Upload
aron-hutchinson
View
220
Download
0
Embed Size (px)
DESCRIPTION
Cavity BPM model. TM110 mode
Citation preview
BPM for FF test (ATF2)
Vladimir Vogel
KEK
2nd Nano Workshop, KEK, December 12, 2004
Three types of BPMs for LC
Main linac, ordinary BPMs
Main linac, special type BPMs
Final Focus BPMs
resolution 5 - 10 m, accuracy 8-16 m, quantity few thousands. (low impedance)
resolution 1 - 5 m, accuracy 4.0-8.0m, quantity few tens, angle, tilt, phase.
resolution 0.002 m (?), (divergence 300 mrad), accuracy 1.0-2.0m
Cavity BPM model. TM110 mode
0.5
0.5 21 11
1max
sin( / 2) ( )( ) ( / ) exp( / 2)/ 2
cav loadb
cav l
RJ kV q R QJ Q
Cross-sectional view of BINP cavity BPM 6426 MHz, (5p. in KEK ATF + 1p.). 2000. 1.- Cavity sensor . 2- Heater. 3 – Temperature sensor. 5 – Coupling slot. 6 – Output waveguide. 7 – Output feedthrough. 8 – Beam pipe. 9 – Vacuum flange. 10 – Support plate. 11 – Y position output. 12 - X position output. 13 – Heater control connector.
Std = 0.5929/1.225
Calculate position (micron)
-120 -100 -80 -60 -40 -20 0
BP
M#2
(mic
ron)
-80
-70
-60
-50
-40
-30
-20
-10
0
Std=200 nm
BINP cavity BPM for DESY TTF (2p.now SLAC?), 1999
VLEPP 14 GHz cavity BPM (3p. At BNL ATF) 1997
-24.0 -20.0 -16.0 -12.0 -8.0 -4.0(Yu+Yd)/2, m icrons
-28.0
-24.0
-20.0
-16.0
-12.0
-8.0
Ym, m
icro
ns
F it Y = 0 .99 7 * X - 2 .2 5sig m a = 0 .15 m icron s
BPM for VLEPP, 14GHz, 1991
Cavity BPM 6426 MHz F010=4.4GHz, Qex=2.600,
F110=6.426GHz, Qload=3300,F020=10.2 GHz, Qex=5800
3 1010 4 1010 5 1010 6 1010 7 10101 10 161 10 151 10 141 10 131 10 121 10 111 10 10
1 10 91 10 81 10 71 10 61 10 51 10 41 10 3
0.01
0.1
1
10
100
1 103
1 103
1 10 16
W Q 010 W02 Q 02 W11 Q 110
7.5 101024.0 109
TM010
TM110
TM020
For 1 nm resolutionmax
010 110/ 135P P db
Frequency difference:TM010 - 60 dbTM020 - 65 dbSpace mode selection:For TM010 - 40 db(?)For TM020 - 25 db(?)
Sum:TM010 - 35 db, ~ +60 nmTM020 - 25 db, ~ -17 nm
max020 110/ 125P P db
Seemingly no big problem, only electrical center of cavity move up to +43 nm, but!!!
2 2
* * ( )sin( /2* )( ) /2*
( ) exp( * / 2* )
z
z
z z
zz
U Q k ScS c
S c
For rectangular bunch charge distribution
For Gaussian bunch charge distribution
ATF beam size ~ 6 mm, if
U010/U110 ~ 6%
U110/U020 ~ 22%Position of electrical center of cavity = (60 nm +/- 3.6nm) – (17 nm-/+ 3.7nm)
For LC 300z m
BPM frequency about 18 GHz, this effect seems will be small.
Move the X-band phase sensor cavity from linac to extraction line to start study of depends BPMs resolution from bunch length
Proposal
Phase sensor F010=5712 MHz, F020=11424MHz
Reference cavity, F010=2856MHz, F020=6426MHz) Position sensor cavity 6426MHz
Angle monitor
Sensor cavity signal versus the beam trajectory angle, the phase shifter tune to +90°2002, KEK ATF
We should investigate possibility to useelectrical type mode in cavity to measurementbunch angle (Frequency ~ 8 GHz)
TE111
MHz
referencecavity
BPM cavity
Sin
Cos
714 MHz
Sin
Cos
Uin
Usw.
Q010
Q110
Principle of electronics for FF BPM
Uout=U0*T(Q)
Q010=500Q110=3300nSec
T(Q)=exp(-*/2*Q)
20*log(U010/U110) = 35db
5712 MHz
6426 MHzdF 50 MHz
U
F
714 MHz
6426
ATF2 cavity BPM, frequency ~ 9 GHz with damped Q for symmetrical modes, and magic T inside BPM
ИН
п.1
ИН
Test BPM for FFcomposite of two cavity.Not real size!Not real bunch length!
reference phase andbunch length measurement.
First:for position measurement.
Second:Cavity with very short gap 0.5-1 mm (for big divergence 300 rad.)
?
Conclusion
BPM for FF, it seems will be no problem with thermal noise,but problems with common mode rejection and angle/ tilt signals.
Further experimental studies at ATF extraction line will be required to getfull understanding of the common mode effect in cavity.
New I/Q electronics should be tested.
The new type of position sensor cavity, angle, tilt and divergence sensor cavity have be studies at ATF2.