1pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems

Peter Quigley

2pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:Overview

• RF Hardware

• Cryogenic Systems

• Warmup/Cooldown

• Tuning

• RF Control

• Future Plans

3pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems: RF HardwareInjector Cryomodule (ICM)

1.3 GHz 2-cell SRFcavity, blade tuner.

HOM load at 80Kbetween cavities

Twin Input PowerCoupler

Number of 2-cell cavities 5 Number of HOM loads 6

Energy gain per cavity 1 – 3 MeV HOM Power per cavity 40 W

Gradient 4.3 – 13.0 MV/m Couplers per cavity 2

R/Q (Linac definition) 222 Ω RF power per cavity 120 kW

Qext 4.6 x 104 – 4.1 x 105 Amplitude/phase stability 10-4/0.1º (rms)

Total 2K / 5K/ 80K loads 30 W / 60 W / 700 W Module Length 5 m

CBETA Operating Temperature 2K Current Temperature 80K

HGRP with three sections

Support Posts300K to 2K

Isolation

µ-metal “Lunch Box”around cavities

Wire Position Monitor (WPM) tube

WPM, (one on each cavity)

4pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems: RF HardwareMain LINAC Cryomodule (MLC)

6 7-cell Cavities• ΔE = 6 MeV• σA/A ~ 10-4, σφ ~ 0.1°

7 HOM Absorbers(Max 400 W)

Based on TESLA cryomodule designwith important differences:• Optimized for CW operation.• Designed for ERLs.• Cavities hang from the HGRP which is

used to align them.

Helium Gas Return Pipe (1 section)Input Power Coupler(Max 10 kW)

2K 2-PhaseHelium Line

5pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

SSAs

5 kW

5 kW

5 kW

10 kW

10 kW

10 kW

RF Power Isolators

• Status:• MLC is currently at 1.2 K (12.5 Torr Helium Pressure).• Vacuum:

• Insulation: 8.0x10-6 Torr• Cavity Beamline: 1.8x10-11 Torr• Input Power Couplers: 6.0x10-10 Torr (average of six couplers)

Stiffened CavityStiffening Rings

Unstiffened Cavity

Input Power Coupler

40K Flange and cooling

Warm Ceramic Window

BellowsCavity

Flange (1.8)

Antenna 5K Intercept

Cold Ceramic WindowInstrumentation Port

Air Cooling

Waveguide Flange

Pump Port

300K Flange

Slow Cavity Tuner

3- Stub WGTuner

Piezo Tuner

2K TunerMotor

CBETA RF Systems: RF HardwareMain LINAC Cryomodule (MLC), Input Coupler, Tuner, Solid State Amplifiers (SSA)

6pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems: RF HardwareWhat Happened Since 2018 AC

• ICM

• Klystron #3 needed solenoid current adjustment.

• ICM delivers 6 MeV reliably.• MLC

• SSA firmware upgrade: 1/20/2019.

• SSA power up with shorted waveguide and interlocks bypassed.

• Tuned cavities with network analyzer. Motors are vulnerable.• CM2, SECOND 1.3 GHZ CRYOMODULE FABRICATION AT FERMILAB* T. Arkan, PAC2013

• Connected RF power to cavities, all initially tested for operation at 6 MeV, no

issues.

7pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems: RF HardwareWhat Happened Since 2018 AC

• MLC (continued)

• SSA operating condition

• Firmware update introduced new bug.

• External interlock trip requires AC power cycle to reset.

• Put external interlocks in series with PPS. Works well enough.

• Working with manufacturer to resolve.

• SSA #6 48 VDC power supply interlock false failure indication.

• Measurements show power supply is working.

• Interlock is bypassed. Checking with manufacturer to see if operating in

this state is ok.

• Ordering spare supply

8pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:MLC SSA Test After RF Power Circulator Repair

All isolators were repaired: (Slide From October 2018 AC)1. Tuning screws were removed and the resistive load were disassembled.

2. Broken ferrite tiles were removed and the load surface was cleaned.3. Plastic residue was blown out with dry nitrogen.4. The isolator was reassembled and the tuning screws were adjusted to optimize isolation using

a network analyzer.5. All SSAs and isolators were tested to full power CW!

Ferrite damage on 10 kW loads Damage to load surface on 5 kW loads

Loads damaged due to arcing triggered by damaged plastic on tuning screws.

Results of SSA Nominal Power Test After Isolator Repair

Cavity # 1 2 3 4 5 6

Max Pf (kW) 10 5 10 5 10 5

Max Pr (W) 130 18 118 75 13 3.5

9pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems: RF HardwareRF Power Circulators

• RF Power Circulators• AFT refuses to warranty RF power circulator damage.

• Concern is water leak on cooling plate in pitted locations.

• Adding automatic valve for cooling water ON/OFF.

• Agreed to fix at factory but confidence in a timely turn around is low.

• Requesting that AFT send new ferrite plates for repairs to be done at Cornell.

Port 1

Port 2Port 3

Water Cooled Ferrite Load InsideTapered Waveguide

Tuning Screws

Arc Detector Port

New

Damaged • Isolators tuning screw insulatordisintegrated on the initial testdepositing a power-like substanceon the interior surface.

• No Arcing detected at any timeduring RF operations.

10pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:Cryogenics

• Cryogenic Systems:

• Added sleeves to all MLC cryogenic valves (microphonics suppression).

• Modified MLC cryogenic pumping lines to mitigate oil flow between skids.

• Checking microphonics impact when using different pump skids.

• 2K 2-Phase Helium Level Control:

• RF OFF: JT regulates helium level.

• RF ON: Either 2K 2-Phase heater or the JT regulates helium level.

• Working on optimizing both.

11pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:Warmup/ Cooldown

• Warmup/Cooldown:• ICM

• Idle at 80K since 6/14/2018 through 2/28/2019.

• Cooldown to 2K 3/4/2019, no issues.• MLC

• (Warmed to room temperature 5/23/2018.)

• MLC Beamline height correction: 3/4/2019

• Beam based measurements show beam line is ~4 mm too high.

• Survey could only account for 2 mm offset.

• Beamline thermal shrinkage ~1 mm.

• Lowered MLC vacuum vessel 2mm, beamline 1.2mm (Next Slide).

12pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:MLC Vertical Offset

Lowered MLC vacuum vessel 2mm

• Thermal shrinkage is~1.2 mm. Notaccounted for duringMLC assembly.

Two room temperatureheight adjustmentscrews on each supportpost.

• Survey shows ~ 1mmerror on the BPMposition.

BPM just downstream of theMLC exit flange.

MLC Support Stand

• Beam based measurements show beam line is ~4 mmtoo high.

• Survey could only account for 2 mm offset.• Beamline thermal shrinkage ~1 mm• Lowered MLC vacuum vessel 2mm, beamline 1.2mm

13pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:MLC Cooldown March 2019

14pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:Cavity Tuning

• Tuning

• ICM Cavity #2 cannot be tuned to 1299.9 MHz, detuned, Klystron HVdisconnected.

• MLC cavity #6 mechanical tuner limit forces the CBETA operatingfrequency to be 1299.9 MHz.

• This tuner is not easily accessible in-situ. Risky, Time consuming.

15pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

MLC Tuner Motor Harmonic Drive

16pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

• ICM

• Cavities require occasional tuning otherwise operation is reliable.

• Field stability is optimized

• MLC

• Microphonics and LDF compensation is working well.

CBETA RF Systems:Cavity Tuning

17pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:RF Control

• RF Control

• MLC cavity field stability.

• Measured noise/crosstalk on LLRF cavity field signal.

• ICM ~1 kV rms.

• MLC ~10 kV rms.

• Likely source being on the RF high power side.

• Waveguide is a likely source.

• Flanges.

• Directional couplers.

• RF leak checking on the schedule.

• Cavity #5 is not operating in klystron or cavity loop.

• Investigating.

18pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

MLC Microphonics

Cavity Stiffened Old PeakDetuning (Hz)

New PeakDetuning (Hz)

Major VibrationFrequencies (Hz)

Field (MV)

1 No 30 40 41, 59 6

2 Yes 25 29 41, 100 6

3 No 50 45 41, 59, 100 6

4 Yes 20 19 100 6

5 No 41 41 8, 41, 59 6

6 Yes 18 25 8, 41 6

Slight increase in peak microphonics detuning on most cavities, but we are still within ourRF power budget for 36 MeV operations. Slide By Nilanjan Banerjee

19pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:Future Plans

• RF• Continue to optimize loop parameters as conditions require.• Measure and characterize RF noise/vibration sources

• Mechanical• New vibration sources added since FAT.

• Added additional cryogenic valve sleeves.• Cause return of the 41 Hz vibration?

• Cooling ventilation duct work.• Cooling water systems.• New equipment platform.• New cable tray and conduits.

• Clamp waveguides with Sorbothan.• Decouple SSA waveguide from Klystron mezzanine.• Measure 2K Helium pumping line vibrations, (using different skids).

• Electrical:• Locate and isolate RF leaks.• Shield electronics if necessary.• Check for ground currents/loops.

• A fair amount of ground connections were made according to electricalcode requirements.

• Cryogenics• Continue to optimize loop parameters as operating conditions require.• Automating Skid bypass control valves.

20pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:Conclusion

• CBETA RF Systems have delivered up to 59 MeV energy gain, (during FAT) and can

reliably deliver 42 MeV.

• CBETA RF system Team continues to work system optimization and address issues

both current and as they arise.

21pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

Extra Slides Follow

22pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

Initial Test of Solid State RF Power Amplifiers (SSA)(Power is not applied to cavity, See test setup)

SSA NominalPower

SSA SerialNumber

MLCCavity

PeakForward

Power (Pf)(kW)

Peak ForwarPower (Pr)

(kW)

SSA DisipatedPower(kW)

RF PowerIsolator

DissipatedPower (kW)

RF PowerIsolator HighTemperature

(°C)

Comments

10 kW0001 #5 9.03 0.31 15.40 8.90 62 Cable Over heated on SSA power module #20002 #3 9.52 0.15 13.20 9.00 74 Trip on high Pf high Pr

0003 #1 10.00 0.43 12.50 11.40 72 No Issues

5 kW0001 #6 4.55 0.31 5.10 8.90 90 High isolator temperature0002 #4 3.00 0.30 2.90 No Data 35 Trip cause unknown. Pulse operation to 5 kW0003 #2 5.02 0.15 5.20 7.00 37 No Issues

Port 1

Port 2Port 3

Water Cooled FerriteLoad Inside TaperedWaveguide

Tuning ScrewsArc Detector Port

Isolator (AFT)

SSA (SigmaPhi)

3 Stub Tuner

DirectionalCoupler

Short install atwaveguide output

SSA Test Setup

New

Damaged

CBETA RF Systems: MLCSolid State Amplifier (SSA) Initial Test

• Isolators tuning screw insulatordisintegrated on the initial testdepositing a power-like substanceon the interior surface.

• No Arcing detected at any timeduring RF operations.

Circulating Ferrites(Slide From October 2018 AC)

23pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

25

27

29

31

33

35

37

39

41

0 2000 4000 6000 8000 10000 12000

Tem

pera

ture

(°C)

Time (seconds)

AFT Isolator Tuning Screw TemperatureDuring SSA Nominal Power Test

SN-1040621 SN-1040195SN-1040620 SN-1040196SN-1040619 SN-1040194

Pf = 5kW

Pf = 10kW Peak

10kWIsolator

5kWIsolator

AFT Isolator tuning screw temperature during high power test followingtuning screw insulator replacement. Tests were not simultaneous andduration of tests varied for arbitrary reasons.

CBETA RF Systems: MLCSSA Test After Isolator Repairs

Temperature monitoredat this location

Port 1

Port 2Port 3

Water Cooled FerriteLoad Inside TaperedWaveguide

Tuning ScrewsArc Detector Port

(Slide From October 2018 AC)

24pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

Energy Scan

The MLC successfully reached an energy gain of 53.2 MeV during operations.

• Isolator screw temperatures werebelow 30 C at all times!

• Peak blower speed was 67.5% forboth skids.

Exceeded design energy gain by 50%!

TimeCavity #1 Cavity #2 Cavity #3 Cavity #4 Cavity #5 Cavity #6

Field(MV) Pf (W) Pr (W) Field

(MV)Pf

(W) Pr (W) Field(MV) Pf (W) Pr (W) Field

(MV) Pf (W) Pr (W) Field(MV) Pf (W) Pr (W) Field

(MV) Pf (W) Pr (W)

19:45 6 260 385 6 208 198 6 180 161 6 195 319 6 240 35 11 790 1000 47

19:32 6 260 385 6 208 198 6 180 161 8 353 579 6 241 36 11 791 1001 49

19:58 6 260 385 8 375 356 6 180 161 8 353 579 6 242 37 11 792 1002 51

20:00 6 260 385 8 375 356 6 180 161 8 353 579 8 446 62 11 793 1003 53

21:20 9.25 609 900 8 375 356 7.5 288 257 8.5 399 652 8.5 503 70 11.25 833 1115 59

21:31 9.45 614 900 8 375 356 7.5 288 257 8.4 390 638 8.5 503 70 11.35 849 1135 59.2

Total Energy Gain (6 MeV from ICM)

SSA Isolator Temperature30

29

27

26

28

Kelv

ins

Time (Hours)-20 -15 -10 -5 22:45:16

May 18, 2018

(Slide From October 2018 AC)

25pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

CBETA RF Systems:MLC Tuning

• Tuner assembly mounted on unstiffened cavity.

26pgq1@cornell.edu - May 9, 2019 – CBETA Advisory Committee Meeting, Cornell

Waveguide motion showing effect of strikingthe structure in the “wrong” spot.

Slide By Tom Powers, LLRF Microphonics Workshop Oct. 201826

• I made the mistake of striking the waveguide at point 2 which made it look like the secondwaveguide from the left was more sensitive than all of the rest.

• I should have struck it on the insulating vessel at one end of in the center in order to excite allof the waveguides about the same.

• Even still we got the information that we needed as this design had a beam between all of thewaveguides and we found a 20 Hz mode of that structure which would have been “amplified”to the 21 Hz half string mode when it got to the cavities.