1. System tests at CEA O. Piquet 19/03/2019

2. System tests at CEA 5 RFQ sections Pick-ups (x28) Tuners x60
Power couplersx2
RFQ support

3. Typical flow chart for the RFQ section fabrication
ESS RFQ section
Typical flow chart for the RFQ section fabrication

4. Check report about tridimensional measurements sent by mecachrome
RFQ section machining
RFQ machining done at Mecachrome
Vane assembly with 30µm tolerance
Check report about tridimensional measurements sent by mecachrome
Vane machining with 20µm tolerance
The manufacturing of the RFQ is very closely followed with weekly meetings and visit to Mécachrome

5. Mechanical error study
Beadpull measurement
Why beadpull measurements?
Check the machining and the assembly of the 4 vanes according to RF design at different step of section fabrication
2D RF simulations of the cross-section vs. abcsissa
Electrical parameters of RFQ vs. abscissa in order that Transmission Line model (TLM) mimics physical RFQ
Mechanical error study
Definition of CQQ, CSQ and CTQ parameters
Vane machining with 20µm tolerance
Geometry errors ~ Capacitance perturbations of the TLM
Tolerances given by tuner range
Vane assembly with 30µm tolerance

6. Magnetic field measurement for the 4 RFQ quadrants
Beadpull measurement
Beadpull principle:
Measure the magnetic field inside each RFQ quadrant
Define TLM parameters according these measurements
Compare these measured capacitances with theoretical values defined in the RF design study
Principle of beadpull measurement: resonance frequency is shifted proportionally to the square of field at bead location; frequency shift is too small to be directly measured, phase shift is measured instead using a VNA.
4 assembled vanes
Magnetic field measurement for the 4 RFQ quadrants

7. Beadpull measurement │CQQ │ /C≤1.85.10-2 │CSQ │ /C≤2.35.10-2
First beadpull measurement at Mecachrome
Mathematical processing of the magnetic field measurement with the same process used for the RF design of the RFQ
Beadpull results
│CQQ │ /C≤
│CSQ │ /C≤
│CTQ │ /C≤
Beadpull testbench

8. Comparison with first assembly beadpull
Brazing at bodycote
Beadpull of the RFQ section with all these definitive ports and flanges
Comparison with first assembly beadpull
Differences could be explain by the use of ‘’test’’ ports for the first beadpull
Beadpull results
│CQQ │ /C≤
│CSQ │ /C≤
│CTQ │ /C≤

9. Brazing At bodycote
Brazing at 850°C

10. Leak test at bodycote
Defined by the CEA (and ESS) RFQ Helium Leak Testing Procedure :
First check by helium spraying of the different interfaces (welding and brazing part, seals, …)
Leaks on seals are fixed (changing the gasket, sealing surface preparation, …)
Global (or Partial) leak testing using a bag
The leak should be less than mbar.l.s-1
Done by Mecachrome subcontractor with CEA team

11. FINAL machining At Mecachrome
Tridimensional measurements of the section after brazing
Final machining of the section (end faces and locating)
Definition of the beam axis
and interfaces with the next section
Hydraulic tests of the cooling channels and cooling plates
Final tridimensional measurements before transportation to Saclay

12. Final leak test at Saclay Final beadpull at Saclay
Reception tests at CEA
Final leak test at Saclay
Done by Mecachrome subcontractor with attendance CEA #
Value
Method S1
mbar.l.s-1
Final global test at Saclay
Beadpull results
Final beadpull at Saclay
│CQQ │ /C≤
│CSQ │ /C≤
│CTQ │ /C≤

13. Installation of the first section on the RFQ support
ESS RFQ section
Installation of the first section on the RFQ support
Documentation to manage
Check of the installation procedure

14. RFQ couplers
- 2 power coupling loops (in Section 3) for 1.6MW maximum power
- Similar RF window designed for cryomodule couplers (only frequency adaptation)
- Produced by PMB (same company for 120 cryomodule couplers)
- A third coupler built in order to mitigate risk

15. RFQ couplers Coupler description: Electron current measurement +
Vacuum gauge
Cooling for RF loop
Cooling for ceramic window
Coupling performed by rotating the coupler around its rotation axis
Air side arc-detector
Vacuum side arc-detector

16. Tests of sub-assemblies
Tridimensional measurements for each element
Vacuum test of the different parts of the couplers
hydraulic test of the cooling circuits
SAT report
For welding and brazing parts
Different bags to isolate EPDM (temporary) gasket from nominal interface
Visual inspection (Grooves, surface…) #
Value
Method
Brazing/CF parts
< mbar.l.s-1
Partial test before assembly

17. Coupler assembly Vacuum test of the coupler: (2 EPDM gaskets)
Assembly of 3 power couplers
Assembly procedure #
Value
Method
EPDM seals
< mbar.l.s-1 *
Partial test after assembly
* no instant leak, only permeation after several minutes

18. Coupler qualification tests
Couplers are assembled on the cavity test:
- Installation of EPDM seals
- Installation of RF seals
- Rotation of the coupler to get the optimal coupling
- Leak test of the coupler-cavity interface
- Coupler (and cavity) instrumentation installation

19. Coupler qualification tests
Instrumentation:
Protection of systems (RF source, coupler, cavity…)
Stop the RF in less than 20µs in case of interlock
Acquisition of data (RF, arc, electron current, temperatures, vacuum…)
Fast interlocks:
- Electron current (*2)
- Arc detection (*4)
- Reflected power (*2)
- Vacuum: coupler (*2) and coupling cavity
Automatic procedure:
Start at low power (from Pmin=1kW to Pmax=1000kW)
Start with short pulses (from 100µs to 3.6ms)
Start at low repetition rate (from1Hz to nominal repetition rate: 14Hz)
Increase the RF power according the level of vacuum inside couplers and coupling cavity

20. Coupler qualification tests
Typical conditioning process
Coupler qualification report
3 days long run test at maximum power (1MW), maximum width (3.6ms) and maximum repetition rate (14Hz)
Power
Temperatures
Vacuum

21. And ready for transportation at ESS
RFQ couplers
3 conditioned couplers
Requirements
2 power couplers
Maximum power per coupler: 1MW
Voltage pulse length: 3.5ms
Voltage pulse rate: 14Hz
Achievement
3 power couplers
Maximum power per coupler: 1MW
Voltage pulse length: 3.6ms
Voltage pulse rate: 14Hz
And ready for transportation at ESS
Threshold used during coupler test at Saclay
Fast interlocks
Threshold for ligth émission
1.3 Lux
Threshold for current electron
9mA
Vacuum
Hardware upper threshold
6*10-6mbar
Hardware lower threshold
4*10-6mbar
Software threshlod
2.5*10-6mbar
Temperatures
window part
40°C
RF loop
Water flows
4.5l/min
3l/min
All the interlocks (Thresholds) defined by the coupler test done at Saclay will be used as a baseline for the RFQ conditioning

22. Visual inspection (Grooves, surface, hydraulic connections…)
Tuners (60)
Used for the final tuning of the RFQ:
Setting of the RFQ frequency and the voltage law
= correction of mechanical defaults of the RFQ (fabrication…)
Control the allowable range
Position range on the RFQ = 60mm
Visual inspection (Grooves, surface, hydraulic connections…)

23. Tuners (60) Helium leak test for each Tuners:
Performed by the company, with a CEA procedure (global leak test), before and after hydraulic tests.
At Saclay, leak test on 2 tuners per transport box have been performed (in the max and min position) -> 8 Tuners
FAT (with attendance of CEA ) and SAT reports
Tuner assembled on RFQ section 1

24. Conclusion Status of Tuners, Couplers and RFQ sections
Vacuum
RF conditioning
Dimensions
Beadpull
Tuner
Passed (10-9mbar l s-1)
N.A. OK
Couplers
Done in March 2018
1MW
RFQ sections
S1: mbar l s-1
At ESS in Nov 2019
S1: Ok
S1: OK
S2: < 10-10mbar l s-1 after brazing
S2: OK
S2: OK before brazing
S3: mbar l s-1 after brazing
S3: OK before brazing
S4: May 19
S4: First in April
S5: May 19
S5: First in April
: SAT of Section1 at Saclay
Requirement for RFQ installation/conditioning at ESS
Before the conditioning of RFQ, some ESS systems must be characterized and qualified:
- RF power sources
- Local protection System of RFQ (interlocks, speed…)
- LLRF
- Acquisition of the voltage Law
- Control/command for RFQ (automatic software for conditioning…)
- Vacuum system fully operational with downstream/upstream beam valves
- Beam before RFQ entrance