Stretched Wire Measurements on Medium Bore Booster Cavity

Stretched Wire Measurements on Medium Bore Booster Cavity Robyn Madrak, Chandra Bhat, and John Reid Joint PSP/Taskforce Meeting 08 October 2020

Medium Bore Cavity • Needs to be modified (ferrites) to get the necessary f vs. Ibias – Bias current necessary right now to get to 53 MHz is too high • John temporarily modified the bias supply to go to higher current for a short time so that we could perform measurements • High power test is complete • We measured mode frequencies, Q, and S 21 2 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements

Wires have matching resistors (not shown) 3 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements

Setup Rsh(1 gap) • Single gap impedance = Rsh(1 gap) • This is the final number which is corrected for everything 4 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements

Measurement of S 21 with Mock beampipe only Rsh(1 gap) Rbp S 21, bp meas was -27. 2 in d. B => Rbp = 574 ohms • 5 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements

Rsh(1 gap) Rbp + 2 Rsh(1 gap) • 6 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements

Tim Berenc PA note Kathy Harkay thesis 7 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements

Comparison of Fundamental Mode Results Single Gap Impedance Measurements 60 Harkay, 1993 Rsh(k. Ohm) 50 3. 25" bore, 2020 Berenc PA note, 2001 40 3. 25" bore, corrected for Q(no wire)/Q(wire) 30 20 10 0 35 40 45 f(MHz) 50 55 Note: ferrite mu and losses for same frequency are lower, due to higher bias 8 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements

Example Q comparison Q with and without wire at 3000 A 2000 3000 A, Q no wire 1800 3000 A, Q with wire 1600 1400 Q 1200 1000 800 600 400 200 0 0 9 100 200 300 f(MHz) 400 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements 500 600

Legacy Cavity Measurements Single Gap Impedance, Kathy Harkay, 1993 25 t=9 ms 12 15 17 18 19 20 21 23 25 29 t = 35 ms Rsh(k. Ohm) 20 15 10 5 0 10 0 50 100 150 200 f(MHz) 250 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements 300 350 400

Comparison for HOMs up to 210 MHz 15 17 18 19 20 21 23 25 29 35 250 A 500 A 1000 A 2000 A 3000 A Single Gap Impedance Measurements, HOMs, up to 220 MHz 7 6 Rsh(k. Ohm) 5 4 3 2 1 0 11 60 80 100 120 140 f(MHz) 160 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements 180 200 220

Comparison of HOMs above 210 MHz Single Gap Impedance Measurements, HOMs, 210 - 500 MHz 7 15 17 18 6 19 20 Rsh(k. Ohm) 5 21 23 4 25 3 29 35 2 250 A 500 A 1 1000 A 0 12 2000 A 210 260 310 360 f(MHz) 410 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements 460 510 3000 A

Conclusion • Fundamental Impedance is higher in medium bore prototype than in legacy cavity at higher currents – Not surprising since losses are smaller at higher I • It does not appear that HOMs are any worse than in a legacy booster cavity 13 10/8/2020 Robyn Madrak | Medium Bore Stretched Wire Measurements