Lband klystron development for the CLIC Drive Beam

L-band klystron development for the CLIC Drive Beam Ø Drive Beam klystron requirements Ø Optimization of parameters Ø Development and purchasing strategy and status CLIC workshop, CERN, February 3 rd-7 th, 2014 Steffen Döbert, BE-RF

CLIC Layout at 3 Te. V Drive Beam Generation Complex Main Beam Generation Complex 2

CLIC DB front end, Post CDR Project Modulator-klystrons, 1 GHz, 15 MW 500 MHz Diagnostics Gun SHB 1 -2 -3 PB ~ 140 ke. V Buncher ~ 3 Me. V Acc. Structures ~ 12 Me. V For time being only major component development: GUN, SHB, high bandwidth 500 MHz source, 1 GHZ MBK, modulator and fully loaded accelerating structure

CLIC Drive Beam requirements 3 Te. V CLIC (CDR): 1638 klystrons, 15 MW, 150 ms, 50 Hz 24. 57 GW peak power, 184 MW average 0. 05 º intra bunch jitter, 0. 2% amplitude 500 Ge. V about half the klystrons and factor 6 in beam power depending on scenario Main power ‘eater’ in CLIC (~50 % for 3 Te. V)

CLIC Drive Beam optimization • Rebaselineing effort after the CDR with emphasis on low energy machine, cost and power consumption • Obviously drive beam and its power source in the focus • On the other hand need to fix some parameters to start developing hardware which takes a long time • Frequency dependence on cost and power consumption briefly studied • Linac cost studied as a function of klystron peak power

Parameter Studies, Frequency & Power

Frequency dependence Thales assuming constant power

Klystron cost model Ckl = 0. 08 x V + 0. 28 x I 1/3 +0. 2 x V 1/2 + 0. 1 +0. 12 x P + 0. 22 x V 1/2 P 1/10 + t 1/2. 75 Gun Where Body RF circuit ⇨ Collector Solenoid Pulse length Ckl = Ckl (Pk) Fixing efficiency (=70%) and number of beamlets Igor Syratchev, Roberto Corsini

Klystron cost vs peak power Klystron cost scaling with peak power Erk Igor Erk Per MW h=0. 5 h~0. 2+0. 3 x. Voltage 3 h=0. 2 Per tube Igor Applying learning curves and lifetime evaluation Roberto Corsini

Total cost klystron/modulator Total cost of klystron/modulators units as a function of Pklystron [MCHF] Update, Davide’s model [MW] Roberto Corsini

Total Linac cost Total cost [GCHF] t [us] [GCHF] Pk [MW] t [us] Pk [MW] Roberto Corsini

Klystron parameters PARAMETER RF Frequency VALUE 999. 516 UNITS MHz Bandwidth at -1 d. B ≥ 1 MHz RF Power: Peak Power ≥ 20 MW Average Power 150 k. W RF Pulse width (at -3 d. B) 150 μs HV pulse width (at full width half height) 165 μs Repetition Rate 50 Hz High Voltage applied to the cathode tbd, ≤ 180 k. V Tolerable peak reverse voltage tbd k. V Efficiency at peak power 67 ≤ 70 % RF gain at peak power tbd, > 48 d. B Perveance tbd μA/V 1. 5 Stability of RF output signal at nominal working point RF phase ripple [*] ± 1 (max) RF deg RF amplitude ripple ± 1 (max) % Pulse failures (arcs etc. ) during 14 hour continuous test period < 1 -2 Matching load, fundamental and 2 nd harmonic tbd VSWR Average radiation at 0. 1 m distance from klystron < 1 μSv/h Output waveguide type, WR 975 pressurised 2 -3 bar

State of the Art

State of the Art

State of the Art In terms of achieved RF efficiency, the klystrons with RF circuit adopted by Toshiba and CPI provides values very close to the 70%, as is specified in CLIC CDR (67. 8% for CPI and 68. 8% for Toshiba. These values validate the feasibility of a slightly higher efficiency with minimised design/fabrication efforts, when scaled in frequency down to 1. 0 GHz. Igor Syratchev

Tentative klystron parameters Efficiency for 20 MW for different voltages (Thales study)

Parameter Studies

Status of the CLIC L-band klystron • Strategy: Try to develop prototypes with two different vendors to minimize technical and financial risk • Launched call for tender for design and prototype fabrication of such klystrons with the CLIC specifications • In parallel modulator development program in the power group • Frist contract signed with Thales ? • Preparing second one for next finance committee in March

Tentative Development schedule Thales

Klystron Test Stand Together with the Modulator team a test stand will be created to test the rf unit in detail with special emphasis on the stability measurements Structure test bunker Modulator MBK Load Acc Structure LLRF: Driver and Diagnostics Feedback ? Possible location: Bldg: 112

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Parameter Studies