Re-entrant Cavity at CALIFES
Environment Noise RMS: 66 µV (measured at FLASH)
Δ signal (gain adjusted to get an RF signal ~ 0 dBm, simulated in single bunch) with 5 mm offset : 590 mV (simulated), Noise: 0.5 mV (calculated) Resolution : 3.2 µm (simulated)
with 0.1 mm offset : 555 mV (simulated), Noise: 0.1 mV (calculated) Resolution : 100 nm (simulated)
Noise is determined by :
Thermal Noise :
kb = Boltzmann constant, BW (Hz) = Bandwidth, T (K) = Room Temperature.
Noise from signal processing channel :
with
Simulations (2)
.** thn PGNFP
BWTb
kPth **
...*
11
21
3
1
21
GG
F
G
FFNF
Pth = Thermal noise, NF=Total noise figure of the signal processing, Fi and Gi respectively the noise factor and the gain of component i.
927/01/09 CTF3 Meeting
BPM calibration (1)
All BPMs have same electronics and same losses coefficients should be the same
Charge calibrated with charge calculated by ICT
CA
.BP
M 0
22
0
CA
.IC
T 0
21
0
1027/01/09 CTF3 Meeting
Beam studies (1)
channels
Amplitude of signals corresponds to 6 nC with 150 bunches determined thanks to ICT
• τ too long on channel (green) problem with diode
• Impedance problem? -> Move lowpass filter
BPMs in the probe beam linac tunnel
beam positionmonitor 1
x1
x2
y2
y1
180°hybrid
180°
hybrid
phaseshifter
3 dBcombiner
beam positionmonitor 6
x1
x2
y2
y1
180°hybrid
180°
hybrid
3 dBcombiner
.
.
.
6 to 1multiportswitch
phaseshifter
x
y
6 dB
6 dB
18 dBm leak.
18 dBm leak.
Filter 5997 MHz600 MHz BW
0 to 70 dB
0 to 70 dB
18 dBm leak.
Lowpass Filter120 MHz
0 to 70 dB
3 dBsplitter
reference2.891 GHz
14 dBm
RF electronics in the hall
8channel
videoamp
Gv = 10
4channel10 bits2 Gs/sADC
2channel10 bits2 Gs/sADC
DAQ in the hall
control unit
VME Crate
signals for switchesand variable
attenuators control
Ix
Qx
Iy
Qy
Filter 5997 MHz600 MHz BW
RF
LO
II-Q
demodulator
Q
RF
LO
II-Q
demodulator
Q
Lowpass Filter200 MHz
Filter 3990 MHz400 MHz BW
AcqirisDigitizers
ICT
1127/01/09 CTF3 Meeting
Beam studies (2)
Charge ~ 6 nC read by the first and second BPM. ~ 100 % transmission behind 1st section
channels
y I and Q channels
Signals minimized
beam offset minimized
1227/01/09 CTF3 Meeting
Beam studies (3)
Channel
y I and Q channels
• Signal frequency: 100 MHz
• Shape of y shows in the pulse train :
- charge not constant
or
-beam position not constant
Simulation of I and Q signals
1327/01/09 CTF3 Meeting
BPM calibration (2)
Magnets switched off between steerers and studied BPM to reduce errors and simplify calculation.
Move beam with one steerer in horizontal and vertical frame.
Average of 500 points for each steerer setting.
R = transfer matrix from steerer to BPM
Calculate for each steerer setting, the relative beam position in using a transfer matrix between steerer and BPM :
Dx = R12*Dx’(angle at steerer)
CA
.BP
M 0
380
CA
.DH
G/D
VG
032
0
1427/01/09 CTF3 Meeting
Summary
Reentrant cavity BPM features for CALIFES:
• Operated in single and multi-bunches
• Single bunch resolution potential < 1 µm
• Charge of beam measured
Software under development.
First beam seen by BPMs Dec. 2008
New beam tests end of March 2009
1527/01/09 CTF3 Meeting
Acknowledgements
Thanks to CERN and CEA teams
Thanks to Pascal ContrepoisAline CurtoniStéphane DeghayeMick DraperPatrick GirardotFrancis HarrraultPierre-Alain LeroyFabienne OrsiniFranck PeaugerAnastasiya Radeva Lars Soby
Thank you for your attention