Detuning of T18 after high power test
description
Transcript of Detuning of T18 after high power test
Detuning of T18 after high power test
Jiaru Shi18.04.2012
Outline
• RF measurement of CERN-Build T18– Comparison before and after high power test– Detuning Analysis
• Old results– (From Juwen Wang and Toshiyasu Higo)
• Related simulation• Geometry Change and analysis
RF measurementBefore high power test
after high power test
CERN built T18
Faya Wang @ SLAC
Faya Wang @ SLAC
After high power testBefore high power test
Increased standing waveRegular cells are fine
Analysis using the code for tuning from bead-pull data
• See detuning of input matching cell• The detuning of last two cells are calculated from the standing wave patter,
or the reflection from the output matching. Details next slides. (Note: while tuning, these two cells are tuned to correct the standing wave).
0 5 10 15 20-3
-2
-1
0
1
2
3
4
5x 10
6
number of cells
df a
fter h
igh
pow
er te
stin
g (H
z)
Standing wave patternReflection (both phase and amplitude)
• The imaginary part of this reflection can come from detuning of the last regular cell cell(N-1). Decrease of frequency
• Or the matching cell: Cell(N) Increase of frequency:
• Important note: the phase advance between the last two cells is ~100deg. Not 120 deg!
• Note: imag part of reflection comes from detuning, while real part of reflection comes from unmatched coupling
0.02
0.04
0.06
30
210
60
240
90
270
120
300
150
330
180 0
afterbefore
before last regular cell(N-1)
before Matching cell(N)
0.02
0.04
0.06
30
210
60
240
90
270
120
300
150
330
180 0
Amplitude Measurement of T18-SLAC #1 Before and After High Power Test
11421.7 MHz at 21.32°C, N2 Before high Power test
11421.87 MHz at 20.4°C, N2 After high power test
Juwen Wang @ SLAC
1350 hours
11421.7 MHz at 21.32°C, N2 ore high Power test
11421.87 MHz at 20.4°C, N2 After high power test
Phase Measurement of T18-SLAC #1 Before and After High Power Test
Juwen Wang @ SLAC
Amplitude Measurement of TD18-SLAC Before and After High Power Test
11424.5 MHz at 21.46°C, N2 Before high Power test
11424.56 MHz at 21.1°C, N2 After high power test
Juwen Wang @ SLAC
Phase Measurement of TD18-SLAC Before and After High Power Test
16.5°
11424.5 MHz at 21.46°C, N2 ore high Power test
11424.56 MHz at 21.1°C, N2 After high power test
Select bead pulling frequencies based on the same measurement condition for both before and after high power test
Juwen Wang @ SLAC
Amplitude Measurement of T18-SLAC #1 Before and After High Power Test
11424.1 MHz at 20.02°C, N2 Before high Power test
11424.15 MHz at 20.4°C, N2 After high power test
T24Juwen Wang @ SLAC
Phase Measurement of T24-SLAC Before and After 800 Hours High Power Test
Select bead pulling frequencies based on the measurement condition to get 2π/3 phase advance for both before and after high power test
6º
11424.1 MHz at 21.1°C, N2 After high Power test
11424.1 MHz at 21.2°C, N2 Before high power test
Juwen Wang @ SLAC
Similar Standing-Wave pattern for T(D)18
T18-CERN T18-SLAC
TD18-SLAC T24-SLAC
Summary of the detuningT18 SLAC N1 TD18 SLAC T24 SLAC T18 CERN N2
Measured at SLAC SLAC SLAC CERN
Output matching
Standing Wave(SWR)
1.06 1.2 1.05 1.1
(reflection) 0.03, -30dB 0.1,-20dB 0.025, -32dB 0.05, -26dB
Estimate df if one cell detuned
2MHz 7MHz 2.5MHz 3MHz
from standing wave pattern
+F@N cell or -F@N-1 cell
+F@N cell or -F@N-1 cell
+F@N cell +F@N cell or -F@N-1 cell
Regular cells
Total phase shift -16 deg +6 deg
~df +1 MHz -0.3 MHz
Note: T(D)18 structures have similar design where the phase advance between last two cells is ~100 deg. Making it hard to tell at Nth or at N-1th cell. It seems at the last cell.
RF measurement before/after baking• T24 12G N1
– Same configration– Temperature df
calculated
Phase S21
• Delta f ~10kHz
S21 magdf ~30kHz
11.8856 11.8857 11.8858 11.8859-36.84
-36.82
-36.8
-36.78
f / GHz
Com
bined
tran
smis
sion
S21
/ dB
-2.7775
-2.7644
11.9927
12.0344 12.0345 12.0346 12.0347
-40.6
-40.4
-40.2
-40
-39.8
-39.6
f / GHzCom
bined
tran
smis
sion
S21
/ dB
• T24 12G N2, leak fix at mode launcher– With and without wire, no direct comparison– Phase compare N/A because change of RF flange
adapter– df < 50kHz, Reflection increase
100k grid
• CERN PSI N2 after baking, df<100kHz– (same situation)
TD18 post-HPT @CERN• TD18 post-HPT (High Power Test) analysis
– 1. Chamfer
From: Markus Aicheler
TD18 Chamfer100 um -1MHz
Chamfer TD18
20.00 40.00 60.00 80.00 100.00r_chamfer [um]
-0.13
0.00
0.13
0.25
0.38
0.50
0.63
0.75
(re(
Mod
e(1)
)-11
425M
Hz)
/1M
Hz
Ansoft LLC f0XY Plot 2 ANSOFT
Curve Info
(re(Mode(1))-11425MHz)/1MHzSetup1 : LastAdaptive
Fill the 100um Chamfer +1MHz
T18 chamfer100 um -0.5MHz
10.00 30.00 50.00 70.00 90.00r_chamfer [um]
0.05
0.15
0.25
0.35
0.45
0.50
(re(
Mod
e(1)
)-11
424M
Hz)
/1M
Hz
Ansoft LLC cell_1XY Plot 1 ANSOFT
Curve Info
(re(Mode(1))-11424MHz)/1MHzSetup1 : LastAdaptive
Electromagnetic field
• Scaled to 150 MV/m Eacc• P = (-epsilon0 E^2 + mu0 H^2)/4• static simulation• Material: Copper E = 110GPa• Max deform: 0.06um, very
small. • 0.06um 12kHz• not the right direction
• HFSS result: Iris deform 10um ~ 2MHz
Circular Wg
Matching cell
E field pull B field
push
Asymmetry heating?
Circular Wg
Matching cell
Surface heating expansion?
• The source of detuning is not clear, but we find that. The MHz detuning corresponds to a geometry change that can be measured!
• The structure is cut open and critical dimensions are measured
T18 CERN N2 Cut
T18 CERN N2 Cut• 1: measure the profile of tuning bump,
compare with the tuning history
Tuning bump visible by eye
Height of tuning bump v.s. recorded tuning
• Good agreement “< +/- 1MHz”
11 12 13 14 15 16 17 18 19 200
1
2
3
4
5
6
7
8
0
10
20
30
40
50
60
70
80
90
delta f tuned (MHz)
average bump height (um)
Cell #
T18 CERN N2 Cut• 2: measure the distance between irises.
Distance between irises (gap)
12 13 14 15 16 17 18 19 20
-0.02
-0.015
-0.01
-0.005
0
0.005
g - g_RFdesign
Leftcenterright
mm
12 13 14 15 16 17 18 19 20
-0.025
-0.02
-0.015
-0.01
-0.005
0
0.005
g - g_RFdesign
leftcenterright
mm
Half-A Half-B
Error +-3 um. Three points are measured:“left” and “right” close to the cell wall, “center” close to the iris regionLast cell is longer in “center”.
12 13 14 15 16 17 18 19 20
-0.01
-0.005
0
0.005
0.01
0.015
0.02
0.025
0.03
g(center) - average(g(left,right))
Half-AHalf-B
mm
Simulation with deformed output matching iris in HFSS
• Single cell simulation gives 3MHz detuning from ~15 um “iris deform”.
• Full structure simulation shows similar standing wave pattern.
0.00 50.00 100.00 150.00 200.00Distance [mm]
0.00E+000
2.00E+004
4.00E+004
6.00E+004
8.00E+004
1.00E+005
1.20E+005
Com
plex
Mag
_E [V
_per
_met
er]
HFSSDesign1XY Plot 1 ANSOFT
Curve Info
ComplexMag_ESetup1 : LastAdaptivedz_iris='0.01mm' Freq='11.424GHz' Phase='0deg'
Summary (1)
• It’s a critical issue for the reliability and the lifetime of the accelerating structures.
• Almost every structure has an increased reflection from output, causing a standing wave pattern. For the same type of structure, the patterns are very similar.
• Geometry measurement on the T18 (CERN N2) shows deformation on the output matching iris This explains the increased reflection. (Most probably, this is also the case for the other 3 structures)
• In CLIC nominal design with compact coupler from the side, there will be no iris with such field asymmetry.
• Input side, cut into halves? Or take it iris by iris. Measure the profile of the whole input matching iris
• multiple-physics-coupled simulation: the deform of matching iris and the asymmetrical pulsed heating.
Summary (2)• Frequency change of regular cells is observed
in several structures, in TD18, but not in T18s; in T24s. in TD24?
• To be analyzed in near future: TD24 taken out from TBTS.– RF measurement, Cut, and dimensional control.