hom issues in ler ring and ir. recent measurements and calculations
DESCRIPTION
HOM Issues in LER Ring and IR. Recent measurements and calculations. Sasha Novokhatski SLAC. More LER & HER currents – more HOM Heating. LER ring TSP feed-through & Bellows Vacuum pumps & NEGs (new) HER ring Bellows (new) Interaction region Vertex bellows & near bellows. - PowerPoint PPT PresentationTRANSCRIPT
PEP-II Machine Advisory Committee Meeting SLAC,
April 15-17, 2004
HOM Issues in LER Ring and IR.HOM Issues in LER Ring and IR.Recent measurements and calculations.Recent measurements and calculations.
Sasha Novokhatski
SLAC
15-April-2004 PEP-II MAC Session 2SN
More LER & HER currents –More LER & HER currents – more HOM Heating more HOM Heating
LER ring– TSP feed-through & Bellows – Vacuum pumps & NEGs (new)
HER ring– Bellows (new)
Interaction region– Vertex bellows & near bellows
15-April-2004 PEP-II MAC Session 3SN
Fight against high temperaturesFight against high temperatures
Water and air cooling– Fans for bellows in all LER and HER regions– Special cooling for vertex bellows
Damping High Order Modes by water cooled RF absorbers– HOM absorber in LER arc chamber
Improving RF screens
15-April-2004 PEP-II MAC Session 4SN
HOM measurements and HOM measurements and computer simulationscomputer simulations
HOM spectrum measurement:– Signals from BPMs– RF antenna near TSP feed-through– RF antenna near HV cable in vacuum pumps
HOM power measurement:– Thermocouples on input and output water
cooling system with water-flow measurement
Computer simulation:– Calculations with MAFIA and other wake field
programs
15-April-2004 PEP-II MAC Session 5SN
HOM absorber in region 4HOM absorber in region 4
HOM Absorber
TSP
1162
Bellows2012
15-April-2004 PEP-II MAC Session 6SN
Absorber: ceramic tiles with large Absorber: ceramic tiles with large loss tangent and water cooling tubeloss tangent and water cooling tube
15-April-2004 PEP-II MAC Session 7SN
Effect of absorberEffect of absorberon TSP feed-throughon TSP feed-through
Temperature
LER current
Nov. 2002-Apr. 2004
15-April-2004 PEP-II MAC Session 8SN
TSP in the next arc chamber 1153TSP in the next arc chamber 1153
Nov. 2002-Apr. 2004
15-April-2004 PEP-II MAC Session 9SN
Analog TSPs in region 12 do not Analog TSPs in region 12 do not have high temperatureshave high temperatures
Artem KulikovHOM detectors
installed in June 2003
15-April-2004 PEP-II MAC Session 10SN
HOM spectrum measurement: antenna HOM spectrum measurement: antenna and spectrum analyzer near TSP 1163and spectrum analyzer near TSP 1163
15-April-2004 PEP-II MAC Session 11SN
HOM power measurement: digital HOM power measurement: digital water flow meter and thermocoupleswater flow meter and thermocouples
15-April-2004 PEP-II MAC Session 12SN
Power Power relationsrelations
2 1360
3.8
200
RF
bunches
VP Z I
MV N
Z Ohm
Prediction for HOM power
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 1000 2000 3000 4000
LER current [mA]
HO
M p
ow
er [
W]
V=3.2MVN=1200
V=3.8MVN=1360
V=5.6MVN=1700
V=6.4MVN=1715
Now we are here
15-April-2004 PEP-II MAC Session 13SN
The hottest bellows in the LERThe hottest bellows in the LER
LER Bellow 2012 PR04with ‘super” fan
Nov. 2002-Apr. 2004
15-April-2004 PEP-II MAC Session 14SN
Examples of RF modes. S. WeathersbyExamples of RF modes. S. Weathersby
Magnetic field Electric field
15-April-2004 PEP-II MAC Session 15SN
Proposal for absorber for arc bellowsProposal for absorber for arc bellows
Copper buttons
Absorber tiles
Water cooling tubes
15-April-2004 PEP-II MAC Session 16SN
MAFIA . Stephen Weathersby computation.
1.E+01
1.E+02
1.E+03
1.E+04
1.4E+09 1.9E+09 2.4E+09 2.9E+09 3.4E+09 3.9E+09 4.4E+09
frequency [Hz]
Q wall-mag
3-az-mag
no abs mag
Comparison of 1-tile thick covered Comparison of 1-tile thick covered flange absorber with azimuthal 2x3-tile flange absorber with azimuthal 2x3-tile mount and the no absorber Q values.mount and the no absorber Q values.
15-April-2004 PEP-II MAC Session 17SN
HOM spectrum HOM spectrum in IP region. in IP region.
15-April-2004 PEP-II MAC Session 18SN
Vertex bellowsVertex bellows
Bellow
Cavity
bunch field ‘‘Mode Converter”
15-April-2004 PEP-II MAC Session 19SN
Vertex bellows. RF Modes .Vertex bellows. RF Modes .Stephen Weathersby computation.
15-April-2004 PEP-II MAC Session 20SN
Quadruple modeQuadruple mode
15-April-2004 PEP-II MAC Session 21SN
Damping HOMs in vertex bellows. Damping HOMs in vertex bellows. Simulation study by S. Weathersby.Simulation study by S. Weathersby.
Decreasing Q-value of a bellow cavity by placing absorber
Best position of absorber.
Low Q decreases power dissipation.
10
0
1 022
1 0
0 1
20 1
1
1
in
4(1 )
( )
4 /
(1 / )
cav
waveguide
cav inc inc
cav inc
Reflection from cavity
ZQQ
Z Q
Power a cavity
Q QP P P
Q Q
Q QP P
Q Q
15-April-2004 PEP-II MAC Session 22SN
Power dissipation a bellow cavityPower dissipation a bellow cavity
Q/QbettaPower in cavity 0.01 0.04
0.1 0.330.2 0.560.5 0.890.7 0.97
1 12 0.895 0.56
10 0.3315 0.2320 0.18
Power in cavity
0
0.2
0.4
0.6
0.8
1
1.2
0 1 2 3 4 5 6 7 8 9 10
Q0/Qbetta
15-April-2004 PEP-II MAC Session 23SN
Absorber on the one side does not well damp modes!
Vertex Bellows
1.00E+00
1.00E+01
1.00E+02
1.00E+03
3.00E+09 5.00E+09 7.00E+09 9.00E+09 1.10E+10 1.30E+10
Frequency
Q-v
alu
e
no absorber mag mag
no absorber elec mag
mag mag
mag elec
15-April-2004 PEP-II MAC Session 24SN
Absorber on the other side. Still not good damping.
15-April-2004 PEP-II MAC Session 25SN
Q value
10
100
1000
10000
4.0E+09 5.0E+09 6.0E+09 7.0E+09 8.0E+09 9.0E+09 1.0E+10 1.1E+10 1.2E+10 1.3E+10
frequency [Hz]
QQ Cu no absorber
Q absorber 0.5mm
Q absorber 1.0mm
Q absorber 1.25mm
Q absorber 1.5mm
Absorber on the wall
15-April-2004 PEP-II MAC Session 26SN
Power in a cavityPower in a cavityX Power in cavity
0.01 0.0392120.1 0.3305790.2 0.5555560.5 0.8888890.7 0.968858
1 12 0.8888895 0.555556
10 0.33057915 0.23437520 0.181406
Power in cavity
0
0.2
0.4
0.6
0.8
1
1.2
0 2 4 6 8 10
Q0/Qbetta
15-April-2004 PEP-II MAC Session 27SN
HOMs in vacuum pumpsHOMs in vacuum pumps
15-April-2004 PEP-II MAC Session 28SN
Vacuum pump (LER PR2:3044) HOM Vacuum pump (LER PR2:3044) HOM spectrum. Frequency range 0-10 GHzspectrum. Frequency range 0-10 GHz
Antenna in HV connector
15-April-2004 PEP-II MAC Session 29SN
Frequency range 3-6 GHzFrequency range 3-6 GHz
15-April-2004 PEP-II MAC Session 30SN
Q-value estimationQ-value estimation
0
5
10
15
20
25
30
-1 -0.5 0 0.5 1 1.5 2 2.5 3
Delta Frequency [MHz]
Sp
ectr
um
F=4.046119 GHz Breit-Vigner Q=6100
02468
101214161820
-1 -0.5 0 0.5 1
Delta frequency [MHz]
Sp
ectr
um
F=5.236GHz Breit-Vigner Q=12000
15-April-2004 PEP-II MAC Session 31SN
RF screen for vacuum pumpRF screen for vacuum pump
15-April-2004 PEP-II MAC Session 32SN
RF screens for NEGsRF screens for NEGs
15-April-2004 PEP-II MAC Session 33SN
Other screenOther screen
15-April-2004 PEP-II MAC Session 34SN
SummarySummary
More water and air coolingDamping High Order Modes by water
cooled RF absorbersSimulation studies on improvement of
beam chamber elements and RF screens