Status of SRF Modules, LLRF, RF Amplifiers & Network

Dr. Ozlem KARSLIAnkara University

On behalf of TARLA Team

OUTLINE

■ Superconducting Modules

■ Buncher Cavities

■ RF Amplifiers & Network

■ LLRF

■ Conclusion

SRF cavities 1&2TARLA-Cavities 1 and 2 were treated according to the XFEL-recipe (major steps mentioned only):• Main EP (110µm removal)• 800 °C hydrogen degassing• Tuning of pi-mode and field flatness to >98%• Fine EP (40 µm removal)• Control of pi-mode and field flatness (>98%)• Welding of ring & bellow• Control of pi-mode and field flatness (>98%)• Welding of helium vessel• Leak check of helium vessel• Control of pi-mode and field flatness (>98%)

The cavities are currently undergoing the final surface preparation procedures:• High pressure rinsing• 120 °C bake

Afterwards the couplers and components for the horizontal tests at HoBiCaT will be assembled to the cavities.

The achieved RF parameters are listed after the next slide.

SRF cavities 3&4

TARLA-Cavities 3 and 4 were treated according to the XFEL-recipe (major steps mentioned only):• Main EP (110µm removal)• 800 °C hydrogen degassing• Tuning of pi-mode and field flatness to >98%• Fine EP (40 µm removal)• Control of pi-mode and field flatness (>98%)The next steps will be welding of ring and bellow and helium vessel integration.The achieved RF parameters are listed on the next slide.

SRF cavities

Cavity Serial # Status Pi-mode Field flatness

TARLA #1 RI-PL01 In He-vesselFMS installed

1297,354 MHz

96,2 %

TARLA #2 RI-PL02 In He-vesselFMS installed

1297,304 MHz

95,3 %

TARLA #3 RI-CAV003 FMS installed

1297,398 MHz

97,5 %

TARLA #4 RI-CAV004 FMS installed

1297,394 MHz

98,1 %FMS = Field Measurement System – allows measurement of field distribution in a clean cavity

Target frequency with FMS installed: 1297,380 MHz (+/- 0,1 MHz)

For reference:Frequency change from FMS to cavity under vacuum (warm): about 390 kHz -> 1297,770 MHzFrequency change during cooldown: 2 MHz -> 1299,770 MHzRemaining 230 kHz are required for tuner pre-tension.

RF input couplers

The RF input couplers were manufactured at RI according to the ELBE-design.

The required antenna length of the couplers were determined by RF measurements on the SRF cavities with a coupler and different antenna tips (different length).

The couplers were equipped with the proper antenna tip and two couplers were assembled to a test waveguide.After bake out and leak check, the coupler pairs were moved to HZDR for high power testing.

The warm windows were also preassembled and sent to HZDR for high power testing.

RF input couplers - test setup 1Each pair of RF input couplers (cold part, coaxial transition, door knob) was integrated to the resonant ring test facility at HZDR.The test waveguide was connected to a clean pump stand and the vacuum was monitored.

The power was raised in pulsed mode to a peak power of about 50 kW and in CW mode to about 16 kW.

The couplers were protected by interlocks on: • Coupler temperature (inner conductor

at cold part)• Arc detection• Vacuum

To improve the cooling, the outer walls and the cooling channel (fro LN2) were cooled with forced air.

Both coupler pairs passed the test, the results are summarized on the next slides.

RF input couplers - test setup 2Two warm RF windows were assembled to the resonant ring test facility at HZDR.The waveguide H-bends between the RF windows was evacuated and the vacuum was monitored.

The power was raised in pulsed mode to a peak power of about 55 kW and in CW mode to about 10 kW.

The windows were protected by interlocks on: • window temperature (IR sensor)• Arc detection• Vacuum

Warm windows 3&4 did pass the test without problems, windows 1&2 have to be retested due to a small leakage at an O-ring joint.

RF input couplers - test results pulsed

Coupler pair 1&2 was tested in pulsed mode to a peak power of about 55 kW, corresponding to an average power of about 20 kW (duty cycle 36%).

The temperatures of the inner conductor raised to arround 110 deg C (air cooling only).Vacuum activity was still visible, but can be improved by better cleaning.Coupler pair 3&4 was tested in pulsed mode to a peak power of about 50 kW, corresponding to an average power of about 40 kW (duty cycle 80%).

The temperatures of the inner conductor raised to arround 110 deg C (air cooling only).Vacuum activity was still visible, but less than coupler pair 1&2 due to improved cleaning and bake out procedure.

RF input couplers - test results CW 8 kW

Coupler pair 1&2 was operated in CW mode at a power of 8 kW for 6 hours.

The temperatures of the inner conductors stabilized at arround 65 / 80 deg C (air cooling only).The imbalance is due to a slight mismatch of the couplers to the testwaveguide at 1,3 GHz.

The vacuum stabilized at arround 1,5E-7 mbar.Coupler pair 3&4 was operated in CW mode at a power of 8 kW for 8 hours.

The temperatures of the inner conductors stabilized at arround 65 / 70 deg C (air cooling only).

The vacuum stabilized at arround 2E-7 mbar.

RF input couplers - test results CW 16kW

Coupler pair 1&2 was operated in CW mode at a power of 16 kW for about 20 minutes.

The temperatures of the inner conductors raised up constantly until the interlock threshold was reached. Operation was stopped by the temperatures reaching 110 deg C (limit).

The vacuum was changeable arround at 3E-7 mbar and became unstable with temperatures > 80 deg C.

Coupler pair 3&4 was operated in CW mode at a power of 16 kW for 55 minutes.

The temperatures of the inner conductors raised up constantly until the interlock threshold was reached. Operation was stopped by the temperatures reaching 110 deg C (limit).

The vacuum was stable arround at 2,6E-7 mbar.

RF input couplers - test results summary

Coupler pair 1&2 showed stable operation at 8 kW CW.The operation at 16 kW CW was sufficient.

Due to a short pumping time (the test was started immediately after arrival of the parts at HZDR), the vacuum still shows activity which could be reduced by a longer pumping time.Coupler pair 3&4 showed stable operation at 8 kW and 16 kW in CW mode.

The vacuum was stable in both operating conditions, as the vacuum was pumped some days before the test was started.

Cryostat

The cryostats are pre-assembled and ready for the integration of the cavity string.

The thermal shield was re-designed to a more reliable welding design and build in RI.

Beamtube components

The beamtube components have been manufactured and are ready for further assembly after the horizontal test.

Beam entrance / exit section.

Between outer gate valve and thermal

shield.

Section between thermal shield and inner gate

valve.

Section between inner gate valve and cavity flange (diameter reduction with Taper)

Gate valves

The inner and outer gate valves have been delivered and are on stock, ready for string assembly.

The outer gate valves are VAT DN40CF all metal (series 48, right).

The inner gate valves are VAT DN40CF Viton sealed (series 01, bottom picture), but were specially manufactured at VAT with a permeability of less than 1.05.

Tuner

The tuner levers, the flexible joints and the respective tuner rings have been manufactured and are ready for assembly.

InstrumentationThe instrumentation of the SRF modules has been procured. All sensors like helium- and nitrogen level sensors, temperature sensors, photo multipliers, IR-sensorsare on stock and ready for integration.The heaters for helium vessel, helium port are on stock.The RF pick up and HOM antenna feedthroughs have been delivered and are on stock.

The feedthroughs for sensors, heaters and RF signals have been procured and the required flanges were produced, preassembled and leak tested (see picture).

RF System Each SC and NC cavities will be powered by a SSPA.Amplifiers and cavities will be controlled by RF controllers.All RF system is driven by a single master oscillator(MO), thus each individual RF system is synchronized.

Buncher Cavities

Resonance frequency 260 MHz

Theoretical Q ≥ 4.000

Tuning range 200 kHz

Leakage rate < 1E-9 mbar l/s

Resonance frequency 1.3 GHz

Theoretical Q ≥ 11.000

Tuning range 2.2 MHz

Leakage rate < 1E-9 mbar l/s

FB

Buncher cavities were delivered in December 2014. The acceptance parameters of the cavities are shown in Tables. Factory Acceptance Tests of buncher cavities were performed between July 1-3, 2014. Factory Acceptance Tests was including;

Resonance FrequencyUnloaded QTuning rangeLeak rate

SHB

RF Measurements of Buncher Cavities

■ Data will be taken by a network analyzer for several discrete positions along several paths parallel to the cavity axis for gradient measurements.

RF measurements for buncher cavities :

Leak rateResonance frequency Power, Gradient & Field

measurement tests

Sample test measurement setup

■ The requirements for the tests generally are;

►Vector Network Analyzer,►RF power amplifiers,►Directional Coupler,►Powermeter,►Open or close loop RF controller (LLRF)►Auxilaries, (coaxial cables, etc.)..

■ The technical spec. documents of these equipments are ready, sent to the Purchasing Department of AU and waiting for the tender.

RF Measurements of Buncher Cavities

RF amplifiers for BunchersParameter SHB FB

Input Power 0 dBm O dBm

Central Frequency 260 MHz 1300 MHz

RF Output Connector N type N type

Output Power (@1 dB compression point, cw)

1.3 kW @ 1 dB 500 W @1 dB

■ We completed the parameter set of power amplifiers for bunchers.

■ We are planning to make the acceptance tests including; Linearity, Efficiency, Coupling/Parameter & Stability tests, etc.

High Power RF Amplifiers & RF Network ■ Design Parameters

were completed in 2013.

■ The technical specification document as well as the contract were done and sent to the SigmaPhi.

■ The agreement on the contract was completed, however the procurement is waiting for the budget.

■ Additionally, RF network design works are completed, the documents relating the procurement are at the Purchasing Department of AU, waiting for the tender.

LLRF Figure shows the block diagram of TARLA MO that we purchase for backup. It includes oven controlled quartz crystals. Several signals locked each other can be obtainable with this MO. The jitter of available TARLA MO output for LLRF is <~8 fs.

LLRF

DESY μTCA.4 LLRF for TARLA

LLRF

MTCA-12S-RF2 MicroTCA.4 Chassis of powerBridge Computer Vertriebs GmbH

μTCA.4 Chassis Layout for TARLA LLRF Configuration

The 12 slot crate that will be in use at TARLA and the RF backplane which is introducedby μTCA.4 standard.

LLRF

LLRF Server Architecture and Control System Integration

Conclusion■ Technical specifications of LLRF is ready. In this

procurement;

► Hardware procurement is TARLA scope.► LLRF can be delivered about a year after signing

the contract which means at the 4thQ of 2016 , however stable/steady operation can be completed in a year after the delivery.

■ RF amplifiers (260 MHz – 1.3 kW for SHB, 1.3 GHz-500 W for FB, 1.3 GHz – 4 kW for SRF modules testing) will be delivered at most in 10 months after signing the contract. Expected delivery date is 3rdQ of 2016.

■ RF network is completed and waiting for the tender.

■ The budget has been waiting for high power RF amplifiers.

■ 1st SRF module has been waiting in the first half of the 2016, depending on the horizontal test timing.

■ Cryomodule tests can be started at 4thQ of 2016.