TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
Denis Kostin, MHF-SL, DESY.
Findings in RF Power Couplers
after operation on cavities in PXFEL2
Findings in RF Power Couplers after operation on cavities in PXFEL2
Overview
 RF Power Coupler
 Module Test
 RF Power Couplers Investigation
 Summary
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
2
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Power Coupler
3
cavity
warm 300K window
warm part
cold part
cold 70K window
waveguide part
RF power coupler
cavity
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Coupler Sensors / Diagnostics
4
interlock
all sensors data is stored for the analysis
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
low level RF gate on klystron
3 times e- (charged particles)
light in coupler vacuum
light in wave guide (air side)
temperature cold ceramic
temperature warm ceramic
vacuum coupler
vacuum cavity
bias voltage
cryogenic OK
Findings in RF Power Couplers after operation on cavities in PXFEL2
Cryo Module Test Bench
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
5
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Couplers Conditioning History/Data (1)
warm part vacuum
at low RF power
module PXFEL2: 20 µs pulses
6
warm coupler conditioning
coupler 2 e- probe signal
warm part 1,3 activity
Light.C1 IL events
 Warm
RF
power
coupler
conditioning with 20μs pulse up
to 800kW was limited by warm
parts of couplers 1 and 3.
 Coupler 2 electron probe current
was increased.
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Couplers Conditioning History/Data (2)
warm part vacuum
limiting
50, 100, 200, 400, 800, 1300 μs pulses
coupler 2 e- probe signal
warm part 1,3 activity
Light.C1 IL events
7
warm coupler conditioning
 Warm RF power coupler conditioning was
generally limited by warm parts of
couplers 1 and 3. Coupler 2 electron
probe current was increased as well.
 High level of light (PM) signals with warm
window temperature increase and
relatively low measured electron probe
current for couplers 1 and 3 points to the
warm window problems.
T300K1,3 is increased
 Warm couplers conditioning was not
completed: warm parts 1 and 3 activity
persisted.
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Couplers Conditioning History/Data (3)
cold coupler conditioning
warm part vacuum
jumps
50, 100, 200, 400, 800, 1300 μs pulses
8
Light 1,3 IL events
T300K3 is increased
 Cold RF power coupler conditioning on
CMTB was also affected by warm parts
of couplers 1 and 3.
 High level of light (PM) signals with
warm window temperature increase for
couplers 1 and 3 measured.
 Warm parts 1 and 3 activity persisted.
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Couplers Warm Conditioning Time
130
120
110
100
90
-6
IGP vacuum pressure IL limit set to 10 mbar
60
50
40
30
20
C1 warm part light
TSP saturated
80
70
coupler warm parts problems
not finished
140
C1, C3 warm part light
pulse length:
1300s
800 s
400 s
200 s
100 s
50 s
20 s
PMAX=700kW
TSP saturated
MTS couplers test: RF power rise time [hr]
150
9
10
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
PXFEL3
PXFEL2
PXFEL1
M3**
M8
M5-1256
M5-3478
M7-3478
M7-1256
M6-3478
module
M6-1256
0
Findings in RF Power Couplers after operation on cavities in PXFEL2
Module Test Results: PXFEL2 cavities gradients
Cavity tests:
Vertical ( CW )
Horizontal(10Hz)
CMTB
(10Hz)
Cavities gradient limits
XFEL goal
35
EACC [MV/m]
30
MP
25
20
15
10
5
0
1 - Z141
2 - AC150
3 - Z133
4 - Z139
5 - AC122 6 - AC121 7 - AC128 8 - AC115
cavity

Denis Kostin, MHF-SL, DESY.
04.05.2010
module performance was limited by the cavities, not couplers
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
10
Findings in RF Power Couplers after operation on cavities in PXFEL2
Cu-ceramics transition
outer coax
Denis Kostin, MHF-SL, DESY.
warm part 1
CP3H45
coupler conditioning problems: light signal
RF Power Couplers Inner Inspection (1)
11
inner coax – conical part
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
inner coax
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Power Couplers Inner Inspection (2)
coupler conditioning problems: e- probe signal
warm part 2
CP3H2
cold 70K window CF100 flange
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
12
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Power Couplers Inner Inspection (3)
13
outer coax
Denis Kostin, MHF-SL, DESY.
warm part 3
CP3H52
coupler conditioning problems: light signal
Cu-ceramics transition
ceramics
inner coax
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Power Couplers Inner Inspection (4)
Cu-ceramics transition
warm part 7, CP3H46
did not have direct impact on
the coupler conditioning
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
14
Findings in RF Power Couplers after operation on cavities in PXFEL2
RF Power Couplers Inner Inspection Summary

Warm part 1 (CP3H45): boroscope inner inspection revealed many dark points on conical
part of inner conductor at top and bottom position of mounted coupler, discoloration near EBwelding, spots near discoloration at outer conductor, on inner conductor near ceramics some
black spots, at conical part of inner conductor to ceramics transition a few black lines, and a
very rough surface.

Warm part 2 (CP3H2): in cold 70K window CF100 flange vicinity copper coating is
deteriorated.

Warm part 3 (CP3H52): boroscope inner inspection revealed some big dark colored spots
on the inside surface of ceramics with some thick lines around discolorations on the
ceramics, dark colored area at 9-12-3 o'clock position of mounted coupler on the conical part
of inner conductor to ceramic transition, copper coating damage on the surface of inner
conductor at 3 o'clock position, rather rough surface of inner conductor at transition to the
conical part, also rough surface of outer conductor near ceramics, some small black points
on surfaces of inner and outer conductors.

Warm part 7 (CP3H46): boroscope inner inspection revealed a few black lines and spots on
conical part of inner conductor, in this area surface is very rough, in the area between the
conical part of the inner conductor and ceramics dark colored area found, few black points on
conical part of inner conductor discovered as well.
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
15
Findings in RF Power Couplers after operation on cavities in PXFEL2
Summary
 Warm coupler conditioning was slowed down due to activity (RF discharge) in
several warm TTF3 coupler parts and was not completed for PXFEL2. Some
other modules (module 8, PXFEL1,3) did have similar problems during the
warm coupler conditioning.
 For the problem cases RF discharge was mostly concentrated near the warm
window: Light (PM) signal was limiting the conditioning, in some cases the
spark detector (diode) was following the light signal - detecting the discharge
light emission through the ceramic window.
 Coupler warm parts boroscope inner inspection revealed several surface
defects: scratches on the copper or ceramics surfaces, dark spots,
discolorations and copper coating deterioration in warm window vicinity. One
warm part did have copper coating deterioration (flaking) near cold window
flange (electron probe signal was detected for this part during the conditioning).
 Coupler warm parts post-production inspection did show the marks from the
circonium ceramics EBW covers on the ceramics for the parts 1,3 in this test,
but not the traces on the copper surfaces.
 Coupler inner surfaces deteriorations are clearly connected with performance
degradation and conditioning slow-down. Post-production inspection is
important for the coupler parts.
Denis Kostin, MHF-SL, DESY.
TESLA Technology Collaboration (TTC) Meeting, February 28 - March 3 2011, Milano, Italy
16