Boris Keil, PSIDEELS Workshop 201412.5.14 Cavity BPM Pickups for SwissFEL Boris Keil for the PSI/GFA...

Boris Keil, PSI DEELS Workshop 2014 12.5.14

Cavity BPM Pickups for SwissFEL

Boris Keil for the PSI/GFA Beam Diagnostics Team

Paul Scherrer Institut


12.5.14DEELS Workshop 2014


2Introduction

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"), 0.1-0.7nmo Soft X-ray ("Athos"), 0.7-7nm

1st construction phase 2nd construction phase

Linac 3Linac 1Injector Linac 2

Athos 0.7-7nm

Aramis 0.1-0.7 nm0.35 GeV 2.0 GeV 3.0 GeV 2.1-5.8 GeV

user stations2.6-3.4 GeVBC1 BC2


SwissFEL

PSI EastPSI West

SLS

SwissFEL Site 3


4SwissFEL Site


5SwissFEL Site 6/2013

PSI West

PSI East

Injector

Experiment End Stations



Gun area

Injector & Linac below ground

level, technical gallery (incl. klystrons) on

top



Experimental area


• Alignment of beam trajectory. Orbit feedback.

• Measurement of beam Energy:- In bunch compressors:

Standard BPMs in bunch compressor “arms” (no special large-aperture BPM needed), plus twonon-dispersive REFerence BPMs for x/y jitter removal.

- In dog-legs / beam dumpsStandard BPMs used to measure energy in log-leg / beam dump “arms”. No special ultra-large-aperture beam dump BPM needed.

• Relative beam charge measurement (absolute calibration via dedicated Bergoz charge monitor).

• Correction of position-/charge-dependent measurement errors of other systems (BAM, wire scanner, ...).

REFE E

REFE

EREF

beam

BPM Usage 8


9BPM 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 1

Max. Bunch Train Rep Rate 100Hz

Min. Bunch Spacing 28 ns -

* Desired: Support of larger/smaller range (via remote gain control), but with lower/higher resolution.


D

M

f

E(f)

D

M

f

E(f)

D

M

f

E(f)

D

M

f

E(f)

Pickup Button Matched Stripline Resonant Stripline Cavity

Frequency Spectrum(M=Monopole, D=Dipole Mode)

Monopole Mode Suppression

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 …

Fullfill requirements for all BPMsFulfill requirement for injector, linac, TL

BPM Type Choice

Evaluation of BPM Types For SwissFEL

10


Pickup Parameters

Pickup Name: BPM38 BPM16 BPM8.1 BPM8.2

Usage Injector, Linac, TL, BC Undulators Undulators (Alternative)

Quantity 6 111 27+23 ←

Pickup Type Cavity (2 Resonators, Mode-Suppressing Couplers)

Frequency 3.2844GHz 4.8552GHz

Loaded Q ~40 ~200 ~1000

Material Stainless Steel 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 IQ Downconversion*

IF Frequency ~0Hz ~50MHz

ADC 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.

11


SwissFEL BPM16 Pickup

Position resonator (used signal ~ position*charge).

Reference resonator (used signal ~ charge)

Resonator gap width

“Waveguide depth”

Waveguides connected to beam pipe

• Based on E-XFEL/SACLA design• Optimized for low charge & low production costs.

12


13

16 m

m

100 mm



14SwissFEL BPM38 Pickup

Reference resonator (2 RF feed-throughs): Signal ~ charge

Dipole resonator (4 RF feed-throughs) Signal ~charge*pos.

TM010-suppressing waveguide

38 m

m

255 mm


15

Motorized X-Y mover

(BPM+quad. magnet

8 mm inner beam pipe aperture. Pickup

length 100 mm.



16BPM16 Pickup Production Steps

Production Steps (Complete Pickup):

• Machining of three pickup body parts from metal block [Company]• Mechanical measurement [Company]• RF test (Q, frequency) [PSI]• Brazing of three body parts (foil) [PSI]• Leak test, RF test (Q, frequency) [PSI]• Welding of RF feed-throughs to body [PSI]• Final vacuum & RF test. [PSI]

Production Steps (Feedthroughs):

• Machining of pickup metal parts [Company]• Production of boro-silicate "pill" (sintered granulate) [Company]• Loose assembly, then oven to melt glass [Company]• Tests: Vacuum, dimensions [Company]• Test: RF (reflection) [PSI]


17BPM16 Pickup Costs

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.


18SwissFEL Cavity BPM Feedthrough

Feedthrough production (@BC-Tech AG): Some iterations were necessary until our requirements were met (size of glass pearl, modification of graphite stamp, ...)


19Neutron Scattering Images of FTs

air side

Borosilicate glass seal (good

neutron absorber, not

well visible with X-rays ...)

Idea: M. Rohrer (had neutron

scattering image of gun bullet on his desk ...). Did not show difference between good &

bad VSWR. But: ...

Bad vacuum design: Risk of

inner leaks.

Vacuum side

Also feedthtoughs from other companies evaluated ...


20Feedthrough RF Testing Tool

50 Ω broadband loadFeedthroughto be tested

APC7-N adapter

Series production: Tool for fast RF test of all feedthroughs.


21S11 for Feedthrough Pre-Series

0 1.625 3.25 4.875 6.5 8.125-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10S

11

[dB

]

Frequency [GHz]0 1.625 3.25 4.875 6.5 8.125

1

1.1

1.2

1.3

1.4

1.5

1.6

VS

WR

Frequency [GHz]


22

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.52

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.53

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.54

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.55

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.56

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.57

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.58

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.59

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.60

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.61

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.62

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.63

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.64

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.65

0 3.3 6.6 9.9-50

-40

-30

-20

-10S

11

[dB

]FT no.66

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.67

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.68

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.69

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.70

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.71

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.72

0 3.3 6.6 9.9-50

-40

-30

-20

-10S

11

[dB

]

FT no.73

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.74

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.75

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.76

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.77

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.78

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.79

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.80

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.81

S11 for Feedthrough Pre-Series


23

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.82

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.83

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.84

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.85

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.86

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.87

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.88

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.89

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.90

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.91

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.92

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.93

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.94

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.95

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.96

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.97

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.98

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.99

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.100

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.101

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.102

0 3.3 6.6 9.9-50

-40

-30

-20

-10S

11

[dB

]FT no.103

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.104

0 3.3 6.6 9.9-50

-40

-30

-20

-10

S11

[

dB]

FT no.105

S11 for Feedthrough Pre-Series


24BPM16 Pickup & Support

• 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)


25Mechanical Dimension Def.

Position Cavity

Reference Cavity


26BPM16 Mechanical & RF Tolerances


27BPM16 Mechanical & RF Tolerances


28Pre-Brazing Pickup RF Test

• 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.


29RF Meas. Before Brazing

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

-6

-4

-2

0

2

4

6

after brazing the three body partsmeasured with Vacom feedthroughs

pickup no.

f-f 0 [

MH

z]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1638.5

39

39.5

40

40.5

41

41.5

pickup no.

QL

position-Xplane position-Yplane reference


30RF Meas. After Brazing

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

-9

-7

-5

-3

-1

1

3

before brazing the three body partsmeasured with the same set of VACOM feedthroughs

tool for assembling not yet available

pickup no.

f-f 0 [

MH

z]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1636

38

40

42

44

pickup no.

QL

position-Xplane position-Yplane reference


31BPM16 Pickup: Beam Signals

Raw signals of SwissFEL BPM16 (QL=40) & E-XFEL undulator cavity pickup (QL=70)

Decay to 0.07%

Decay to 1.6%


32BPM16 RFFE Output Signals

SwissFEL BPM prototype: RFFE output signals (IQ outputs, just Q shown)

Low bunch-bunch crosstalk

28ns bunch spacing


33BPM16 Position Resolution

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)


34BPM16 Charge Resolution

SwissFEL BPM16 Charge resolution

measurement: Correlation with E-

XFEL undulator BPM. <0.1pC RMS

charge noise at 135pC bunch

charge.


35Summary & Conclusions

• 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.


36Team & Acknowledgements

• 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)



Thank you for yourattention!


38Supplementary Slides …


39BPM16 Pre-Series: Dimensions

pickup 1 2 3 4 5 6 7 8 9 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

wgW-

12,5 -10 -5 1,5 -5 -20 -25 -10 -15 -10 -10 -15 -5 -5 -5 -5

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


40BPM16 Pre-Series: Frequency

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

2

4

6

pickup no.

f-f 0 [

MH

z]

measured frequency deviation on brazed pickup

measured frequency deviation on brazed pickup

freq deviation calculated from mechanical tolerances

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

-6

-4

-2

0

2

4

pickup no.

f-f 0 [

MH

z]

Position Cavity

Reference Cavity

Boris Keil, PSIDEELS Workshop 201412.5.14 Cavity BPM Pickups for SwissFEL Boris Keil for the PSI/GFA...

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Transcript of Boris Keil, PSIDEELS Workshop 201412.5.14 Cavity BPM Pickups for SwissFEL Boris Keil for the PSI/GFA...