Paul Scherrer Institut Cavity BPM Pickups for Swiss

Paul Scherrer Institut Cavity BPM Pickups for Swiss. FEL Boris Keil for the PSI/GFA Beam Diagnostics Team Paul Scherrer Institut Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Introduction Swiss. FEL • • Linac-based FEL, photocathode RF gun Injector and linac: 2 bunches, 28 ns spacing, 100 Hz Fast beam distribution kicker 2 Undulators, 1 bunch each o Hard X-ray ("Aramis"), 0. 1 -0. 7 nm o Soft X-ray ("Athos"), 0. 7 -7 nm 2 nd construction phase Athos 0. 7 -7 nm 1 st construction phase BC 1 Injector Linac 1 0. 35 Ge. V Boris Keil, PSI 2. 6 -3. 4 Ge. V BC 2 Linac 2 2. 0 Ge. V 3. 0 Ge. V Linac 3 2. 1 -5. 8 Ge. V DEELS Workshop 2014 user stations Aramis 0. 1 -0. 7 nm 12. 5. 14

Swiss. FEL Site PSI West PSI East Swiss. FEL SLS Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Swiss. FEL Site Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Swiss. FEL Site 6/2013 PSI East PSI West Experiment End Stations Injector Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Swiss. FEL Site 4/2014 Gun area Injector & Linac below ground level, technical gallery (incl. klystrons) on top Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Swiss. FEL Site 4/2014 Experimental area Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

BPM Usage • Alignment of beam trajectory. Orbit feedback. • Measurement of beam Energy: - In bunch compressors: REF E 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 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 "BPM 38" Type 2 "BPM 16" Type 3 "BPM 8" Inner Beam Pipe Aperture 38 mm 16 mm 8 mm Pickup Length 250 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% Nominal Charge 10 -200 p. C # Bunches per Train 1 -3 Max. Bunch Train Rep Rate Min. Bunch Spacing 1 100 Hz 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 Evaluation of BPM Types For Swiss. FEL Fulfill requirement for injector, linac, TL Pickup Fullfill requirements for all BPMs Button Matched Stripline Resonant Stripline Cavity Monopole Mode Suppression Modal (hybrid) / electronics Modal (coupler), frequency, phase (sync. det. ) Typical RMS Noise, 10 p. C, 20 mm pipe ~200μm <80μm <4μm ~1μm 300… 800 MHz 500 -1500 MHz 3 -6 GHz Frequency Spectrum (M=Monopole, D=Dipole Mode) Typical Electronics Frequency “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: BPM 38 Usage Injector, Linac, TL, BC Quantity BPM 16 6 111 Pickup Type BPM 8. 1 BPM 8. 2 Undulators (Alternative) 27+23 ← Cavity (2 Resonators, Mode-Suppressing Couplers) Frequency 3. 2844 GHz Loaded Q ~40 Material 4. 8552 GHz ~200 Stainless Steel ~1000 Copper/Steel Hybrid Gap Width 14 mm 7 mm 14 mm 12 mm Reson. Distance 180 mm 60 mm 50 mm Signal [V/mm/n. C] 5. 7 7. 1 5. 2 4. 3 RFFE IF Frequency ADC IQ Downconversion* ~0 Hz ~50 MHz 16 -Bit 160 MSPS (Linac/Injector: 12 -Bit 500 MSPS 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/n. C (Q=70) -> ~3 x improved low charge resolution for Swiss. FEL. Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Swiss. FEL BPM 16 Pickup • 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

16 mm Swiss. FEL BPM 16 Pickup m m 0 0 1 Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Swiss. FEL BPM 38 Pickup m 255 m 38 mm Reference resonator (2 RF feedthroughs): Signal ~ charge TM 010 -suppressing waveguide Dipole resonator (4 RF feedthroughs) Signal ~charge*pos. Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Swiss. FEL BPM 8 Pickup 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

BPM 16 Pickup 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] [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] [PSI] 12. 5. 14

BPM 16 Pickup Costs Body Parts (316 LN Stainless Steel) • • • Design already well optimized by SACLA/DESY Swiss. FEL: Only low-charge performance optimized Costs of different companies differ a lot (1400 CHF to 3800 EUR per pickup, material + machining + meas. . ). Feedthroughs (FTs) • Few years ago: SACLA designed FT for their cavity BPMs. Single supplier, PSI paid ~500 EUR 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 ~5 x compared to initial design. Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Swiss. FEL Cavity BPM 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 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 50 Ω broadband load Feedthrough to be tested APC 7 -N adapter Series production: Tool for fast RF test of all feedthroughs. Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

S 11 for Feedthrough Pre-Series Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

BPM 16 Pickup & Support • Most pickups: Cheap rigid support, adjustment via shimming (~10 um X/Y steps/reproducibility) • Few pickups: Support adjustable via screws with differential threads (~1 um X/Y steps/reproducibility) Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Mechanical Dimension Def. Position Cavity Reference Cavity Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

BPM 16 Mechanical & RF Tolerances Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Pre-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. Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

RF Meas. Before Brazing Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

RF Meas. After Brazing Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

BPM 16 Pickup: Beam Signals Decay to 0. 07% Decay to 1. 6% Raw signals of Swiss. FEL BPM 16 (QL=40) & EXFEL undulator cavity pickup (QL=70) Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

BPM 16 RFFE Output Signals Swiss. FEL BPM prototype: RFFE output signals (IQ outputs, just Q shown) Low bunch-bunch crosstalk 28 ns bunch spacing Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

BPM 16 Position Resolution Swiss. FEL BPM 16 position resolution measurement: Difference of Swiss. FEL & E -XFEL (extrapolated) BPM position reading. <0. 8μm RMS noise at 135 p. C & 0. 35 mm offset (range > ± 1 mm) Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

BPM 16 Charge Resolution Swiss. FEL BPM 16 Charge resolution measurement: Correlation with EXFEL undulator BPM. <0. 1 p. C RMS charge noise at 135 p. C bunch charge. Boris Keil, PSI DEELS Workshop 2014 12. 5. 14

Summary & Conclusions • Swiss. FEL uses only cavity BPM pickups. • In-house feedthrough design & collaboration with Swiss large-scale (automotive/medical) non-RF feedthrough manufacturer allowed significant price reduction. • BPM 16 prototypes meet requirements. Currently doing minor redesign, removing systematic Q and frequency shift of final version (with BC-Tech feedthroughs) • BPM 38 and BPM 8 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 • 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

BPM 16 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 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 -50 -40 -40 -60 -80 -70 -50 -60 -70 -60 b -20 -10 -20 -30 -20 -20 -10 -10 10 -20 -10 wg. H 18 17 8 12 15 7 3 8 9 2 4 2 2 15 -5 -9 wg. L -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 -10 -15 -5 -5 wg. W 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

BPM 16 Pre-Series: Frequency Position Cavity Reference Cavity Boris Keil, PSI DEELS Workshop 2014 12. 5. 14