Paul Scherrer Institut
Cavity BPM Pickups for SwissFEL
Boris Keil for the PSI/GFA Beam Diagnostics Team
Paul Scherrer Institut
Boris Keil, PSI
DEELS Workshop 2014 DEELS Workshop 2014
12.5.14
Introduction
1
SwissFEL
•
•
•
•
Linac-based FEL, photocathode RF gun
Injector and linac: 2 bunches, 28ns spacing, 100Hz
Fast beam distribution kicker
2 Undulators, 1 bunch each
o Hard X-ray ("Aramis"), 0.1-0.7nm
o Soft X-ray ("Athos"), 0.7-7nm
2nd construction phase
Athos 0.7-7nm
1st construction phase
BC1
Injector
Linac 1
0.35 GeV
Boris Keil, PSI
2.6-3.4 GeV
BC2
Linac 2
2.0 GeV
3.0 GeV
Linac 3
2.1-5.8 GeV
DEELS Workshop 2014
user
stations
Aramis 0.1-0.7 nm
12.5.14
SwissFEL Site
2
PSI East
PSI West
SwissFEL
SLS
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
SwissFEL Site
Boris Keil, PSI
DEELS Workshop 2014
3
12.5.14
SwissFEL Site 6/2013
4
PSI East
PSI West
Experiment
End Stations
Injector
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
SwissFEL Site 4/2014
5
Gun area
Injector & Linac
below ground
level, technical
gallery (incl.
klystrons) on
top
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
SwissFEL Site 4/2014
6
Experimental
area
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
BPM Usage
7
• Alignment of beam trajectory. Orbit feedback.
• Measurement of beam Energy:
- In bunch compressors:
E
REF
E
beam
Standard BPMs in bunch compressor “arms”
(no special large-aperture BPM needed), plus two
non-dispersive REFerence BPMs for x/y jitter removal.
- In dog-legs / beam dumps
Standard BPMs used to measure energy in log-leg /
beam dump “arms”. No special ultra-large-aperture
beam dump BPM needed.
E
REF
REF
E
• Relative beam charge measurement (absolute
calibration via dedicated Bergoz charge monitor).
• Correction of position-/charge-dependent measurement
errors of other systems (BAM, wire scanner, ...).
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
BPM Requirements / Specifications
Type 1
"BPM38"
Type 2
"BPM16"
Type 3
"BPM8"
Inner Beam Pipe Aperture
38 mm
16 mm
8 mm
Pickup Length
250 mm
100 mm
100 mm
Usage
Injector & Linac
Undulators
Position Range*
±10 mm
±5 mm
±1 mm
RMS Position Noise
<10 μm
<5 μm
<1 μm
Position Drift (per week)
<10 μm
<5 μm
<1 μm
Relative RMS Charge Noise
<0.1%
<0.1%
<0.1%
Nominal Charge
10-200 pC
# Bunches per Train
1-3
Max. Bunch Train Rep Rate
Min. Bunch Spacing
8
1
100Hz
28 ns
-
* Desired: Support of larger/smaller range (via remote gain control), but with lower/higher resolution.
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
BPM Type Choice
9
Evaluation of BPM Types For SwissFEL
Fulfill requirement for injector, linac, TL
Pickup
Frequency
Spectrum
(M=Monopole,
D=Dipole
Mode)
Button
E(f)
Fullfill requirements for all BPMs
Matched Stripline
E(f)
M
Resonant Stripline
M
E(f)
M
Cavity
E(f)
M
D
D
D
D
f
f
f
f
Monopole
Mode
Suppression
Modal (hybrid) /
electronics
Modal (hybrid) /
electronics
Modal (hybrid) /
electronics
Modal (coupler),
frequency,
phase (sync. det.)
Typical RMS
Noise, 10pC,
20mm pipe
~200μm
<80μm
<4μm
~1μm
Typical
Electronics
Frequency
300…800MHz
300…800MHz
500-1500MHz
3-6GHz
“Typical” noise: Examples & estimates (scaling, …) based on existing systems, not theoretical limit …
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
Pickup Parameters
Pickup Name:
BPM38
Usage
Injector, Linac, TL, BC
Quantity
BPM16
6
111
Pickup Type
10
BPM8.1
BPM8.2
Undulators
Undulators (Alternative)
27+23
←
Cavity (2 Resonators, Mode-Suppressing Couplers)
Frequency
3.2844GHz
Loaded Q
~40
Material
4.8552GHz
~200
Stainless Steel
~1000
Copper/Steel Hybrid
Gap Width
14mm
7mm
14mm
12mm
Reson. Distance
180mm
60mm
50mm
50mm
Signal [V/mm/nC]
5.7
7.1
5.2
4.3
RFFE
IF Frequency
ADC
IQ Downconversion*
~0Hz
~50MHz
16-Bit 160MSPS (Linac/Injector: 12-Bit 500MSPS Option)**
* Undulators (Alternative Option): Single-channel downconversion feasible, being evaluated.
** Sample rates of available ADCs for European XFEL (E-XFEL) BPM electronics built by PSI
*** E-XFEL Undulator: 2.9 V/mm/nC (Q=70) -> ~3x improved low charge resolution for SwissFEL.
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
SwissFEL BPM16 Pickup
11
• Based on E-XFEL/SACLA design
• Optimized for low charge & low
production costs.
Position resonator (used
signal ~ position*charge).
Resonator gap width
“Waveguide depth”
Reference resonator
(used signal ~ charge)
Boris Keil, PSI
DEELS Workshop 2014
Waveguides connected to
beam pipe
12.5.14
SwissFEL BPM16 Pickup
16 mm
12
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
SwissFEL BPM38 Pickup
13
38 mm
Reference resonator (2 RF feedthroughs): Signal ~ charge
TM010-suppressing waveguide
Dipole resonator (4 RF feedthroughs) Signal ~charge*pos.
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
SwissFEL BPM8 Pickup
14
8 mm inner
beam pipe
aperture.
Pickup
length 100
mm.
Motorized X-Y
mover (BPM+quad.
magnet
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
BPM16 Pickup Production Steps
15
Production Steps (Complete Pickup):
•
•
•
•
•
•
•
Machining of three pickup body parts from metal block
Mechanical measurement
RF test (Q, frequency)
Brazing of three body parts (foil)
Leak test, RF test (Q, frequency)
Welding of RF feed-throughs to body
Final vacuum & RF test.
[Company]
[Company]
[PSI]
[PSI]
[PSI]
[PSI]
[PSI]
Production Steps (Feedthroughs):
•
•
•
•
•
Machining of pickup metal parts
Production of boro-silicate "pill" (sintered granulate)
Loose assembly, then oven to melt glass
Tests: Vacuum, dimensions
Test: RF (reflection)
Boris Keil, PSI
DEELS Workshop 2014
[Company]
[Company]
[Company]
[Company]
[PSI]
12.5.14
BPM16 Pickup Costs
16
Body Parts (316LN Stainless Steel)
•
•
•
Design already well optimized by SACLA/DESY
SwissFEL: Only low-charge performance optimized
Costs of different companies differ a lot (1400CHF
to 3800EUR per pickup, material + machining + meas. ...).
Feedthroughs (FTs)
• Few years ago: SACLA designed FT for their cavity
BPMs. Single supplier, PSI paid ~500EUR per FT in 2010
= ~half of overall pickup costs!
• Several companies offered compatible type for E-XFEL,
typ. few 10% cheaper
• PSI developed FT in collaboration with Swiss company
specialized in high-volume low-cost glass FTs (airbags:
few million glass ceramic FTs per year!, medical, ...).
Price reduced ~5x compared to initial design.
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
SwissFEL Cavity BPM Feedthrough
17
Feedthrough production (@BC-Tech AG): Some iterations were necessary until our
requirements were met (size of glass pearl, modification of graphite stamp, ...)
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
Neutron Scattering Images of FTs
18
Also feedthtoughs from other companies evaluated ...
Vacuum side
Idea: M. Rohrer
(had neutron
scattering image of
gun bullet on his
desk ...). Did not
show difference
between good &
bad VSWR. But: ...
Borosilicate
glass seal (good
neutron
absorber, not
well visible with
X-rays ...)
air side
Bad vacuum
design: Risk of
inner leaks.
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
Feedthrough RF Testing Tool
19
50 Ω broadband load
Feedthrough
to be tested
APC7-N adapter
Series production: Tool for fast RF test of all feedthroughs.
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
S11 for Feedthrough Pre-Series
-10
20
1.6
-15
1.5
-20
-25
1.4
VSWR
S11 [dB]
-30
-35
1.3
-40
1.2
-45
-50
1.1
-55
-60
Boris Keil, PSI
0
1.625 3.25 4.875 6.5 8.125
Frequency [GHz]
1
0
DEELS Workshop 2014
1.625 3.25 4.875 6.5 8.125
Frequency [GHz]
12.5.14
S11 for Feedthrough Pre-Series
FT no.53
-20
-20
-20
-20
-30
-40
0
3.3
6.6
-30
-40
-50
9.9
0
3.3
6.6
-30
-40
-50
9.9
0
FT no.59
3.3
6.6
-30
-40
-50
9.9
0
FT no.60
3.3
6.6
-30
-40
-50
9.9
S11 [dB]
-20
S11 [dB]
-20
S11 [dB]
-10
S11 [dB]
-10
0
FT no.61
3.3
6.6
-30
-40
-50
9.9
-20
-20
-20
-20
-20
-20
-40
0
3.3
6.6
-40
-50
9.9
0
FT no.64
3.3
6.6
-30
-40
-50
9.9
0
FT no.65
3.3
6.6
-30
-40
-50
9.9
0
FT no.66
3.3
6.6
-30
-40
-50
9.9
S11 [dB]
-10
S11 [dB]
-10
S11 [dB]
-10
S11 [dB]
-10
-30
0
FT no.67
3.3
6.6
-50
9.9
-20
-20
-20
-50
0
3.3
6.6
-50
9.9
0
FT no.70
3.3
6.6
-40
-50
9.9
0
FT no.71
3.3
6.6
-30
-40
-50
9.9
0
FT no.72
3.3
6.6
-30
-40
-50
9.9
S11 [dB]
-20
S11 [dB]
-20
S11 [dB]
-20
S11 [dB]
-10
S11 [dB]
-10
-30
0
FT no.73
3.3
6.6
-50
9.9
-50
0
3.3
6.6
-40
-50
9.9
0
FT no.76
3.3
6.6
-40
-50
9.9
0
FT no.77
3.3
6.6
-40
-50
9.9
0
FT no.78
3.3
6.6
-30
-40
-50
9.9
S11 [dB]
-20
S11 [dB]
-10
-20
S11 [dB]
-10
-20
S11 [dB]
-10
-20
S11 [dB]
-10
-30
0
FT no.79
3.3
6.6
-50
9.9
-20
-20
-20
-50
0
3.3
Boris Keil, PSI
6.6
9.9
-40
-50
0
3.3
6.6
9.9
-40
-50
0
3.3
6.6
9.9
-40
-50
0
3.3
6.6
DEELS Workshop 2014
9.9
S11 [dB]
-20
S11 [dB]
-20
S11 [dB]
-20
S11 [dB]
-10
S11 [dB]
-10
-30
-30
-40
-50
0
3.3
6.6
3.3
6.6
9.9
FT no.81
-10
-40
0
FT no.80
-10
-30
9.9
-40
-10
-30
6.6
-30
-10
-30
3.3
FT no.75
-20
-40
0
FT no.74
-10
-30
9.9
-40
-20
-30
6.6
-30
-10
-30
3.3
FT no.69
-10
-40
0
FT no.68
-10
-30
9.9
-40
-10
-40
6.6
-30
-10
-30
3.3
FT no.63
-10
-30
0
FT no.62
-10
S11 [dB]
S11 [dB]
FT no.57
-10
-50
S11 [dB]
FT no.56
-10
FT no.58
S11 [dB]
FT no.55
-10
-50
S11 [dB]
FT no.54
-10
S11 [dB]
S11 [dB]
FT no.52
21
9.9
-30
-40
-50
0
3.3
6.6
9.9
12.5.14
S11 for Feedthrough Pre-Series
FT no.83
FT no.87
-20
-20
-20
-20
-20
-30
-40
0
3.3
6.6
-30
-40
-50
9.9
0
3.3
6.6
-30
-40
-50
9.9
0
FT no.89
3.3
6.6
-30
-40
-50
9.9
0
FT no.90
3.3
6.6
-30
-40
-50
9.9
S11 [dB]
-20
S11 [dB]
-10
S11 [dB]
-10
S11 [dB]
-10
0
FT no.91
3.3
6.6
-30
-40
-50
9.9
-20
-20
-20
-20
-20
-20
-50
0
3.3
6.6
-30
-40
-50
9.9
0
FT no.94
3.3
6.6
-30
-40
-50
9.9
0
FT no.95
3.3
6.6
-30
-40
-50
9.9
0
FT no.96
3.3
6.6
-30
-40
-50
9.9
S11 [dB]
-10
S11 [dB]
-10
S11 [dB]
-10
S11 [dB]
-10
-40
0
FT no.97
3.3
6.6
-50
9.9
-20
-20
-20
-50
0
3.3
6.6
-50
9.9
0
FT no.100
3.3
6.6
-40
-50
9.9
0
FT no.101
3.3
6.6
-30
-40
-50
9.9
0
FT no.102
3.3
6.6
-30
-40
-50
9.9
S11 [dB]
-20
S11 [dB]
-20
S11 [dB]
-20
S11 [dB]
-10
S11 [dB]
-10
-30
0
FT no.103
3.3
6.6
-50
9.9
-20
-20
-20
-50
0
3.3
Boris Keil, PSI
6.6
9.9
-50
0
3.3
6.6
9.9
-40
-50
0
3.3
6.6
9.9
-30
-40
-50
0
3.3
DEELS Workshop 2014
6.6
9.9
S11 [dB]
-20
S11 [dB]
-20
S11 [dB]
-20
S11 [dB]
-10
S11 [dB]
-10
-30
-30
-40
-50
0
3.3
6.6
3.3
6.6
9.9
FT no.105
-10
-40
0
FT no.104
-10
-30
9.9
-40
-10
-40
6.6
-30
-10
-30
3.3
FT no.99
-10
-40
0
FT no.98
-10
-30
9.9
-40
-10
-40
6.6
-30
-10
-30
3.3
FT no.93
-10
-30
0
FT no.92
-10
S11 [dB]
S11 [dB]
FT no.86
-10
FT no.88
S11 [dB]
FT no.85
-10
-50
S11 [dB]
FT no.84
-10
S11 [dB]
S11 [dB]
FT no.82
22
9.9
-30
-40
-50
0
3.3
6.6
9.9
12.5.14
BPM16 Pickup & Support
23
• Most pickups: Cheap rigid support,
adjustment via shimming (~10um
X/Y steps/reproducibility)
• Few pickups: Support adjustable
via screws with differential threads
(~1um X/Y steps/reproducibility)
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
Mechanical Dimension Def.
24
Position Cavity
Reference Cavity
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
BPM16 Mechanical & RF Tolerances
Boris Keil, PSI
DEELS Workshop 2014
25
12.5.14
BPM16 Mechanical & RF Tolerances
Boris Keil, PSI
DEELS Workshop 2014
26
12.5.14
Pre-Brazing Pickup RF Test
27
• Tool fixes body
parts and RF
feedthroughs in
correct position
• pressure/weight
used to get
contact.
• Measure Q and
frequency of
all pickups
before and after
brazing/welding.
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
RF Meas. Before Brazing
28
after brazing the three body parts
measured with Vacom feedthroughs
6
2
0
0
f-f [MHz]
4
-2
-4
-6
1
2
3
4
5
6
position-Xplane
7
8
9
pickup no.
10
11
12
position-Yplane
13
14
15
16
15
16
reference
41.5
41
Q
L
40.5
40
39.5
39
38.5
Boris Keil, PSI
1
2
3
4
5
6
7
8
9
pickup no.
10
11
DEELS Workshop 2014
12
13
14
12.5.14
RF Meas. After Brazing
29
before brazing the three body parts
measured with the same set of VACOM feedthroughs
tool for assembling not yet available
3
0
f-f [MHz]
1
-1
-3
-5
-7
-9
1
2
3
4
5
6
position-Xplane
7
8
9
pickup no.
10
11
12
position-Yplane
13
14
15
16
15
16
reference
44
Q
L
42
40
38
36
Boris Keil, PSI
1
2
3
4
5
6
7
8
9
pickup no.
10
DEELS Workshop 2014
11
12
13
14
12.5.14
BPM16 Pickup: Beam Signals
30
Decay to 0.07%
Decay to 1.6%
Raw signals of SwissFEL BPM16 (QL=40) & EXFEL undulator cavity pickup (QL=70)
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
BPM16 RFFE Output Signals
SwissFEL BPM prototype:
RFFE output signals (IQ
outputs, just Q shown)
31
Low bunch-bunch
crosstalk
28ns bunch spacing
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
BPM16 Position Resolution
32
SwissFEL BPM16 position
resolution measurement:
Difference of SwissFEL &
E-XFEL (extrapolated)
BPM position reading.
<0.8μm RMS noise at
135pC & 0.35 mm offset
(range > ±1mm)
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
BPM16 Charge Resolution
33
SwissFEL BPM16
Charge resolution
measurement:
Correlation with EXFEL undulator
BPM. <0.1pC RMS
charge noise at
135pC bunch
charge.
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
Summary & Conclusions
34
• SwissFEL uses only cavity BPM pickups.
• In-house feedthrough design & collaboration with
Swiss large-scale (automotive/medical) non-RF feedthrough manufacturer allowed significant price reduction.
• BPM16 prototypes meet requirements. Currently doing
minor redesign, removing systematic Q and frequency
shift of final version (with BC-Tech feedthroughs)
• BPM38 and BPM8 prototype beam tests 7-9/2014
• Neutron scattering allowed non-desctructive analysis
of feedthroughs from alternative manufacturer.
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
Team & Acknowledgements
35
• F. Marcellini, M. Rohrer (Cavity pickup & feedthrough design & test)
• M. Stadler (Cavity RFFE, algorithms, overall system tests)
• M. Roggli, R. Ditter, R. Kramert (ADC Mezzanine, BPM crate)
• R. Baldinger (FPGA carrier board)
• G. Marinkovic, W. Koprek (Software & FPGA firmware)
and
• PSI Mechanical Department (Pickup construction & prototyping)
• Colleagues from DESY and SACLA (Pickup infos & tips)
• C. Bargähr (RF feedthroughs, www.bctech.ch)
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
Paul Scherrer Institut
Thank you for your
attention!
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
Supplementary Slides …
Boris Keil, PSI
DEELS Workshop 2014
37
12.5.14
BPM16 Pre-Series: Dimensions
pickup
1
2
3
4
5
6
7
8
9
38
10
11
12
13
14
15
16
Position cavity: Deviation from nominal mechanical dimension
R
-5
-10
-4,5
-6,5
-10
-5
-1,5
-6,5
-8
-8,5
-2,5
0
-5,5
-6,5
-3
-8,5
L
-1
-6
-4
-5
-10
0
-15
-4
-4
-5
1
1
-3
-4
-4
2
G
5
6
1
6
10
9
4
2
8
4
7
4
4
5
3
7
T
-2
-2
1
3
-3
27
5
5
2
1
1
-2
-3
3
-2
8
a
-30
-30
-50
-40
-40
-40
-60
-80
-60
-80
-70
-50
-60
-60
-70
-60
b
-20
-10
-20
-30
-20
-20
-20
-10
-10
-20
-10
-10
10
-20
-20
-10
wgH
18
17
8
12
15
7
3
8
9
2
4
2
2
15
-5
-9
wgL
-5
20
5
6
10
6
2
10
4
-1
-7
-9
-7
7
-3
-5
12,5
-10
-5
1,5
-5
-20
-25
-10
-15
-10
-10
-15
-5
-5
-5
-5
wgW
Reference cavity: Deviation from nominal mechanical dimension
R
-12
-15
-5
-1
-3
-3,5
-16
-6,5
-4,5
12,5
-2
-7
-5
-6
-2
-8,5
G
-10
-3
-6
-13
-11
-10
-7
-3
3
-17
-12
-3
-2
-6
-9
2
L
7
12
5
-5
3
18
-3
11
22
-10
3
0
5
3
-5
9
T
-7
7
5
4
6
4
-3
-4
-1
-4
3
-3
3
-1
2
1
D
8
17
10
17
0
8
13
44
9
-8
9
21
9
7
1
31
Boris Keil, PSI
DEELS Workshop 2014
12.5.14
BPM16 Pre-Series: Frequency
39
Position Cavity
0
f-f [MHz]
6
4
2
1
2
3
4
5
6
7
8
9
pickup no.
10
11
12
13
14
15
16
14
15
16
measured frequency deviation on brazed pickup
measured frequency deviation on brazed pickup
freq deviation calculated from mechanical tolerances
Reference Cavity
4
2
-2
0
f-f [MHz]
0
-4
-6
1
Boris Keil, PSI
2
3
4
5
6
7
8
9
pickup no.
10
11
DEELS Workshop 2014
12
13
12.5.14