Report

SRF Results and Requirements cavities, coupler, tuner, HOM loads, & SC magnet MLC Review October 3, 2012 Matthias Liepe 1 One-Cavity Unit Beamline HOM absorber SRF cavity inside LHe tank RF input coupler Cavity frequency tuner Matthias Liepe 2 SRF Cavity Matthias Liepe 3 ERL Main Linac SRF Cavity Static Heat Load 1.8 K <1 W Dynamic Dynamic Load Load (worst (average) case) 11 W/cavity 44 W/cavity Parameter Accelerating mode Fundamental frequency Design gradient Intrinsic quality factor Loaded quality factor Cavity half bandwidth at QL= 6.5107 Operating temperature Number of cells Active length Cell-to-cell coupling (fundamental mode) Iris diameter center cell / end cells Beam tube diameter Geometry factor (fundamental mode) R/Q (fundamental mode) Epeak/Eacc (fundamental mode) Hpeak/Eacc (fundamental mode) f/L Lorentz-force detuning constant Cavity longitudinal loss factor for σ=0.6mm, non-fundamental Cavity transverse loss factor for σ=0.6mm Matthias Liepe Value TM010 1300 MHz 16.2 MV/m >21010 6.5107 10 Hz 1.8K 7 0.81 m 2.2% 36 mm / 36 mm 110 mm 270.7 Ohm 387 Ohm 2.06 41.96 Oe/(MV/m) 1.6 kHz/mm ~1.5 Hz / (MV/m)^2 13.1 V/pC 13.7 V/pC/m 4 Prototype Cavity Fabrication Electron Beam Welding Quality control: CMM and frequency check Finished main linac cavity with very tight (±0.25 mm) shape precision important for supporting high currents (avoid risk of trapped HOMs!) Matthias Liepe 5 Full System Test of a 1-Cavity Main Linac Unit in a Cryomodule 80K shield HGRP Gate valve HOM load cavity HOM load First full main linac system test • 1st test: cavity and tuner only (completed) • 2nd test: add high power RF input coupler (under test) • 3rd test: add HOM beamline loads (next year) Test cryomodule installed at Wilson Lab Matthias Liepe 6 1st Cryomodule Test of ERL Main Linac Cavity (with high Qext input coupler) Cavity surface was prepared for high Q0 while keeping it as simple as possible: bulk BCP, 650C outgassing, final BCP, 120C bake Administrative limit. Cavity can go to higher fields Cavity exceeds ERL gradient and Q0 specifications: Q0=4 to 61010 at 1.6K in a cryomodule! Matthias Liepe 7 Quality factor Q0 2nd Cryomodule Test of ERL Main Linac Cavity (with RF input coupler) Q0 ~ 2*1010 at 16 MV/m and 1.8 K Eacc [MV/m] Matthias Liepe 8 High Q0 Results from Elsewhere Average performance of eight 9-cell cavities in a FLASH cryomodule at DESY 9-cell Cavity test in Horizontal Test Cryostat at HZB 1.6K 1.8K 2K Q0 ~ 2*1010 at 16 MV/m and 1.8 K Q0 > 2*1010 at 16 MV/m and 1.8 K Matthias Liepe 9 Alignment Results from the Injector Cryomodule using fixed Supports • High precision supports on cavities, HOM loads, and HGRP for “self” alignment of beam line – Rigid, stable support – Shift of beamline during cool-down as predicted X position [mm] • Cavity string is aligned to 0.2 mm after cooldown! 1.00 0.50 X1 [mm] 0.00 -0.50 X3 [mm] ERL Injector Cooldown WPM Horizontal X4 [mm] X5 [mm] -1.00 4/29/08 0:00 4/30/08 0:00 Date-Time Matthias Liepe 5/1/08 0:00 5/2/08 0:00 10 MLC Requirements: Cavities • RF performance: – 16.2 MV/m (13 MV) average (5GeV from 384 cavities) • 20 MV/m max (16 MeV) for overhead – Q0 = 2*1010 on average at 16.2 MV/m (~11 W per cavity) • Cryosystem should support individual cavities with Q0>5*109 • Cryosystem should support individual cryomodules with Q0,avg= 1*1010 • Magnetic field at cavity location should be < 3 mG for Rres<1 nOhm • Field stability (assuming non-correlated errors): – Allowable relative amplitude error: (1 sigma) 6*10-3 – Allowable phase error: (1 sigma): 1 deg Matthias Liepe 11 MLC Requirements: Cavities • Alignment: – Cavities: • Allowable transverse offset (x,y): (1 sigma) 2 mm • Allowable pitch (1 sigma): 1.5 mrad (1.2 mm over length of cavity) – Quadrupole: • Allowable transverse offset (x,y): (1 sigma): 1.6 mm Matthias Liepe 12 Input Coupler Matthias Liepe 13 Main Linac RF Input Coupler Design Main Linac Input Coupler Operating frequency 1.3 GHz Maximum power (CW) Qext (fixed) Waveguide Flange 5 kW Warm Ceramic Window 6.5×107 Air Cooling 300K Flange 40K Flange and cooling Cavity Flange (1.8K) Bellows Instrumentation Port Pump Port Antenna 5K Intercept Cold Ceramic Window Matthias Liepe 14 Beamline: Input Coupler • • • • 2 kW average RF power 5 kW peak RF power Fixed coupling Large transverse flexibility (~1 cm transverse motion during cool down) • 5K and 40 – 80 K intercepts Static Heat Load Dynamic Heat Load Full Heat Load To 1.8K 0.05 W 0.06 W 0.11 W To 5K 0.64 W 0.32 W 0.96 W To 40K 3.78 W 5.94 W 9.72 W Matthias Liepe 15 Main Linac RF Input Coupler Prototype and Test • Prototype fabricated and tested successfully • Tested up to full power specification of 5 kW CW Matthias Liepe 16 MLC Requirements: RF Input Coupler • RF input coupler: – 5kW peak – 2 kW CW average – Fixed coupling with Qext = 6.5*107 – >1 cm transverse flexibility for motion during cool down – Cryoloads per coupler: 0.1W at 1.8K, 1W at 5K, 10W at 40K Matthias Liepe 17 Frequency Tuner Matthias Liepe 18 Design of Main Linac Cavity Frequency Tuner Design optimized for CW cavity operation with very high loaded quality factor • High stiffness • Fast piezo actuators for fast control of cavity frequency Stepper motor for slow control Stresses at 26 kN tuner force Piezoelectric actuators for fast control Matthias Liepe 19 Frequency Tuner f [Hz] f [Hz] • Prototype tested successfully with prototype main linac cavity in test cryomodule 500 100 0 • Excellent stiffness and linearity with 80 -500 0 100 200 very small hysteresis 60 Motor Steps - Injector Cavity • >400 kHz slow tuning range 40 • 2 kHz fast piezo tuning range 20 0 0 Matthias Liepe 20 40 60 80 Motor Steps - Main Linac Cavity 100 20 Microphonics Results From the HTC and Elsewhere 4 Counts 80K shield 3 HGRP Gate HOM load valve cavity HOM load x 10 Sigma = 4.6 Hz Peak = 18 Hz 2 1 0 -20 Matthias Liepe -10 0 f [Hz] 10 20 21 MLC Requirements: Frequency Tuner • Frequency tuner and microphonics: – Slow tuner range: ~500 kHz – Fast tuner range: >1 kHz – Peak microphonics detuning: <20 Hz • Sigma ~ 3.3 to 4 Hz (assuming peak = 5 to 6 sigma) • Peak detuning counts (determines maximum RF power)! – 5 kW sufficient for 16.2 MV/m and 20 Hz detuning Matthias Liepe 22 HOM Beamline Load Matthias Liepe 23 HOM Beamline Absorber 40 to 80K intercept Flange for disassembly 5K intercept Flange to cavity Shielded bellow • Broadband SiC absorber ring • Full-circumference heat sink to allow >500W dissipation @ 40K • Includes bellow sections • Flanges allow easy cleaning • Zero-impedance beamline flanges SiC absorber ring brazed to metal ring Matthias Liepe 24 HOM Beamline Absorbers Cavity at 1.8K HOM load at 40 to 80K Cavity at 1.8K 5K intercept 5K intercept 40 to 80K intercept Matthias Liepe 25 MLC Requirements: HOM Load • Beam and HOM damping: – Maximum beam current: 2 * 100 mA (ERL mode) – Bunch charge: 77 pC – Bunch length: 0.6 mm (2 ps) – Longitudinal loss factor of cavity: 13.1 V/pC – Average HOM power per cavity: 200 W at 40K – Peak HOM power per cavity: >400 W at 40K – Average HOM power per module: ~1.4 kW at 40K Matthias Liepe 26 SC Magnet Matthias Liepe 27 Superconducting Magnet • One superconducting quadrupole • X-Y dipoles • Cooled at 1.8 K Matthias Liepe 28 MLC Requirements: SC Magnet • Superconducting quadrupole – Operating temperature: 1.8 K – Maximum current: 110 A – Maximum gradient: 19.4 T/m Matthias Liepe 29 The End Matthias Liepe 30