Progress with High Bandwidth Transverse Feedback CERN - May 2015 Reported by W. Hofle

Overview Progress with stripline kickers Progress with slot-line kicker, CERN concentrates on this MD results, December 2014 (old kickers) and April 2015 (new kickers) Closed orbit suppression, improved phase compensation electronics work at CERN in collaboration with LARP team (new fellow started, students from LARP) Control with Q20, slow advance. MD work concentrated on single bunch and Q26 as the first (and easier) step H. Bartosik and B. Salvant reproducing “real” TMCI unstable beam  fast instability ! US LARP meeting ongoing  will present more results at LIU at a later stage; positive feedback, funding by LARP until 2016 review

Kicker designs Tests before LS1 with exponential stripline, i.e. existing pick-up used as kicker  bandwidth limited to 200 MHz The two new kicker designs: 1 GHz bandwidth LARP (SLAC, LBNL), INFN, CERN electromagnetic design needs completion  mechanical design can commence Slot-line (“Faltin” type) Strip-line Electromagnetic design completed (S. De Santis) Mechanical design at CERN (BE-RF-PM) Fabrication under supervision of BE-RF-PM Installation of two kickers completed in LS1, one spare, one kicker equipped with 2x 250 W amplifiers J. Cesaratto see J. Cesaratto et al. (2013) CERN ACC-Note SLAC-R-1037

Complementarity of strip and slot-line

Stripline kicker installation in SPS LSS3+ shielded bellows kicker equipped with amplifiers elliptical bellows kicker without amplifiers  observation of beam induced signals possible thermal tests alignment vacuum impedance Insulation (flanges) feed-throughs (up to 2 kW by design) Cables ECR (being updated EDMS ) naming (ADKCV) E. Montesinos, D. Aguilera Murciano, S. Calvo.

Bench Measurements strip-line at CERN 107 Ω 57 Ω π π NWA Δ 50 Ω π π Δ NWA 57 Ω -10 dB 107 Ω 57 Ω π π π π NWA Δ 57 Ω -10 dB NWA Δ Thru Measurement -10 dB S. De Santis

Results of Bench Meaurements Oscillations around 500 and 2 GHz due to imperfect matching of the measuring wires. Also, high order modes propagate above 1.5 GHz. Values are quite close to estimates from CST model. S. De Santis

Strip-line: Shunt impedance Using CST Microwave Studio we can simulate the classical 2-wire method for measuring the kicker shunt impedance. Blue curve is the actual kicker model. Red curve is same length, untapered, striplines. Dotted curve is the theoretical impedance using analytical formulas.

Strip-line kickers as installed completed installation of amplifiers for one strip-line before 2015 start-up selected location with low radiation (below last quadrupole of StraightSection) special monitoring of radiation levels put in place (CERN R2E team)

Time domain amplifier response Visit of R&K at CERN in spring 2015, commissioning of amplifiers Control circuits: U. Wehrle

R&K amplifiers 5 MHz  1 GHz, 250 W Need to re-visit and re-design the overall phase equalizing circuit

R&K amplifiers 5 MHz  1 GHz, 250 W

Phase response cable to new kicker a = b = c = d = fit: length factor with respect to sample length: 7.85 (from comparison with in-situ measurement) length if sample length is m  m; sample length of lab sample taken from Gerd for one way to kicker

Phase response cable to new kicker a = b = c = d =  = ns this term is displayed

Strip-line beam induced signals 780 V 195 V upstream port (load) downstream port (amp) 3.5x10 11 protons bunch – sigma 333 ps Even mode stripline impedance: 74 Ω Stripline ports impedance: 50 Ω C. Zannini, B. Salvant

Measured beam induced signals mV x 20 = - 5 V 300 mV x 141 = 42 V downstream upstream 1.7x10 11 protons/bunch 4  = 2.7 ns attenuation: 800 MHz: 3.8 dB/100 m 400 MHz: 2.4 dB/100 m 200 MHz: 1.65 dB/100 m preliminary U. Wehrle

Slot-line kicker design and fabrication Fixation pins to hold the electrode to the body in order to prevent it from bending & to provide as much as possible thermal transfer to the body, material choices need input from thermal calculations 1180 mm long copper electrode Mechanical design/fabrication: Refined electromagnetic design: see J. Cesaratto et al. (2013) CERN ACC-Note SLAC-R-1037 E. Montesinos, D. Aguilera Murciano S. Calvo. S. Verdu (matching)  see separate talk T. Rogen, R. Calaga (thermal) M. Wendt (time domain) Work in progress design for 2x2 kW amplifier power

Manufacturing considerations for slotline If built all-in-one, on the inner side, sharp edges of the slits are difficult to round off

Slot-line kicker: material choices for supports ItemPorosity Thermal conductivity [W/mC] Maximum operating T [C] Dielectric constant ԐrLoss angle Youngs Modulus [GPa] Aluminum nitride (AIN) x10-4 (1 MHz) Boron Nitride Alumina Vespel (23 C, 1KHz) (1 MHz) PEEK (23 C, 1 KHz) (25 C, 1MHz)4.0 “Blue stone”(3D printing material) Sapphire4111.5/9.3<1 (1 MHz)470 Diamond x MACOR (25 C, 1 KHz)4.7x10-3 (25 C, 1KHz)66.9 Shapal Tan 10 x 10-4 E. Montesinos, D. Aguilera Murciano, S. Calvo.

Model for thermal calculations T. Roggen

Thermal calculations Work in progress assume 700 MHz, 2 kW cw per strip Feed-through critical: more detailed simulation required assumptions on boundary conditions also critical T. Roggen

Matching of slot-line (S. Verdu)

Time domain simulation Shapal spacers Coaxial-to-stripline transition, based on Kyocera RF UHV feedthrough M. Wendt

Time domain (w/o coax to strip transition) Z0Z0 Z 0e Z 0o

MD results December (old kicker) open loop

MD results December (old kicker) closed loop

MD results with new kicker

Q20 controller design

Summary and outlook Stripline kickers ready for use as planned One strip-line equipped with amplifiers already used with beam, permits now MDs with larger bandwidth Second strip-line will be equipped once sure about radiation resistance of power amplifiers for period of demonstrator and frequency response circuits are optimised Slot-line kicker design ongoing, thermal calculations critical for material choices and detailed mechanical design To do: firmware for treating bunch train ! I would like to acknowledge the excellent progress made by the US LARP team and all contributors at CERN as well as at INFN Frascati and KEK for their participation and advice.