Overview of Thesis 1. Design of the room temperature QWR for PXIE MEBT 2. Studies of the slow frequency tuner for 650 MHz cavities 3. Analysis of the LFD compensation in long pulse operation test in CM1 at NML Roman Kostin APC Beam Physics Meeting, May 18, 2012
Overview of Thesis 1. Design of the room temperature QWR for PXIE MEBT 2. Studies of the slow frequency tuner for 650 MHz cavities 3. Analysis of the LFD compensation in long pulse operation test in CM1 at NML
Mechanical Design of Room Temperature Quarter Wave Buncher Tuners ports
Main RF Parameters
Tuner Goal: Range of frequency change 200 kHz for two tuners Detuning range vs. tuner insertion for two different diameters of tuner Frequency detuning (kHz) Length, L (mm)
Frequency change due to Atmospheric pressure Units mm inches Thickness of cylindrical wall 7,937 5/16 Thickness of Up and Bottom walls 9,525 3/8 Total displacement (left) and von Mises stresses of CW re-buncher under 1 atm pressure. Frequency of undeformed cavity, MHz 162,420376 Yield Stress Frequency of deformed cavity, MHz 162,416223 250 MPa -4,1 Frequency shift, kHz
Termo Analysis for two designs of cooling channel in the spoke (Voltage 130 kV) Two types of cooling channels: • Inside spoke • In cylindrical part of cavity Table: Parameters of cooling system Inside In spoke cylindrical Inner diameter of cooling channel d, mm 4,73 5,95 Temperature of cooling water, о С 30 30 Velocity of water, m/s 3 3 Convection coefficient, W/(m 2о С ) 14700 14100 “All around tubing” design (left) and “V -Channel ” design *Note: Nominal Voltage is 70 kV (right)
“V - channel” Design 30.5 64.7 Temperature distribution ( T° C) Geometry Voltage 130 kV
Deformation and stresses Yield Stress 250 MPa 4000 8E6 0 0.95E-4 Displacements, m Von Mises Stress, Pa Frequency of undeformed cavity, MHz 162,420336 Frequency of deformed cavity, MHz 162,371870 Frequency shift, kHz -48,466
“All around tubing” Design 30.5 50.5 Geometry Temperature distribution ( T° C) Voltage 130 kV
“All - around tubing”: Deformation and stresses Yield Stress 250 MPa 8910 120E6 Displacements, m Von Mises Stress, Pa Frequency of undeformed cavity, MHz 162,421487 Frequency of deformed cavity, MHz 162,383582 Frequency shift, kHz -37,9
“All Around Tubing” Design for V=100 kV 0 30.3 41.5 0.3E-4 Temperature distribution (T° C) Displacements (m)
Yield Stress 250 MPa 5003 6.72E6 Von Mises Stress, Pa Frequency of undeformed cavity, MHz 162,421487 Frequency of deformed cavity, MHz 162,400165 -21,3 Frequency shift, kHz
Spoke Vibration: Stability requirements Goals: • Determine frequencies of mechanical modes • Determine Amplitude of ground motion and evaluate amplitude of the spoke oscillation • Determine a value of spoke shift to exceed the criteria of stability RF constrains from Beam dynamics: • Shift of the Phase < 1 degree • Reduction of the Gain < 1 keV
Natural frequencies of QWR Perpendicular Oscillations 134 Hz 351 Hz 418 Hz
Longitudinal Oscillations 110 Hz 342 Hz 418 Hz
Ground Motion data Was taken the most noisy case, i.e. HERA. Simplified mechanical model: Stiffness of the Spoke k, MN/m 0.2 Ground Motion Amplitude A g , nm 1 Q 1000 Mass of the Spoke m, kg 2.5 Resonance frequency f 0 , Hz 110 Spoke Amplitude X max , mkm 0.6
Deviation of cavity amplitude and phase vs. amplitude of spoke shift.
Summary • The tuner design is fixed to 40 mm dia. Two of them will provide the frequency up to 200 kHz. • Frequency shift because of the atmosphere pressure is -4.1 kHz • Expected frequency shift due to heating for 100 kV is -21.3 kHz • Expected amplitude of vibration of the spoke because of the ground motion is far away to exceed criteria of stability (0.6 mkm << 600 mkm) • The QWR design meets all requirements
Overview of Thesis 1. Design of the room temperature QWR for PXIE MEBT 2. Studies of the slow frequency tuner for 650 MHz cavities 3. Analysis of the LFD compensation in long pulse operation test in CM1 at NML
Principle (similar to Saclay I tuner) Tuners tested in HoBiCaT Modified piezo holder frame: Higher wall thickness Oct. 19-29, 2008 Lecture 7: SCRF & ILC
Principle (similar to Saclay I tuner) Tuners tested in HoBiCaT Modified piezo holder frame: Higher wall thickness Oct. 19-29, 2008 Lecture 7: SCRF & ILC
Tuner for 650 MHz elliptical cavity with β=0.61 Frequency range, kHz 200 Advantage (transformation ratio) 30 Cavity Sensitivity, Hz/mkm 300 Cavity Stiffness, kN/mm 19
Geometry of Half Model Bars Joint 2 Driving Lever Joint 1 Driving Pin Pins for Driving Motor Main Lever Joint 3
Analysis without Cavity Displacements Displacements, m
Stress Von Mises Stress, Pa
Analysis with Cavity Displacements Displacements, m
Stress Von Mises Stress, Pa
Summary • ANSYS Analysis shows that proposed model is fully operational • Advantage is about 30 • Maximum value of stress is far away from yield stress of stainless steel ( 400 MPa) Without Cavity With Cavity 38.9 Advantage 32.5 56 Max Stress, MPa 9.4
Overview of Thesis 1. Design of the room temperature QWR for PXIE MEBT 2. Studies of the slow frequency tuner for 650 MHz cavities 3. Analysis of the LFD compensation in long pulse operation test in CM1 at NML
Project X Pulsed Linac requirements • TESLA-style cavity. Gradient 25 MV/m, Q L =1·10 7 ; • LFD below 20 – 30 Hz • Long RF Pulse 9 ms, were fill time is 4 ms and flattop is 5 ms
Data were collected from CM1 in NML Was used only one 120 kW klystron, because of that only two cavities were powered (#5 and #6) Collected data consist 3 cases Q L : 3·10 6 ; 6·10 6 ; 1·10 7 ; E acc : 18MV/m; 25 MV/m; 24.5 MV/m; RF power per cavity: 40 kW; 50 kW, 60 kW
LORENTZ FORCE COMPENSATION FOR LONG PULSES IN SRF CAVITIES LFD Compensation in C5 and C6 during a 9ms RF pulse at E acc =25MV/m and Q L = 6*10 7 . (A): Baseband envelopes of the forward and cavity field probe signals. (B): Residual detuning using following compensation. Adaptive LFD algorithm. (C): Piezo drive waveforms.
Summary • In all 3 cases detuning pk-to-pk is about ±10 Hz • Analyzing shape of forward signal were discovered that were used wrong settings for cavity gradient • Vector Sum of Amplitude and Phase much more stable than for individual cavities
Special thanks to: • N. Solyak • V. Yakovlev I am very • W. Schappert pleased to • Y. Pischalnikov work with • I. Gonin you! • G. Romanov • E. Borisov
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