First Measurements of an Electro-Optical
Bunch Arrival-Time Monitor Prototype
with PCB-based Pickups for ELBE
B. E. J. Scheible1,4, M. K. Czwalinna2, N. T. A. Nazer2, S. Vilcins-Czvitkovits2, H. Schlarb2,
M. Freitag3, M. Kuntzsch3, W. Ackermann4, H. De Gersem4, A. Penirschke1(1) Technische Hochschule Mittelhessen, Wilhelm-Leuschner-Str. 13, 61169 Friedberg, Germany(2) Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany(3) Helmholtz-Zentrum Dresden Rossendorf HZDR, Bautzner Landstr. 400, 01328 Dresden(4) Technische Universität Darmstadt, Karolinenplatz 5, 64289 Darmstadt, Germany

Abstract

Measurements

A vacuum sealed prototype of an electro-optical bunch-arrival-time monitor has been commissioned in 2023. It comprises of a pickup-structure and a low-𝜋-voltage ultra-wideband travelingwave electro-optical modulator. The stainless-steel body of the pickup structure is partially
produced by additive manufacturing and comprises four pickups as well as an integrated
combination network on a printed circuit board. This novel design aims to enable single-shotbunch-arrival-time measurements for electron beams in FELs with single-digit fs precision for low
bunch charges down to 1 pC. The theoretical jitter charge product has been estimated bysimulation and modeling to be in the order of 9 fs pC. The new prototype is tailored for validation
experiments at the ELBE accelerator beamline.

▪ THz-beamline of ELBE @HZDR▪ Repetition rate: 0.41 MHz CW-mode▪ 1.4 m of v-cables▪ 110 GHz real-time oscilloscope (UXR1102A)
BAM prototypeV-cable

Optical Synchronization System𝑆ZC (3.45 pC) ≈ 99.27 ± 10.62

mV
ps

Lead encasementfor UXR1102A
oscilloscope

Set of 1024 measured pulses (gray) & average signal (red)Measurement setup at ELBE

Discussion

Schematic overview of the main building blocks of the optical synchronization system at EuXFEL [1].

mV
𝑆ZC (3.45 pC) ≈ 273.36 ± 34.26
ps

BAM working principle [3].

Scattering parameter of the cable assembly

De-embedded measured pulses (gray) & average (red)Basic cabling layout, adapted from [2].

▪ High attenuation by coaxial cables→ De-embedding necessary:
𝑈meas 𝑓
𝑈PU 𝑡 ≈ IFFT
𝑆21 𝑓

Pickup Design▪ 𝑆ZC ≈ 79.9

mV
ps pC

▪ Slew rate below simulation with optimal material▪ Close to the bunch, the measurement coincides
with a simulation using the same substrate
De-embedded & simulated signal

a = 2.42 mm d = 1.62 mm
b = 5.60 mm h = 6.0 mm
c = 0.70 mm e = 40.50 mm

Conclusions and Outlook

Pickup structure of the state-of-the-art BAM [4].

Slew rate at zero crossing (𝑺𝐙𝐂 ):
mV
15.0
ps pC

[5]

mV𝑆ZC ≈ 187.7
ps pC[6]Cone-shaped: 𝑆ZC >Planar rPCB:

Tapered planar sheet pickups on a reduced
substrate (rPCB), proposed in [6].

▪ Successful proof-of-concept for
PCB-based arrival-time measurement▪ Results promise fs precision down to 2 pC
▪ 1 pC with desired resolution possible:
Thin fused-silica substrate▪ In-depth evaluation of the measurements▪ Bunch charge & length, beam position▪ Measurements with new and old EOM▪ Design of an improved prototype▪ Final BAM design for FLASH & EuXFEL

References

67-GHz PCB-BAM Prototype for ELBE

[1] T. Lamb et al, in Proc. IPAC’19, pp 3835 - 3838. doi:10.18429/JACoW-IPAC2019-THPRB018[2] H. Dinter et al., in Proc. FEL’15, pp. 478–482. doi:10.18429/JACoW-FEL2015-TUP049.
[3] F. Löhl et al., Phys. Rev. Lett., Vol.104, No.14, 2010. doi: 10.1103/PhysRevLett.104.144801[4] A. Angelovski et al., Phys. Rev. ST Accel. Beams 15, 2012. doi:10.1103/PhysRevSTAB.15.112803[5] A. Angelovski et al., IBIC’2013, pp. 778-781. paper WEPC40[6] B. E. J. Scheible et al., IPAC’23, pp. 4828-4831. doi:/JACoW-IPAC2023-THPL190 (pre-press)

feedthrough module
dowel pin

DN25 CF

Acknowledgements

67-GHzconnector

DN40 CFPCB

3.6 cmModel of the feedthrough module (left) & raw
additive manufactured part without flange (right).
sheet
pickups

stopper
dowel pin

Manufacturing model (in Inventor®) of the firstvacuum-sealed prototype for ELBE at HZDR.

Printed Circuit Board (PCB):▪ Substrate: 380 μm TMM® 10i▪ Cladding: 35 μm Copper▪ In-house fabrication at THM

Vacuum sealed body:▪ Stainless steel 1.4301▪ Feedthrough module (DN25 CF)▪ Manufactured by NTG

TUP012
Bernhard E. J. Scheible
bernhard.scheible@iem.thm.dehere at booth 10

Related WorkvCard

Presenter:

Work supported by the German Federal Ministry of Education and Research (BMBF) undercontracts No. 05K19RO1 and No. 05K22RO2. We would like to thank Keysight for their generous
offer, to provide the UXR1102A oscilloscope for these measurements, as well as Dr. Thomas
Kirchner from Keysight, for his technical support. We would also like to thank the HelmholtzZentrum Dresden Rossendorf (HZDR) for granting us beam time and all the staff involved ininstalling the BAM or working in the control room during measurements. Finally, we would also liketo thank Neue Technologien GmbH & Co. KG (NTG) for the close cooperation during constructionof the prototype and the opportunity to carry out the final assembly on their premises.

Technische Hochschule Mittelhessen
Information Technology | Electrical Engineering | Mechatronics

IBIC’19

IBIC’20PRAB (21)IBIC’21

IPAC’22

IBIC’22

IPAC’23